JP6745395B1 - Optical resonator, optical modulator, optical frequency comb generator, optical oscillator, and method of manufacturing the optical resonator and optical modulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the chipping and rounding at the time of processing the corners of the end face of a waveguide and to stably adhere the respective reflection films without peeling off at the corners of the uppermost end face of each of the reflection films, thereby making the reflectance of the reflection film and the resonator. Improve the finesse of. SOLUTION: An incident side reflection film 93 and an emission side reflection film 94 are provided so that light incident through the incident side reflection film 93 is resonated and penetrates from the incident side reflection film 93 to the emission side reflection film 94. A waveguide 12 for propagating the resonated light, a substrate 11 for forming the waveguide 12 from the upper surface, a first protective material 86 and a second protective material 87 corresponding to the material of the substrate 11. Of the waveguide 12 so that at least one end face thereof forms the same plane 91, 92 as the first end face 84 and the second end face 85 of the substrate 11 including the light incident end or the light exit end of the waveguide 12. The incident-side reflection film 93 and the emission-side reflection film 94, which are disposed on the upper portion, are formed as single-layer or multilayer vapor-deposition films on flat surfaces 91 and 92 perpendicular to the optical waveguide 12 to be formed. [Selection diagram]

Description

The present invention provides a standard light source having high coherence at multiple wavelengths such as optical communication, optical CT, and an optical frequency standard, or an optical resonator applied to a field requiring a light source that can also utilize coherence between wavelengths, The present invention relates to an optical modulator, an optical frequency comb generator, an optical oscillator, an optical resonator thereof, and a method for manufacturing the optical modulator.

With the development of optoelectronics in recent years, a waveguide optical resonator that resonates the light confined in an optical waveguide in order to meet the demands of laser light control for frequency multiplex communication and frequency measurement of absorption lines distributed over a wide range. Has become popular.

When the optical frequency is measured with high accuracy, the light to be measured is interfered with other light, and heterodyne detection is performed to detect the electric signal of the generated optical beat frequency. The band of light that can be measured in this heterodyne detection is limited to the band of the light receiving element used in the detection system, and is approximately several tens GHz.

On the other hand, with the recent development of optoelectronics, it is necessary to further expand the measurable band of light in order to perform optical control for frequency multiplex communication and frequency measurement of absorption lines distributed over a wide range.

In order to meet the demand for expanding the measurable band, a broadband heterodyne detection system using an optical frequency comb generator (see, for example, Patent Document 1) has been conventionally proposed. This optical frequency comb generator generates comb-shaped sidebands arranged at equal intervals on the frequency axis over a wide band. The frequency stability of this sideband is almost equal to the frequency stability of incident light. Is. By heterodyne-detecting the generated sideband and the measured light, it is possible to construct a wideband heterodyne detection system over several THz.

FIG. 32 shows the principle structure of the conventional optical frequency comb generator 1003.

The optical frequency comb generator 1003 uses an optical resonator 1000 including an optical phase modulator 1031 and reflecting mirrors 1032 and 1033 installed so as to face each other via the optical phase modulator 1031.

The optical resonator 1000 resonates the light L _in that is incident with a small transmittance through the reflecting mirror 1032 between the reflecting mirrors 1032 and 1033, and emits a part of the light L _out through the reflecting mirror 1033. Let The optical phase modulator 1031 is composed of an electro-optic crystal for optical phase modulation in which the refractive index changes by applying an electric field, and the frequency applied to the electrode 1036 with respect to the light passing through the optical resonator 1000. multiplying the phase-modulated in response to an electrical signal of f _m.

In this optical frequency comb generator 1003, an electric signal synchronized with the time when light reciprocates in the optical resonator 1000 is driven and input from the electrode 1036 to the optical phase modulator 31, so that the optical phase modulator 1031 is operated only once. It is possible to apply deep phase modulation that is several tens of times deeper than when passing through. Thus, it is possible to generate hundreds of higher order sidebands, becomes equal to the frequency f _m of the frequency interval f _m are all input electric signals of adjacent sidebands.

Further, the conventional optical frequency comb generator is not limited to the above-mentioned bulk type. For example, as shown in FIG. 33, it is also applicable to a waveguide type optical frequency comb generator 1020 using an optical waveguide.

The waveguide type optical frequency comb generator 1020 is composed of a waveguide type optical modulator 1200. The waveguide type optical modulator 1200 includes a substrate 1201, an optical waveguide 1202, an electrode 1203, an incident side reflection film 1204, an emission side reflection film 1205, and an oscillator 1206.

The substrate 1201 is obtained by cutting a large crystal such as LiNbO ₃ or GaAs having a diameter of 3 to 4 inches grown by a pulling method into a wafer. The cut-out substrate 1201 is subjected to processing such as mechanical polishing and chemical polishing.

The optical waveguide 1202 is arranged to propagate light, and the refractive index of the layers forming the optical waveguide 1202 is set higher than that of other layers such as the substrate 1201. The light incident on the optical waveguide 1202 propagates while being totally reflected at the boundary surface of the optical waveguide 1202. Generally, the optical waveguide 1202 can be manufactured by diffusing Ti atoms in the substrate 1201 or by epitaxially growing it on the substrate 1201.

A LiNbO ₃ crystal optical waveguide may be applied as the optical waveguide 1202. This LiNbO ₃ crystal optical waveguide can be formed by diffusing Ti on the surface of the substrate 1201 made of LiNbO ₃ or the like. In the case of actually producing this LiNbO ₃ crystal optical waveguide, first, a photoresist pattern is produced on the surface of the substrate 1201, Ti is vapor-deposited thereon, and then the photoresist is removed. A Ti thin wire having a width is prepared. Next, by heating the thin wire of Ti, it is thermally diffused into the substrate 1201.

By the way, when this Ti is thermally diffused in the substrate 1201 made of LiNbO ₃ , the region where the Ti is diffused has a higher refractive index than the other regions and can confine light. That is, the optical waveguide 1202 capable of propagating light is formed in the region where Ti is diffused. Since the LiNbO ₃ crystal type optical waveguide 1202 produced based on such a method has an electro-optical effect, the refractive index can be changed by applying an electric field thereto.

Electrode 1203, for example, Al and Cu, Pt, a metal material such as Au, and drives the input electrical signals supplied frequency _{f m} from the outside to the optical waveguide 1202. Further, the propagation direction of light in the optical waveguide 1202 and the traveling direction of the modulation electric field are the same. By adjusting the width and thickness of the electrode 1203, the speed of light propagating in the optical waveguide 1202 and the speed of an electric signal propagating on the electrode 1203 may be matched. This makes it possible to keep the phase of the electric signal felt by the light propagating through the optical waveguide 1202 constant.

The incident side reflection film 1204 and the emission side reflection film 1205 are provided to resonate the light incident on the optical waveguide 1202, and resonate the light passing through the optical waveguide 1202 by reciprocating it. The oscillator 1206 is connected to the electrode 1203 and supplies an electric signal having a frequency f _m .

The incident side reflection film 1204 is arranged on the light incident side of the waveguide type optical modulator 1200, and light of frequency ν ₁ is incident from a light source (not shown). Further, the incident side reflection film 1204 reflects the light reflected by the emission side reflection film 1205 and passing through the optical waveguide 1202.

The emission side reflection film 1205 is arranged on the light emission side of the waveguide type optical modulator 1200 and reflects the light passing through the optical waveguide 1202. Further, the emitting side reflection film 1205 emits the light passing through the optical waveguide 1202 to the outside at a constant rate.

In the waveguide type optical frequency comb generator 1020 configured as described above, an electric signal synchronized with the time when light travels back and forth in the optical waveguide 1202 is input from the electrode 1203 to the waveguide type optical modulator 1200 as a driving input. As compared with the case where the light passes through the optical phase modulator only once, it becomes possible to perform deep phase modulation of several ten times or more. Accordingly, similar to the bulk type optical frequency comb generator 1003, an optical frequency comb having a wide sideband can be generated, and the frequency intervals of adjacent sidebands are all the frequency f _{m of the} input electric signal. Is equivalent to

The characteristic of the waveguide type optical frequency comb generator 1020 is that the interaction area of light and electric signal is smaller. Since light propagates while being confined in the optical waveguide 1202 having a micron-order having a higher refractive index than the surroundings, by mounting the electrode 1203 in the immediate vicinity of the optical waveguide 1202, the electric field strength in the optical waveguide 1202 is locally increased. It is possible to raise it. Therefore, as compared with the bulk type optical frequency comb generator 1003, the electro-optical effect generated in the optical waveguide 1202 becomes large, and it becomes possible to obtain a large modulation with a small electric power.

However, in the above-described conventional waveguide type optical frequency comb generator 1020, due to the structure of the optical waveguide 1202, it is difficult to adhere the incident side reflection film 1204 and the emission side reflection film 1205 and to polish the end faces to which these are adhered. It was difficult to make a high finesse resonator with good reproducibility. In order to improve the performance of the waveguide type optical frequency comb generator 1020, it is indispensable to increase the finesse of the resonator constituted by the incident side reflection film 1204 and the emission side reflection film 1205. Even if the modulation index of the optical waveguide 1202 is high only in the forward direction or the backward direction, if the finesse itself is low, the number of round trips of light cannot be increased, so that a high-strength sideband is generated over a wide band. Because you can't.

Further, an optical comb generator and an optical modulator have been proposed in which not only the light propagating in the forward direction in the optical waveguide but also the light propagating in the return direction are subjected to phase modulation (for example, see Patent Document 2). ).

Further, FIG. 34 shows an end face of the waveguide type optical frequency comb generator 1020 on which the incident side reflection film 1204 is formed. According to FIG. 34, an optical waveguide 1202 is formed on the upper end of a substrate 1201, a thin buffer layer is laminated on the optical waveguide 1202, and an electrode 1203 is further formed thereon. That is, the optical waveguide 1202 is located at the uppermost corner of the end face of the waveguide type optical frequency comb generator 1020. Since the uppermost corner of the end face is sharp, a chip is often generated during polishing as shown in FIG. When a chip is generated at the uppermost end face, the light to be resonated is scattered and lost.

Further, depending on the state of the end surface polishing, the corners may be rounded even if the corners are not chipped at the uppermost portion of the end surface. When the corners are rounded, a part of the reflected light deviates from the waveguide mode of the optical waveguide 1202 and becomes a loss.

In addition, in some rare cases, the top edge of the end face may not be chipped and may be polished in a state where the corner is not rounded. Even in such a case, when the incident side reflection film 1204 is formed on the end face. Problem occurs. The high-reflection film such as the incident-side reflection film 1204 is usually produced by alternately depositing a film having a high refractive index and a film having a low refractive index, but the film itself is easily peeled off at the corner portion at the uppermost end face. There is also a problem that the film thickness cannot be controlled as designed as a result of the film thickness changing due to the material of the high reflection film wrapping around from the end surface to the side surface.

That is, in the optical waveguide in which the core is formed in the substrate by diffusion or the like, the core is formed on the surface of the substrate, so that at the end face, at least one side of the outer periphery of the core is located on the outer periphery of the substrate. When an optical thin film such as a reflective film is formed on the end surface of such an optical waveguide by a vapor deposition method, a sputtering method, a chemical vapor deposition method, or the like, in the outer peripheral part of the end surface of the substrate, the wraparound of the film-forming particles to the side surface, and Since the film-forming particles flying from the side surface wrap around to the end face, it is difficult to obtain a uniform film thickness at the outer peripheral portion of the end face of the substrate. Therefore, it is very difficult to form a film that is thin enough to act as a reflection film and has a small film thickness distribution on the end surface of the core located on the outer peripheral portion of the end surface of the substrate.

Here, the applicant of the present application suppresses chipping and rounding during processing of the corners of the end faces of the optical waveguide, and allows each reflective film to be stably applied without peeling off at the corners of the uppermost end face of the reflective film, so that We have previously proposed an optical resonator, an optical modulator, an optical comb generator, and an optical oscillator that improve the function of the device itself by improving the reflectance and finesse of the optical resonator. (For example, refer to Patent Document 3).

That is, a member having the same hardness as the substrate for forming the optical waveguide from the upper surface is formed, and at least one end face of the member forms the same plane as the end face of the substrate including the light incident end or the light emitting end of the optical waveguide. As described above, the incident side reflection film and the emission side reflection film forming the resonance means are covered on the plane formed by polishing the end face of the member and the end face of the substrate. Since it is attached, it is possible to suppress chipping and rounding during processing of the corners of the end face of the optical waveguide, and it is possible to adhere stably without peeling off at the corners of the top end face of each reflection film. It is possible to improve the finesse of the optical resonator and enhance the function of the device itself.

JP, 2003-202609, A Japanese Patent No. 3891977 Japanese Patent No. 4781648

By the way, in the conventional waveguide type optical frequency comb generator 1020, since the end face of the optical waveguide 1202 is located at the uppermost corner of the end face, the optical method such as the reflection film is formed by the vapor deposition method, the sputtering method, the chemical vapor deposition method or the like. When a single-layer or multilayer vapor-deposited film is formed on the end face as a thin film, at the outer peripheral portion of the end face of the substrate, the wraparound of the film-forming particles to the side surface and the wrap-around of the film-forming particles flying from the side direction occur. , It is difficult to obtain a uniform film thickness on the outer peripheral part of the end face of the substrate, and it is thin enough to act as a reflective film on the end face of the core located on the outer peripheral part of the end face of the substrate, and the film thickness distribution is small. There is a problem that it is very difficult to form a film.

Further, when polishing the end surface of the optical waveguide 1202, the corners of the end surface of the optical waveguide 1202 are likely to be chipped during the processing, and the corners of the end surface of the optical waveguide 1202 may be rounded during the processing. There is a problem that the formed reflective film is easily peeled off at the corners at the uppermost end face.

These problems are the reduction of the reflectance of the reflection film deposited on the end face of the optical waveguide 1202, the reduction of the finesse of the resonator formed by the incidence side reflection film 204 and the emission side reflection film 1205, and the waveguide type optical frequency comb. Since the function of the generator 1020 itself is deteriorated and it depends on the manufacturing environment, the performance of the waveguide type optical frequency comb generator 20 and the waveguide type Fabry-Perot resonator to which the same is applied is reduced. The reproducibility could not be guaranteed, which was a factor to reduce the yield.

Conventionally, in a waveguide type optical resonator that resonates the light confined in the optical waveguide, an optical waveguide that transmits a polarization component in which orthogonal modes are mixed is used, and an optical modulator and an optical frequency comb generator are constructed. The optical output obtained in this case also contained a polarization component in which orthogonal modes were mixed.

In the conventional optical frequency comb generator, when using the optical frequency comb for measurement, in order to obtain a stable output, a part of the light emitted from the optical resonator is detected by the photodetector, The resonance length of the optical resonator is feedback-controlled so that the resonance length is obtained. However, since an optical waveguide that transmits a polarization component in which orthogonal modes are mixed is used, a circle is added to FIG. As shown by the above, the transmission mode waveform due to the orthogonal polarization components may be deformed. Moreover, the places where the transmission mode waveform is deformed by the orthogonal polarization components (relative positions with respect to the main mode) are scattered and there are a plurality of local minimum portions, which becomes an unstable factor when controlling the resonance length.

That is, when generating an optical frequency comb in an optical comb generator that uses a waveguide type optical resonator that resonates the light confined in the optical waveguide, the orthogonal polarization components match the resonant frequency of the optical frequency comb generator with the laser frequency. The control for making it unstable may cause a shift of the control point, oscillation of control, etc., and when the optical frequency comb is used for a measuring device that measures the distance or height to the measurement target, The orthogonal polarization components were the cause of the measurement error.

Therefore, the present invention has been devised in view of the conventional problems as described above, and the purpose thereof is to suppress chipping or rounding during processing of the corners of the optical waveguide end face, A single-layer or multi-layer vapor-deposited film is stably applied without peeling at the uppermost corners of the end face to improve the reflectance of the reflective film and the finesse of the resonator, and to enhance the function of the device itself. An object of the present invention is to provide a resonator, an optical modulator, an optical frequency comb generator, an optical oscillator, and an optical resonator having such a function and a method of manufacturing the optical modulator.

Another object of the present invention is to make it possible to stabilize the resonator control without causing deformation of the transmission mode waveform of the optical waveguide.

Another object of the present invention is to suppress the output of orthogonal polarization components that do not contribute to the generation of an optical frequency comb, improve the polarization extinction ratio, and obtain an optical frequency comb output with an increased single polarization degree. Is to

Further, another object of the present invention is to make it possible to stabilize the optical frequency comb generator, improve the accuracy of a measuring device including the optical frequency comb, and reduce errors.

Other objects of the present invention and specific advantages obtained by the present invention will become more apparent from the description of the embodiments described below.

The present invention relates to a method of manufacturing an optical resonator for propagating and resonating light incident through the incident side reflection film, by an optical waveguide formed so as to penetrate from the incident side reflection film to the emission side reflection film. An optical waveguide forming step of forming the optical waveguide from the upper surface of the substrate, and a protective member having the same hardness as the substrate, the substrate having at least one end face thereof including a light incident end or a light emitting end of the optical waveguide. The step of disposing the optical waveguide so as to form the same plane as the end surface of the optical waveguide, and polishing the end surface of the protective member and the end surface of the substrate arranged in the disposing step, thereby forming the optical waveguide. A polishing step of forming a flat surface perpendicular to the optical waveguide as a flat polishing surface including a light incident end or a light emitting end of the waveguide, and the incident side reflection film or the reflection film on the flat surface formed in the polishing step. A reflection film applying step of applying a single-layer or multi-layer vapor deposition film as the emission side reflecting film, and in the providing step, the protective member is provided by being adhered to the upper part of the optical waveguide with an adhesive. Then, in the reflection film deposition step, a single-layer or multi-layer deposition film is deposited over the entire plane formed by the end face of the protective member and the end face of the substrate, which are adhered by the adhesive. Thus, the incident side reflection film or the emission side reflection film is formed on a plane perpendicular to the optical waveguide.
In the method for manufacturing an optical resonator according to the present invention, in the reflection film deposition step, with respect to a loss rate according to a crystal length in a light propagation direction of the optical waveguide, a light incident end or a light emission of the optical waveguide is generated. A single-layer or multi-layer vapor deposition film having an optimized film thickness in the end face region including the end can be applied.

The present invention relates to a method of manufacturing an optical modulator for propagating and modulating light incident through the incident side reflection film by the optical waveguide having an incident side reflection film and an emission side reflection film formed thereon. Is formed from the upper surface of the substrate, a laminating step of laminating a buffer layer on the substrate so as to cover at least the optical waveguide formed in the optical waveguide forming step, and an electric field is applied to the optical waveguide. An electrode forming step of forming an electrode for applying on the buffer layer laminated in the laminating step, and a protective member having the same hardness as that of the substrate, at least one end face of which is a light incident end or a light in the optical waveguide. A disposing step of disposing the optical waveguide so as to form the same plane as the end surface of the substrate including the emitting end, and polishing the end surface of the protective member and the end surface of the substrate arranged in the disposing step. By doing so, as a flat polishing surface including the light incident end or the light emitting end of the optical waveguide, a polishing step of forming a flat surface perpendicular to the optical waveguide, and on the flat surface formed in the polishing step. A reflection film applying step of applying a single-layer or multi-layer vapor deposition film as the entrance-side reflecting film or the exit-side reflecting film, and in the arranging step, the protective member is attached to the upper part of the optical waveguide by an adhesive. In the reflection film applying step, a single-layer or multi-layer vapor deposition is performed over the entire plane formed by the end surface of the protective member and the end surface of the substrate, which are attached by the adhesive. By depositing a film, the incident side reflection film or the emission side reflection film is formed on a plane perpendicular to the optical waveguide.
In the method for manufacturing an optical modulator according to the present invention, in the reflection film deposition step, a light incident end or a light exit of the optical waveguide is generated with respect to a loss rate according to a crystal length in a light propagation direction of the optical waveguide. A single-layer or multi-layer vapor deposition film having an optimized film thickness in the end face region including the end can be applied.
Further, in the method for manufacturing an optical modulator according to the present invention, in the optical waveguide forming step, a waveguide mode exists only for a single polarization component by proton exchange from at least the upper surface of the substrate having an electro-optical effect. The above-mentioned optical waveguide can be formed as a region in which the above-mentioned optical waveguide is formed.
Further, in the method for manufacturing an optical modulator according to the present invention, there is a ridge structure forming step of forming a ridge structure on the substrate, and in the electrode forming step, the ridge structure is formed on the substrate in the laminating step. An electrode having a ridge structure can be formed on the buffer layer as an electrode for applying an electric field to the optical waveguide.

The present invention is an optical resonator, which is composed of an incident side reflection film and an emission side reflection film, and resonates means for resonating light incident through the incidence side reflection film, and the emission side from the incidence side reflection film. An optical waveguide that is formed so as to penetrate through the side reflection film and propagates the light resonated by the resonance means, a substrate on which the optical waveguide is formed from the upper surface, and a protective member having the same hardness as the substrate. The protective member is adhesive on the upper part of the optical waveguide so that at least one end face of the protective member forms the same plane as the end face of the substrate including the light incident end or the light emitting end of the optical waveguide. And an end face protection means provided by pasting, wherein the incident side reflection film and the emission side reflection film are flat surfaces formed by the end face of the protection member and the end face of the substrate pasted with the adhesive. Of a single layer or a multi-layer deposited on a plane perpendicular to the optical waveguide formed as a flat polished surface including the light incident end or the light emitting end of the optical waveguide by polishing all of the above. It is characterized by being a film.
In the optical resonator according to the present invention, the incident-side reflection film and the emission-side reflection film have a light incident end of the optical waveguide or a light incident end of the optical waveguide with respect to a loss rate according to a crystal length in a light propagation direction of the optical waveguide. The vapor deposition film may be a single-layer or multi-layer vapor deposition film having an optimized film thickness in the end face region including the light emitting end .
Further, in the optical resonance according to the present invention, the protection member constituting the end face protection means is made of the same material as the substrate, and the end face of the protection member forming the plane and the end face of the substrate are the same as each other. The end face protection means has a crystal orientation so that one end face of the protection member forms the same plane as the end face of the substrate including the light incident end of the optical waveguide, and another end face of the protection member. It may be arranged above the optical waveguide so that the end surface forms the same plane as the end surface of the substrate including the light emitting end of the optical waveguide.

The present invention is an optical modulator, which comprises an oscillating means for oscillating a modulation signal of a predetermined frequency, an incident side reflection film and an emission side reflection film, and resonates light incident through the incident side reflection film. And a resonance unit for penetrating from the incident side reflection film to the emission side reflection film, and modulates the phase of the light resonated by the resonance unit according to the modulation signal supplied from the oscillation unit. An optical waveguide, a substrate on which the optical waveguide is formed from an upper surface, and a protective member having the same hardness as the substrate, and at least one end face of the protective member has a light incident end or a light emitting end in the optical waveguide. And an end face protection means in which the protective member is disposed on the upper portion of the optical waveguide by an adhesive so as to form the same plane as the end face of the substrate including the incident side reflection film and the emission side. The reflection film includes a light incident end or a light emitting end of the optical waveguide by polishing over the entire plane formed by the end surface of the protective member and the end surface of the substrate, which are adhered with the adhesive. It is characterized in that it is a single-layer or multi-layer vapor deposition film deposited on a plane perpendicular to the optical waveguide formed as a flat polished surface.

In the optical modulator according to the present invention, the incident-side reflection film and the emission-side reflection film have a light incident end of the optical waveguide or a light incident end of the optical waveguide with respect to a loss rate according to a crystal length in a light propagation direction of the optical waveguide. It may be a single-layer or multi-layer vapor deposition film in which the film thickness in the end face region including the light emitting end is optimized .

Further, the present invention is an optical modulator, which is composed of an incident side reflection film and an emission side reflection film, and resonates the light incident through the incident side reflection film, and the incident side reflection film. From the optical waveguide formed so as to penetrate through the emission side reflection film, the substrate on which the optical waveguide is formed from the upper surface, and the electrode formed on the substrate for propagating the modulation signal in the forward direction or the backward direction. The light modulating means for modulating the phase of the light propagating in the optical waveguide according to the wavelength of the electric signal supplied to the electrode, and the protective member having the same hardness as the substrate, The protective member is placed on the upper portion of the optical waveguide with an adhesive so that at least one end face of the member forms the same plane as the end face of the substrate including the light incident end or the light emitting end of the optical waveguide. The incident side reflection film and the emission side reflection film are provided over the entire plane formed by the end face of the protection member and the end face of the substrate, which are attached with the adhesive. A single-layer or multilayer vapor-deposited film deposited on a plane perpendicular to the optical waveguide, which is formed as a flat polished surface including the light incident end or the light emitting end of the optical waveguide by polishing. Is characterized by.

In the optical modulator according to the present invention, the incident-side reflection film and the emission-side reflection film have a light incident end of the optical waveguide or a light incident end of the optical waveguide with respect to a loss rate according to a crystal length in a light propagation direction of the optical waveguide. It may be a single-layer or multi-layer vapor deposition film in which the film thickness in the end face region including the light emitting end is optimized .
Further, in the optical modulator according to the present invention, the optical waveguide is formed on the substrate having at least an electro-optical effect as a region where a waveguide mode exists only for a single polarization component. Can be
Further, in the optical modulator according to the present invention, the electrode of the optical modulator may have a ridge structure.

The present invention is an optical frequency comb generator comprising an oscillating means for oscillating a modulated signal of a predetermined frequency, an incident side reflection film and an emission side reflection film, and light incident through the incidence side reflection film. Is formed so as to penetrate from the incident side reflection film to the emission side reflection film, and resonates the phase of the light resonated by the resonance means according to the modulation signal supplied from the oscillation means. An optical waveguide that modulates and generates sidebands centering on the frequency of the incident light at intervals of the frequency of the modulation signal, a substrate on which the optical waveguide is formed from the upper surface, and a modulation formed on the substrate. An optical modulator that includes an electrode for propagating a signal in a forward or backward direction, and modulates the phase of light propagating in the optical waveguide according to the wavelength of an electric signal supplied to the electrode, and the substrate. And the optical waveguide so that at least one end face of the protective member forms the same plane as the end face of the substrate including the light incident end or the light emitting end of the optical waveguide. And an end face protection means in which the protective member is disposed by being adhered with an adhesive, and the incident side reflection film and the emission side reflective film are the end face of the protective member adhered with the adhesive. By polishing over the entire plane formed by the end face of the substrate, a plane perpendicular to the optical waveguide formed as a flat polished surface including the light incident end or the light emitting end of the optical waveguide. It is characterized in that it is a deposited single-layer or multi-layer vapor deposition film.

In the optical frequency comb generator according to the present invention, the incident-side reflection film and the emission-side reflection film have a loss factor corresponding to a crystal length in a light propagation direction of the optical waveguide with respect to a light incidence of the optical waveguide. It may be a single-layer or multi-layer vapor deposition film having an optimized film thickness in the end surface region including the end or the light emitting end .
Further, the optical frequency comb generator according to the present invention may further include a reflecting mirror that reflects the light that is resonated by the resonating means and that is transmitted to the outside through the incident side reflection film. ..

The present invention is an optical oscillator, which is composed of an incident side reflection film and an emission side reflection film, and resonating means for resonating light incident through the incident side reflection film or light generated by laser amplification, An optical waveguide which is formed so as to penetrate from the incident side reflection film to the emission side reflection film, amplifies the light resonated by the resonance means, and emits the light to the outside through the emission side reflection film; The optical waveguide is composed of a substrate on which an optical waveguide is formed from the upper surface, and an electrode formed on the substrate for propagating a modulation signal in a forward direction or a backward direction, and the optical waveguide according to the wavelength of an electric signal supplied to the electrode. The light modulating means for modulating the phase of the light propagating in the inside and a protective member having the same hardness as the substrate, and at least one end face of the protective member is a light incident end or a light emitting end in the optical waveguide. And an end face protection means in which the protective member is disposed on the upper portion of the optical waveguide by an adhesive so as to form the same plane as the end face of the substrate including the incident side reflection film and the emission side. The reflection film includes a light incident end or a light emitting end of the optical waveguide by polishing over the entire plane formed by the end surface of the protective member and the end surface of the substrate, which are adhered with the adhesive. Characterized by being a single-layer or multilayer vapor-deposited film deposited on a plane perpendicular to the optical waveguide formed as a flat polished surface.

In the optical oscillator according to the present invention, the incident-side reflection film and the emission-side reflection film are the light incident end or the light of the optical waveguide with respect to the loss rate according to the crystal length in the light propagation direction of the optical waveguide. It may be a single-layer or multilayer vapor-deposited film in which the film thickness in the end face region including the emission end is optimized .
Also, in the optical oscillator according to the present invention, the optical waveguide is formed by diffusing a medium that absorbs light incident through the incident side reflection film and has an amplification characteristic with respect to the wavelength of light peculiar to the medium. Can be something.
Further, in the optical oscillator according to the present invention, the optical waveguide may be made of a non-linear optical crystal.

The present invention is an optical oscillator, comprising an oscillating means for oscillating a modulation signal of a predetermined frequency, an incident side reflection film and an emission side reflection film, and light or laser incident through the incident side reflection film. Resonant means for resonating the light generated by amplification and penetrating from the incident side reflection film to the emission side reflection film, and resonated by the resonance means according to the modulation signal supplied from the oscillation means. The optical waveguide that amplifies the generated light and emits it to the outside through the reflection film on the emission side, the substrate on which the optical waveguide is formed, and the modulation signal formed on the substrate in the forward or backward direction. Optical modulation means for modulating the phase of the light propagating in the optical waveguide according to the wavelength of the electric signal supplied to the electrode, and having the same hardness as the substrate. The protective member is formed on the optical waveguide so that at least one end face of the protective member forms the same plane as the end face of the substrate including the light incident end or the light emitting end of the optical waveguide. Is provided with an end face protection means that is attached by an adhesive, and the incident side reflection film and the emission side reflection film are formed by an end face of the protection member and an end face of the substrate that are adhered by the adhesive. A single layer deposited on a plane perpendicular to the optical waveguide formed as a flat polished surface including the light incident end or the light emitting end of the optical waveguide by polishing the entire formed plane. Alternatively, it is a multi-layer vapor deposition film, and is characterized in that phase synchronization is achieved between multiple modes of laser oscillation.

In the optical oscillator according to the present invention, the incident-side reflection film and the emission-side reflection film are the light incident end or the light of the optical waveguide with respect to the loss rate according to the crystal length in the light propagation direction of the optical waveguide. It may be a single-layer or multilayer vapor-deposited film in which the film thickness in the end face region including the emission end is optimized .

In the present invention, a protective member having the same hardness as the substrate for forming the optical waveguide from the upper surface is provided, and at least one end face thereof is the same as the end face of the substrate including the light incident end or the light emitting end of the optical waveguide. The optical waveguide is provided on the upper portion of the optical waveguide by being adhered thereto with an adhesive so as to form a flat surface, and the end face of the protective member and the end face of the substrate are polished to include the light incident end or the light emitting end of the optical waveguide. A single-layer or multi-layer vapor-deposited film as an incident side reflection film and an emission side reflection film forming a resonance means on a plane perpendicular to the optical waveguide formed as a flat polished surface and the end surface of the protection member and the substrate. Since it is applied over the entire surface formed with the end face of the optical waveguide, it suppresses chipping and rounding when processing the corners of the optical waveguide end face, and it is stable without peeling off at the top corner of the end face for each reflective film. It can be deposited, and the reflectance of the reflective film and the finesse of the resonator can be improved to enhance the function of the device itself. The incident side reflection film and the emission side reflection film are films in an end face region including a light incident end or a light emission end of the optical waveguide with respect to a loss rate according to a crystal length in a light propagation direction of the optical waveguide. the thickness can be assumed to be vapor-deposited film of an optimized single-layer or multilayer.

Further, in the present invention, an optical waveguide formed as a region in which a waveguide mode exists only for a single polarized component in a substrate having at least an electro-optical effect so as to penetrate from an incident end to an outgoing end. Therefore, only a single polarized component of the light incident through the incident side reflection film is propagated through the optical waveguide, phase-modulated, and emitted from the emission end. By providing the incident side reflection film and the emission side reflection film that form the resonance means, it is possible to generate an optical comb as an optical modulation output of only a single polarization component via the emission side reflection film.

Further, according to the present invention, at least the modulation signal supplied to the electrode having the ridge structure formed on the optical waveguide path formed of the substrate having the electro-optical effect and having the ridge structure for propagating the modulation signal in the forward direction or the backward direction is provided. By providing the optical modulation means for modulating the phase of the light propagating in the optical waveguide, the electric power of the microwave used as the modulation signal necessary for driving can be reduced.

That is, according to the present invention, by polishing the end face of the member having the same hardness as the substrate for forming the optical waveguide and the end face of the substrate, it is possible to suppress chipping or rounding during processing of the corner of the optical waveguide end face. Low power drive by using an optical waveguide having electrodes having a ridge structure while having a single-layer or multi-layer vapor deposition film as a light incident end surface and a light emitting end surface formed on a plane perpendicular to the optical waveguide. It is possible to provide an optical modulator and an optical comb generator that realizes energy saving, low heat generation, small size/light weight, improved reliability, and low cost.

It is a figure which shows the structure of the optical modulator to which this invention is applied. It is a side view of an optical modulator to which the present invention is applied. It is a figure which shows the plane in which the incident side reflective film is formed in the optical modulator to which this invention is applied. 6 is a flowchart for explaining a method of manufacturing an optical modulator to which the present invention is applied. It is a figure for demonstrating the experimental result of the loss characteristic of the optical modulator to which this invention is applied. It is a figure which shows the structure of the optical modulator which has a wafer which played the role of the protective material and the buffer layer together. It is a figure which shows the structure of the optical modulator of a reciprocal modulation type to which the present invention is applied. It is a figure which shows the intensity distribution in each frequency (wavelength) of a sideband at the time of applying this invention to an optical frequency comb generator. It is a figure which shows the structure of the optical waveguide type laser oscillator to which this invention is applied. It is a figure which shows the structure of the laser oscillator to which this invention is applied. It is a figure which shows the structure of the modified FP electro-optic modulator to which this invention is applied. It is a figure for demonstrating the example of the communication system which mounted the optical modulator which applied this invention in the base station. It is a figure for demonstrating the case where the length of the optical modulator to which this invention is applied is limited. It is another figure for demonstrating the case where the length of the optical modulator to which this invention is applied is limited. It is a perspective view which shows the other structural example of the optical modulator to which this invention is applied. It is a side view of the said optical modulator. FIG. 6 is a vertical cross-sectional view of a main part in each step for explaining the manufacturing method of the optical modulator. It is a perspective view of the board|substrate which provided three optical waveguides produced in order to measure the end surface reflectance of the optical modulator to which this invention is applied. It is a front view which shows the incident side end surface of the said board|substrate. It is a top view of the said board|substrate. It is a perspective view showing the composition of the optical modulator (optical comb generator) provided with the electrode which has the ridge structure to which the present invention is applied. FIG. 6 is a longitudinal sectional view of a main part in each step for explaining a method for manufacturing the optical modulator (optical comb generator). It is a perspective view showing a substrate which forms an electrode which has a ridge structure of the above-mentioned optical modulator (optical comb generator). It is a principal part longitudinal cross-sectional front view which shows the electrode which has a ridge structure of the said optical modulator (optical comb generator). It is a figure for demonstrating the result of having measured the change of the drive voltage (AC Vpi) in 25 GHz by the presence or absence of the ridge structure of an electrode about the optical modulator to which this invention is applied. FIG. 6 is a diagram for explaining the results of actual measurement of changes in direct-current drive voltage (DC Vpi) depending on the presence or absence of a ridge structure of electrodes in the optical modulator to which the present invention is applied. It is a block diagram which shows the structural example of the optical comb generator using the low power type optical comb module to which this invention is applied. It is a block diagram which shows the other structural example of the optical comb generator using the low power type optical comb module to which this invention is applied. It is a block diagram which shows the structural example of the optical comb light source constructed using the low power type optical comb module to which this invention is applied. It is a block diagram which shows the structure of the optical comb range finder comprised using the said optical comb light source. FIG. 10 is a characteristic diagram showing a transmission mode waveform without deformation obtained when feedback controlling the resonance length of an optical resonator in an optical comb generator using an optical waveguide that allows only a single polarization component to which the present invention is applied. It is a figure which shows the principle structure of the conventional optical frequency comb generator. It is a figure which shows the principle structure of the conventional waveguide type optical frequency comb generator. It is a figure which shows the end surface in which the incident side reflective film is formed in the conventional waveguide type optical frequency comb generator. In a conventional optical comb generator that uses an optical waveguide that transmits polarization components with mixed orthogonal modes, a characteristic diagram showing the deformation of the transmission mode waveform due to orthogonal polarization components that occurs when feedback controlling the resonance length of the optical resonator. Is.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that common components will be described with common reference numerals in the drawings. Further, it is needless to say that the present invention is not limited to the following examples and can be arbitrarily modified without departing from the gist of the present invention.

The present invention is applied to the optical modulator 8 shown in FIGS. This optical modulator 8 includes a substrate 11, an optical waveguide 12 formed on the substrate 11 for modulating the phase of propagating light, and a buffer layer 14 laminated on the substrate 11 so as to cover the optical waveguide 12. And the electrode 83 provided on the upper surface of the optical waveguide 12 so that the direction of the modulation electric field is substantially perpendicular to the light propagation direction, and the first electrode provided so as to face each other through the optical waveguide 12. The end face 84 and the second end face 85, the first protective member 86 disposed on the optical waveguide 12 so as to form the same plane as the first end face 84, and the second end face 85 are the same. On the flat surface 91 formed between the second protective material 87 arranged above the optical waveguide 12 so as to form a flat surface, the first end surface 84 and the end surface 86a of the first protective material 86. It is applied on a flat surface 92 formed between the incident side reflection film 93 made of a single-layer or multilayer vapor deposition film and the second end surface 85 and the end surface 87a of the second protective material 87. The emitting-side reflecting film 94 formed of a single-layer or multilayer vapor-deposited film, the oscillator 16 arranged at one end of the electrode 83 to oscillate a modulation signal of the frequency f _m , and the termination arranged at the other end of the electrode 83. And a resistor 18.

The substrate 11 is obtained by cutting a large crystal such as LiNbO ₃ or GaAs having a diameter of 3 to 4 inches grown by a pulling method into a wafer. The cut-out substrate 11 is subjected to processing such as mechanical polishing and chemical polishing.

The optical waveguide 12 is formed so as to penetrate from the incident side reflection film 93 to the emission side reflection film 94, and is formed to propagate the resonated light. The refractive index of the layer forming the optical waveguide 12 is set higher than that of other layers such as the substrate 11. The light incident on the optical waveguide 12 propagates while being totally reflected at the boundary surface of the optical waveguide 12. In general, the optical waveguide 12 can be manufactured by diffusing Ti atoms in the substrate 11 or by epitaxially growing it on the substrate 11.

A LiNbO ₃ crystal optical waveguide may be applied as the optical waveguide 12. This LiNbO ₃ crystal optical waveguide can be formed by diffusing Ti on the surface of the substrate 11 made of LiNbO ₃ or the like. In the region where Ti is diffused, the light can be confined where the refractive index is higher than the other regions, so that the optical waveguide 12 capable of propagating the light can be formed. The LiNbO ₃ crystal type optical waveguide 12 manufactured based on such a method has electrical properties such as the Pockels effect in which the refractive index changes in proportion to the electric field and the Kerr effect in which the refractive index changes in proportion to the square of the electric field. Since it has an optical effect, it is possible to modulate light using such a physical phenomenon.

The buffer layer 14 covers the optical waveguide 12 in order to suppress the propagation loss of light. By the way, if the buffer layer 14 is made too thick, the electric field strength is lowered and the modulation efficiency is lowered. Therefore, the film thickness may be set as thin as possible within the range where the propagation loss of light does not increase.

The electrode 83 is made of, for example, a metal material such as Ti, Pt, or Au, and drives the modulation signal of the frequency f _m supplied from the oscillator 16 into the optical waveguide 12 to phase the light propagating in the optical waveguide 12. Apply modulation.

Each of the first protective material 86 and the second protective material 87 is composed of a member corresponding to the material of the substrate 11. The first protective material 86 and the second protective material 87 may be made of the same material as the substrate 11. Further, the end face 86a and the first end face 84 of the first protective material 86 forming the flat surface 91 may be processed so as to have the same crystal orientation, and similarly, the flat surface 92 forming the flat surface 92 may be formed. The end surface 87a of the second protective material 87 and the second end surface 85 may be processed so as to have the same crystal orientation.

The incident side reflection film 93 and the emission side reflection film 94 are provided so as to be parallel to each other in order to resonate the light incident on the optical waveguide 12, and reflect the light passing through the optical waveguide 12 back and forth. The optical resonator 5 that resonates is constituted by.

Light of frequency ν ₁ is incident on the incident side reflection film 93 from a light source (not shown). The incident side reflection film 93 also reflects the light reflected by the emission side reflection film 94 and having passed through the optical waveguide 12. The emission side reflection film 94 reflects the light that has passed through the optical waveguide 12. Further, the emitting side reflection film 94 emits the light passing through the optical waveguide 12 to the outside at a constant rate.

The incident side reflection film 93 and/or the emission side reflection film 94 may be formed over the entire surfaces of the planes 91 and 92, but they are formed so as to cover at least only the end portion of the optical waveguide 12. It should have been done.

The terminating resistor 18 is a resistor attached to the terminating end of the electrode 83, and prevents reflection of an electric signal at the terminating end to prevent the waveform from being disturbed.

FIG. 3 shows the plane 91 on which the incident side reflection film 93 is formed, from the direction A in FIG.

The first end face 84 including the light incident end of the optical waveguide 12 and the end face 86a of the protective material 86 form the same plane 91. The formed plane 91 has an inclination of 0.05° or less. The loss when light with a 1/e ² beam diameter of 10 μm is reflected by an end face with an inclination of 0.05° with respect to the plane 91 with an inclination of 0.05° is 4×10 ⁻⁴ It is negligibly smaller than the reflectance of the side reflection film 93.

By thus forming the first end face 91 and the second end face 92 substantially perpendicular to the optical waveguide 12, the incident side reflection film 93 and the emission side, which are deposited as a single-layer or multi-layer vapor deposition film on the optical waveguide 12. Light can be efficiently resonated by the side reflection film 94.

In the optical modulator 8 having the above-described configuration, the light incident from the outside through the incident side reflection film 93 propagates in the optical waveguide 12 in the outward direction, is reflected by the emission side reflection film 94, and is partially outside. Penetrates into. The light reflected by the emission side reflection film 94 propagates in the optical waveguide 12 in the backward direction and is reflected by the incidence side reflection film 93. By repeating this, the light resonates in the optical waveguide 12.

In addition, as compared with the case where the light passes through the optical modulator 8 only once, an electric signal synchronized with the time when the light travels back and forth in the optical waveguide 12 is input as a drive input through the electrode 83. It is possible to apply deep phase modulation of several tens of times or more. In addition, hundreds of sidebands can be generated over a wide band around the frequency ν ₁ of the incident light. By the way, the frequency intervals of the generated sidebands are all equal to the frequency f _{m of the} input electric signal. Therefore, the optical modulator 8 can also be applied as an optical frequency comb generator including a large number of sidebands.

Next, a method for manufacturing the optical modulator 8 to which the present invention is applied will be described with reference to FIG.

First, in step S11, a photoresist pattern is formed on the surface of the substrate 11 made of LiNbO ₃ crystal, and Ti is deposited thereon. Then, the photoresist is removed to form a Ti fine line having a width of micron size.

Next, the process proceeds to step S12, and the substrate 11 on which the thin wires of Ti are formed is heated to thermally diffuse Ti atoms into the substrate 11 to form the optical waveguide 12.

Next, in step S13, a SiO ₂ thin film as the buffer layer 14 is deposited on the surface of the substrate 11. In this step S13, the buffer layer 14 may be formed by a method of attaching a SiO ₂ wafer to the surface of the substrate 11. In such a case, the vapor deposition buffer layer 14 may be polished to control the film thickness to an appropriate thickness in consideration of the electrode attachment region in step S14 described later.

Next, in step S14, the electrode 83 is formed on the buffer layer 14. Next, in step S15, the protective materials 86 and 87 are adhered to the upper portion of the optical waveguide 12. Regarding the method of adhering the protective members 86 and 87, they may be attached by an adhesive, or they may be directly joined based on another method. When the substrate 11 is made of LiNbO ₃ crystal, the protective materials 86 and 87 may be made of the same material, LiNbO ₃ . In this step S15, it is possible to form the flat surfaces 91 and 92 between the end surfaces 86a and 87a of the attached protective materials 86 and 87 and the first end surface 84 and the second end surface 85, respectively. And cut them into pieces.

Finally, the process proceeds to step S16, and the obtained flat surfaces 91 and 92 are polished into flat surfaces perpendicular to the optical waveguide 12. Then, an incident-side reflection film 93 and an emission-side reflection film 94 are formed over the respective planes 91, 92 perpendicular to the polished optical waveguide 12.

Here, the incident side reflection film 93 and the emission side reflection film 94 are deposited and formed on the planes 91 and 92 as a single layer or a multilayer vapor deposition film by a vapor deposition method, a sputtering method, a chemical vapor deposition method or the like.

As described above, in the optical modulator 8 to which the present invention is applied, since the protective materials 86 and 87 are attached at each end portion, the end surface of the optical waveguide 12 that is conventionally located at the uppermost corner of the end surface is formed. Moves to substantially the center of the plane 91 (92) as shown in FIG. As a result, even when the corner of the flat surface 91 (92) is chipped during the polishing in step S16, the end face of the optical waveguide 12 is not chipped. That is, it becomes possible to make the end face of the optical waveguide 12 less likely to be chipped. This makes it possible to suppress the optical loss from each end face of the optical waveguide 12 as much as possible.

Further, by configuring the material of the protective materials 86 and 87 with an optimum material corresponding to the material of the substrate 11, the polishing rate in step S16 can be adjusted from the first end surface 84, the second end surface 85 to the end surface 86a of the substrate 11. It is possible to make it uniform over 87a. As a result, the end face of the optical waveguide 12 is not rounded during processing, and it is possible to obtain flat surfaces 91 and 92 that are made of a flat polished surface and are perpendicular to the optical waveguide 12, and to minimize the reflection loss at the end face of the optical waveguide 12. It is possible to limit it. Further, the reflection loss can be further suppressed by making the crystal orientations of the end faces forming the planes 91 and 92 the same.

Further, by intentionally providing the protective materials 86 and 87, the polishing accuracy in step S16 is improved, and the perpendicularity of the obtained flat surface 91 (92) to the optical waveguide 12 is also improved. As a result, it is possible to minimize the light loss due to the deviation of the verticality.

Further, by providing the protective materials 86 and 87, the incident-side reflection film 93 and the emission-side reflection film 94, which are to be deposited as a single-layer or multi-layer vapor deposition film, are formed on the other side surfaces from the flat surfaces 91 and 92. It is possible to suppress the change in the film thickness due to the wraparound on the side surface and the wraparound of the film-forming particles flying from the side surface direction to the end surface. Therefore, the film thickness near the end face of the optical waveguide 12, which is important for securing the reflectance, can be optimized, and the reflectance can be further improved.

Further, the incident-side reflection film 93 and the emission-side reflection film 94 are extremely stable because they are formed over a wide range from the first end face 84, the second end face 85 to the end faces 86a, 87a of the substrate 11. It is difficult for the film to peel off and the reproducibility of film formation can be improved.

Actually, in order to experimentally verify the effect of providing the protective materials 86 and 87, the flat surface 91 (92) after the protective materials 86 and 87 were attached was polished, and the end face of the optical waveguide 12 was polished. No chipping or bending occurred in any part, and it was confirmed that flat optical polishing suitable for deposition of the incident side reflection film 93 and the emission side reflection film 94 consisting of a single-layer or multi-layer vapor deposition film was applied. can do.

Particularly, the first protective material 86 and the second protective material 87 are made of the same material as the substrate 11, and the end surfaces 86a, 87a and the first end surface 84 of the protective materials 86, 87 forming the flat surfaces 91, 92 are formed. By processing so that the second end surface 85 and the second end surface 85 have the same crystal orientation, the hardness of the crystal becomes the same between the two, so that the planes 91 and 92 do not tilt due to the difference in polishing rate.

As described above, in the optical modulator 8 to which the present invention is applied, the end faces of the optical waveguide 12 can be moved to the substantially central portion of the flat surface 91 (92) by attaching the protective materials 86 and 87 at the respective end portions. Therefore, the end face of the optical waveguide 12 is chipped or rounded, the verticality between the optical waveguide 12 and the planes 91 and 92 is secured, the polishing accuracy on the planes 91 and 92 is improved, and the incident side reflection film 93 and the emission side reflection film 94 are formed. It is possible to suppress peeling and wraparound, improve reflectance of the incident-side reflection film 93 and the emission-side reflection film 94, realize designed reflection characteristics, and improve performance reproducibility of the reflection film. As a result, the finesse of the optical resonator 5 composed of the incident-side reflection film 93 and the emission-side reflection film 94 can be improved, and an optical modulator and an optical frequency comb generator having good performance can be manufactured with good reproducibility. It is possible to improve the yield.

The optical modulator 8 having the above-described structure was actually manufactured by depositing the reflection films 93 and 94 having a reflectance of 97% on the polished planes 91 and 92 as a single-layer or multi-layer vapor deposition film. As a result, when the crystal length of the optical waveguide 12 is 27.4 mm (hereinafter referred to as a short resonator), a finesse of up to 61 can be obtained, and the crystal length of the optical waveguide 12 is 54.7 mm. In this case (hereinafter referred to as a long resonator), a finesse of up to 38 could be obtained. Since the finesse of the conventional waveguide type optical resonator (IEEE Photonics Technology Letters, Vol.8, No. 10, 1996) was 30 at the highest, the optical quality of this end face polishing and coating precision was improved. It can be seen that the modulator 8 can significantly improve finesse. In particular, it is also shown that a finesse of 30 or more can be obtained for all six samples of the manufactured optical modulator 8, and the reproducibility of the manufacturing process is high.

FIG. 5 shows the internal loss of the optical resonator 5 in one of the forward and backward directions in the optical waveguide 12. In FIG. 5, the loss per propagation direction of the optical modulator 8 composed of the above-described long resonator is measured and plotted over three samples (indicated by ● in the figure). The loss in the propagation direction of the constructed optical modulator 8 was measured and plotted over three samples (indicated by ▪ in the figure), and each obtained plot is approximated by a straight line.

From the obtained straight line, the internal loss Ls per propagation direction in the optical waveguide 12 of the optical resonator 5 having the length l is the reflectance R in the reflection films 93 and 94, and the loss per unit length in the optical waveguide 12. Is represented by α, and is represented by Ls=α ₁ −lnR when the loss itself is small. When the measured finesse is F, the loss Ls per propagation direction is calculated as Ls=π/F. When the internal loss Ls is calculated from the measured finesse F and is plotted in a graph, it can be seen that the internal loss due to the optical waveguide 12 increases as the crystal length of the optical waveguide 12 increases, as shown in FIG.

Incidentally, in FIG. 5, the internal loss when the length of the optical resonator 5 is 0 is based on the loss generated at the crystal facet. That is, since the reflective films 93 and 94 having a reflectance of 97% (transmittance of 3%) are coated, a loss of at least 3% occurs. However, it can be seen from FIG. 5 that there is no conspicuous loss other than the transmission to the reflection films 93 and 94 on the planes 91 and 92.

Matching the waveguide loss ratio of the optical waveguide with the transmittance of the mirror enhances the finesse and the transmittance of the resonator, and improves the performance of the resonator. Since the loss rate of the optical waveguide that can be used as the optical comb generator is approximately in the range of 1% to 5% per one way, the reflection films 93 and 94 having the reflectance of 95% to 99% are applied. By doing so, an optical resonator with good performance can be manufactured.

Similarly, when the optical modulator 8 is applied to an optical frequency comb generator, the flat surfaces 91 and 92 are polished and the incident side reflection film 93 and the emission side reflection film 94 are attached with the protective materials 86 and 87 attached. Therefore, it is possible to improve the reflectance of the reflective films 93 and 94. As a result, the finesse of the optical resonator 5 can be improved and the sideband generation frequency band can be expanded.

By the way, when the optical modulator 8 is applied to an optical frequency comb generator, the incident side reflection film 93 allows only the light incident on the optical waveguide 12 to pass therethrough, and the sideband generated in the optical waveguide 12 is generated. It may be replaced with a narrow band filter that reflects light. By replacing with such a narrow band filter, the conversion efficiency of the incident light into the side band can be improved.

Similarly, the emission side reflection film 94 may be replaced with a filter for flattening the output spectrum. In a conventional optical frequency comb generator, the obtained sideband light intensity decreases exponentially as its order increases. Therefore, by substituting the emission side reflection film 94 with a filter having a characteristic of canceling the decrease of the light intensity according to the order, it is possible to flatten the light intensity of each side band obtained.

Each of the incident side reflection film 93 and the emission side reflection film 94 may be replaced with each of the filters described above, or any one of the reflection films 93, 94 may be replaced with each of the filters described above.

The optical modulator 8 to which the present invention is applied and the optical frequency comb generator to which the present invention is applied are of a monolithic type in which the incident side reflection film 93 and the emission side reflection film 94 are directly formed on the planes 91 and 92. It is configured. In other words, since the optical modulator 8 is not configured to provide the reflection films 93 and 94 at positions spatially separated from the planes 91 and 92, the FSR (Free Spectral Range) of the optical resonator 5 is determined by step S16. It is governed by the crystal length from the plane 91 to the plane 92 of the crystal forming the optical waveguide 12 after polishing. Therefore, the optical modulator 8 is required to control the crystal length very precisely so that an integral multiple of the FSR of the optical resonator 5 becomes a desired modulation frequency.

For example, when the FSR of the optical resonator 5 is matched with the frequency f _FSR , the group refractive index n _g of the optical waveguide 12 and the average value τ _g of the group delay times of the incident side reflection film 93 and the emission side reflection film 94 are considered. Then, the crystal length (the distance from the first end face 84 to the second end face 85 of the substrate 11) L of the optical waveguide 12 is calculated by the following equation (1).
_{L = c / 2n g f FSR} -cτ g / n g ··········· (1)
(C is the speed of light in a vacuum)
The FSR of the optical resonator 5 can be made to coincide with the f _FSR by adjusting to, and the modulation efficiency can be significantly improved.

The present invention is not limited to the above embodiment. For example, it can be applied to the optical modulator 9 as shown in FIG. Regarding the configuration and elements of the optical modulator 9 that are the same as those of the optical modulator 8 described above, the description in FIGS. 1 and 2 is cited, and the description thereof is omitted here.

The optical modulator 9 includes a substrate 11, an optical waveguide 12 formed on the substrate 11 for modulating the phase of propagating light, a wafer 95 provided on the upper surface of the optical waveguide 12, and a direction of a modulation electric field is optical. An electrode 83 provided on the upper surface of the wafer 95 so as to be substantially perpendicular to the propagation direction of the first end face 84 and a second end face 85 provided so as to face each other via the optical waveguide 12. , The incident side reflection film 93 formed of a single-layer or multilayer vapor deposition film deposited on the flat surface 101 formed between the first end surface 84 and the end surface 96a of the wafer 95, and the second end surface 85 and the wafer. The emitting-side reflection film 94 is formed of a single-layer or multi-layer evaporation film deposited on the flat surface 102 formed between the end surface 97a of the light beam 95 and the end surface 97a.

Also in the optical modulator 9, similarly to the optical modulator 8 described above, an oscillator (not shown) that oscillates a modulation signal of the frequency f _m and a terminating resistor (not shown) are connected.

The wafer 95 is made of SiO ₂ or the like and has a length substantially the same as that of the optical waveguide 12 and has a U-shape. The wafer 95 has a thick end portion and a thin central portion where the electrode 83 is disposed. As a result, the modulation electric field can be efficiently applied from the electrode 83 to the light propagating in the optical waveguide 12.

The wafer 95 plays a role as the buffer layer 14 described above, and covers the optical waveguide 12 formed immediately below the surface of the substrate 11 to suppress optical loss. The wafer 95 also plays a role as the first protective material 86 and the second protective material 87 in the above-mentioned optical modulator 8, and the end surfaces 96a and 97a are respectively the first end surface 84 and the second end surface 85. Are cut and aligned so that planes 101 and 102 can be formed respectively.

When this wafer 95 is provided, a SiO ₂ wafer having a thickness corresponding to the end portion is attached onto the substrate 11, and the portion where the electrode 83 is to be provided is then cut, as shown in FIG. It is possible to finish it in a square U shape.

That is, the optical modulator 9 has the advantages that the same effect as that of the optical modulator 8 can be obtained and that the labor of attaching the protective material can be omitted.

The present invention is not limited to the above embodiment. For example, it can be applied to a reciprocal modulation type optical modulator 51 as shown in FIG. Regarding the configuration and elements of the optical modulator 51 that are the same as those of the optical modulator 8 described above, the descriptions in FIGS. 1 and 2 are cited, and the description thereof is omitted here.

Further, the optical modulator 51 is provided with an emission side reflection film 94 made of a single-layer or multi-layer vapor deposition film as a high-reflection film at one end of the optical waveguide 12, and a single-layer or multi-layer at the other end. By providing the antireflection film 63 made of a vapor deposition film, as shown in FIG. 7, it is possible to operate as a so-called reciprocal modulation type optical modulator 51.

As shown in FIG. 7( a ), the optical modulator 51 includes a substrate 11, an optical waveguide 12 formed on the substrate 11 for modulating the phase of propagating light, and the substrate 11 covering the optical waveguide 12. The buffer layer 14 laminated as described above, the electrode 83 provided on the upper surface of the optical waveguide 12 so that the direction of the modulation electric field is substantially perpendicular to the light propagation direction, and the electrode 83 provided on the optical waveguide 12. The first protective material 86 and the second protective material 87, the antireflection film 63 made of a single-layer or multilayer vapor deposition film deposited on the flat surface 91, and the single layer deposited on the flat surface 92. Alternatively, it is provided with an emission side reflection film 94 formed of a multilayer vapor deposition film.

When the optical modulator 51 is actually used, as shown in FIG. 7B, the input light from a light source (not shown) is transmitted or the output light output from the optical modulator 51 is output to the outside. An optical system including an optical transmission line 23 configured by an optical fiber or the like for transmitting to the optical path, an optical circulator 21 for separating the input light and the output light, and a focuser 22 optically connected to the optical circulator 21. is implemented, an oscillator 16 for oscillating a modulation signal of one end disposed on the side frequency f _m of the electrode 83, the phase shifter 19a to the other end of the electrode 83, a reflector 19b is further disposed.

The antireflection film 63 is deposited on the flat surface 91 formed between the first end surface 84 and the end surface 86a of the first protective material 86. The antireflection film 63 may be formed of a low reflection film, or may be formed uncoated to obtain the same effect as when the low reflection film is applied.

The focuser 22 focuses the input light that has passed through the optical circulator 21 on the end portion of the optical waveguide 12, collects the output light that has passed through the antireflection film 63 from the end portion of the optical waveguide 12, and collects the output light. Send to. The focuser 22 may be composed of a lens or the like for optically coupling the input light so that the spot diameter corresponds to the diameter of the optical waveguide 12.

In the optical modulator 51 having such a configuration, a so-called reciprocating film is provided by providing the emission side reflection film 94 as a high reflection film at one end of the optical waveguide 12 and the antireflection film 63 at the other end. It operates as a modulation type optical modulator. The input light incident on the optical waveguide 12 is modulated while propagating through the optical waveguide 12, is reflected by the exit side reflection film 94 on the end face, and then propagates through the optical waveguide 12 again and is transmitted through the antireflection film 63. The light is emitted to the focuser 22 side and becomes output light. At the same time, the electric signal of the frequency f _m supplied from the oscillator 16 propagates on the electrode 83 while modulating the input light, and then is reflected by the reflector 19b.

In this optical modulator 51, when the modulation signal of the frequency f _m oscillated by the oscillator 16 is supplied to the electrode 83, the modulation signal propagates through the electrode 83 in the outward direction, and It is possible to modulate the phase of light propagating in the forward direction. The modulated signal propagating on the electrode 83 in the outward direction is directly reflected by the anti-reflector 19b, the phase is adjusted by the phase shifter 19a, and then propagates through the electrode 83 in the returning direction. As a result, the light propagating in the optical waveguide 12 in the backward direction can be phase-modulated. By the way, the phase adjusted by the phase shifter 19a is set so that the phase modulation applied to the light propagating in the optical waveguide 12 in the backward direction is the same as the phase modulation for the light propagating in the outgoing direction. Good.

In this optical modulator 51, not only the light propagating in the forward direction through the optical waveguide 12 but also the light propagating in the backward direction can be subjected to phase modulation, so that the modulation efficiency can be increased.

Further, in this optical modulator 51, an electric signal synchronized with the time when light travels back and forth in the optical waveguide 12 is input as a driving input from the electrode 83, so that the optical modulator 51 passes through the optical waveguide 12 only once. It is possible to apply more than double deep phase modulation. Thereby, an optical frequency comb having a wide sideband can be generated, and the frequency intervals of the adjacent sidebands are all equal to the frequency f _{m of the} input electric signal.

Further, since the optical modulator 51 can push light into the narrow optical waveguide 12 and modulate it, the modulation index can be increased, and the optical modulator 51 functions as the optical frequency comb generator 1 to perform bulk-type optical modulation. The number of sidebands generated and the amount of light in the sidebands can be increased as compared with the frequency comb generator.

In the optical frequency comb generator 1 using the optical modulator 51, the phase of the modulation signal reflected by the reflector 19b and adjusted by the phase shifter 19a is determined by the shape of the electrode 83, the frequency f _{m of the} modulation signal. , And by adjusting according to the group refractive index _ng of the optical waveguide 12 to adjust the phase of light with high accuracy, the optical waveguide 12 propagates not only in the light propagating in the forward direction but also in the backward direction. With respect to light, it is possible to perform phase modulation with high efficiency, and it is possible to increase the modulation efficiency up to nearly double. Further, since the modulation efficiency can be effectively improved without increasing the voltage applied to the electrode 83, the power consumption can be reduced and the heterodyne detection system itself in which the optical frequency comb generator 1 is arranged can be made slim. Therefore, the cost can be significantly reduced.

Further, in the optical modulator 51, as shown in FIG. 7C, the oscillator 25 and the terminating resistor 27 are provided on one end side of the electrode 83, and the electric signal supplied from the oscillator 25 is propagated on the electrode 83. In the above, this may be reflected on the other end side of the electrode 83. At this time, an isolator 26 for separating the electric signal supplied from the oscillator 25 and the electric signal reflected on the other end side of the electrode 83 may be provided. Further, in the optical modulator 51, the incident side reflection film 93 made of a single-layer or multi-layer vapor deposition film having a high reflectance is deposited. This allows light to resonate inside the optical waveguide 12. Further, as an alternative to the incident side reflection film 93, the above-described antireflection film 63 having a low reflectance may be applied. This makes it possible to perform phase modulation while the light is reciprocated once in the optical waveguide 12.

In this optical modulator 51, the reflection phase of the electric signal is adjusted in accordance with the phase of the light reflected by the emission side reflection film 94, so that the phase of the light can be modulated by each electric signal that reciprocates through the electrode 83. Therefore, the modulation efficiency can be increased. In particular, by attaching the protective materials 86 and 87, the peeling and chipping of the films 63, 93 and 94 are suppressed as described above, and the optical modulator 51 in which the finesse is further improved can further increase the optical modulation efficiency. Is possible.

Further, when these optical modulators 51 are applied to an optical frequency comb generator, it is possible to perform reciprocal modulation on light that resonates in the optical waveguide 12 by an electric signal that reciprocates through the electrodes. In such a case, the intensity distribution at each frequency (wavelength) of the generated sideband is as shown in FIG. 8 when the modulation frequency of the electric signal applied to the electrode 83 is 25 GHz and its power is 0.5 W. In, the modulation index expressed as the magnitude of the modulation applied in the optical waveguide 12 is π radian per propagation direction. From this result, it can be seen that the half-wave voltage Vπ defined as the voltage required to move the phase by half a wavelength is 7.1V.

The optical modulator 8 configured by the short resonator has a higher finesse as described above, and thus the sideband generation efficiency is higher than that of the optical modulator 8 configured by the long resonator. The generated frequency bandwidth Δf reaches 11 THz. Further, the length of the electrode 83 of the optical modulator 8 composed of the short resonator is only 20 mm, but a modulation efficiency comparable to that of the optical modulator 8 composed of the long resonator can be obtained. .. That is, it can be seen that the reciprocal modulation works effectively.

The optical modulator 51 may divide the output of the oscillator 16 as a signal source, instead of reflecting the electric signal, to separately drive and input the electric signal from both ends of the electrode 83. This may be performed by connecting different oscillators 16 to both ends of the electrode 83, respectively.

The present invention can also be applied to an optical waveguide type laser oscillator 52 as shown in FIG. 9, for example. In this laser oscillator 52, the same constituent elements as those of the above-described optical modulator 8 will be referred to the description in FIGS. 1 and 2, and the description thereof will be omitted here.

As shown in FIG. 9, the laser oscillator 52 includes a substrate 11, an optical waveguide 12 formed on the substrate 11, a buffer layer 14 laminated on the substrate 11 so as to cover the optical waveguide 12, and an optical waveguide. The first protective material 86 and the second protective material 87 disposed on the waveguide 12; the incident-side reflecting film 93 made of a single-layer or multi-layer vapor deposition film deposited on the flat surface 91; and the flat surface 92. The optical resonator 5 is provided with the emitting-side reflecting film 94 formed of a single-layer or multilayer vapor-deposited film deposited on the upper side, and the incident-side reflecting film 93 and the emitting-side reflecting film 94. When the laser oscillator 52 is actually used, the pumping light source 28 that emits light of wavelength λ ₀ is mounted.

In the optical waveguide 12 of the laser oscillator 52, an amplification medium such as erbium ion that absorbs light incident through the incident-side reflection film 93 and has an amplification characteristic with respect to the wavelength of light peculiar to the medium. To spread. This allows the optical waveguide 12 to function as a light amplification medium. Further, when light of an appropriate wavelength is made incident on the optical waveguide 12 as such an amplification medium, it acts as an amplifier for light of a specific wavelength determined by the energy level. Further, it also acts as an oscillator that amplifies and oscillates the light generated by the spontaneous emission transition. Since the laser oscillation occurs when the amplification factor in the optical resonator 5 exceeds the loss factor, the protective materials 86 and 87 are attached to prevent the peeling or chipping of the reflection films 93 and 94 and the optical waveguide. By increasing the reflection characteristics at the end face of 12, the loss rate in the optical resonator 5 is also lowered, so that the threshold value of laser oscillation can be lowered.

Even if a special amplifying medium is not introduced into the optical waveguide 12, by configuring the optical waveguide 12 with a non-linear optical crystal such as LiNbO ₃ crystal, the non-linearity induced by the light entering the optical waveguide 12 can be improved. The polarization makes it possible to give an amplification gain to a wavelength different from that of the incident light. For example, the optical waveguide 12 may be configured by using a non-linear optical crystal having a periodically poled structure.

The incident-side reflection film 93 that constitutes the optical resonator 5 of the laser oscillator 52 has a low reflectance with respect to the light from the excitation light source 28 and a high reflection with respect to the wavelength of the light oscillated by the optical waveguide 12. Rate membranes may be used. Further, as the emission side reflection film 94 constituting the optical resonator 5, a film having a reflectance capable of optimal output coupling with respect to the wavelength of the light oscillated by the optical waveguide 12 may be used.

Incidentally, the laser oscillator 52 may be applied as an optical parametric oscillator. In such a case, oscillation occurs when the amplification factor in the optical resonator 5 exceeds the loss factor, so that the reflection films 93 and 94 to which the protective materials 86 and 87 are adhered are not peeled or chipped. By configuring the finesse optical resonator 5, the oscillation threshold can be lowered.

As described above, the advantages of using the optical waveguide 12 in the laser oscillator 52 and the optical parametric oscillator to which the laser oscillator 52 is applied are that light can be confined in a narrow region and that the amplification factor is improved because the electric field strength can be increased. In particular, with the laser oscillator 52 and the like, higher finesse can be obtained as compared with the conventional oscillator, so that the advantage of using the optical waveguide 12 is further promoted.

The present invention can also be applied to a laser oscillator 53 that oscillates light whose modes are synchronized as shown in FIG. 10, for example. The light in which the modes are synchronized is one in which the phases of many modes oscillating at equal frequency intervals are aligned. In this laser oscillator 53, the same configurations and elements as those of the optical modulator 8 and the laser oscillator 52 described above are referred to the description in FIGS. 1, 2, and 9, and the description thereof is omitted here.

As shown in FIGS. 10A and 10B, the laser oscillator 53 includes a substrate 11, an optical waveguide 12 formed on the substrate 11 for modulating the phase of propagating light, and an optical waveguide in the substrate 11. A buffer layer 14 laminated so as to cover 12; an electrode 83 provided on the upper surface of the optical waveguide 12 so that the direction of the modulation electric field is substantially perpendicular to the light propagation direction; and the upper portion of the optical waveguide 12. A first protective material 86 and a second protective material 87, an incident-side reflection film 93 made of a single-layer or multi-layer vapor deposition film deposited on a flat surface 91, and a flat surface 92 deposited on the flat surface 92. The exit side reflection film 94 formed of a single-layer or multilayer vapor deposition film is formed, and the optical resonator 5 is configured between the entrance side reflection film 93 and the exit side reflection film 94. Further, when the laser oscillator 53 is actually used, the excitation light source 28 for emitting the light of the wavelength λ ₀ is mounted, and is further arranged at one end of the electrode 83 to oscillate the modulation signal of the frequency f _m. 16 and a terminating resistor 18 arranged on the other end side of the electrode 83. The incident side reflection film 93 and the emission side reflection film 94 each have a function of achieving phase synchronization between laser-oscillated multimodes.

In the laser oscillator 53 having such a configuration, by arranging the electrode 83 above the optical waveguide 12 in the laser oscillator 52 described above, it is possible to oscillate a mode-locked laser synchronized with each mode. Here, based on the electro-optical effect of the optical waveguide 12 that oscillates multi-mode light, a phase of each mode is driven by drivingly inputting a modulation signal of a frequency that matches an integer multiple of FSR of the optical resonator 5 from the oscillator 16. As a result of the synchronization, the laser operates as a laser oscillator that oscillates a mode-locked laser.

When this mode locking is performed, the time waveform of the light oscillated by the laser oscillator 53 becomes a short pulse having a time width that is approximately the reciprocal of the amplification frequency bandwidth. The waveform on the frequency axis is an optical frequency comb in which sidebands are arranged at regular frequency intervals. Therefore, by optimizing the control of the laser oscillator 53, it is possible to apply to the frequency measurement of light and to the multi-wavelength light source. It is needless to say that the laser oscillator 53 may be applied as an optical parametric oscillator like the laser oscillator 52 described above. Particularly, in the laser oscillator 53, since the protective materials 86 and 87 are adhered, the reflection films 93 and 94 are not peeled or chipped, the finesse of the entire optical resonator 5 can be improved, and the mode-locked laser can be efficiently used. It is possible to oscillate well.

By the way, the mode-locking in the laser oscillator 53 is not limited to the one utilizing the above-mentioned electro-optical effect, but is based on any phenomenon as long as it utilizes the nonlinear effect of the optical element in the optical resonator 5. May be For example, by using a LiNbO ₃ crystal for the optical waveguide 12, the effect can be made more prominent.

The present invention can also be applied to a modified Fabry-Perot (FP) electro-optic modulator 54 as shown in FIG. 11, for example. In this modified FP electro-optical modulator 54, the same configurations and elements as those of the optical modulator 8 and the laser oscillator 52 described above are referred to the description in FIGS. 1, 2, and 9, and the description thereof is omitted here.

As shown in FIG. 11, the modified FP electro-optic modulator 54 includes a substrate 11, an optical waveguide 12 formed on the substrate 11 for modulating the phase of propagating light, and the optical waveguide 12 covered on the substrate 11. The buffer layer 14 laminated as described above, the electrode 83 provided on the upper surface of the optical waveguide 12 so that the direction of the modulation electric field is substantially perpendicular to the light propagation direction, and the electrode 83 provided on the optical waveguide 12. The first protective material 86 and the second protective material 87, the incident side reflection film 93 made of a single-layer or multilayer vapor deposition film deposited on the flat surface 91, and the single protective material deposited on the flat surface 92. The optical resonator 5 is provided with the emission side reflection film 94 formed of a layer or a multilayer vapor deposition film, and the optical resonator 5 is configured between the incidence side reflection film 93 and the emission side reflection film 94. Further, when the modified FP electro-optical modulator 54 is actually used, the reflecting mirror 31 is mounted, and if necessary, it is further arranged on one end side of the electrode and oscillates a modulation signal of the frequency f _m. An oscillator (not shown) and a terminating resistor (not shown) provided on the other end side of the electrode are provided.

The reflecting mirror 31 transmits the light supplied from the outside, guides it to the end of the optical waveguide 12 on the modified FP electro-optic modulator 54 side, and reflects the light emitted from the end of the optical waveguide 12. That is, by providing the reflecting mirror 31, only the light incident on the optical waveguide 12 can be transmitted and the sidebands generated on the optical waveguide 12 can be reflected. Therefore, the incident light is converted into the sideband. The efficiency can be improved. That is, in the modified FP electro-optic modulator 54 having such a configuration, the incident side reflection film 93 is replaced with a narrow band filter that transmits only the light incident on the optical waveguide 12 and reflects the generated side band. The same effect as can be obtained. In particular, in this modified FP electro-optical modulator 54, since the protective materials 86 and 87 are attached, there is no peeling or chipping of the reflective films 93 and 94, and the finesse of the entire optical resonator 5 can be improved. It becomes possible to further improve the conversion efficiency to the sideband.

The optical modulator 8 to which the present invention is applied can also be applied to a communication system 55 described below.

As the communication system 55, for example, a system for performing code division multiple connection based on the WDM communication system is applied, and as shown in FIG. 12A, a mobile communication device 57 as a mobile terminal that can be carried by a pedestrian. , A plurality of base stations 58 for relaying communication by transmitting and receiving radio signals to and from the mobile communication device 57, and a network including the base station 58 via the connected optical fiber communication networks 35, 38. The host controller 59 controls the communication in the whole.

The mobile communication device 57 is configured so that it can be carried in a vehicle or carried so as to transmit and receive radio signals to and from a base station 58 provided in each district. That is, the portable communication device 57 includes a device for carrying out data communication by being installed in, for example, a facsimile communication, a personal computer or the like, but in general, it is a mobile phone or PHS (personal handyphone system) for making a voice call. ), etc., and is configured as a device that is particularly small and lightweight and specialized for portability.

An optical modulator 8 is mounted on each base station 58, as shown in FIG. An antenna 33 for transmitting and receiving microwaves to and from the mobile communication device 57 is connected to the electrode 83 of the optical modulator 8. Further, in the optical modulator 8, a part of the light transmitted from the host controller 59 via the optical fiber communication network 35 enters the optical waveguide 12 via the incident side reflection film 93. The light incident on the inside of the optical waveguide 12 is resonated by the incident side reflection film 93 and the emission side reflection film 94 arranged substantially in parallel. Further, in the optical modulator 8, the microwave supplied from the portable communication device 57 is received via the antenna 33, and a modulation signal corresponding to the microwave is converted into light propagating in the optical waveguide 12 via the electrode 83. Since it can be applied, it becomes possible to perform phase modulation on it according to the transmission information from the mobile communication device 57. The optical modulator 8 causes the phase-modulated light to be emitted through the emission side reflection film 94. The emitted light is transmitted to the host controller 59 via the optical fiber communication network 38.

The host controller 59 generates light for transmission to the base station 58, and photoelectrically converts the light modulated in the base station 58 to obtain a detection output. That is, the host control device 59 can collectively manage the detection outputs from various base stations.

In such a communication system 55, the light output from the host controller 59 is transmitted to the base station 58 via the optical fiber communication network 35. The base station 58 propagates the transmitted light in the optical waveguide 12 of the optical modulator 8 and further performs phase modulation in accordance with microwaves, and then hosts it via the optical fiber communication network 38. It is transmitted to the control device 59.

That is, when the light transmitted to the base station 58 is called from the portable communication device 57 in the vicinity of the base station 58, the light is subjected to phase modulation according to the call content included in the microwave. become. On the other hand, the light transmitted to the base station 58 is not subjected to the above-mentioned phase modulation when the mobile communication device 57 around the base station 58 does not make a call. In the host controller 59, when the phase modulation is applied to the light transmitted from the base station 58 via the optical fiber communication network 38, the host controller 59 photoelectrically converts the phase modulated light to obtain a detection output according to the content of the call. It becomes possible to acquire.

In this communication system 55, since the optical modulator 8 having a high finesse resonator to which the protective materials 86 and 87 are attached is mounted on the base station 58, the number of round trips of light propagating in the optical waveguide 12 can be increased. Therefore, the sensitivity of the optical modulator 8 itself can be improved.

Of course, in the communication system 55, as shown in FIG. 12(b), optical transmission may be performed in a one-core bidirectional manner.

Furthermore, in the optical modulator 8 to which the present invention is applied, even if the crystal length LC ₁ of the optical waveguide 12 in the forward direction (return direction) is adjusted to about 27 mm (or 54 mm) as shown in FIG. Good. The effect obtained by setting such a crystal length will be described below.

When the loss of light propagating in the outward direction (backward direction) in the light guide 12 was set to Lo _1, showing the relationship between the crystal length LC ₁ such loss ratio Lo ₁ and the optical waveguide 12 in FIG. 13 (a). It has been shown that the loss of propagating light gradually increases as the crystal length LC ₁ increases. Further, FIG. 13B shows the relationship of finesse with respect to the crystal length LC ₁ . As shown in FIG. 13(b), the finesse is generally represented by π/Lo ₁ , but it can be seen that the smaller the crystal length LC _{1, the} higher the finesse.

The figure of merit of the optical modulator 8 can be represented by Vπ/(finesse) (Vπ is a voltage required to modulate the optical phase by π radians). The smaller the figure of merit, the better the performance as the optical modulator 8 and the optical frequency comb generator using the optical modulator 8.

FIG. 14 shows the figure of merit calculated based on the finesse and the loss rate Lo ₁ in relation to the crystal length LC ₁ . In FIG. 14, lm represents the difference in the length of the electrode 83 with respect to the crystal length LC ₁ . In general, electrodes cannot be provided within a few mm from both ends of the optical waveguide 12. Therefore, calculation is performed by taking the case where lm is 6 mm and the case where lm is 1 mm as an example.

As shown in FIG. 14, it can be seen that when lm=6 mm, the figure of merit decreases when the crystal length LC ₁ is 15 to 30 mm. Further, when the FSR corresponding to the crystal length LC ₁ of such a figure of merit is plotted, it can be seen that the best performance is obtained in the vicinity of 2.5 GHz. Incidentally, in simulating the tendency in FIG. 14, it is assumed that the modulation frequency is 25 GHz and the microwave transmission loss by the electrode 83 is −10 dB/50 mm@25 GHz, and the modulation efficiency is Pin=0 at the time of reciprocal modulation. Considering that the modulation index is π radians when the crystal length LC ₁ =27 mm (when the length of the electrode 83 is 21 mm), the transmission loss α of light is −0.0106/cm. Assuming there are cases. Further, the reflectance of the mirror is optimized with respect to the loss rate according to the crystal length.

Therefore, when lm=6 mm, by setting the crystal length LC ₁ of the optical waveguide 12 to about 27 mm, it becomes possible to further improve the performance as the optical modulator 8. Incidentally, the crystal length LC ₁ is not limited to the case of 27 mm, and may be of any length as long as it is in the range of 24±6 mm. Note that the practical crystal length LC ₁ is the maximum common divisor of 10 GHz in time division multiplexing (TDM) optical communication in the field of optical communication and 25 GHz in wavelength division multiplexing (WDM) optical communication. It is preferable to make it an integral fraction of 5 GHz, and 27 mm corresponds to 2.5 GHz.

Further, even when the FSR plot corresponding to the crystal length LC ₁ is 1.25 GHz, similarly excellent performance is exhibited. Therefore, the crystal length LC ₁ corresponding to this may be configured to be about 54 mm. ..

Further, even when lm=1 mm, similar simulation shows excellent performance at about 10 GHz. Therefore, by making the crystal length LC ₁ correspond to this, the performance as the optical modulator 8 can be further improved. Is possible.

In the method of manufacturing the optical modulator 8 to which the present invention shown in FIG. 4 is applied, Ti atoms are thermally diffused in the substrate 11 to form the optical waveguide 12 in the steps of manufacturing the optical waveguide 12 in steps S11 and S12. Although formed, this may be replaced by a proton exchange method in which LiNbO ₃ crystals are immersed in benzoic acid to replace Li with H ⁺ .

Here, in the optical comb generation in the optical comb generator using the waveguide type optical resonator that resonates the light confined in the optical waveguide, the orthogonal polarization components make the resonance frequency of the optical comb generator match the laser frequency. Control may become unstable, causing control point shifts, control oscillations, etc., and when the optical comb is used in a measuring device that measures the distance or height to the measurement target, for example, they are orthogonal to each other. Although the polarization component has been a factor of the measurement error, for example, it has the optical waveguide 12A formed as a region where the waveguide mode exists only for a single polarization component having the configuration shown in FIG. By adopting the waveguide type optical modulator 8A, the output of the orthogonal polarization component that does not contribute to the generation of the optical comb is suppressed, the polarization extinction ratio is improved, and the optical comb output with an increased single polarization degree is obtained. By doing so, the transmission mode waveform of the optical waveguide is not deformed, the resonator control can be stabilized, the stabilization as an optical comb generator, the accuracy improvement of the measuring device including the optical comb, and the error Can be reduced.

The waveguide type optical modulator 8A shown in FIG. 15 is the waveguide shown in FIG. 1 except for the configuration of the optical waveguide 12A formed as a region in which a waveguide mode exists only for a single polarization component. Since it is the same as that of the optical modulator 8, the same components will be denoted by the same reference numerals and detailed description thereof will be omitted.

FIG. 16 is a side view of the waveguide type optical modulator 8A.

In this waveguide type optical modulator 8A, the optical waveguide 12A is converted into a single polarization component in the substrate 11 having at least the electro-optical effect so as to penetrate from the incident side antireflection film 63 to the emission side antireflection film 64. It is formed as a region in which the guided mode exists only for the other.

In the light incident on the optical waveguide 12A via the incident-side antireflection film 63, only a single polarization component propagates while being totally reflected at the boundary surface of the optical waveguide 12A.

Here, the optical waveguide 12A that allows only a single polarization component to pass through the substrate 11 having the electro-optical effect is formed by the optical waveguide formation method that causes a change in the refractive index only to a specific polarization component, for example, the proton exchange method. Can be formed as a region having a high refractive index only for the polarized wave component.

The optical waveguide 12A can be formed on the substrate 11 made of, for example, LiNbO ₃ as a region in which a waveguide mode exists only for a single polarization component by the proton exchange method.

Further, when the optical waveguide 12A is manufactured by diffusing Ti atoms in the substrate 11 or by epitaxially growing it on the substrate 11, the waveguide mode is changed to a single polarization by devising the refractive index distribution. It can be formed as a limited region. For the optical waveguide 12A, for example, a LiNbO ₃ crystal optical waveguide can be used and can be formed by diffusing Ti on the surface of the substrate 11 made of LiNbO ₃ or the like. The region in which Ti is diffused has a higher refractive index than other regions and can confine the light of a single polarization component, and thus can propagate the light of a single polarization component. The waveguide 12A can be formed. Although the refractive index is high for both polarization components orthogonal to each other, there is also a condition that the guided mode is established only for a single polarization component.

The LiNbO ₃ crystal type optical waveguide 12A produced based on such a method has electrical properties such as the Pockels effect in which the refractive index changes in proportion to the electric field and the Kerr effect in which the refractive index changes in proportion to the square of the electric field. Since it has an optical effect, the light of a single polarization component can be modulated by utilizing such a physical phenomenon.

The buffer layer 14 covers the optical waveguide 12A in order to suppress the propagation loss of light of a single polarization component. By the way, if the buffer layer 14 is made too thick, the electric field strength is lowered and the modulation efficiency is lowered. Therefore, the film thickness is set as thin as possible within a range in which the propagation loss of light of a single polarization component does not increase. You may do so.

The electrode 83 is made of, for example, a metal material such as Ti, Pt, or Au, and drives the modulation signal of the frequency f _m supplied from the oscillator 16 into the optical waveguide 12A to phase the light propagating in the optical waveguide 12A. Apply modulation.

Each of the first protective material 86 and the second protective material 87 is composed of a member corresponding to the material of the substrate 11. The first protective material 86 and the second protective material 87 may be made of the same material as the substrate 11. Further, the end face 86a and the first end face 84 of the first protective material 86 forming the flat surface 91 may be processed so as to have the same crystal orientation, and similarly, the flat surface 92 forming the flat surface 92 may be formed. The end surface 87a of the second protective material 87 and the second end surface 85 may be processed so as to have the same crystal orientation.

The incident-side antireflection film 63 is a single-layer or multi-layer vapor deposition film on a plane 91 perpendicular to the optical waveguide 12A formed between the first end face 84 and the end face 86a of the first protective material 86. Deposition is formed. The emission-side antireflection film 64 is a single-layer or multilayer vapor-deposition film on the plane 92 perpendicular to the optical waveguide 12A formed between the second end surface 85 and the end surface 87a of the second protective material 87. Deposition is formed. These antireflection films 63 and 64 may be made of a low reflection film, or may be made uncoated to obtain the same effect as when the low reflection film is applied. ..

The terminating resistor 18 is a resistor attached to the terminating end of the electrode 83, and prevents reflection of an electric signal at the terminating end to prevent the waveform from being disturbed.

Next, a method for manufacturing the optical modulator 8A to which the present invention is applied will be described with reference to FIG.

First, in step S21, a photoresist pattern 13 is formed on the surface of the substrate 11 made of LiNbO ₃ crystal.

Next, in step S22, the LiNbO ₃ crystal substrate 11 having the photoresist pattern 13 formed on the surface is heated while being immersed in a proton exchange liquid such as benzoic acid to remove Li in the surface layer portion of the substrate 11. By the proton exchange method of substituting with H ⁺ , the optical waveguide 12A is formed as a region where the guided mode exists only for a single polarized component.

The step of producing the optical waveguide 12A in steps S21 and S22 is not limited to the proton exchange method. For example, in step S21, the photoresist pattern 13 is formed on the surface of the substrate 11 made of LiNbO ₃ crystal. Then, Ti is vapor-deposited on the surface of the substrate 11 made of LiNbO ₃ crystal, and the photoresist is removed to produce a Ti fine line having a micron-sized width. By heating the substrate 11 on which the thin wire of Ti is formed, the Ti atoms are thermally diffused in the substrate 11 and the optical waveguide 12A is formed as a region where the waveguide mode exists only for a single polarization component. This may be replaced by the Ti diffusion method to be formed.

Next, in step S23, the resist pattern 13 is removed and a SiO ₂ thin film as the buffer layer 14 is deposited on the surface of the substrate 11. In this step S23, the buffer layer 14 may be formed by a method of attaching a SiO ₂ wafer to the surface of the substrate 11. In such a case, in consideration of the electrode attachment area in the next step S24, the vapor-deposited buffer layer 24 may be polished so as to be controlled to have an appropriate film thickness.

Next, in step S24, the electrode 83 is formed on the buffer layer 14.

Next, in step S25, the protective materials 86 and 87 are adhered to the upper portion of the optical waveguide 12A. Regarding the method of adhering the protective members 86 and 87, they may be attached by an adhesive, or they may be directly joined based on another method. When the substrate 11 is made of LiNbO ₃ crystal, the protective materials 86 and 87 may be made of the same material, LiNbO ₃ . In this step S25, it is possible to form flat surfaces 91 and 92 between the end surfaces 86a and 87a of the attached protective materials 86 and 87 and the first end surface 84 and the second end surface 85, respectively. And cut them into pieces.

Finally, in step S26, the obtained flat surfaces 91 and 92 are polished into flat surfaces perpendicular to the optical waveguide 12A. Then, an incident-side antireflection film 63 and an outgoing-side antireflection film 64 are formed over the respective planes 91 and 92 perpendicular to the polished optical waveguide 12A.

As described above, in the optical modulator 8A to which the present invention is applied, since the protective materials 86 and 87 are attached at the respective end portions, the end surface of the optical waveguide 12A that is conventionally located at the uppermost corner of the end surface is formed. Moves to approximately the center of the plane 91 (92). As a result, even when the corner of the flat surface 91 (92) is chipped during the polishing in step S26, the end face of the optical waveguide 12A is not chipped. That is, it becomes possible to make the end surface itself of the optical waveguide 12A less likely to be chipped. This makes it possible to suppress the optical loss from each end face of the optical waveguide 12A as much as possible.

Further, by configuring the material of the protective materials 86, 87 with an optimum material corresponding to the material of the substrate 11, the polishing rate in step S26 can be adjusted from the first end face 84, the second end face 85 to the end face 86a of the substrate 11. It is possible to make it uniform over 87a. As a result, the end face of the optical waveguide 12A does not become round during processing, flat surfaces 91 and 92 made of flat polished surfaces can be obtained, and reflection loss at the end face of the optical waveguide 12A can be minimized. Become. Further, the reflection loss can be further suppressed by making the crystal orientations of the end faces forming the planes 91 and 92 the same.

Further, by intentionally providing the protective materials 86 and 87, the accuracy of polishing in step S26 is improved, and the perpendicularity of the obtained flat surface 91 (92) to the optical waveguide 12A is also improved. As a result, it is possible to minimize the light loss due to the deviation of the verticality.

Further, since the incident side antireflection film 63 and the emission side antireflection film 64 are formed over a wide range from the first end face 84, the second end face 85 to the end faces 86a, 87a of the substrate 11, they are very stable. Therefore, peeling is difficult, and the reproducibility of film formation can be improved.

Actually, in order to experimentally verify the effect of providing the protective materials 86 and 87, the flat surface 91 (92) after the protective materials 86 and 87 were attached was polished, and the end face of the optical waveguide 12A was polished. No chipping or bending occurs at any part, and flat optical polishing suitable for deposition of the incident side antireflection film 63 and the emission antireflection film 64 made of a single-layer or multilayer vapor deposition film is performed. I was able to confirm.

Particularly, the first protective material 86 and the second protective material 87 are made of the same material as the substrate 11, and the end surfaces 86a, 87a and the first end surface 84 of the protective materials 86, 87 forming the flat surfaces 91, 92 are formed. By processing so that the second end surface 85 and the second end surface 85 have the same crystal orientation, the hardness of the crystal becomes the same between the two, so that the planes 91 and 92 do not tilt due to the difference in polishing rate.

In the optical modulator 8A having such a configuration, light of only a single polarization component that is incident through the incident-side antireflection film 63 and propagates in the optical waveguide 12A is modulated at the frequency f _m supplied from the oscillator 16. The signal is phase-modulated by the signal and emitted through the emission-side antireflection film 64. Moreover, in the optical modulator 8A to which the present invention is applied, the end face of the optical waveguide 12A can be moved to the substantially central portion of the flat surface 91 (92) by attaching the protective material 86, 87 at each end portion. The chipping or rounding of the end surface of the optical waveguide 12A, the perpendicularity between the optical waveguide 12A and the planes 91, 92 can be secured, and the polishing accuracy on the planes 91, 92 can be improved, and the yield can be improved.

Here, only a single polarization type optical waveguide made by the proton exchange method in which only a single polarization component of the incident light is propagated and only orthogonal polarization components of the incident light are propagated Regarding the orthogonal polarization type optical waveguide manufactured by the Ti diffusion method, as shown in FIGS. 18, 19, and 20, width W ₁ =1.9 [mm], length L ₁ =27.4 [mm], Three optical waveguides 112A, 112B and 112C are formed on a LiNbO ₃ crystal substrate 11 having a thickness T ₁ =0.5 [mm], and a width W _{2 is} 1.9 [mm] above the optical waveguides 112A, 112B and 112C. ], the length L ₂ =1.5 [mm], and the thickness T ₂ =0.5 [mm], the protective materials 86 and 87 are adhered to each other, and the end surfaces of the protective materials 86 and 87 and the end surface of the LiNbO ₃ crystal substrate 11 are bonded. By polishing the three optical waveguides 112A, 112B, and 112C into a flat LiNbO ₃ crystal substrate block, the optical path width W3 of the three optical waveguides 112A, 112B, and 112C is reduced. 10 samples of 6 kinds of 6.0 [μm], 6.3 [μm], 6.6 [μm], 6.9 [μm], 7.2 [μm], 7.5 [μm] Then, the reflectances on the incident surfaces A ₁ , B ₁ , C ₁ and the emission surfaces A ₂ , B ₂ , C ₂ of the three optical waveguides 112A, 112B, 112C are measured, and the finesse and the transmittance of each sample are measured. When asked, the following results were obtained.

That is, the finesse of the orthogonal polarization type optical waveguide is about 30 to 45, whereas the finesse of the single polarization type optical waveguide is about 50 to 65. Further, the transmittance of the orthogonal polarization type optical waveguide was about 12.5 to 25[%], whereas the transmittance of about 20 to 32.5[%] was obtained with the single polarization type optical waveguide. Has been.

In this optical modulator 8A, the output side reflection film as a high reflection film is formed at one end of the optical waveguide 12A formed as a region where a waveguide mode exists only for a single polarization component. By providing 94 and the antireflection film 63 at the other end, a so-called reciprocal modulation type optical modulator having the configuration shown in FIG. 7a, FIG. 7b, and FIG. 7c described above is provided, like the optical modulator 8. It can also be operated as.

Further, in the step S26, the optical modulator 8A polishes the flat surfaces 91 and 92 in parallel with each other, and the incident-side antireflection film 63 and the exit-side antireflection film 64 are polished on the polished flat surfaces 91 and 92. In place of the above, the incident side reflection film 93 and the emission side reflection film 94 are formed over one surface, respectively, to function as the optical comb generator 1A.

That is, in the optical comb generator 1A, the incident side reflection film 93 and the emission side reflection film 94 are provided so as to be parallel to each other in order to resonate the light incident on the optical waveguide 12A. The optical resonator 5 is configured to resonate the light passing therethrough to resonate.

By forming the first end face 84 and the second end face 85 substantially perpendicular to the optical waveguide 12A, the incident side reflection film 93 and the emission side reflection film formed of a single-layer or multi-layer vapor deposition film attached to the optical waveguide 12A are formed. The film 94 can efficiently resonate light of a single polarized component.

In the optical comb generator 1A having the above-described configuration, the light incident from the outside through the incident-side reflection film 93 has a single polarized light component propagating in the optical waveguide 12A in the outward direction and is emitted from the emitting side. The light is reflected by the reflection film 94 and partially transmitted to the outside. The light of the single polarization component reflected by the emission side reflection film 94 propagates in the optical waveguide 12A in the backward direction and is reflected by the incidence side reflection film 93. By repeating this, light having a single polarization component resonates in the optical waveguide 12A.

Further, by inputting the electric signal synchronized with the time when the light of the single polarization component makes a round trip in the optical waveguide 12A as a drive input through the electrode 83, the light of the single polarization component becomes the optical modulator. It is possible to perform deep phase modulation of several tens of times or more as compared with the case of passing through the inside of 8A only once. In addition, hundreds of sidebands can be generated over a wide band around the frequency ν ₁ of the incident light. By the way, the frequency intervals of the generated sidebands are all equal to the frequency f _{m of the} input electric signal. Therefore, in the optical modulator 8A, the incident-side antireflection film 63 and the emission-side antireflection film 64 are replaced with the incident-side reflection film 93 and the emission-side reflection film 94, so that a single polarized light having a plurality of sidebands is formed. It functions as an optical comb generator 1A that generates an optical comb of wave components.

That is, the optical comb generator 1A has only a single polarization component on the substrate 11 having at least the electro-optical effect so as to penetrate from the incident side reflection film 93 to the emission side reflection film 94 which form the resonance means. Since the optical waveguide 12A formed as a region where the waveguide mode exists is provided, only a single polarization component of the light incident through the incident side reflection film 93 is propagated through the optical waveguide 12A. As a result, an optical comb can be generated as an optical modulation output of only a single polarization component via the emitting side reflection film 94.

Here, in the optical modulators 8, 8A, and 51 according to the present invention, the electrode 83 provided on the upper surface of the optical waveguide 12A to which the modulation signal is supplied is, for example, a waveguide type optical modulation having a configuration as shown in FIG. By having a ridge structure like the device 8B (optical comb generator 1B), the optical modulation efficiency can be further improved.

In this waveguide type optical modulator 8B (optical comb generator 1B), the electrode 83 in the waveguide type optical modulator 8A (optical comb generator 1A) shown in FIGS. 15 and 16 has a ridge structure. For the same components as those of the optical modulator 8A (optical comb generator 1A) described above, the description in FIGS. 15 and 16 is cited, and the description thereof is omitted here.

In this waveguide type optical modulator 8B (optical comb generator 1B), the substrate 11 is obtained by cutting a large crystal such as LiNbO ₃ or GaAs having a diameter of 3 to 4 inches grown by a pulling method into a wafer. is there. The ridges 20 for forming the electrodes 83A having a ridge structure are provided on the cut-out substrate 11 by subjecting it to mechanical polishing, chemical polishing, or the like.

The optical waveguide 12A is formed so as to penetrate from the entrance end to the exit end by the proton exchange method or the Ti diffusion method, and guides only the single polarization component in order to propagate the light of the single polarization component. Formed as a region where wave modes are present.

The refractive index of the layer forming the optical waveguide 12A is set higher than that of other layers such as the substrate 11 only for a single polarized component. In the light incident on the optical waveguide 12A, only a single polarization component propagates while being totally reflected at the boundary surface of the optical waveguide 12A.

The LiNbO ₃ crystal type optical waveguide 12A produced based on such a method has electrical properties such as the Pockels effect in which the refractive index changes in proportion to the electric field and the Kerr effect in which the refractive index changes in proportion to the square of the electric field. Since it has an optical effect, the light of a single polarization component can be modulated by utilizing such a physical phenomenon.

The electrode 83A having a ridge structure has a main electrode formed on the ridge portion 20, and is made of a metal material such as Ti, Pt, or Au. The electrode 83A having a ridge structure in which the main electrode is formed on the ridge portion 20 propagates in the optical waveguide 12A by inputting the modulation signal of the frequency f _m supplied from the oscillator 16 to the optical waveguide 12A as a driving input. Phase modulation is applied to the light.

A method of manufacturing the waveguide type optical modulator 8B (optical comb generator 1B) having such a structure will be described with reference to FIG.

That is, first, in step S31, a photoresist pattern 13 is formed on the surface of the substrate 11 made of LiNbO ₃ crystal.

Next, in step S32, the LiNbO3 crystal substrate 11 having the photoresist pattern 13 formed on the surface is heated while being immersed in a proton exchange liquid such as benzoic acid, and Li in the surface layer portion of the substrate 11 is changed to H. ^{By the} proton exchange method of substituting with ⁺ , the optical waveguide 12A is formed as a region where the guided mode exists only for a single polarized component.

The step of forming the optical waveguide 12A in steps S31 and S32 is not limited to the proton exchange method. For example, in step S31, the photoresist pattern 13 is formed on the surface of the substrate 11 made of LiNbO ₃ crystal. Then, Ti is vapor-deposited on the surface of the substrate 11 made of LiNbO ₃ crystal, and the photoresist is removed to produce a Ti fine line having a width of a micron size. By heating the substrate 11 on which the thin wire of Ti is formed, the Ti atoms are thermally diffused in the substrate 11 and the optical waveguide 12A is formed as a region where the waveguide mode exists only for a single polarization component. This may be replaced by the Ti diffusion method to be formed.

Next, the process proceeds to step S33, the resist pattern 13 of the substrate 11 on which the optical waveguide 12A is formed is removed, and the electrode 83A having a ridge structure is formed by a process such as mechanical polishing or chemical polishing as shown in FIG. A ridge portion 20 for forming the ridge is provided.

Next, in step S34, a SiO ₂ thin film as the buffer layer 14 is deposited on the surface of the substrate 11. In this step S34, the buffer layer 14 may be formed by a method of attaching a SiO ₂ wafer to the surface of the substrate 11. In this case, the vapor deposition buffer layer 14 may be polished to control the film thickness to an appropriate thickness in consideration of the electrode attachment region in step S35 described later.

Next, the process proceeds to step S35, and an electrode 83A having a ridge structure is formed on the buffer layer 14 of the substrate 11 as shown in the vertical cross section of the main part of FIG.

Next, in step S36, the protective materials 86 and 87 are adhered to the upper portion of the optical waveguide 12A. Regarding the method of adhering the protective members 86 and 87, they may be attached by an adhesive, or they may be directly joined based on another method. When the substrate 11 is made of LiNbO ₃ crystal, the protective materials 86 and 87 may be made of the same material, LiNbO ₃ . In this step S36, it is possible to form flat surfaces 91 and 92 between the end surfaces 86a and 87a of the attached protective materials 86 and 87 and the first end surface 84 and the second end surface 85, respectively. And cut them into pieces.

In the optical modulator 8B to which the present invention is applied, in the final step S37, the obtained planes 91 and 92 are polished into a plane perpendicular to the optical waveguide 12A, and the polished planes 91 and 92 are placed on the polished planes 91 and 92. The entrance-side antireflection film 63 and the exit-side antireflection film 64 are formed over the respective surfaces.

Further, in the optical comb generator 1B to which the present invention is applied, in the above step S37, the flat surfaces 91 and 92 are polished parallel to each other, and the flat surfaces 91 and 92 perpendicular to the polished optical waveguide 12A are Instead of the incident-side antireflection film 63 and the emission-side antireflection film 64, an incident-side reflection film 93 and an emission-side reflection film 94 are formed over one surface.

In the optical modulator 8B and the optical comb generator 1B having such a configuration, the oscillator 16 is provided in the electrode 83A having the ridge structure for only the light of the single polarization component which is incident from the incident end and propagates in the optical waveguide 12A. The phase modulation can be efficiently applied by the modulation signal of the frequency f _m supplied from

In addition, in the optical modulator 8B and the optical comb generator 1B to which the present invention is applied, the end faces of the optical waveguide 12A are made substantially central in the plane 91 (92) by attaching the protective materials 86 and 87 at each end. Since it can be moved, chipping or rounding of the end surface of the optical waveguide 12A, verticality between the optical waveguide 12A and the flat surfaces 91, 92 can be secured, and polishing accuracy on the flat surfaces 91, 92 can be improved, thereby improving the yield. Will also be possible.

Further, in the optical comb generator 1B, only a single polarization component of the light incident from the outside via the incident side reflection film 93 propagates in the optical waveguide 12A in the outward direction and is reflected by the emission side reflection film 94. And partly penetrates to the outside. The light of the single polarization component reflected by the emission side reflection film 94 propagates in the optical waveguide 12A in the backward direction and is reflected by the incidence side reflection film 93. By repeating this, the light of the single polarization component resonates in the optical waveguide 12A.

Further, by inputting the electric signal synchronized with the time when the light of the single polarization component travels back and forth in the optical waveguide 12A as a drive input through the electrode 83A, the light of the single polarization component becomes the optical modulator. It is possible to perform deep phase modulation several tens of times or more as compared with the case where the signal passes through 8B only once. In addition, hundreds of sidebands can be generated over a wide band around the frequency ν ₁ of the incident light. By the way, the frequency intervals of the generated sidebands are all equal to the frequency f _{m of the} input electric signal. Therefore, the optical modulator 8B functions as an optical comb generator 1B that generates an optical comb of a single polarization component formed by a number of sidebands.

As described above, in the optical comb generator 1B to which the present invention is applied, a single polarization is formed on a substrate having at least an electro-optical effect so as to penetrate from the incident side reflection film 93 forming the resonance means to the emission side reflection film 94. Since the optical waveguide 12A formed as the region in which the guided mode exists only for the wave component is provided, only a single polarization component of the light incident through the incident side reflection film 93 is generated. After being propagated through the optical waveguide 12A, an optical comb can be generated as an optical modulation output of only a single polarization component via the emission side reflection film 94, and the protective material 86, 87 is attached at each end. Since it is attached, the end face of the optical waveguide 12A, which has been positioned at the uppermost corner of the end face in the past, moves to the substantially central portion of the flat surface 91 (92). As a result, even when the corner of the flat surface 91 (92) is chipped during the polishing in step S37, the end face of the optical waveguide 12A is not chipped. That is, it becomes possible to make the end surface itself of the optical waveguide 12A less likely to be chipped. This makes it possible to suppress the optical loss from each end face of the optical waveguide 12A as much as possible.

Moreover, since the optical modulator 8B is provided with the electrode 83A having the ridge structure formed on the buffer layer 14 of the substrate 11, as shown in the longitudinal cross section of the main part of FIG. 24, the modulation efficiency is further improved. Can be made.

Here, in this optical modulator 8B, the ridge width RW of the electrode 83A having the ridge structure formed on the buffer layer 14 of the substrate 11 is 10, 12, 14, 16, and 18 [μm], and the average of the ridge grooves is A sample of the optical modulator 8A having depths of AVD (Average depths) of 3.3, 2.96, 4.79, and 4.72 [μm] was prepared, and the drive voltage (AC Vpi) at 25 GHz and the direct current were measured. The drive voltage (DC Vpi) was measured and the results are shown in FIGS. 25 and 26. Vpi is the voltage required to modulate the phase by π radians.

That is, in the conventional optical modulator having an electrode structure having no ridge structure, the drive voltage (AC Vpi) at 25 GHz is about 8 to 10 V, and the DC drive voltage (DC Vpi) is about 6 to 6.5 V. On the other hand, in the optical modulator 8B including the electrode 83A having the ridge structure, the drive voltage (AC Vpi) at 25 GHz is about 3.5 to 7.5 V, and the DC drive voltage (DC Vpi) is 5 to 6 V. It has become a degree.

By providing the ridge structure in this way, the driving voltage (AC Vpi) at 25 GHz is reduced to about 70% of the original average voltage as compared with the case without the ridge structure, and the power is about 50%. Equivalent to a decrease in Further, the DC drive voltage (DC Vpi) has an average voltage reduced to about 80% of the original voltage as compared with the case without the ridge structure, which corresponds to a reduction of about 50% in electric power.

That is, the optical modulator 8B and the optical comb generator 1B are composed of a member having the same hardness as the substrate 11 of the optical waveguide 12A, and at least one end face of the member is a light incident end or a light in the optical waveguide 12A. A first protective material 86 and a second protective material 87, which are arranged on the optical waveguide 12A so as to form the same plane as the end surface of the substrate 11 including the emission end, are provided. The incident-side antireflection film 63 or the incident-side reflection film 93 and the emission-side antireflection film 64 or the emission-side reflection film 94 are respectively formed on a plane perpendicular to the optical waveguide 12A formed by polishing the end face of the substrate. Since it is deposited as a layer or a multi-layered vapor deposition film, it is possible to prevent the occurrence of chipping on the end face of the optical waveguide, to stabilize the attachment of the high reflection film, and to configure the incident side reflection film 93 and the emission side reflection film 94. The finesse of the optical resonator 5 can be improved, and the driving power can be reduced by providing the electrode 83A having the ridge structure.

Therefore, in the optical modulators 8A, 8B and the optical modulator 51 having the above-described configurations, the members 86, 87 having the same hardness as that of the substrate 11 for forming the optical waveguide 12A from the upper surface have at least one end surface thereof. The optical waveguide 12A is disposed above the optical waveguide 12A so as to form the same plane as the end face of the substrate 11 including the light incident end or the light emitting end, and the end faces of the members 86 and 87 and the substrate 11 are disposed. The incident-side reflection film 93 and the emission-side reflection film 94, which are single-layer or multilayer vapor-deposited films constituting the resonance means, are deposited on the plane perpendicular to the optical waveguide 12A formed by polishing the end face of As a result, it is possible to suppress chipping and rounding during processing of the corners of the end face of the optical waveguide, and it is possible to adhere stably without peeling off at the top corners of the end face of each reflective film. The finesse of the resonator can be improved, the function of the device itself can be enhanced, and at least the substrate 11 having the electro-optical effect is formed so as to penetrate from the incident side reflection film 93 to the emission side reflection film 94 which form the resonance means. By providing the optical waveguide 12A formed as a region in which the waveguide mode exists only for one polarization component, only a single polarization component of light incident through the incident side reflection film 93 is provided. However, an optical comb that propagates through the optical waveguide 12A and can generate a stable optical comb as an optical modulation output of only a single polarization component via the emission side reflection film 94 functions as the generators 1 and 1A. To do.

The optical waveguide 12A in the optical modulator 8B and the optical modulator 51 as described above penetrates from the incident-side reflection film 93 to the emission-side reflection film 94 so that a single polarization component is formed on the substrate 11 having at least an electro-optical effect. A low power type capable of outputting a laser beam or an optical comb having only a single polarization component by providing an electrode 83A having a ridge structure which is formed as a region in which a waveguide mode exists only for It is possible to build a laser light source or optical comb generator.

In the optical modulators 8A and 8B (optical comb generators 1A and 1B), the reflection films 93 and 94 having the reflectance in the range of 95% to 99% are deposited to guide the optical waveguide 12A. By matching the loss rate and the transmittances of the reflective films 93 and 94, the finesse and the transmittance of the resonator can be increased and the performance of the resonator can be improved.

Next, a block diagram of FIG. 27 shows a configuration of an optical comb generator 210 using the low power type optical comb module to which the present invention is applied.

The optical comb generator 210 includes an optical coupler 211 that branches a part of the optical comb output from the low-power type optical comb module 200A to which the present invention is applied, and a photodetector that detects the light branched by the optical coupler 211. And a control circuit 213 to which the photodetection signal obtained by the photodetector 212 is supplied.

The optical comb module 200A receives laser light from a laser light source (not shown) and inputs an RF modulation signal via the bias tee 214, so that a single polarization component of the incident laser light is received. An optical comb is generated and output by performing phase modulation with the RF modulation signal. In this optical comb module 200A, the resonance length of the resonance means by the incident side reflection film and the emission side reflection film provided in the optical waveguide is controlled by the temperature control by the temperature adjustment circuit 219.

The control circuit 213 obtains an error with respect to the control target from the light detection signal, generates a control signal such that the error becomes zero, and supplies the control signal to the bias tee 214.

By adding to the DC bias of the optical comb module 200A, the resonance frequency of the optical comb module 200A can be made to follow the input laser frequency.

The control circuit 213 may be a printed circuit board alone or a combination of an RF mixer or an isolator and a printed circuit board. By mixing the photodetection signal of the photodetector 212 and the synchronizing signal, a control signal corresponding to the error amount from the control target is generated.

A part of the output of the RF modulation signal source can be used as the synchronization signal. In that case, the operating band of the photodetector 212 needs to be equal to or higher than the RF driving frequency.

In the control circuit 213, the low frequency component of the signal obtained by inputting the photodetection signal and the synchronizing signal to the mixer via the phase adjuster is taken as an error signal. Alternatively, another modulation signal (dither signal) can be used as the RF drive signal as the synchronization signal. The laser frequency or the resonance frequency of the optical comb module 200A is modulated with a smaller amplitude than the FSR in the resonance mode, and the output signal of the photodetector 212 and the synchronization signal are mixed. If the dither signal frequency is low, it is also possible to generate the error signal by the product-sum operation of digital signal processing after converting the photodetection signal into a digital signal by an analog-digital converter.

The adjusted frequency characteristic of the error signal is added as a control signal to the DC bias of the optical comb module 200A via the bias tee 214. In general, the error signal is input to a circuit having functions of proportional, integral, and derivative, and the frequency characteristics of the control loop are determined by adjusting the amplitudes of those components, and the resonance frequency of the optical comb module 200A is the input laser. It is controlled so as to follow the oscillation frequency.

28 is a block diagram showing the configuration of the optical comb generator 220 using the low power type optical comb module to which the present invention is applied.

The optical comb generator 220 performs resonator control by utilizing the reflected light of the low power type optical comb module 200A to which the present invention is applied, and a part of the reflected light of the low power type optical comb module 100A is optical. It is adapted to be branched by the coupler 211 and be incident on the photodetector 212.

Each constituent element of the optical comb generator 220 is the same as the constituent element of the optical comb generator 210 shown in FIG. 27. Corresponding constituent elements are designated by the same reference numerals in FIG. 28 and detailed description thereof is omitted. To do.

The control circuit 213 obtains an error with respect to the control target from the photodetection signal obtained by the photodetector 212, and outputs a control signal such that the error becomes zero. The resonance frequency of the optical comb module 200A can be made to follow the input laser frequency by applying the control signal to the DC bias of the optical comb module.

Further, the low power type optical comb module to which the present invention is applied can construct an optical comb light source 300 having a configuration as shown in FIG. 29, for example.

The optical comb light source 300 includes a laser light source 301 of single frequency oscillation, a separation optical system 302 such as an optical coupler or an optical beam splitter for separating a single frequency laser light emitted from the laser light source 301 into two laser lights, A frequency shifter 305 for shifting the frequency of one of the laser beams separated by the separation optical system 302, two optical comb generators (OFCG1, OFCG2) 320A, 320B each using a low power type optical comb module, and the like are provided.

In this optical comb light source 300, laser light emitted from one single frequency oscillation laser light source 301 is separated into two laser lights by a separation optical system 302, and two optical comb generators (OFCG1 and OFCG2) are provided. It is adapted to be input to 320A and 320B.

The two optical comb generators 320A and 320B are driven by oscillators 303A and 303B that oscillate at different frequencies f _m and f _m +Δf _m . Since the respective oscillators 303A and 303B are phase-locked by the common reference oscillator 304, the relative frequency between f _m and f _m +Δf _m becomes stable. A frequency shifter 305 such as an acousto-optic frequency shifter (AOFS) is provided in front of the optical comb generator (OFCG2) 320B so that the inputted laser light is given an optical frequency shift of frequency fa by this frequency shifter 305. It has become. As a result, the beat frequency between the carrier frequencies becomes an AC signal having a frequency fa rather than a DC signal. As a result, the beat signal of the high-frequency sideband and the beat signal of the low-frequency sideband of the carrier frequency are generated in the frequency regions facing each other across the beat frequency fa between the carrier frequencies of the beat signals, which is convenient for phase comparison. ..

The two optical comb generators (OFCG1, OFCG2) 320A and 320B are each configured by a low power type optical comb module to which the present invention is applied, and only a single polarization component of the input laser light is phased. By modulating, it is possible to output an optical comb having a single polarization component.

In this optical comb light source 300, one laser light source 301 of single frequency oscillation is used in common, and two optical combs having different center frequencies and frequency intervals of two optical comb generators (OFCG1, OFCG2) 320A and 320B are used. For example, the first and second light sources in the range finder and the optical three-dimensional shape measuring machine according to Japanese Patent No. 5231883 previously proposed by the inventor of the present invention, that is, the intensity or the phase, respectively, are periodically generated. Are modulated, and two optical comb generators (OFCG1 and OFCG2) are used by using the above-mentioned optical comb light source 300 as the first and second light sources for emitting the reference light and the measuring light having the coherence and having different modulation periods. The optical comb output for measuring the polarization components of 320A and 320B is emitted while scanning the surface of the measurement target, and the reflected light from the surface is detected for each irradiation point to calculate the distance (height). By doing so, it is possible to construct a measurement system for a range finder or an optical three-dimensional shape measuring machine that performs a stable measurement operation.

FIG. 30 is a block diagram showing a configuration of an optical comb distance meter 400 configured using the optical comb light source 300.

An optical comb distance meter 400 shown in the block diagram of FIG. 30 measures a distance by using an optical frequency comb interferometer, and has a center frequency emitted from the first and second optical comb light sources 401 and 402. The two optical frequency combs having different frequency intervals are periodically modulated in intensity or phase, and the reference light S1 and the measuring light S2, which have different modulation periods and have coherence, are measured with the reference plane 404 via the interference optical system 410. The reference light detector 403 detects the interference light S3 of the reference light S1 and the measurement light S2 that irradiates the surface 405 and irradiates the reference surface 404 and the measurement surface 405, and the reference light reflected by the reference surface 404. The interference light S4 of S1' and the measurement light S2' reflected by the measurement surface 305 is detected by the measurement light detector 406, and the signal processing unit 407 detects the interference light S3 by the reference light detector 403. The difference between the distance L1 to the reference surface 404 and the distance L2 to the measurement surface 405 is calculated from the time difference between the signal and the interference signal in which the interference light S4 is detected by the measurement light detector 406 and the refractive index at the measurement wavelength. be able to. There are multiple forms of interferometers and detectors.

This optical comb distance meter 400 is combined with an optical scanning device to irradiate the surface of the measurement object with the measurement light S2 while scanning it, detect reflected light from the surface for each irradiation point, and detect the distance ( It is possible to configure an optical comb shape measuring instrument that calculates the height and obtains the surface shape of the object from the scan coordinates and the distance (height) distribution. There are various forms of scanner optics. The use of telecentric optics makes it possible for the light to be incident almost vertically on the object in the measuring range.

In addition, for example, the light source in the vibration measuring device according to Japanese Patent No. 5336921 or Japanese Patent No. 5363231 previously proposed by the present inventor, that is, a spectrum having a predetermined frequency interval, the modulation frequency and the center frequency are different from each other, By using the optical comb light source 300 as a light source unit that emits the phase-synchronized and coherent reference light and measurement light, a single light emitted from the two optical comb generators (OFCG1 and OFCG2) 320A and 320B can be obtained. It is possible to construct a measurement system of a vibration measurement device that performs a stable multipoint vibration measurement operation by irradiating an optical comb of a polarized component to a place that differs depending on the wavelength via an element that divides for each wavelength.

Here, in the measuring device using the optical comb obtained by the optical comb generator using the optical waveguide that transmits the polarization component in which the orthogonal modes are mixed, as shown by the circle mark in FIG. The transmission mode waveform may be deformed, and the locations (relative positions with respect to the main mode) that occur may vary, and multiple minima may cause unstable control, but only a single polarization component As shown in FIG. 31, by using the optical waveguide that passes through, the transmission mode waveform is prevented from being deformed, the optical comb generator is stabilized, the accuracy of the measuring device including the optical comb is improved, and the error is reduced. Can be planned.

That is, when the optical comb is used for measurement, the polarization component orthogonal to the generation of the optical comb causes a measurement error in the distance and the height, and the polarization component orthogonal to the generation of the optical comb is generated by the optical comb generator. The control for matching the resonance frequency to the laser frequency may become unstable, which may cause a shift of the control point and oscillation of the control. Also, when using the optical comb for measurement, the distance and height are measured. Although it was a cause of error, by generating an optical comb using an optical waveguide that passes only a single polarization component, the output of the orthogonal polarization component that does not contribute to the generation of the optical comb is suppressed, and the polarization of the optical comb output is reduced. The extinction ratio can be improved, the single polarization degree can be increased, the resonator control can be stabilized, unnecessary interference signals can be removed, and measurement errors in distance measurement and shape measurement using an optical comb can be removed. It is possible to improve the measurement accuracy and the reliability of the entire system.

1, 1A, 1B, 210, 220, 320A, 320B optical comb generator, 5 optical resonator, 8, 8A, 8B, 51 optical modulator, 11 substrate, 12, 12A optical waveguide, 14 buffer layer, 16 oscillator, 18 terminating resistance, 19a phase shifter, 19b reflector, 20 convex section, 21 optical circulator, 22 focuser, 63 antireflection film, 83, 83A electrode, 84 first end face, 85 second end face, 86 first Protective material, 86a, 87a end face, 87 second protective material, 91, 92 plane, 93 incident side reflection film, 94 emission side reflection film, 200A low power type optical comb module, 210, 220 optical comb generator, 211 Optical coupler, 212 photo detector, 213 control circuit, 214 bias tee, 130,300 optical comb light source, 301 laser light source, 302 separation optical system, 303A, 303B oscillator, 304 reference oscillator, 305 frequency shifter, 320A, 320B light Comb generator (OFCG1, OFCG2), 400 optical comb rangefinder, 401, 402 optical comb light source, 403 reference photodetector, 404 reference plane, 405 measurement plane, 406 measurement photodetector, 407 signal processing unit

Claims (23)

By the optical waveguide formed so as to penetrate from the incident side reflection film to the emission side reflection film, in the method of manufacturing an optical resonator for propagating and resonating the light incident through the incident side reflection film,
An optical waveguide forming step of forming the optical waveguide from the upper surface of the substrate,
A protective member having the same hardness as the substrate is provided on the optical waveguide so that at least one end face thereof forms the same plane as the end face of the substrate including the light incident end or the light emitting end of the optical waveguide. An arranging step of arranging,
By polishing the end surface of the protective member and the end surface of the substrate arranged in the arrangement step, a flat polished surface including a light incident end or a light emitting end of the optical waveguide is formed perpendicular to the optical waveguide. A polishing step for forming a flat surface,
A reflective film deposition step of depositing a single layer or a multilayer vapor deposition film as the incident side reflective film or the output side reflective film on the plane formed in the polishing step,
In the disposing step, the protective member is disposed on the upper portion of the optical waveguide with an adhesive.
In the reflective film deposition step, by depositing a single-layer or multi-layer vapor deposition film over all of the plane formed by the end face of the protective member and the end face of the substrate that are pasted with the adhesive, A method for manufacturing an optical resonator, characterized in that the incident side reflection film or the emission side reflection film is formed on a plane perpendicular to the optical waveguide. In the reflection film deposition step, the film thickness in the end face region including the light incident end or the light emission end of the optical waveguide is optimized with respect to the loss rate according to the crystal length in the light propagation direction of the optical waveguide. The method for producing an optical resonator according to claim 1, wherein a single-layer or multi-layer vapor deposition film is deposited. In the method of manufacturing an optical modulator that propagates and modulates light incident through the incident side reflection film by the optical waveguide in which the incident side reflection film and the emission side reflection film are formed,
An optical waveguide forming step of forming the optical waveguide from the upper surface of the substrate,
A laminating step of laminating a buffer layer on the substrate so as to cover at least the optical waveguide formed in the optical waveguide forming step;
An electrode forming step of forming an electrode for applying an electric field to the optical waveguide on the buffer layer laminated in the laminating step,
A protective member having the same hardness as the substrate is provided on the optical waveguide so that at least one end face thereof forms the same plane as the end face of the substrate including the light incident end or the light emitting end of the optical waveguide. An arranging step of arranging,
By polishing the end surface of the protective member and the end surface of the substrate arranged in the arrangement step, a flat polished surface including a light incident end or a light emitting end of the optical waveguide is formed perpendicular to the optical waveguide. A polishing step for forming a flat surface,
A reflective film deposition step of depositing a single layer or a multilayer vapor deposition film as the incident side reflective film or the output side reflective film on the plane formed in the polishing step,
In the disposing step, the protective member is disposed on the upper portion of the optical waveguide with an adhesive.
In the reflective film deposition step, by depositing a single-layer or multi-layer vapor deposition film over all of the plane formed by the end face of the protective member and the end face of the substrate that are pasted with the adhesive, A method of manufacturing an optical modulator, characterized in that the incident side reflection film or the emission side reflection film is formed on a plane perpendicular to the optical waveguide. In the reflection film deposition step, the film thickness in the end face region including the light incident end or the light emission end of the optical waveguide is optimized with respect to the loss rate according to the crystal length in the light propagation direction of the optical waveguide. The method for producing an optical modulator according to claim 3 , wherein a single-layer or multi-layer vapor deposition film is applied. In the optical waveguide forming step, the optical waveguide is formed as a region in which a waveguide mode exists only for a single polarization component by proton exchange from at least the upper surface of the substrate having an electro-optical effect. The method for manufacturing the optical modulator according to claim 3 or 4 . A ridge structure forming step of forming a ridge structure on the substrate,
Forming an electrode having a ridge structure as an electrode for applying an electric field to the optical waveguide on the buffer layer laminated in the laminating process on the substrate having the ridge structure formed in the electrode forming process; manufacturing method for an optical modulator according to any one of claims 3 to 5, characterized in. Resonant means composed of an incident side reflection film and an emission side reflection film, for resonating light incident through the incident side reflection film,
An optical waveguide that is formed so as to penetrate from the incident side reflection film to the emission side reflection film, and propagates the light resonated by the resonance means.
A substrate on which the optical waveguide is formed from the upper surface,
The protective member has the same hardness as the substrate, and at least one end face of the protective member forms the same plane as the end face of the substrate including the light incident end or the light emitting end of the optical waveguide. The end face protection means is provided on the upper portion of the optical waveguide, the protection member being attached by an adhesive.
The incident-side reflection film and the emission-side reflection film are polished on the entire plane formed by the end face of the protective member and the end face of the substrate, which are adhered with the adhesive, so that the optical waveguide An optical resonator comprising a single-layer or multilayer vapor-deposited film deposited on a plane perpendicular to the optical waveguide formed as a flat polished surface including an incident end or a light emitting end. The incident side reflection film and the emission side reflection film are films in an end face region including a light incident end or a light emission end of the optical waveguide with respect to a loss rate according to a crystal length in a light propagation direction of the optical waveguide. The optical resonator according to claim 7 , wherein the optical resonator is a single-layer or multilayer vapor-deposited film having an optimized thickness. The protection member constituting the end face protection means is made of the same material as the substrate, and the end face of the protection member forming the plane and the end face of the substrate have the same crystal orientation,
The end face protection means is such that one end face of the protection member forms the same plane as the end face of the substrate including the light incident end of the optical waveguide, and the other end face of the protection member is the optical waveguide. 9. The optical resonator according to claim 7 or 8 , wherein the optical resonator is disposed above the optical waveguide so as to form the same plane as the end surface of the substrate including the light emitting end. Oscillation means for oscillating a modulation signal of a predetermined frequency,
Resonant means composed of an incident side reflection film and an emission side reflection film, for resonating light incident through the incident side reflection film,
An optical waveguide that is formed so as to penetrate from the incident side reflection film to the emission side reflection film, and modulates the phase of the light resonated by the resonance means according to the modulation signal supplied from the oscillation means,
A substrate on which the optical waveguide is formed from the upper surface,
The protective member has the same hardness as the substrate, and at least one end face of the protective member forms the same plane as the end face of the substrate including the light incident end or the light emitting end of the optical waveguide. The end face protection means is provided on the upper portion of the optical waveguide, the protection member being attached by an adhesive.
The incident-side reflection film and the emission-side reflection film are polished on the entire plane formed by the end face of the protective member and the end face of the substrate, which are adhered with the adhesive, so that the optical waveguide An optical modulator, which is a single-layer or multilayer vapor-deposited film deposited on a plane perpendicular to the optical waveguide formed as a flat polished surface including an incident end or a light emitting end. The incident side reflection film and the emission side reflection film are films in an end face region including a light incident end or a light emission end of the optical waveguide with respect to a loss rate according to a crystal length in a light propagation direction of the optical waveguide. The optical modulator according to claim 10 , wherein the optical modulator is a vapor-deposited film of a single layer or a multilayer having an optimized thickness. Resonant means composed of an incident side reflection film and an emission side reflection film, for resonating light incident through the incident side reflection film,
An optical waveguide formed so as to penetrate from the incident side reflection film to the emission side reflection film,
A substrate on which the optical waveguide is formed from the upper surface,
The electrode is formed on the substrate for propagating the modulation signal in the forward direction or the backward direction, and modulates the phase of the light propagating in the optical waveguide according to the wavelength of the electric signal supplied to the electrode. Light modulation means,
The protective member has the same hardness as the substrate, and at least one end face of the protective member forms the same plane as the end face of the substrate including the light incident end or the light emitting end of the optical waveguide. The end face protection means is provided on the upper portion of the optical waveguide, the protection member being attached by an adhesive.
The incident-side reflection film and the emission-side reflection film are polished on the entire plane formed by the end face of the protective member and the end face of the substrate, which are adhered with the adhesive, so that the optical waveguide An optical modulator, which is a single-layer or multilayer vapor-deposited film deposited on a plane perpendicular to the optical waveguide formed as a flat polished surface including an incident end or a light emitting end. The incident side reflection film and the emission side reflection film are films in an end face region including a light incident end or a light emission end of the optical waveguide with respect to a loss rate according to a crystal length in a light propagation direction of the optical waveguide. The optical modulator according to claim 12 , wherein the optical modulator is a single-layer or multilayer vapor-deposited film having an optimized thickness. The optical waveguide according to claim 12 or claim, characterized in that it is formed on the substrate having at least an electro-optical effect as a region guided mode exists only for a single polarization component 13 The optical modulator according to. Electrode of the light modulating means, optical modulator according to claim 12 or claim 13 characterized by having a ridge structure. Oscillation means for oscillating a modulation signal of a predetermined frequency,
Resonant means composed of an incident side reflection film and an emission side reflection film, for resonating light incident through the incident side reflection film,
It is formed so as to penetrate from the incident side reflection film to the emission side reflection film, modulates the phase of the light resonated by the resonance means in accordance with the modulation signal supplied from the oscillation means, and the incident light is incident. An optical waveguide that generates sidebands centered on the frequency of light at intervals of the frequency of the modulation signal,
A substrate on which the optical waveguide is formed from the upper surface,
The electrode is formed on the substrate for propagating the modulation signal in the forward direction or the backward direction, and modulates the phase of the light propagating in the optical waveguide according to the wavelength of the electric signal supplied to the electrode. Light modulation means,
The protective member has the same hardness as the substrate, and at least one end face of the protective member forms the same plane as the end face of the substrate including the light incident end or the light emitting end of the optical waveguide. The end face protection means is provided on the upper portion of the optical waveguide, the protection member being attached by an adhesive.
The incident-side reflection film and the emission-side reflection film are polished on the entire plane formed by the end face of the protective member and the end face of the substrate, which are adhered with the adhesive, so that the optical waveguide An optical frequency comb generator, which is a single-layer or multilayer vapor-deposited film deposited on a plane perpendicular to the optical waveguide formed as a flat polished surface including an incident end or a light emitting end. The incident side reflection film and the emission side reflection film are films in an end face region including a light incident end or a light emission end of the optical waveguide with respect to a loss rate according to a crystal length in a light propagation direction of the optical waveguide. 17. The optical frequency comb generator according to claim 16 , which is a vapor-deposited film of a single layer or a multilayer with optimized thickness. Resonance means configured of an incident side reflection film and an emission side reflection film, for resonating light incident through the incident side reflection film or light generated by laser amplification,
An optical waveguide that is formed so as to penetrate from the incident side reflection film to the emission side reflection film, amplifies the light resonated by the resonance means, and emits the light to the outside through the emission side reflection film.
A substrate on which the optical waveguide is formed from the upper surface,
The electrode is formed on the substrate for propagating the modulation signal in the forward direction or the backward direction, and modulates the phase of the light propagating in the optical waveguide according to the wavelength of the electric signal supplied to the electrode. Light modulation means,
The protective member has the same hardness as the substrate, and at least one end face of the protective member forms the same plane as the end face of the substrate including the light incident end or the light emitting end of the optical waveguide. The end face protection means is provided on the upper portion of the optical waveguide, the protection member being attached by an adhesive.
The incident-side reflection film and the emission-side reflection film are polished on the entire plane formed by the end face of the protective member and the end face of the substrate, which are adhered with the adhesive, so that the optical waveguide An optical oscillator, which is a single-layer or multilayer vapor-deposited film deposited on a plane perpendicular to the optical waveguide formed as a flat polished surface including an incident end or a light emitting end. The incident side reflection film and the emission side reflection film are films in an end face region including a light incident end or a light emission end of the optical waveguide with respect to a loss rate according to a crystal length in a light propagation direction of the optical waveguide. The optical oscillator according to claim 18 , wherein the optical oscillator is a vapor-deposited film of a single layer or a multilayer having an optimized thickness. 19. The medium according to claim 18 , wherein the optical waveguide is formed by diffusing a medium that absorbs light incident through the incident side reflection film and has an amplification characteristic with respect to a wavelength of light peculiar to the medium. Item 21. The optical oscillator according to Item 19 . The optical oscillator according to claim 18 or 19 , wherein the optical waveguide is made of a non-linear optical crystal. Oscillation means for oscillating a modulation signal of a predetermined frequency,
Resonance means configured of an incident side reflection film and an emission side reflection film, for resonating light incident through the incident side reflection film or light generated by laser amplification,
It is formed so as to penetrate from the incident side reflection film to the emission side reflection film, amplifies the light resonated by the resonance means according to the modulation signal supplied from the oscillation means, and reflects it on the emission side reflection. An optical waveguide that emits to the outside through the film,
A substrate on which the optical waveguide is formed from the upper surface,
The electrode is formed on the substrate for propagating the modulation signal in the forward direction or the backward direction, and modulates the phase of the light propagating in the optical waveguide according to the wavelength of the electric signal supplied to the electrode. Light modulation means,
The protective member has the same hardness as the substrate, and at least one end face of the protective member forms the same plane as the end face of the substrate including the light incident end or the light emitting end of the optical waveguide. The end face protection means is provided on the upper part of the optical waveguide, the protection member being attached by an adhesive.
The incident-side reflection film and the emission-side reflection film are polished on the entire plane formed by the end face of the protective member and the end face of the substrate, which are adhered with the adhesive, so that the optical waveguide It is a single-layer or multi-layer vapor deposition film deposited on a plane perpendicular to the optical waveguide formed as a flat polished surface including the incident end or the light emitting end. An optical oscillator characterized by taking. The incident side reflection film and the emission side reflection film are films in an end face region including a light incident end or a light emission end of the optical waveguide with respect to a loss rate according to a crystal length in a light propagation direction of the optical waveguide. 23. The optical oscillator according to claim 22 , wherein the optical oscillator is a vapor-deposited film of a single layer or a multilayer having an optimized thickness.