JP2000171650A - Optical waveguide, method of manufacturing the same, and optical device using the optical waveguide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a configuration capable of realizing a bent optical waveguide having a low loss and a small radius of curvature and a branch optical waveguide having a low loss and a large branch angle, and a manufacturing method thereof. In addition, a small optical device using these optical waveguides is provided. SOLUTION: A lower cladding layer 2 is formed on a substrate 1 by an ozone oxidation type CVD method, and a core layer 3 is formed on the lower cladding layer 2 and a metal cladding is formed on a side of the core layer constituting a bent portion of the optical waveguide. A layer 4 is provided, and an upper clad layer 5 is formed on the core layer 3 and the metal clad layer 4 by the above-mentioned ozone oxidation type CVD.
The film was formed at a temperature of 600 ° C. or less by the method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical waveguide having a bent optical waveguide or a branched optical waveguide, which is an important component in the field of optical communications and optical computers, a method of manufacturing the same, an optical device using this optical waveguide, and the like. The present invention relates to an optical device including an optical integrated circuit.

[0002]

2. Description of the Related Art An optical integrated circuit is formed by connecting optical elements such as a light emitting / receiving element, an optical switch, an optical branching coupler, etc. on the same substrate and connecting them. It is an optical device capable of operating at a low voltage with a stable function. Further, in order to further reduce power consumption and reduce size and weight, further integration is required. As limiting factors in integrating more optical elements, (1) the voltage required to modulate the light intensity is inversely proportional to the element length. (2) Electrical or optical interference occurs between adjacent elements. (3) Bending for coupling each element The optical waveguide cannot be sharply bent. (Usually, the radius of curvature R is several mm to several tens mm: see FIG. 30A). (4) When the optical waveguide mode propagating in the waveguide is branched, the branch angle θ cannot be increased. (Usually, the branch angle θ of the Y-branch optical waveguide is within several degrees: refer to FIG. 30B).

When a device is connected by using a curved optical waveguide, the loss in the optical waveguide mode depends on the refractive index difference Δn between the cladding and the core and the curvature. The loss decreases as Δn increases and the curvature increases. LiN
In a curved optical waveguide in which Ti is diffused into a bO ₃ substrate, a value of 0.5 dB / cm or less is obtained when the radius of curvature is about 30 to 40 mm. However, when the radius of curvature is reduced, the loss increases. (M. Kondo, et al: IEEE
EJ. Quantum Electron. , QE-
18 (1982), 1759) On the other hand, as shown in FIG. 31, a method has been devised in which the optical waveguide mode is totally reflected by a mirror to bend the optical path vertically, but the loss is as large as about 4 dB. (Megada, et al .: 1985 IEICE General Conference, 966.) Considering the effect of loss on actual optical devices, the radius of curvature is m
A curved bend optical waveguide of m to several tens mm or a Y-branch optical waveguide having a branch angle of several degrees or less is used. For example, an optical filter using a curved bend optical waveguide has a length of about 20 mm. Would.

Recently, an L-bend optical waveguide having a metal clad layer and a T-shaped waveguide have been obtained by electromagnetic field calculation using the FD-TD method.
It was confirmed that the propagation direction of the optical waveguide mode can be changed vertically with low loss by combining the wave impedance matching circuit and the mode filter in the branch optical waveguide. FIG. 32 shows an example of such an L-bend optical waveguide (FIG. 32 (a)) and a T-branch optical waveguide (FIG. 32 (b)). In the figure, 3 is a core, λ is the wavelength of light, a portion indicated by D is a wave impedance matching circuit, and a portion indicated by E is a mode filter. In the optical waveguide shown in FIG. 32, metal is used for the clad for the purpose of increasing the refractive index difference Δn between the clad and the core. Further, by changing the waveguide width of the L-bend portion and the waveguide width of the T-branch portion as shown at D in FIG. 32 to match the wave impedance, the L-bend optical waveguide and the T-branch optical waveguide having low loss can be obtained. Wave path is realized. If the wave impedance is not matched, the amount of reflected light when light enters the L-bend and the T-branch increases. In addition, the constricted portion on the emission side of the L-bent portion and the T-branch portion has a filter characteristic for suppressing a higher-order mode. In an optical waveguide having a core width of several μm and made of only a quartz-based material, only a single mode exists, whereas a metal clad waveguide has a multimode structure, and the mode conversion is usually performed in a bent portion and a branch portion, and the loss is reduced. growing. By combining the mode filters, only a single mode is propagated to the emission side, and a low-loss L-bend optical waveguide and a T-branch optical waveguide can be formed. However, it is difficult to manufacture such an L-bend optical waveguide and a T-branch optical waveguide. That is, since a metal clad having a relatively low melting point must be provided on the side surface of the core, the metal clad is easily damaged when the upper clad layer is formed thereon,
Therefore, when manufacturing such an L-bend optical waveguide and a T-branch optical waveguide, it is necessary to apply a material or a film forming method that does not damage the metal clad layer.

[0005]

The conventional bent optical waveguide and branch optical waveguide are configured as described above.
In an ordinary curved optical waveguide, the radiation loss increases if the radius of curvature of the waveguide is reduced, and the loss in the optical waveguide mode also increases when the optical path is bent vertically using a waveguide mirror. Therefore, in an actual optical device, a curved optical waveguide having a radius of curvature of several mm to several tens of mm or a Y-branch optical waveguide having a branch angle within several degrees is used.
This has been a major factor preventing an increase in the degree of integration.
However, in order to realize further integration, a bent optical waveguide having a small loss and a small radius of curvature and a branch optical waveguide having a small loss and a large branch angle are required.

In order to satisfy the above-mentioned requirements, the present invention combines the above-described wave impedance matching circuit and mode filter, and further provides a material for the L-bend optical waveguide and the T-branch optical waveguide having a metal clad layer. And optimize the manufacturing method, bend vertically with low loss,
Alternatively, a vertically branched optical waveguide with low loss is realized. In addition, an ordinary curved optical waveguide, Y
It is also an object of the present invention to provide a configuration capable of realizing a curved optical waveguide having a low loss and a small radius of curvature and a Y-branch optical waveguide having a low loss and a large branch angle. It is another object of the present invention to reduce the size of an optical device such as an optical filter using these optical waveguides and to improve the degree of integration of an optical integrated circuit.

[0007]

According to a first aspect of the present invention, there is provided an optical waveguide having a metal clad layer provided on a side surface of a core layer at a bent portion or a branch portion of the optical waveguide, and a waveguide other than the metal clad layer. The material is made of a quartz-based material, and at least one of a wave impedance matching circuit and a mode filter that preserves a mode is provided in the bent portion or the branch portion.

The optical waveguide according to the second aspect of the present invention is an optical waveguide composed of a core layer and a clad layer, or a core layer, a clad layer, and a metal clad layer. The refractive index of the layer is such that the refractive index on the center side of the curvature in the bending direction is larger than the refractive index on the outer side of the center of the curvature.

In the optical waveguide according to the third configuration of the present invention, in the optical waveguide according to the second configuration, at least one or more triangular high refractive index regions are provided in the core layer at the bent portion or the branch portion. It is a distribution with a ratio.

An optical waveguide according to a fourth aspect of the present invention is an optical waveguide comprising a core layer and a clad layer, or a core layer, a clad layer, and a metal clad layer, wherein the bent portion or the branched portion of the optical waveguide has a core. A layer having a Gaussian distribution of refractive index distribution along a bending direction in a layer, and a peak position of the refractive index distribution is located closer to a curvature center side in a bending direction than a center of a core width. It is.

According to a fifth aspect of the present invention, there is provided an optical waveguide including a core layer and a cladding layer, or an optical waveguide including a core layer, a cladding layer, and a metal cladding layer, and a core layer having a width different from that of the optical waveguide. In the optical waveguide joined to the optical waveguide, a metal clad layer is provided on the side of the core layer at the junction, and the junction has a core structure having a stepped taper shape.

The method for manufacturing an optical waveguide according to the first method of the present invention is a method for manufacturing an optical waveguide in which a metal clad layer is provided on the side of the core layer at a bent portion or a branch portion of the optical waveguide. After the metal clad layer is provided, a core layer and a clad layer surrounding the metal clad layer are formed at a temperature of 600 ° C. or less.

The method of manufacturing an optical waveguide according to the second method of the present invention is a method for manufacturing an optical waveguide in which a metal clad layer is provided on the side of a core layer of a bent portion or a branch portion of the optical waveguide. Alternatively, a groove is formed in the branch portion along the side surface of the core, and the groove is filled with a metal to manufacture.

According to a third aspect of the present invention, there is provided a method for manufacturing an optical waveguide, comprising: a bent portion or a branched portion of the optical waveguide in an optical waveguide composed of a core layer and a clad layer, or a core layer, a clad layer, and a metal clad layer. The core layer in the portion is irradiated with ultraviolet light, and the refractive index of the core layer has a distribution.

An optical device according to the present invention uses an optical waveguide having any one of the first to fifth configurations.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a diagram showing an L-bend optical waveguide according to a first embodiment of the present invention in which a wave impedance matching circuit and a mode filter are combined, FIG. 1 (a) is a plan view, and FIG. 1 (b) is FIG.
FIG. 3A is a cross-sectional configuration diagram taken along line bb in FIG. In the figure,
1 is a substrate, 2 is a lower cladding layer made of quartz whose main component is silicon oxide (SiO ₂ ), 3 is a core layer made of quartz whose main component is silicon oxide and doped with about 10% of germanium (Ge), and 4 is The metal clad layer 5 formed on the side surface of the core along the bent portion of the core layer 3 is an upper clad layer mainly composed of quartz of silicon oxide. The light propagates along the core layer 3 in the direction of the arrow.

The vapor phase growth method used when forming a thin film is as follows:
By supplying physical energy to dissociate and vaporize atoms and molecules on the solid surface, and depositing them as a thin film on a substrate, PVD (Physical vapor deposition)
(CVD) method and a CVD (Chemical vapor) method using a volatile substance as a raw material and solidifying through a chemical reaction.
(deposition) method. In the former, a thin film having basically the same composition as the solid of the raw material is generated, whereas in the latter, a specific component in the raw material gas decomposed through a chemical reaction is fixed as a film. Even when the same raw material is used, the composition of the thin film formed varies greatly depending on the reaction conditions. In general, a CVD film has good adhesion to a substrate and wraparound, and can uniformly coat a substrate having a complicated shape. In addition, since the deposition rate is higher than other methods, there are advantages such that mass production is relatively easy and productivity is high.

In this embodiment, an ozone oxidation type CVD is used.
(Chemical vapor deposition
A bent optical waveguide of the type shown in FIG. 1 was manufactured by the method n). FIG. 2 is a configuration diagram showing a film forming apparatus for manufacturing the bent optical waveguide according to the first embodiment. In the figure, 6 is a carrier gas inlet, 7 is a flow controller, 8 is a raw material container, 9
Is a reaction tube, 10 is an oxygen gas inlet, 11 is an ozonizer,
Reference numeral 12 denotes a discharge port. The CVD apparatus shown in FIG. The raw material used was tetraethylorthosilicate (chemical formula: Si (OC ₂ H ₅ ) ₄ : T
EOS), boron tripropoxide (chemical formula B
(OC ₃ H ₇ ) ₃ : hereinafter abbreviated as TEB), germanium tetraoxide (chemical formula Ge (OC ₂ H ₅ ) ₄ : hereinafter T
EG). The carrier gas introduced from the carrier gas inlet 6 and discharged from the outlet 12 was a high-purity argon gas. A flow controller 7 is attached to each raw material container 8, and the flow rate of the vapor of each raw material can be controlled independently. Therefore, three kinds of alkoxide raw materials can be transported onto the substrate 1 in the reaction tube 9 at an arbitrary ratio. The refractive index of the CVD film can be controlled by the ratio of each raw material. Oxygen gas is introduced from the oxygen gas inlet 10 into the ozonizer 11,
The generated oxygen gas containing 8% ozone is introduced into the reaction tube 9 and the temperature of the substrate 1 is set to 300 ° C. to accelerate the decomposition and reaction of the raw material. Is formed. As the substrate 1, a silicon substrate having a diameter of 3 inches was used. The degree of vacuum is 50 Torr, and the deposition rate is 10
μm / hour.

In this embodiment, a bent optical waveguide is manufactured through the process steps shown in FIGS. First,
Using the film forming apparatus shown in FIG.
Only the vapor of EOS and TEB was supplied to form the lower cladding layer 2 made of quartz containing boron (B) in silicon oxide as shown in FIG. The thickness of the lower cladding layer 2 was about 20 μm. At this time, the refractive index of the lower cladding layer 2 was 1.4682. Next, TEOS and T
The alkoxide of EG was simultaneously supplied onto the substrate 1 to form a core film 13 made of quartz containing silicon oxide and germanium to a thickness of 6 μm. In forming the core film 13, the flow rate of the germanium alkoxide vapor was adjusted so that the germanium oxide content was about 10%. The temperature of the substrate 1 was the same as in the case of forming the lower cladding layer 2. Next, a chromium mask 14 having a desired waveguide pattern is formed on the core film 13 by a photoengraving method using electron beam drawing, and is etched by RIE to be patterned into the core layer 3 having a predetermined waveguide width (FIG. 3). (C) (d)).
The shape of the core was as shown in FIG. Next, the bent portion of the manufactured core layer 3 is surrounded by the metal cladding layer 4 by using the sputtering method as shown in FIG. Although gold is used here, silver, platinum, copper, aluminum, molybdenum, tungsten, tantalum, nickel, chromium, and the like can also be used. The metal cladding layer 4 was formed by using a sputtering method from an oblique direction with respect to the substrate 1. Since only one side of the cladding can be formed by one film formation, it is necessary to form the film a plurality of times by changing the inclination direction of the substrate. Some metal film is also formed on the upper surface of the core layer, but can be easily removed by etching. Next, when forming the upper clad layer 5 on the core layer 3 and the metal clad layer 4, it is necessary to form the upper clad layer 4 without damaging the metal clad layer 4. Among the various metals mentioned above, the melting point is 600 ° C. in the case of aluminum having the lowest melting point. So for most metals,
No damage at temperatures below 600 ° C. Therefore, when forming the upper cladding layer 5, it is preferable to form the film at a temperature of 600 ° C. or less. Ozone oxidation type CVD used in this embodiment
In the method, a desired upper cladding layer 5 can be formed at a temperature of 600 ° C. or less. Specifically, on the core layer 3 and the metal cladding layer 4, an upper cladding layer 5 containing boron in silicon oxide is formed with a thickness of about 20 μm using a raw material of TEOS + TEB (FIG. 3F), and an optical waveguide is formed. Produced. The substrate temperature at this time was 300 ° C. By forming the upper cladding layer 5 at a low temperature, the film can be formed without damaging the metal cladding layer 4. The refractive index of the upper cladding layer 5 is 1.468.
2. 1.4788 for the core layer 3 doped with germanium
And the refractive index difference was about 0.7%. The CVD method is
Unlike the flame deposition method, since a quartz film can be formed at a relatively low temperature without a heat treatment process at a high temperature (around 1000 ° C.), an optical waveguide having the metal clad layer 4 can be easily manufactured.

In the bent optical waveguide produced in the present embodiment, a vertically polarized optical waveguide mode was excited by coupling the end face of the fiber with laser light having a wavelength of 1.55 μm.
The light propagating in the waveguide and emitted from the end face of the waveguide was in a single mode. The loss of the entire bent waveguide was 0.9 dB, and a low loss result was obtained. By combining an impedance matching circuit, reflected light is reduced, and since a mode filter is combined, there is no mode conversion, so it can be said that such a good result was obtained.

Here, as the method for producing the metal clad layer 4, a method of sputtering from an oblique direction was used.
The metal clad layer 4 can also be manufactured by the steps shown in FIG. In the step shown in FIG. 4, first, a metal is formed by sputtering so as to surround the core layer 3 (FIG. 4).
(A)), a quartz film containing boron (upper cladding layer 5) is formed thereon (FIG. 4 (b)), and then polished until the upper surface of the core appears (FIG. 4 (c)). By polishing after covering with a quartz film, damage to the metal film due to polishing can be prevented. After polishing, by forming a film of quartz containing boron again (FIG. 4D), a waveguide in which the metal clad layer 4 is in contact with the side surface of the core layer 3 can be manufactured.

In still another method, the spin-coated photoresist is exposed, developed, and wet-etched to form a photoresist 15 on the core layer 3 as shown in FIG. Next, after the metal was sputtered by 1 μm (FIG. 5)
(B)), by etching, the resist 15 and the metal film on the resist 15 can be removed (FIG. 5C). Finally, a similar waveguide can be manufactured by forming quartz (upper cladding layer 5) from above (FIG. 5D).

Embodiment 2 FIG. FIG. 6 is a diagram showing a T-branch optical waveguide according to a second embodiment of the present invention in which a wave impedance matching circuit and a mode filter are combined,
This is a branched optical waveguide manufactured by the same method as in the first embodiment. FIG. 6A is a plan view, and FIG.
FIG. 3A is a cross-sectional configuration diagram taken along line bb in FIG. In the present embodiment, a branched optical waveguide is manufactured through the process steps shown in FIGS. First, using the film forming apparatus shown in FIG. 2, only TEOS and TEB vapors are supplied onto the silicon substrate 1 and made of quartz containing boron (B) in silicon oxide as shown in FIG. The lower cladding layer 2 was formed. The thickness of the lower cladding layer 2 was about 20 μm. At this time, the refractive index of the lower cladding layer 2 was 1.4682. Next, alkoxides of TEOS and TEG were simultaneously supplied onto the substrate 1 to form a core film 13 made of quartz containing silicon oxide and germanium to a thickness of 6 μm. In forming the core film 13, the flow rate of the germanium alkoxide vapor was adjusted so that the germanium oxide content was about 10%. The temperature of the substrate 1 was the same as in the case of forming the lower cladding layer 2. Next, a chromium mask 14 having a desired waveguide pattern is formed on the core film 13 by a photoengraving method using electron beam drawing, and is etched by RIE to be patterned into the core layer 3 having a predetermined waveguide width (FIG. 3). (C) (d)). The shape of the core was as shown in FIG. Next, the branch portion of the manufactured core layer 3 is shown in FIG.
As shown in FIG. 3E, the metal clad layer 4 is used to surround the metal clad layer by using a sputtering method. Although gold is used here, silver, platinum, copper, aluminum, molybdenum, tungsten, tantalum, nickel, chromium, and the like can also be used. Metal clad layer 4
Was formed using a sputtering method from an oblique direction with respect to the substrate. Since only one side of the cladding can be formed by one film formation, it is necessary to form the film a plurality of times by changing the inclination direction of the substrate. Some metal film is also formed on the upper surface of the core layer, but can be easily removed by etching. Next, on the core layer 3 and the metal cladding layer 4, an upper cladding layer 5 containing boron in silicon oxide was formed with a thickness of about 20 μm using a raw material of TEOS + TEB (FIG. 3 (f)) to produce an optical waveguide. . The substrate temperature at this time was 300 ° C. By forming the upper cladding layer 5 at a low temperature, the film can be formed without damaging the metal cladding layer 4.

A vertically polarized optical waveguide mode was excited by coupling end faces from a fiber using laser light having a wavelength of 1.55 μm in the branch optical waveguide produced in the present embodiment. The light propagating in the waveguide and emitted from the end face of the waveguide was in a single mode. The loss of the entire branch optical waveguide is 2.
5 dB, and a low loss result was obtained. By combining an impedance matching circuit, reflected light is reduced, and since a mode filter is combined, there is no mode conversion, so it can be said that such a good result was obtained.

Embodiment 3 In the present embodiment, an L-bend optical waveguide combining a wave impedance matching circuit and a mode filter is manufactured using the flame deposition method. Although the flame deposition method can produce a film with lower loss than the CVD method, if the upper cladding layer 5 is formed after the metal cladding layer 4 is formed as in the first and second embodiments, the flame deposition method is peculiar to the flame deposition method. The metal clad layer 4 is damaged due to the high temperature heat treatment step. Therefore, the configuration of the optical waveguide is different from that of the first embodiment shown in FIG. FIG. 7 is a diagram showing an L-bend optical waveguide according to the third embodiment, and FIG.
FIG. 7B is a plan view, and FIG. 7B is a cross-sectional configuration diagram taken along line bb of FIG. 7A.

FIG. 8 is a view showing a film forming apparatus by the flame deposition method, in which 16 is a hydrogen gas, 17 is a burner, and 18 is a turntable. As shown in the figure, argon gas is supplied from a carrier gas inlet 6 through silicon chloride (SiCl ₄ ),
Boron chloride (BCl ₃ ), germanium chloride (GeCl
₄ ), etc., into a raw material container 8 containing a liquid raw material, and transport these starting materials to an oxyhydrogen burner 17 using hydrogen gas 16 and hydrolyze in a flame to form fine powdered boron. Is produced and sprayed and deposited on the substrate 1 on the turntable 18. A flow controller 7 is attached to each raw material container 8, and three types of starting raw materials can be transported onto the substrate 1 at an arbitrary ratio. The refractive index in the thickness direction of the optical waveguide film formed can be controlled by the ratio of each raw material. That is, at the beginning of the flame deposition, only the silicon oxide containing boron is sprayed to form the lower cladding layer 2, and then about 10% of germanium is doped according to the refractive index to form a core film. However, after depositing the silicon oxide fine particle film, the temperature should be 1000 to 1200 ° C.
It is necessary to perform a heat treatment for transparency at the temperature described above. After the transparency treatment, a metal chromium film is formed on the core film by a sputtering method or a vapor deposition method, and a metal chrome film having a desired waveguide pattern is produced by a photolithography method using electron beam drawing. Thereafter, the core film is etched by RIE (reactive ion etching) to remove the core film that is not covered with the metal chromium film, thereby forming a core 3 having a predetermined width.
Thereafter, fine particles are deposited again by a flame deposition method using a silicon oxide composition containing boron and not containing germanium, and a high-temperature heat treatment is performed to form an upper cladding layer 5 to produce an optical waveguide. The shape of the core was as shown in FIG. The refractive index of the optical waveguide was 1.4572 for the cladding layer and 1.4670 for the core layer, and the difference in refractive index between the core layer and the cladding layer was 0.7%.

A metal clad layer 4 was attached to the optical waveguide thus manufactured through the process shown in FIG. First, a chromium film is formed on the upper cladding layer 5 by a sputtering method, and is masked by a photolithography method using electron beam drawing as shown in FIG. Next, as shown in FIG. 9B, the upper cladding layer is removed along the side surface of the core by wet etching.
Finally, a metal clad layer 4 is formed by a sputtering method (FIG. 9C). As described above, since the groove is formed after the optical waveguide is formed and the metal is filled, the metal clad layer 4 is damaged even if the upper clad layer 5 is formed by a film forming method requiring high-temperature treatment. Never.

A vertically polarized optical waveguide mode was excited by end face coupling using laser light having a wavelength of 1.55 μm in the L-bent optical waveguide produced in the present embodiment. It was confirmed that the light propagating in the waveguide and emitted from the end face of the waveguide was in a single mode, and the loss of the entire bent optical waveguide was 0.5 dB. The combination of an impedance matching circuit reduces reflected light, and the combination of a mode filter eliminates mode conversion. Furthermore, a film made of a quartz-based material can be formed with a small loss. It can be said that such good results were obtained by forming the film by the flame deposition method.

Note that, in the same manner as in the third embodiment,
When the L-bent optical waveguide is formed again, the cladding on the side surface of the core is removed by RIE etching to leave the cladding on the side surface of the core at about 0.5 μm as shown in FIG. However, as a result of measuring the loss, it was found to be about 0.7 dB, and a bent optical waveguide with sufficiently low loss could be obtained even if the cladding remained about 0.5 μm.

Embodiment 4 A T-branch optical waveguide as shown in FIG. 6 was manufactured by using the flame deposition method in the same manner as in the third embodiment. In the flame deposition method, initially, only silicon oxide containing boron is sprayed on the substrate to form the lower cladding layer 2 and then doping with about 10% of germanium according to the refractive index to form a core film. However, it is necessary to perform a heat treatment for transparency at a temperature of 1000 to 1200 ° C. after the deposition of the silicon oxide fine particle film. After the transparency treatment, a metal chromium film is formed on the core film by a sputtering method or a vapor deposition method, and a metal chrome film having a desired waveguide pattern is produced by a photolithography method using electron beam drawing. Then, R
The core film is etched by the IE (Reactive Ion Etching) method to remove the core film that is not covered with the metal chromium film, thereby forming the core 3 having a predetermined width. Thereafter, fine particles are deposited again by a flame deposition method using a silicon oxide composition containing boron and not containing germanium, and a high-temperature heat treatment is performed to form an upper cladding layer 5 to produce an optical waveguide. The shape of the core was as shown in FIG.

The metal clad layer 4 was attached to the T-branch optical waveguide thus manufactured through the process shown in FIG. First,
A chromium film is formed on the upper cladding layer 5 by a sputtering method, and FIG.
Mask as shown in FIG. Next, as shown in FIG. 9B, the upper clad layer is removed along the side surface of the core by wet etching, and finally the metal clad layer 4 is formed by a sputtering method (FIG. 9C). As described above, since the groove is formed after the optical waveguide is formed and the metal is filled, the metal clad layer 4 is damaged even if the upper clad layer 5 is formed by a film forming method requiring high-temperature treatment. Never.

A vertically polarized optical waveguide mode was excited by end face coupling using laser light having a wavelength of 1.55 μm in the branch optical waveguide produced in the present embodiment. It was confirmed that the light propagating in the waveguide and emitted from the end face of the waveguide was due to a single mode, and the loss of the entire branch optical waveguide was 1.4 dB. The combination of an impedance matching circuit reduces reflected light, and the combination of a mode filter eliminates mode conversion. Furthermore, a film made of a quartz-based material can be formed with a small loss. It can be said that such good results were obtained by forming the film by the flame deposition method.

Embodiment 5 FIG. The core width of a silica-based linear optical waveguide generally used for optical communication is about 6 to 8 μm. However, the core width of the L-bend optical waveguide having the metal clad layer 4 and the T-branch optical waveguide is about 3 μm in the wavelength band of 1.55 μm used for optical communication (core width = 2λ). Therefore, when those waveguides are directly coupled, the coupling loss increases. In the present embodiment, a coupling loss is reduced by using a stepped taper structure at a coupling portion between a quartz-based linear optical waveguide and an L-bent optical waveguide having a metal clad layer 4.

FIG. 11 is a view showing an L-bend optical waveguide according to the fifth embodiment, and FIG. 11 (a) is a plan view and FIG.
FIG. 12B is a cross-sectional configuration diagram taken along line bb of FIG. FIG. 12 is a view showing a coupling portion between a silica-based linear optical waveguide and an L-bent optical waveguide according to the fifth embodiment. The size of the stepped taper structure is the same as that of the L-bent optical waveguide and the L-bend optical waveguide described in each of the above embodiments. As in the case of the T-branch optical waveguide, the wave impedance is designed to be matched. FIG. 12 shows the design values.

The quartz film is formed by a thermal decomposition CVD method. The thermal decomposition CVD apparatus includes three raw material containers 8 as in the apparatus shown in FIG. 2, and can supply three types of raw material vapors onto the substrate 1 at the same time. Each raw material is filled in a closed vessel 8 whose temperature can be controlled, and the flow rate of each vapor can be independently controlled by a flow controller 7 capable of accurately adjusting the flow rate of the raw material vapor, so that three kinds of alkoxide raw materials can be mixed at an arbitrary ratio. Can be transported onto the substrate 1 in the reaction tube 9. Thereby, the refractive index of the CVD film can be controlled. Nitrous oxide gas (N ₂ O) was introduced into the reaction tube 9, and the temperature of the substrate 1 was set to 950 ° C.
As a result, the decomposition and reaction of the raw materials are promoted by heat, and a film is formed on the substrate 1 provided. As the substrate 1, a silicon substrate having a diameter of 3 inches was used. The deposition rate was 4 μm / hour.
The thermal decomposition CVD method includes an ozone oxidation CVD method and a plasma CV
A film having a smaller loss can be formed as compared with the method D or the like.

In this embodiment, first, an ozone oxidation type CV
As in the case of the method D, a lower cladding layer 2 containing boron in silicon oxide is formed to a thickness of 20 μm (the raw material is TEOS +
TEB), and then a core film containing germanium in silicon oxide is formed (the raw material is TEOS + TEG). Thereafter, a metal chromium film is formed on the core film by a sputtering method or a vapor deposition method, and a metal chromium film having a desired waveguide pattern is formed by a photoengraving method using electron beam drawing. Thereafter, the core film is etched by RIE (reactive ion etching) to remove the core film that is not covered with the metal chromium film, thereby forming a core 3 having a predetermined width. afterwards,
Again, a CVD film is deposited with a silicon oxide composition containing boron and no germanium to produce an optical waveguide (the raw material is TEOS + TEB). The shape of the bent core is shown in FIG.
As shown in FIG. 12A, the shape of the core at the joint between the bent optical waveguide and the silica-based linear optical waveguide was as shown in FIG.

The optical waveguide thus manufactured is subjected to the steps shown in FIG.
Was attached. However, in the present embodiment, when masking the chrome mask 14 in the step of FIG.
An optical waveguide as shown in FIG. 11A can be formed by masking the region other than the region where the metal clad layer 4 exists in FIG. With such a configuration, the coupling loss between the bent optical waveguide and the silica-based linear optical waveguide can be reduced. The refractive index of each manufactured quartz film was 1.4 in the cladding layer.
585, 1.471 for germanium-doped core layer
0 and the refractive index difference was about 0.8%.

A vertically polarized optical waveguide mode was excited in the bent optical waveguide produced in the present embodiment through a linear optical waveguide. It was confirmed that the light emitted from the end face of the waveguide was due to a single mode, and the loss of the entire waveguide was 0.2 dB. When the tapered structure was not formed at the joint between the bent optical waveguide and the linear optical waveguide, the loss was 0.5 dB, so the loss could be reduced by the tapered structure.

The present embodiment relates to a joint between an L-bend optical waveguide having a metal clad layer and a silica-based linear optical waveguide. Can be similarly implemented. If a stepped taper structure is formed on the end face of the optical waveguide having a metal clad layer and the optical waveguide is coupled to a fiber connector, coupling loss can be reduced.

Embodiment 6 FIG. 13A and 13B are diagrams showing a T-branch optical waveguide according to a sixth embodiment, where FIG. 13A is a plan view, and FIG. 13B is a cross-sectional configuration diagram along line bb in FIG. . In the present embodiment, similarly to the fifth embodiment, a step-type taper structure is provided at a coupling portion with a quartz-based linear optical waveguide, and the size of the step-type taper structure is designed so that wave impedance is matched. I do. The optical waveguide according to the present embodiment has a thermal decomposition C
It can be formed by the VD method. In the T-branch optical waveguide manufactured in the present embodiment, a vertically polarized optical waveguide mode was excited through a linear optical waveguide. The light emitted from the end face of the waveguide is due to a single mode, and the loss of the entire waveguide is 0.
It was confirmed to be 9 dB. When the tapered structure was not formed at the joint between the T-branch optical waveguide and the linear optical waveguide, the loss was 1.4 dB, so the loss could be reduced by the tapered structure.

Embodiment 7 FIG. 14A and 14B are views showing a bent optical waveguide according to the seventh embodiment, FIG. 14A is a plan view showing a bent optical waveguide, and FIG. 14B is a sectional view. In the figure, 19 indicates a high refractive index region in the core layer 3. When light passes through an ordinary quartz-based curved optical waveguide, the light is bent by reflection at the side surface of the waveguide. However, in that case, if the radius of curvature is reduced, the radiation loss to the outside of the curve increases. In the present embodiment, in order to reduce radiation loss, a distribution of the refractive index is generated in the core of the curved optical waveguide, so that the optical waveguide mode is easily bent. That is, when light passes through the prism in free space, the light is bent. Similarly, in the case of the guided light propagating in the waveguide, if the refractive index distribution occurs in the core, the guided light is bent in a certain direction. By making the direction in which the waveguide is bent and the direction bent by the refractive index distribution the same, the guided light is bent efficiently, and radiation loss is reduced. In the present embodiment, a high refractive index region 19 is provided inside the core layer 3 of the curved optical waveguide, so that light is easily bent.

In this embodiment, a quartz-based curved optical waveguide having a radius of curvature of 1 mm containing germanium in the core was manufactured by the ozone oxidation type CVD method. First, as a manufacturing method,
Using the film forming apparatus shown in FIG.
Only the vapor of EOS and TEB was supplied to form the lower cladding layer 2 made of quartz containing boron (B) in silicon oxide. The temperature during film formation was 500 degrees. The thickness of the lower cladding layer 2 was about 20 μm. At this time, the refractive index of the lower cladding layer 2 was 1.4682. Next, TE
The alkoxides of OS and TEG were simultaneously supplied onto the substrate 1 to form a high refractive index layer (core film) made of quartz containing silicon oxide and germanium to a thickness of 6 μm. In the formation of the core film, the content of germanium oxide is about 10
%, The flow rate of the germanium alkoxide vapor was adjusted. The temperature of the substrate 1 was the same as in the case of forming the lower cladding layer 2. Next, a chrome mask having a desired waveguide pattern was formed on the core film by a photoengraving method using electron beam drawing, and was etched by RIE to pattern the core layer 3 having a predetermined waveguide width. The shape of the core was curved. Next, on the core layer 3, an upper clad layer 5 containing boron in silicon oxide was formed with a thickness of about 20 μm using a raw material of TEOS + TEB, and an optical waveguide was manufactured. The substrate temperature at this time was 500 ° C. The refractive index of the upper cladding layer 5 was 1.4682, and that of the core layer 3 doped with germanium was 1.4788, and the difference in refractive index was about 0.7%. When an ultraviolet light (excimer laser, KrF: wavelength of 248 nm) is applied to a curved optical waveguide after a quartz optical waveguide is manufactured, the refractive index of the core portion irradiated with the ultraviolet light increases. This is a phenomenon in which the refractive index changes in a color center produced by strong light energy. By irradiating the core layer 3 with ultraviolet light through an appropriately shaped metal mask, an arbitrary refractive index distribution can be generated in the core layer 3. A curved optical waveguide irradiated with ultraviolet light through a metal mask has a configuration as shown in FIG.
Since light has the property of being refracted in the direction of higher refractive index, the optical waveguide mode is easily bent along the core, and radiation loss is reduced.

By providing the high refractive index region 19 as described above, the loss due to the bending of the optical waveguide was 3.5 dB when there was no refractive index distribution, but it was 3.5 dB when there was a refractive index distribution. 1.3 dB, and the effect of the refractive index distribution was obtained.

Embodiment 8 FIG. 15A and 15B show a bent optical waveguide according to the eighth embodiment. FIG. 15A is a plan view showing a bent optical waveguide, and FIG. 15B is a cross-sectional view. In the figure, 19 indicates a high refractive index region in the core layer 3. In the present embodiment, similarly to the seventh embodiment, a quartz-based curved optical waveguide in which a refractive index distribution is formed on the core layer 3 was manufactured. However, here, the shape of the refractive index distribution was triangular as shown in FIG.

In this embodiment, a quartz-based curved optical waveguide having a radius of curvature of 1 mm containing germanium in the core was manufactured by the ozone oxidation type CVD method. First, as a manufacturing method,
Using the film forming apparatus shown in FIG.
Only the vapor of EOS and TEB was supplied to form the lower cladding layer 2 made of quartz containing boron (B) in silicon oxide. The temperature during film formation was 500 degrees. The thickness of the lower cladding layer 2 was about 20 μm. At this time, the refractive index of the lower cladding layer 2 was 1.4682. Next, TE
The alkoxides of OS and TEG were simultaneously supplied onto the substrate 1 to form a high refractive index layer (core film) made of quartz containing silicon oxide and germanium to a thickness of 6 μm. In the formation of the core film, the content of germanium oxide is about 10
%, The flow rate of the germanium alkoxide vapor was adjusted. The temperature of the substrate 1 was the same as in the case of forming the lower cladding layer 2. Next, a chrome mask having a desired waveguide pattern was formed on the core film by a photoengraving method using electron beam drawing, and was etched by RIE to pattern the core layer 3 having a predetermined waveguide width. The shape of the core was curved. Next, on the core layer 3, an upper clad layer 5 containing boron in silicon oxide was formed with a thickness of about 20 μm using a raw material of TEOS + TEB, and an optical waveguide was manufactured. The substrate temperature at this time was 500 ° C. The refractive index of the upper cladding layer 5 was 1.4682, and that of the core layer 3 doped with germanium was 1.4788, and the difference in refractive index was about 0.7%. A refractive index distribution was generated in the core layer 3 of the manufactured silica-based curved optical waveguide having a curvature radius of 1 mm in the same manner as in the seventh embodiment. However, the shape of the refractive index distribution was triangular as shown in FIG. When irradiating the core layer 3 with ultraviolet light, if the triangular holes along the curve of the core layer 3 are irradiated through an innumerable metal mask, a refractive index distribution as shown in FIG. 15 can be obtained.

By providing a large number of triangular high refractive index regions 19 in this manner, a refractive index distribution occurs inside and outside the curved core layer 3, and the cumulative light refraction becomes large. Even if the amount of change in the refractive index due to ultraviolet light irradiation is small, a large refraction effect can be obtained. The radiation loss of the guided light is reduced by the effect of refraction, and when the refractive index distribution is not generated, the loss due to the curved portion is 3.5 dB, but when the refractive index distribution is generated, the loss is 0.5 dB. It became.

Embodiment 9 FIG. FIG. 16 is a diagram showing a Y-branch optical waveguide according to the ninth embodiment. In the figure, 19 indicates a high refractive index region in the core layer 3. Normal quartz Y
In a branch optical waveguide, if the branch angle is increased, the scattering loss at the branch part increases. In the present embodiment, in order to reduce scattering loss, a triangular refractive index distribution is generated in the core layer 3 of the Y-branch optical waveguide having a branch angle of 30 degrees, so that the optical waveguide mode is easily branched. . That is,
Similarly to the seventh and eighth embodiments, if a high refractive index region is provided in the core layer and a refractive index distribution is generated, the guided light is bent in a certain direction. By setting the branching direction of the waveguide and the direction bent by the refractive index distribution to be the same, the guided light is efficiently branched, and the scattering loss is reduced.

In the present embodiment, a quartz-based Y-branch optical waveguide containing germanium in the core was manufactured by the ozone oxidation type CVD method. First, only the TEOS and TEB vapors are supplied onto the silicon substrate 1 using the film forming apparatus shown in FIG. 2 to form the lower cladding layer 2 made of quartz containing boron (B) in silicon oxide. Was formed. The temperature during film formation was 500 degrees. The thickness of the lower cladding layer 2 is 20
It was about μm. At this time, the refractive index of the lower cladding layer 2 was 1.4682. Next, alkoxides of TEOS and TEG were simultaneously supplied onto the substrate 1 to form a high refractive index layer (core film) made of quartz containing silicon oxide and germanium to a thickness of 6 μm. In forming the core film, the flow rate of the germanium alkoxide vapor was adjusted so that the germanium oxide content was about 10%. The temperature of the substrate 1 was the same as in the case of forming the lower cladding layer 2. Next, a chrome mask having a desired waveguide pattern was formed on the core film by a photoengraving method using electron beam drawing, and was etched by RIE to pattern the core layer 3 having a predetermined waveguide width. The shape of the core is Y as shown in FIG.
Branched. Next, on the core layer 3, an upper clad layer 5 containing boron in silicon oxide was formed with a thickness of about 20 μm using a raw material of TEOS + TEB, and an optical waveguide was manufactured. The substrate temperature at this time was 500 ° C. A refractive index distribution was generated in the core layer 3 of the manufactured Y-branch optical waveguide in the same manner as in the seventh embodiment. However, the shape of the refractive index distribution is shown in FIG.
The shape was triangular. When the core layer 3 is irradiated with ultraviolet light through a metal mask having holes of a desired shape, a refractive index distribution as shown in FIG. 16 is obtained.

By providing a large number of triangular high-refractive-index regions 19 in the branching portion to generate a refractive index distribution in the core layer 3, light is easily branched, and scattering loss of guided light is reduced. Is done. When the refractive index distribution was not generated, the loss at the branch portion was 4.1 dB, but when the refractive index distribution was generated, the loss was 2.1 dB.

Embodiment 10 FIG. FIG. 17A shows the magnetic field strength distribution of the optical waveguide mode propagating through the ordinary curved optical waveguide.
As shown in FIG. The radiation loss increases as the exudation increases. In the present embodiment, a refractive index distribution is generated in the core layer 3 of the silica-based curved optical waveguide, and the seepage of the magnetic field intensity distribution is reduced, thereby reducing radiation loss.

In this embodiment, first, Embodiments 7 and 8
Similarly to the above, a silica-based curved optical waveguide having a curvature radius of 1 mm containing germanium in the core was produced by an ozone oxidation type CVD method. The core layer 3 of the manufactured silica-based curved optical waveguide having a radius of curvature of 1 mm was irradiated with ultraviolet light having a Gaussian distribution type beam profile at a beam width about the core width, and the ultraviolet light was irradiated along the curved core. And moved slowly. In addition, the irradiation position of the ultraviolet light is larger than the center of the core width,
Irradiation was performed so that the center of the beam was positioned slightly toward the center of curvature. By doing so, the amount of change in the refractive index of the core increases as the intensity of the ultraviolet light increases, so that a Gaussian refractive index distribution as shown in FIG. 17B reflecting the beam profile is obtained. Can be In addition, since the irradiation is performed so that the center of the beam is located slightly closer to the center of curvature than the center of the core width, the refractive index on the center of curvature of the core is larger than the refractive index on the outside of the center of curvature. By producing such a refractive index distribution, the magnetic field intensity distribution of the optical waveguide mode is shifted toward the center of curvature of the curved optical waveguide as shown in FIG. 17B, and radiation loss is reduced.

When the refractive index distribution is generated at the bent portion of the core layer 3 as described above, the loss at the curved portion was 3.5 dB when the refractive index distribution was not generated. Is 0.4 dB.

Embodiment 11 FIG. FIG. 18 shows Embodiment 11
FIG. 18A is a plan view illustrating a bent optical waveguide, and FIG. 18B is a cross-sectional view illustrating the bent optical waveguide. In the present embodiment, a curved optical waveguide having a curvature radius of 0.3 mm in which the metal clad layer 4 and the core layer 3 provided with the high refractive index region 19 are combined is shown. High refractive index region 19
Compared to the eighth embodiment in which only the metal clad layer 4 is not provided, the manufacturing process of the present embodiment slightly increases the manufacturing process, but hardly causes radiation loss. Can be reduced.

In this embodiment, a curved optical waveguide is manufactured by the flame deposition method. As a manufacturing method, first, only silicon oxide containing boron is sprayed on the silicon substrate 1 by using the film forming apparatus shown in FIG. 8 to form the lower cladding layer 2 and then germanium according to the refractive index. Of about 10% to form a core film. However, it is necessary to perform a heat treatment for transparency at a temperature of 1000 to 1200 ° C. after the deposition of the silicon oxide fine particle film. After the transparency treatment, a metal chromium film is formed on the core film by a sputtering method or a vapor deposition method, and a metal chromium film having a desired waveguide pattern (curved shape) is formed by a photoengraving method using electron beam drawing. After that, RIE (Reactive Ion Etching)
The core film is etched by a method, and the core film not covered with the metal chromium film is removed to form a core layer 3 having a predetermined width. Thereafter, fine particles are deposited again by a flame deposition method using a silicon oxide composition containing boron and not containing germanium, and a high-temperature heat treatment is performed to form an upper cladding layer 5 to produce an optical waveguide. The refractive index of the optical waveguide was 1.4572 for the cladding layer and 1.4670 for the core layer, and the difference in refractive index between the core layer and the cladding layer was 0.7%. The metal clad layer 4 was attached to the manufactured optical waveguide through the process of FIG. First, a chromium film is formed on the upper cladding layer 5 by a sputtering method, and is masked by a photolithography method using electron beam drawing as shown in FIG. Next, as shown in FIG. 9B, the upper clad layer is removed along the side surface of the core by wet etching, and finally the metal clad layer 4 is formed by a sputtering method (FIG. 9C). Since the groove is formed and the metal is filled after the formation of the optical waveguide, the metal clad layer 4 is not damaged even if the upper clad layer 5 is formed by a film forming method requiring high-temperature treatment. In the same manner as in the eighth embodiment, a triangular refractive index distribution as shown in FIG. 18 was generated by irradiating the curved optical waveguide thus manufactured with ultraviolet light through a metal mask.

In the bent optical waveguide according to the present embodiment in which the metal clad layer 4 and the core layer 3 provided with the high refractive index region 19 are combined, scattering loss of guided light is reduced.
The loss at the bent portion before producing the metal cladding layer 4 and the high refractive index region 19 was 5.5 dB, but it was 1.3 dB after the production.

Embodiment 12 FIG. FIG. 19 shows a twelfth embodiment.
FIG. 3 is a diagram showing a Y-branch optical waveguide having a branch angle of 60 degrees, in which a metal clad layer 4 and a core layer 3 provided with a high refractive index region 19 are combined.

In this embodiment, a Y-branch optical waveguide is manufactured by a flame deposition method. As a manufacturing method, first, only silicon oxide containing boron is sprayed on the silicon substrate 1 by using the film forming apparatus shown in FIG. 8 to form the lower cladding layer 2 and then germanium according to the refractive index. Of about 10% to form a core film. However, it is necessary to perform a heat treatment for transparency at a temperature of 1000 to 1200 ° C. after the deposition of the silicon oxide fine particle film. After the transparency treatment, a metal chromium film is formed on the core film by a sputtering method or a vapor deposition method, and a metal chromium film having a desired waveguide pattern (curved shape) is formed by a photoengraving method using electron beam drawing. After that, RIE (Reactive Ion Etching)
The core film is etched by a method, and the core film not covered with the metal chromium film is removed to form a core layer 3 having a predetermined width. Thereafter, fine particles are deposited again by a flame deposition method using a silicon oxide composition containing boron and not containing germanium, and a high-temperature heat treatment is performed to form an upper cladding layer 5 to produce an optical waveguide. The refractive index of the optical waveguide was 1.4572 for the cladding layer and 1.4670 for the core layer, and the difference in refractive index between the core layer and the cladding layer was 0.7%. The metal clad layer 4 was attached to the manufactured optical waveguide through the process of FIG. First, a chromium film is formed on the upper cladding layer 5 by a sputtering method, and is masked by a photolithography method using electron beam drawing as shown in FIG. Next, as shown in FIG. 9B, the upper clad layer is removed along the side surface of the core by wet etching, and finally the metal clad layer 4 is formed by a sputtering method (FIG. 9C). Since the groove is formed and the metal is filled after the formation of the optical waveguide, the metal clad layer 4 is not damaged even if the upper clad layer 5 is formed by a film forming method requiring high-temperature treatment. The Y-branch optical waveguide thus manufactured was irradiated with ultraviolet light through a metal mask in the same manner as in Embodiment 9 to generate a triangular refractive index distribution as shown in FIG.

The Y according to this embodiment in which the metal clad layer 4 and the core layer 3 provided with the high refractive index region 19 are combined.
In the branch optical waveguide, scattering loss of guided light is reduced,
The loss at the branch portion before forming the metal clad layer 4 and the high refractive index region 19 was 7.2 dB, but became 1.5 dB after the formation.

Embodiment 13 FIG. FIG. 20A is a configuration diagram showing a Mach-Zehnder type optical filter to which the L-bent optical waveguide according to the third embodiment is applied. In the figure, 2
0 to 23 are ports, 24a and 24b are couplers, and 25 is a grating. Two 3's consisting of 6 µm wide cores
A grating 25 having a length of 5 mm is formed between the dB couplers 24a and 24b. In the grating 25, the refractive index of the core layer is periodically changed, and only the light that matches the period is reflected, and the other light is transmitted. The light incident from the port 20 is branched into two by the left 3 dB coupler 24 a, and the light passing through the grating 25 is multiplexed by the right 3 dB coupler 24 b and
Output from The light reflected by the grating 25 is output from the port 21. Light incident from the port 22 is split into two by the left 3 dB coupler 24 b, and light transmitted through the grating 25 is multiplexed by the left 3 dB coupler 24 a and output from the port 21. Grating 2
The light reflected at 5 is output from port 23. Such an optical filter is used for an optical signal multiplexer / demultiplexer in wavelength division multiplexing communication.

In this embodiment, a quartz optical waveguide is manufactured by a flame deposition method. First, only silicon oxide containing boron is initially sprayed on a silicon substrate to form a lower cladding layer.
% To form a core film. However, it is necessary to perform a heat treatment for transparency at a temperature of 1000 to 1200 ° C. after the deposition of the silicon oxide fine particle film. After the transparency treatment, a metal chromium film is formed on the core film by a sputtering method or a vapor deposition method, and a metal chromium film having a desired waveguide pattern (Mach-Zehnder type) is produced by a photoengraving method using electron beam drawing. Thereafter, the core film is etched by RIE (Reactive Ion Etching) to remove the core film that is not covered with the metal chromium film, thereby forming a core layer having a predetermined width. Thereafter, fine particles are deposited again by a flame deposition method using a silicon oxide composition containing boron and not containing germanium, and a high-temperature heat treatment is performed to form an upper cladding layer, thereby producing an optical waveguide. The shape of the bent portion of the core is shown in FIG.
(A). The refractive index of the optical waveguide was 1.4572 for the cladding layer and 1.4670 for the core layer, and the difference in refractive index between the core layer and the cladding layer was 0.7%.

A metal clad layer was attached to the waveguide thus manufactured through the process shown in FIG. First, a chromium film is formed on the upper clad layer by a sputtering method, and is masked as shown in FIG. 9A by a photolithography method using electron beam drawing. Next, as shown in FIG. 9B, the upper clad layer is removed along the side surface of the core by wet etching, and finally a metal clad layer is formed by a sputtering method (FIG. 9B).
(C)). Since the groove is formed and the metal is filled after forming the optical waveguide, the metal clad layer is not damaged even if the upper clad layer is formed by a film forming method requiring high-temperature treatment. Thereafter, ultraviolet light is applied to the linear optical waveguide between the couplers through a glass plate having a diffraction grating. Thus, the grating 25 is formed on the core. The wavelength characteristics of the fabricated Mach-Zehnder optical filter of the present embodiment were measured using a broadband light source of an erbium-doped fiber amplifier. FIG. 20B is a diagram illustrating a wavelength characteristic of the Mach-Zehnder type optical filter manufactured in the present embodiment. In the figure, the horizontal axis represents wavelength (nm) and the vertical axis represents light intensity (dB).
nm, the band was 1.8 nm, and the extinction ratio was 25 dB. The insertion loss as an element at the center wavelength is 2.5 dB.
And a low loss value was obtained. Element size is 7m long
m, compared to the case where a normal curved optical waveguide is used.
It was reduced to 1/3.

Embodiment 14 FIG. FIG. 21 shows an optical integrated circuit in which the L-bent optical waveguide according to the first or third embodiment is combined with a plurality of semiconductor lasers and the like, and the core layer and the cladding layer are formed of a semiconductor. Light from individual semiconductor lasers is multiplexed on the same substrate. FIG. 21A is a plan view, and FIG. 21B is a sectional view. In addition,
Some components are omitted for easy understanding. In FIG. 21, reference numeral 70 denotes an n-type compound semiconductor substrate;
Reference numeral 1 denotes a semiconductor layer (hereinafter, referred to as a “semiconductor laser portion” because laser oscillation is performed at this portion); Is a semiconductor layer (this portion has a function of amplifying light, and is hereinafter referred to as a “semiconductor amplifier portion”). Therefore, 75 is a semiconductor laser electrode provided on the semiconductor laser unit 71, 76 is a semiconductor amplifier electrode provided on the semiconductor amplifier unit 73, and 77 is an electrode provided below the compound semiconductor substrate 70. Reference numeral 78 denotes a diffraction grating provided near the semiconductor laser unit 71, and reference numeral 4 denotes a metal clad layer formed around the bent optical waveguide.

Next, the operation will be described. First, when a current flows between the semiconductor laser electrode 75 and the electrode 77, electrons and holes are injected into the semiconductor laser unit 71, and when the electrons and holes are combined, light is generated. Of this light, only a specific wavelength corresponding to the period of the diffraction grating 78 is amplified and reflected, and when a sufficiently high current is applied, laser oscillation occurs at the end. At this time, if the period of each diffraction grating 78 is slightly changed, each semiconductor laser unit 71 emits laser light having a different wavelength. Each light passes through the multiplexer unit 72 and is multiplexed. When the forbidden band width of the multiplexer section 72 is the same as that of the semiconductor laser section 71, a loss of about 1000 dB per 1 cm is received. Therefore, the multiplexer unit 72
Loss can be suppressed to about several tens of dB per cm. The multiplexed light passes through the semiconductor amplifier 73 and is emitted from the right end. When a current flows between the semiconductor amplifier electrode 76 and the electrode 77, the light is amplified and emitted. By combining the semiconductor amplifier section 73 and the vertically bent optical waveguide in this manner, the loss of the optical integrated circuit can be suppressed, and the forbidden bandwidths of the semiconductor laser section, the multiplexer section, and the semiconductor amplifier section can be made the same. As a result, a semiconductor layer can be formed, and a low-cost, high-density optical integrated circuit can be easily manufactured.

Next, a method of manufacturing the above-described embodiment will be described by taking an indium-phosphorus-based optical integrated circuit as an example. First, as shown in FIG. 22A, a semiconductor layer 80 serving as a semiconductor laser unit, a multiplexer unit, and a semiconductor amplifier unit, and a semiconductor layer 90 serving as a diffraction grating are organically formed on an n-type indium phosphide substrate 70. Metal vapor deposition (MO
The layers are sequentially formed using CVD. Here, the semiconductor layer 80
Has a multiple quantum well structure in order to improve laser characteristics. The multiple quantum well structure has, for example, a thickness of 300
N-type indium 0.82 gallium 0.18 arsenic 0.3
9 phosphorus 0.61, 80 ° thick undoped indium 0.47 gallium 0.53 arsenic (7 layers), undoped indium 0.82 gallium 0.18 arsenic 0.39 phosphorus 0.61 (6 layers), p-type indium It consists of 0.82 gallium 0.18 arsenic 0.39 phosphorus 0.61. Further, the semiconductor layer 90 is made of p-type indium 0.78
It consists of gallium 0.22 arsenic 0.47 phosphorus 0.53.
Next, as shown in FIG. 22B, a diffraction grating 78 having a period of about 2400 ° is provided on the semiconductor layer 90 adjacent to the semiconductor laser portion.
To form Next, as shown in FIG.
A p-type indium phosphorus cladding layer 74 is formed on the diffraction grating 78 and the semiconductor layer 90 by using the OVCVD method. Next, as shown in FIGS. 23A and 23B, patterning is performed using a photoengraving technique, etching is performed using a bromomethanol solution, and the semiconductor laser section 71 and the multiplexer section 7 are etched.
2. The semiconductor amplifier 73 is formed. Next, FIG.
As shown in (2), the Fe-doped indium phosphide current blocking layer 81 is formed again using the MOCVD method. Next, FIG.
As shown in FIG. 3D, a groove is formed around the bent optical waveguide of the multiplexer section 72 by using a photolithography technique using electron beam drawing and etching, and then the metal clad layer 4 is formed by a sputtering method, a vapor deposition method, or the like. Fill. The detailed shape of the bent optical waveguide was as shown in FIG. Next, FIG.
(A) As shown in (b), an electrode 77 is formed below the semiconductor substrate 70, a semiconductor laser electrode 75 is formed above the semiconductor laser unit 71, and a semiconductor amplifier electrode 76 is formed above the semiconductor amplifier unit 73. The integrated circuit is completed. Note that FIG.
FIG. 24A is a cross-sectional view of the semiconductor amplifier 73, and FIG.
Shows cross-sectional views of the semiconductor laser unit 71, respectively.
By using a vertically bent optical waveguide for the multiplexer section 72, the length of the multiplexer section 72 could be reduced to 1/10 of the conventional length. Further, the loss of the multiplexer section was about 5 dB, which is a sufficiently practical result, even though the material having the same forbidden band width as that of the semiconductor laser section was used.

In the fourteenth embodiment, the semiconductor laser section 71, the multiplexer section 72, and the semiconductor amplifier section 73 have the same forbidden band width of the semiconductor material. The forbidden band width may be larger than those of the semiconductor laser unit 71 and the semiconductor amplifier unit 73. Thereby, the loss of the multiplexer unit 72 can be reduced. Such a configuration is based on a conventionally used etching method,
If the selective growth method is used, it can be easily implemented. Further, although the optical integrated circuit in the above-described embodiment includes the semiconductor laser section, the multiplexer section, and the semiconductor amplifier section, the optical integrated circuit can be similarly implemented only from the semiconductor laser section and the multiplexer section. The elimination of the semiconductor amplifier simplifies the fabrication of the device.

Embodiment 15 FIG. FIG. 25A is a diagram showing a Mach-Zehnder optical filter to which a curved optical waveguide composed of a core layer having a refractive index distribution according to the seventh embodiment is applied. A grating 25 having a length of 5 mm is formed between two 3 dB couplers 24a and 24b each having a core having a width of 6 μm. In the grating 25, the refractive index of the core layer is periodically changed, and only the light that matches the period is reflected, and the other light is transmitted. The light incident from the port 20 is split into two by the left 3 dB coupler 24 a, and the light transmitted through the grating 25 is multiplexed by the right 3 dB coupler 24 b and
3 is output. The light reflected by the grating 25 is output from the port 21. Light incident from the port 22 is split into two by the left 3 dB coupler 24 b, and light transmitted through the grating 25 is multiplexed by the left 3 dB coupler 24 a and output from the port 21. The light reflected by the grating 25 is output from the port 23. Such an optical filter is used for an optical signal multiplexer / demultiplexer in wavelength division multiplexing communication.

In this embodiment, a quartz optical waveguide is manufactured by a flame deposition method. First, only silicon oxide containing boron is initially sprayed on a silicon substrate to form a lower cladding layer.
% To form a core film. However, it is necessary to perform a heat treatment for transparency at a temperature of 1000 to 1200 ° C. after the deposition of the silicon oxide fine particle film. After the transparency treatment, a metal chromium film is formed on the core film by a sputtering method or a vapor deposition method, and a metal chromium film having a desired waveguide pattern (Mach-Zehnder type) is produced by a photoengraving method using electron beam drawing. Thereafter, the core film is etched by RIE (Reactive Ion Etching) to remove the core film that is not covered with the metal chromium film, thereby forming a core layer having a predetermined width. Thereafter, fine particles are deposited again by a flame deposition method using a silicon oxide composition containing boron and not containing germanium, and a high-temperature heat treatment is performed to form an upper cladding layer, thereby producing an optical waveguide. The shape of the bent portion A of the core is shown in FIG.
It was like the enlarged part of (a). The refractive index of the optical waveguide was 1.4572 for the cladding layer and 1.4670 for the core layer, and the difference in refractive index between the core layer and the cladding layer was 0.7%.

After the silica-based optical waveguide was manufactured in this manner, ultraviolet light (excimer laser, KrF: wavelength 248 nm) was used.
When m) is applied to the curved portion of the optical waveguide, the refractive index of the core portion irradiated with ultraviolet light increases. This is a phenomenon in which the refractive index changes in a color center produced by strong light energy. By irradiating the core layer 3 with ultraviolet light through an appropriately shaped metal mask, an arbitrary refractive index distribution can be generated in the core layer 3. In the present embodiment, the high-refractive-index region 19 is provided inside the core layer 3 of the curved optical waveguide, so that light is easily bent. The curved optical waveguide irradiated with ultraviolet light through a metal mask is shown in FIG.
(A), the light has a property of being refracted in the direction of a higher refractive index, so that the optical waveguide mode is easily bent along the core, and the radiation loss is reduced. Thereafter, ultraviolet light is applied to the linear waveguide between the couplers through a glass plate having a diffraction grating. Thereby, the grating 25 is formed on the core.

The wavelength characteristics of the fabricated Mach-Zehnder type optical filter of the present embodiment were measured using a broadband light source of an erbium-doped fiber amplifier. FIG. 25 (b)
FIG. 4 is a diagram illustrating a wavelength characteristic of the Mach-Zehnder type optical filter manufactured in the present embodiment. In the figure, the horizontal axis represents wavelength (nm) and the vertical axis represents light intensity (dB).
Center wavelength 1567 nm, band 1.8 nm, extinction ratio 2
It was 5 dB. Further, the insertion loss as an element at the center wavelength was 2.2 dB, which was a low loss value. In addition, since the refractive index distribution was generated in the core layer 3 and the radius of curvature of the curved portion could be reduced, the size of the element became 10 mm in length, which was 1/2 that in the case of using a normal curved optical waveguide.
Could be reduced to

Embodiment 16 FIG. FIG. 26A is a diagram showing a Mach-Zehnder type optical switch to which a curved optical waveguide composed of a core layer having a refractive index distribution according to the eighth embodiment is applied. 2 consisting of 6 μm wide core
An electrode 26 is formed on the cladding surface on one side of the core in the linear waveguide portion between the 3 dB couplers 24a and 24b. When the light enters from the port 20, it is normally split into two by the left 3 dB coupler 24 a, propagates through each linear waveguide section, is multiplexed by the right 3 dB coupler 24 b, and is output from the port 23. However, when a voltage is applied to the electrode 26 to apply heat, the refractive index of the heated waveguide changes, the phase of light propagating through the linear waveguide portion shifts, and the light is multiplexed by the right 3 dB coupler portion 24b. The emitted light is output from the port 22. Thus, the optical switch has the function of switching the optical path by turning ON / OFF the voltage applied to the electrode 26.

Hereinafter, a manufacturing method will be described. A quartz-based curved optical waveguide having a radius of curvature of 1 mm containing germanium in the core was produced by an ozone oxidation type CVD method. First, only the TEOS and TEB vapors are supplied onto the silicon substrate 1 using the film forming apparatus shown in FIG. 2 to form the lower cladding layer 2 made of quartz containing boron (B) in silicon oxide. Was formed. The temperature during film formation was 500 degrees.
The thickness of the lower cladding layer 2 was about 20 μm. At this time, the refractive index of the lower cladding layer 2 was 1.4682. Next, alkoxides of TEOS and TEG were simultaneously supplied onto the substrate 1 to form a 6 μm thick core film made of quartz containing silicon oxide and germanium. In the formation of the core film, the content of germanium oxide is about 10
%, The flow rate of the germanium alkoxide vapor was adjusted. The substrate temperature was the same as in the case of forming the lower cladding layer. Next, a chrome mask having a desired waveguide pattern was formed on the core film by a photoengraving method using electron beam drawing, and was etched by RIE to be patterned into a core layer having a predetermined waveguide width. Figure 26 shows the core shape.
It was a Mach-Zehnder type as shown in FIG. Next, on the core, an upper clad layer containing boron in silicon oxide was formed by T
An optical waveguide was formed with a thickness of about 20 μm using the raw material of EOS + TEB. The substrate temperature at this time was 500 ° C. The refractive index of the upper cladding layer was 1.4682, and that of the germanium-doped core layer was 1.4788, and the difference in refractive index was about 0.7%. A large number of triangular high refractive index regions 19 were formed in the core layer of the manufactured quartz-based curved optical waveguide in the same manner as in the eighth embodiment. When irradiating the core with ultraviolet light, triangular holes along the curve of the core are irradiated through a myriad of metal masks as shown in FIG.
A refractive index distribution as shown in FIG. By configuring a large number of triangular refractive index distributions in this manner, the refraction of light as a sum becomes large, and a large refraction effect can be obtained even if the amount of change in the refractive index due to irradiation with ultraviolet light is small.
Losses are reduced.

Next, in order to add a switch function, 3
An electrode 26 made of a chromium film was formed on the clad surface above the core on one side of the linear waveguide section between the dB coupler sections. Electrode 2
No. 6 was produced using a photoengraving method. FIG. 26B shows switching characteristics when light is incident from the port 20 and a voltage is applied to the electrode. The power required for switching was about 0.4 w. The loss was reduced by about 3 dB by causing the refractive index distribution in the core layer. In addition, since the radius of curvature of the curved portion could be reduced, the size of the element became 10 mm in length, which could be reduced to 比 べ compared to the case where a normal curved optical waveguide was used.

Embodiment 17 FIG. FIG. 27A is a diagram illustrating a Mach-Zehnder type optical switch including a core layer having a refractive index distribution according to Embodiment 10 and using a curved optical waveguide. 2 consisting of 6 μm wide core
An electrode 26 is formed on the cladding surface on one side of the core in the linear waveguide portion between the 3 dB couplers 24a and 24b. When the light enters from the port 20, it is normally split into two by the left 3 dB coupler 24 a, propagates through each linear waveguide section, is multiplexed by the right 3 dB coupler 24 b, and is output from the port 23. However, when a voltage is applied to the electrode 26 to apply heat, the refractive index of the heated waveguide changes, the phase of light propagating through the linear waveguide portion shifts, and the light is multiplexed by the right 3 dB coupler portion 24b. The emitted light is output from the port 22. Thus, the optical switch has the function of switching the optical path by turning ON / OFF the voltage applied to the electrode 26.

Hereinafter, a manufacturing method will be described. A quartz-based curved optical waveguide having a radius of curvature of 1 mm containing germanium in the core was produced by an ozone oxidation type CVD method. First, only the TEOS and TEB vapors are supplied onto the silicon substrate 1 using the film forming apparatus shown in FIG. 2 to form the lower cladding layer 2 made of quartz containing boron (B) in silicon oxide. Was formed. The temperature during film formation was 500 degrees.
The thickness of the lower cladding layer 2 was about 20 μm. At this time, the refractive index of the lower cladding layer 2 was 1.4682. Next, alkoxides of TEOS and TEG were simultaneously supplied onto the substrate 1 to form a 6 μm thick core film made of quartz containing silicon oxide and germanium. In the formation of the core film, the content of germanium oxide is about 10
%, The flow rate of the germanium alkoxide vapor was adjusted. The substrate temperature was the same as in the case of forming the lower cladding layer. Next, a chrome mask having a desired waveguide pattern was formed on the core film by a photoengraving method using electron beam drawing, and was etched by RIE to be patterned into a core layer having a predetermined waveguide width. Figure 27 shows the core shape.
It was a Mach-Zehnder type as shown in FIG. Next, on the core, an upper clad layer containing boron in silicon oxide was formed by T
An optical waveguide was formed with a thickness of about 20 μm using the raw material of EOS + TEB. The substrate temperature at this time was 500 ° C. The refractive index of the upper cladding layer was 1.4682, and that of the germanium-doped core layer was 1.4788, and the difference in refractive index was about 0.7%. In the present embodiment, the core layer of the manufactured silica-based curved optical waveguide is irradiated with ultraviolet light having a Gaussian distribution beam profile with a beam width about the core width in the same manner as in Embodiment 10. , It was moved slowly along the curved core. Further, the irradiation position of the ultraviolet light was set so that the center of the beam was slightly closer to the center of curvature than the center of the core width. By doing so, the amount of change in the refractive index of the core increases as the intensity of the ultraviolet light increases, so that a Gaussian refractive index distribution as shown in FIG. 17B reflecting the beam profile is obtained. Can be In addition, since the irradiation is performed so that the center of the beam is located slightly closer to the center of curvature than the center of the core width, the refractive index on the center of curvature of the core is larger than the refractive index on the outside of the center of curvature. By producing such a refractive index distribution, the magnetic field intensity distribution of the optical waveguide mode is shifted toward the center of curvature of the curved optical waveguide as shown in FIG. 17B, and radiation loss is reduced.

Next, in order to add a switch function, 3
An electrode 26 made of a chromium film was formed on the clad surface above the core on one side of the linear waveguide section between the dB coupler sections. Electrode 2
No. 6 was produced using a photoengraving method. FIG. 27B shows switching characteristics when light is incident from the port 20 and a voltage is applied to the electrode 26. The power required for switching was about 0.4 w. By causing the refractive index distribution in the core 3, the loss was reduced by about 4 dB. In addition, since the radius of curvature of the curved portion could be reduced, the size of the element became 10 mm in length, which could be reduced to 比 べ compared to the case where a normal curved optical waveguide was used.

Embodiment 18 FIG. In the present embodiment, an optical power distributor as shown in FIG. 28 using the bent and branched optical waveguides described in Embodiments 11 and 12 was manufactured. The optical power distributor is a device necessary for distributing an optical signal.

First, an optical waveguide made of a quartz-based material is manufactured by a flame deposition method. Initially, only silicon oxide containing boron is sprayed on a silicon substrate to form a lower cladding layer, and then about 10% of germanium is added according to the refractive index.
A core film is formed by doping before and after. However, it is necessary to perform a heat treatment for transparency at a temperature of 1000 to 1200 ° C. after the deposition of the silicon oxide fine particle film. After the transparency treatment, a metal chromium film is formed on the core film by a sputtering method or a vapor deposition method, and a metal chromium film having a desired waveguide pattern (see FIG. 28) is produced by a photoengraving method using electron beam drawing. . After that, RIE (Reactive Ion Etching)
The core film is etched by a method to remove the core film that is not covered with the metal chromium film, thereby forming a core layer having a predetermined width. Thereafter, fine particles are deposited again by a flame deposition method using a silicon oxide composition containing boron and not containing germanium, and a high-temperature heat treatment is performed to form an upper cladding layer, thereby producing an optical waveguide. The refractive index of the optical waveguide is 1.4 for the cladding layer.
572, the core layer was 1.4670, and the refractive index difference between the core and the clad was 0.7%. By applying a method of irradiating the fabricated curved optical waveguide with ultraviolet light through a metal mask, a triangular refractive index distribution as shown in the enlarged portion of FIG.

The bent portion A and the branch portion B are further provided with a structure shown in FIG.
Through the above steps, the metal clad layer was attached. First, a chromium film is formed on the upper clad layer by a sputtering method, and is masked as shown in FIG. 9A by a photolithography method using electron beam drawing. Next, as shown in FIG. 9B, the upper cladding layer is removed along the side surface of the core by wet etching.
Finally, a metal clad layer is formed by a sputtering method (FIG. 9C). Since the groove is formed and the metal is filled after forming the optical waveguide, the metal clad layer is not damaged even if the upper clad layer is formed by a film forming method requiring high-temperature treatment.

The loss at the bent portion A and the branch portion B of the guided light is reduced, and the loss before forming the metal clad layer and the refractive index distribution is 8.5 dB, but after the formation, it is 3.
2 dB. In addition, the radius of curvature of the curved portion of the curved optical waveguide can be reduced, and the branch angle of the branch optical waveguide can be increased, so that the element size becomes 5 mm in length. Was reduced to 1/5 compared to the case where

Embodiment 19 FIG. In the present embodiment, the metal clad layer described in the fifth and sixth embodiments is provided at the junction between the silica-based linear optical waveguide, the bent optical waveguide, and the branch optical waveguide, and the stepped taper structure is provided. An optical power distributor using an optical waveguide as shown in FIG. 29 was manufactured.

The quartz film is formed by a thermal decomposition CVD method.
An optical power distributor was fabricated. The thermal decomposition CVD apparatus is provided with three raw material containers 8 as shown in FIG. Each raw material is filled in a temperature-controllable closed container, and the flow rate of each vapor can be independently controlled by a flow controller 7 capable of accurately adjusting the flow rate of the raw material vapor, so that three kinds of alkoxide raw materials can be mixed at an arbitrary ratio. It can be transported onto the substrate 1 in the reaction tube 9.
Thereby, the refractive index of the CVD film can be controlled. Nitrous oxide gas (N ₂ O) was introduced into the reaction tube 9, and the substrate temperature was adjusted to 9.
At 50 ° C, the decomposition and reaction of the raw materials are promoted by heat,
A film is formed on the placed substrate 1. As the substrate 1, a silicon substrate having a diameter of 3 inches was used. The deposition rate was 4 μm / hour. The thermal decomposition CVD method has a lower deposition rate than the ozone oxidation CVD method, the plasma CVD method, or the like.

In this embodiment, first, an ozone oxidation type CV
As in the case of the method D, a lower cladding layer containing boron in silicon oxide is formed to a thickness of 20 μm (the material is TEOS + T
EB) Then, a core film containing germanium is formed in silicon oxide (the raw material is TEOS + TEG). afterwards,
A metal chromium film is formed on the core film by a sputtering method or a vapor deposition method, and a metal chromium film having a desired waveguide pattern is formed by a photoengraving method using electron beam drawing. afterwards,
The core film is etched by RIE (reactive ion etching) to remove the core film that is not covered with the metal chromium film, thereby forming a core layer having a predetermined width. Thereafter, a CVD film is deposited again with a silicon oxide composition containing boron and no germanium to produce an optical waveguide (the raw material is T
EOS + TEB). The shape of the core was as shown in FIG.

The bent portion A of the optical waveguide manufactured as described above.
Further, the metal clad layer 4 was attached to the branch portion B through the process of FIG. The core shapes of the bent portion A and the branch portion B were as shown in FIGS. 32 (a) and 32 (b). In the present embodiment, in the process of FIG.
A stepped taper structure having a metal clad layer as shown in an enlarged portion of FIG. 27 was formed at a joint C between a branched optical waveguide having a metal clad layer 4 and a silica-based linear optical waveguide. When masking the chromium film in the process of FIG.
An optical waveguide as shown in FIG. 29 can be formed by masking a region other than the region where the metal clad layer exists. With such a configuration, the coupling loss between the bent optical waveguide having the metal clad layer, the branched optical waveguide, and the silica-based linear optical waveguide can be reduced. The refractive index of each of the produced quartz films was 1.4585 for the cladding layer and 1.4710 for the core layer doped with germanium, and the refractive index difference was about 0.8%.

Light was incident on the optical power distributor manufactured in the present embodiment, and it was confirmed that the output light was divided into four. Before making the metal cladding layer for each part, the loss is 1
While it was 2 dB, it decreased to 3.7 dB after the production of the metal clad layer. The device length is 2
mm, which can be reduced to about 1/10 of the optical power distributor combining the ordinary curved optical waveguide and the Y-branch optical waveguide.

[0085]

As described above, according to the optical waveguide according to the first configuration of the present invention, a metal clad layer is provided on the side of the core layer at the bent portion or the branch portion of the optical waveguide, and the metal clad layer other than the metal clad layer is provided. Since the waveguide material is composed of a quartz-based material, and at least one of a wave impedance matching circuit and a mode filter for storing a mode is provided in the bent portion or the branch portion, low loss is achieved.
An optical waveguide that bends vertically or branches vertically with low loss can be manufactured, miniaturization of each element in an optical integrated circuit becomes possible, and the degree of freedom in waveguide wiring for element-to-element connection and arrangement design of each element is possible. And the density of the optical integrated circuit can be increased.

According to the optical waveguide according to the second configuration of the present invention, in the optical waveguide composed of the core layer and the cladding layer, or the core layer, the cladding layer, and the metal cladding layer, a bent portion or a branch portion of the optical waveguide. The refractive index of the core layer at the center of the curvature, which is the direction in which the core layer can be bent, is
Since the refractive index is set to be larger than the refractive index outside the center of curvature, a curved optical waveguide having low loss and a small radius of curvature can be manufactured, miniaturization of each element in the optical integrated circuit becomes possible, and connection between elements can be performed. The degree of freedom in the layout design of the waveguide wiring and each element is increased, and the density of the optical integrated circuit can be increased.

According to the optical waveguide of the third configuration of the present invention, in the optical waveguide of the second configuration, at least one or more triangular high-refractive-index regions are provided in the core layer at the bent portion or the branch portion. To give the refractive index a distribution,
A curved optical waveguide having a low radius of curvature and a small radius of curvature can be manufactured, miniaturization of each element in an optical integrated circuit becomes possible, and flexibility in waveguide wiring for element-to-element connection and arrangement design of each element is increased. Thus, the density of the optical integrated circuit can be increased.

According to the optical waveguide of the fourth configuration of the present invention, in the optical waveguide composed of the core layer and the cladding layer, or the core layer, the cladding layer, and the metal cladding layer, the bent portion or the branched portion of the optical waveguide is used. In the core layer in
Since a refractive index distribution having a Gaussian distribution is provided along the bending direction and the peak position of the refractive index distribution is located closer to the center of curvature in the bending direction than the center of the core width, low loss is achieved. It is possible to produce a curved optical waveguide having a small radius of curvature and a branch optical waveguide having a large branch angle with a low loss, enabling miniaturization of each element in an optical integrated circuit, and a waveguide wiring and a wiring for connecting elements. The degree of freedom in element layout design is increased, and the density of the optical integrated circuit can be increased.

According to the optical waveguide of the fifth configuration of the present invention, an optical waveguide composed of a core layer and a clad layer, or an optical waveguide composed of a core layer, a clad layer, and a metal clad layer, has a different core width from the optical waveguide. In the optical waveguide in which the optical waveguide having a layer is bonded, a metal clad layer is provided on the side of the core layer of the bonding portion, and the bonding portion has a core structure having a stepped tapered shape. The connection loss between the fiber connector and the bent optical waveguide or the branched optical waveguide can be reduced.

According to the first manufacturing method of the present invention, when manufacturing an optical waveguide in which a metal clad layer is provided on the side of the core layer at the bent or branched portion of the optical waveguide, the metal clad layer is formed on the side of the core layer. Since the cladding layer surrounding the core layer and the metal cladding layer is formed at a temperature of 600 ° C. or less after the formation of the metal cladding layer, the metal cladding layer attached to the side surface of the core can be formed without being damaged by heat.

According to the second manufacturing method of the present invention, when manufacturing an optical waveguide in which a metal clad layer is provided on the side of the core layer of the bent or branched portion of the optical waveguide, the bent or branched portion of the optical waveguide is manufactured. Since a groove was formed along the side of the core and the groove was filled with metal, the metal clad layer was formed even when a film forming method at 600 ° C. or higher such as a thermal decomposition CVD method or a flame deposition method was used. A high-quality optical waveguide can be formed without being damaged by heat, and the loss of the optical waveguide can be reduced as compared with a film forming method at 600 ° C. or lower.

According to the third manufacturing method of the present invention, in an optical waveguide composed of a core layer and a clad layer, or a core layer, a clad layer, and a metal clad layer, the core in a bent portion or a branched portion of the optical waveguide is used. The layer is irradiated with ultraviolet light, and the refractive index of the core layer has a distribution, so that the core layer can easily have a refractive index distribution, and a low-loss, curved bend optical waveguide having a small radius of curvature and A branch optical waveguide having a low loss and a large branch angle can be easily manufactured.

According to the optical device according to the first configuration of the present invention, since the optical waveguide according to any one of the first to fifth configurations is used, an optical filter, an optical switch, an optical branching coupler, An optical device such as an optical multiplexer or an optical device such as a high-density optical integrated circuit obtained by integrating them can be manufactured.

[Brief description of the drawings]

FIG. 1 is a diagram showing an L-bent optical waveguide according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a film forming apparatus according to Embodiment 1 of the present invention.

FIG. 3 is a diagram showing a manufacturing process of the L-bent optical waveguide according to the first embodiment of the present invention.

FIG. 4 is a diagram showing another manufacturing process of the L-bent optical waveguide according to the first embodiment of the present invention.

FIG. 5 is a view showing still another manufacturing process of the L-bent optical waveguide according to the first embodiment of the present invention.

FIG. 6 is a diagram showing a T-branch optical waveguide according to a second embodiment of the present invention.

FIG. 7 is a diagram illustrating an L-bent optical waveguide according to a third embodiment of the present invention.

FIG. 8 is a configuration diagram showing a film forming apparatus according to a third embodiment of the present invention.

FIG. 9 is a diagram showing a manufacturing process of the L-bent optical waveguide according to the third embodiment of the present invention.

FIG. 10 is a diagram showing an L-bent optical waveguide according to a third embodiment of the present invention.

FIG. 11 is a diagram showing an L-bent optical waveguide according to a fifth embodiment of the present invention.

FIG. 12 is a diagram showing a coupling portion between a linear optical waveguide and an L-bent optical waveguide according to a fifth embodiment of the present invention.

FIG. 13 is a diagram showing a T-branch optical waveguide according to a sixth embodiment of the present invention.

FIG. 14 is a diagram showing a bent optical waveguide according to a seventh embodiment of the present invention.

FIG. 15 is a diagram showing a bent optical waveguide according to an eighth embodiment of the present invention.

FIG. 16 is a diagram showing a Y-branch optical waveguide according to a ninth embodiment of the present invention.

FIG. 17 is a diagram showing a bent optical waveguide according to a tenth embodiment of the present invention.

FIG. 18 is a diagram showing a bent optical waveguide according to an eleventh embodiment of the present invention.

FIG. 19 is a diagram showing a Y-branch optical waveguide according to a twelfth embodiment of the present invention.

FIG. 20 is a diagram illustrating a Mach-Zehnder optical filter according to a thirteenth embodiment of the present invention and a wavelength characteristic thereof.

FIG. 21 is a diagram showing an optical integrated circuit according to a fourteenth embodiment of the present invention.

FIG. 22 is a diagram illustrating a manufacturing process of the optical integrated circuit according to the fourteenth embodiment of the present invention.

FIG. 23 is a diagram illustrating a manufacturing process of the optical integrated circuit according to the fourteenth embodiment of the present invention;

FIG. 24 is a diagram illustrating a manufacturing process of the optical integrated circuit according to the fourteenth embodiment of the present invention;

FIG. 25 is a diagram showing a Mach-Zehnder type optical filter and a wavelength characteristic thereof according to a fifteenth embodiment of the present invention.

FIG. 26 is a diagram showing a Mach-Zehnder type optical switch according to a sixteenth embodiment of the present invention and its switching characteristics.

FIG. 27 is a diagram illustrating a Mach-Zehnder optical switch according to a seventeenth embodiment of the present invention and its switching characteristics.

FIG. 28 is a diagram showing an optical power distributor according to Embodiment 18 of the present invention.

FIG. 29 is a diagram showing an optical power distributor according to a nineteenth embodiment of the present invention.

FIG. 30 is a diagram showing a conventional curved optical waveguide and a Y-branch optical waveguide.

FIG. 31 is a view showing a conventional metal mirror for bending an optical path vertically.

FIG. 32 is a diagram showing design values of an L-bent optical waveguide and a T-branch optical waveguide having a metal cladding layer.

[Description of Signs] 1 Substrate, 2 Lower cladding layer, 3 Core layer, 4 Metal cladding layer, 5 Upper cladding layer, 6 Carrier gas inlet, 7 Flow controller, 8 Material container, 9 Reaction tube, 10
Oxygen gas inlet, 11 ozonizer, 12 outlet,
13 core film, 14 chromium mask, 15 photoresist, 16 hydrogen gas, 17 burner, 18 turntable, 19 high refractive index region, 20, 21, 22, 23
Port, 24a, 24b coupler, 25 grating, 26 electrodes, 70 n-type compound semiconductor substrate, 7
1, 72, 73, 80, 90 semiconductor layer, 74 p-type semiconductor layer, 75 semiconductor laser electrode, 76 semiconductor amplifier electrode, 77 electrode, 78 diffraction grating, 81 current blocking layer.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshishin Kiyoshi 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Inside Mitsui Electric Co., Ltd. (72) Katsuhiro Imada 2-2-2 Marunouchi, Chiyoda-ku, Tokyo No. 3 Inside Mitsubishi Electric Co., Ltd. (72) Inventor Gen Takeya 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Co., Ltd. (72) Hideko Uchikawa 2-3-2 Marunouchi, Chiyoda-ku, Tokyo No. Mitsubishi Electric Corporation (72) Inventor Masayuki Izutsu 4-2-1 Nukikitamachi, Koganei-shi, Tokyo F-term in the Communications Research Laboratory, Ministry of Posts and Telecommunications (reference) 2H047 KA04 KA12 KA13 LA03 LA12 LA19 PA04 PA05 PA06 PA11 PA22 PA24 QA01 QA02 QA04 QA07 TA05 TA32 TA36 TA43

Claims (9)

[Claims] In an optical waveguide comprising a core layer and a cladding layer, a metal cladding layer is provided on a side surface of a core layer at a bent portion or a branch portion of the optical waveguide, and a waveguide material other than the metal cladding layer is provided. An optical waveguide comprising a quartz-based material, wherein at least one of a wave impedance matching circuit and a mode filter that preserves a mode is provided in the bent portion or the branch portion. 2. An optical waveguide comprising a core layer and a clad layer, or a core layer, a clad layer, and a metal clad layer, wherein the refractive index of the core layer at a bent portion or a branch portion of the optical waveguide is determined by a direction in which the core layer can be bent. An optical waveguide characterized in that the refractive index at the center of curvature is larger than the refractive index outside the center of curvature. 3. The optical waveguide according to claim 2, wherein at least one or more triangular high-refractive-index regions are provided in the core layer at the bent portion or the branch portion of the optical waveguide so that the refractive index is distributed. An optical waveguide characterized in that: 4. An optical waveguide comprising a core layer and a cladding layer, or a core layer, a cladding layer, and a metal cladding layer, wherein the core layer at a bent portion or a branch portion of the optical waveguide has a gauss along a bending direction. An optical waveguide having a distributed refractive index distribution, wherein the peak position of the refractive index distribution is located closer to the center of curvature in the bending direction than the center of the core width. 5. An optical waveguide in which an optical waveguide composed of a core layer and a clad layer, or an optical waveguide composed of a core layer, a clad layer, and a metal clad layer, and an optical waveguide having a core layer different in width from the optical waveguide are joined. In, while providing a metal clad layer on the side of the core layer of the joint, the above-mentioned joint,
An optical waveguide having a stepped tapered core structure. 6. An optical waveguide comprising a core layer and a cladding layer, wherein a metal cladding layer is provided on the side of the core layer at a bent portion or a branch portion of the optical waveguide, and a waveguide material other than the metal cladding layer is formed of a quartz-based material. In the method for manufacturing an optical waveguide, after providing the metal clad layer on the side surface of the core layer, the clad layer surrounding the core layer and the metal clad layer is formed at a temperature of 600 ° C. or less. Production method. 7. An optical waveguide comprising a core layer and a cladding layer, a metal cladding layer is provided on a side of the core layer at a bent portion or a branch portion, and a waveguide material other than the metal cladding layer is made of a quartz-based material. In the method for manufacturing an optical waveguide, the metal clad layer is formed by forming a groove along a side surface of a core at a bent portion or a branch portion of the optical waveguide, and filling the groove with a metal. Manufacturing method of optical waveguide. 8. An optical waveguide comprising a core layer and a clad layer, or a core layer, a clad layer, and a metal clad layer, wherein the core layer at a bent portion or a branch portion of the optical waveguide is irradiated with ultraviolet light. A method for manufacturing an optical waveguide, characterized in that the refractive index of a layer has a distribution. 9. An optical device using the optical waveguide according to claim 1. Description: