JP2012198274A - Optical device and optical modulator - Google Patents

Abstract

An optical device having a plurality of resonance wavelengths is provided.
An optical device disclosed in the present specification includes a core layer that propagates light, a resonance portion that resonates light propagating through the core layer, and a width that varies along the core layer. And a resonant wavelength modulation layer 16 that extends while extending. The resonating unit 14 includes diffraction gratings 13 provided on both sides in the longitudinal direction of the core layer 12 or a plurality of ring optical waveguides 17 arranged so as to be coupled with light propagating through the core layer 12. The resonant wavelength modulation layer 16 changes the resonant wavelength in the light propagation direction of the core layer 12.
[Selection] Figure 3

Description

  The present invention relates to an optical device and an optical modulator.

  Conventionally, an optical resonator is used to change the amplitude or phase of light or to accumulate and delay light.

  Such an optical resonator has a predetermined resonance wavelength, and resonates light having a wavelength that matches the resonance wavelength.

  On the other hand, when the temperature around the optical resonator changes, the wavelength of the input light input to the optical resonator may shift. Thus, if the wavelength of the input light changes and does not coincide with the resonance wavelength of the optical resonator, the optical resonator may not be able to sufficiently resonate the input light. Therefore, the optical resonator is required to have a predetermined width with respect to the resonance frequency.

  In some cases, it is desired to resonate input light having different wavelengths using a single optical resonator. In such a case, the optical resonator is required to have a resonance frequency corresponding to each wavelength of the input light.

  As described above, an optical resonator for resonating input lights having different wavelengths has been proposed.

  FIG. 1A is a plan view showing an optical resonator according to a conventional example, and FIG. 1B is a cross-sectional view taken along line X1-X1 in FIG.

  1A and 1B includes an optical resonator 110 having a core layer 112 that propagates light and diffraction gratings 113 provided on both sides of the core layer 112 in the longitudinal direction, A clad layer 115 surrounding the periphery of the resonance part 114. The optical resonator 110 includes a substrate 111 on which a resonance part 114 and a cladding layer 115 are stacked.

  In the diffraction grating 113, the grating interval increases from the input side end to the output side end, and can resonate each input light having a different wavelength corresponding to the period of the grating interval. .

  For example, the input light Pi having the wavelength λ1 input to the optical resonator 110 is resonated at the portion of the diffraction grating having a grating interval that resonates with the wavelength λ1 while propagating through the core layer 112, and then output as the output light Po. Is done.

  Similarly, the input light Pi having a wavelength λ2 different from the wavelength λ1 is output as output light Po after being resonated at the portion of the diffraction grating having a grating interval resonating with the wavelength λ2 while propagating through the core layer 112. The

  2A is a plan view showing an optical resonator according to another conventional example, and FIG. 2B is a cross-sectional view taken along line X2-X2 in FIG. 2A.

  The optical resonator 110 shown in FIGS. 2A and 2B includes a core layer 112 that propagates light, and a plurality of rings that are arranged along the core layer 112 so as to be coupled with light that propagates through the core layer 112. A resonating unit 114 having a type optical waveguide 117 is provided. The optical resonator 110 includes a clad layer 115 surrounding the resonating unit 114 and a substrate 111 on which the resonating unit 114 and the clad layer 115 are stacked.

  The plurality of ring-type optical waveguides 117 have a ring diameter that increases from the input side end to the output side end so that light having different wavelengths can resonate according to the circumference of the ring. It has become.

  For example, the input light Pi having the wavelength λ1 input to the optical resonator 110 is resonated at the portion of the ring optical waveguide having a diameter that resonates with the wavelength λ1 while propagating through the core layer 112, and then output as the output light Po. Is output.

  Similarly, the input light Pi having a wavelength λ2 different from the wavelength λ1 propagates through the core layer 112 and is resonated at the portion of the ring optical waveguide having a diameter resonating with the wavelength λ1, and then output as the output light Po. Is done.

JP 2002-14307 A

  By the way, in the above-described optical resonator, for example, when resonating light having different resonance wavelengths by 1 nm, it is required to form a change in the lattice spacing or the diameter of the ring optical waveguide on the order of sub-nanometers.

  On the other hand, since it is difficult to process a structure changing on the order of sub-nanometers using photolithography or electron beam drawing, it is difficult to form an optical resonator having a plurality of resonance wavelengths as described above. Therefore, there is a possibility that an optical device with stable quality cannot be manufactured.

  An object of the present specification is to provide an optical device and an optical modulator that can solve the above-described problems.

  According to an aspect of the optical device disclosed in the present specification, the optical device has a core layer that propagates light, and resonates the light that propagates through the core layer, and the width changes along the core layer. An extending resonant wavelength modulation layer.

  Further, according to one mode of the optical device disclosed in the present specification, the core layer, the plurality of ring optical waveguides disposed along the core layer, and the plurality of ring optical waveguides are disposed on the core layer. A resonance wavelength modulation layer, a plurality of the ring-type optical waveguides and a cladding layer disposed between the resonance wavelength modulation layers, and the ring-type optical waveguides adjacent to each other, The ratio of the length of the portion of the optical waveguide covered with the resonant wavelength modulation layer is different.

  Moreover, according to one form of the optical modulator disclosed in this specification, the optical modulator includes a first optical waveguide having a core layer that propagates light, and a second optical waveguide having a core layer that propagates light, The first optical waveguide or the second optical waveguide resonates light propagating through the core layer, and extends along the core layer while changing in width. The resonance of the resonant unit in the direction of light propagation And a resonant wavelength modulation layer for changing the wavelength.

  Furthermore, according to one mode of the optical modulator disclosed in the present specification, the optical modulator includes a first optical waveguide having a core layer through which light propagates, and a second optical waveguide having a core layer through which light propagates, The first optical waveguide or the second optical waveguide includes a plurality of ring-type optical waveguides arranged along the core layer, a plurality of resonant wavelength modulation layers arranged on the plurality of ring-type waveguides, and a plurality of the above-mentioned A cladding layer disposed between the ring-type optical waveguide and the resonance wavelength modulation layer, and the adjacent ring-type optical waveguides are covered with the resonance wavelength modulation layer with respect to the entire length of the optical waveguide. The ratio of the length of the portion of the optical waveguide is different.

  According to one mode of the optical device disclosed in the present specification described above, the optical device has a plurality of resonance wavelengths.

  Moreover, according to one form of the optical modulator disclosed in this specification, the resonance unit has a plurality of resonance wavelengths.

  The objects and advantages of the invention will be realized and obtained by means of the elements and combinations particularly pointed out in the appended claims.

  Both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention as claimed.

(A) is a top view which shows the optical resonator by a prior art example, (B) is X1-X1 sectional view taken on the line of (A). (A) is a top view which shows the optical resonator by other conventional examples, (B) is X2-X2 sectional view taken on the line of (A). (A) is a top view which shows 1st Embodiment of the optical device disclosed by this specification, (B) is the X3-X3 sectional view taken on the line of (A). (A) is a figure which shows the relationship between the equivalent phase refractive index in a resonance part, and the position of the propagation direction of light, (B) shows the relationship between the resonance wavelength in a resonance part, and the position of the propagation direction of light. FIG. FIG. 6 is an electric field intensity distribution diagram in a direction perpendicular to a light propagation direction of light in a waveguide mode of light propagating through a core layer of an optical device. (A) is a figure which shows the modification 1 of the optical device of 1st Embodiment, (B) is a figure which shows the modification 2 of the optical device of 1st Embodiment, (C) It is a figure which shows the modification 3 of the optical device of 1 embodiment. (A) is a top view which shows 2nd Embodiment of the optical device disclosed by this specification, (B) is the X4-X4 sectional view taken on the line of (A). It is a figure which shows the modification of the optical device of 2nd Embodiment. (A) is a figure (the 1) which shows 1st Embodiment of the manufacturing method of the optical device disclosed to this specification, (B) is the X5-X5 sectional view taken on the line of (A). (A) is a figure (the 2) which shows 1st Embodiment of the manufacturing method of the optical device disclosed to this specification, (B) is the X6-X6 sectional view taken on the line of (A). (A) is a figure (the 3) which shows 1st Embodiment of the manufacturing method of the optical device disclosed to this specification, (B) is X7-X7 sectional view taken on the line of (A). (A) is a figure (the 4) which shows 1st Embodiment of the manufacturing method of the optical device disclosed to this specification, (B) is X8-X8 sectional view taken on the line of (A). (A) is a figure (the 1) which shows 2nd Embodiment of the manufacturing method of the optical device disclosed to this specification, (B) is the X9-X9 sectional view taken on the line of (A). (A) is a figure (the 2) which shows 2nd Embodiment of the manufacturing method of the optical device disclosed to this specification, (B) is X10-X10 sectional view taken on the line of (A). (A) is a figure (the 3) which shows 2nd Embodiment of the manufacturing method of the optical device disclosed to this specification, (B) is the X11-X11 sectional view taken on the line of (A). (A) is a figure (the 4) which shows 2nd Embodiment of the manufacturing method of the optical device disclosed to this specification, (B) is X12-X12 sectional view taken on the line of (A). (A) is a figure which shows 1st Embodiment of the optical modulator disclosed by this specification, (B) is a figure which shows 2nd Embodiment of the optical modulator disclosed by this specification.

  Hereinafter, a first preferred embodiment of an optical device disclosed in this specification will be described with reference to the drawings. However, the technical scope of the present invention is not limited to these embodiments, but extends to the invention described in the claims and equivalents thereof.

  FIG. 3A is a plan view showing a first embodiment of the optical device disclosed in this specification, and FIG. 3B is a cross-sectional view taken along line X3-X3 in FIG.

  The optical device 10 according to this embodiment includes a vertically long core layer 12 that propagates input light Pi, and a resonance unit 14 that resonates light propagating through the core layer 12 and a cladding layer that surrounds the resonance unit 14. 15 and a resonant wavelength modulation layer 16 extending while changing in width along the longitudinal direction of the core layer 12. The optical device 10 includes a substrate 11 on which the resonance unit 14 and the cladding layer 15 are stacked. The longitudinal direction of the core layer 12 coincides with the direction in which light propagates through the optical device 10.

  In the optical device 10, since the resonance wavelength of the resonance unit 14 in the direction in which light propagates changes, the input light Pi having a wavelength within a predetermined band can be resonated. That is, the optical device 10 can resonate the input lights λ1 and λ2 having different wavelengths.

  For example, the optical device 10 can be used as an optical delay device that accumulates light by causing the input light Pi to resonate and delays the transmission of light. The optical device 10 can be used as a dispersion compensator that changes the delay time of light by resonating the input light Pi.

  Similar to the core layer 12, the resonating unit 14 has a vertically long shape. The resonance unit 14 includes diffraction gratings 13 provided on both sides of the core layer 12 in the longitudinal direction. The core layer 12 and the diffraction grating 13 are integrally formed. The core layer 12 extends over both ends of the optical device 10 in the longitudinal direction, propagates the input light Pi input from the input side end, and converts the resonated light as output light Po from the output side end. Output.

  The diffraction grating 13 is disposed so as to face both sides in the longitudinal direction of the core layer 12 at the same grating interval, that is, at the same period, and resonates light having a wavelength corresponding to the period of the grating interval.

  Since the diffraction grating 13 of the optical device 10 is formed with the same grating interval, it can be formed using a conventional semiconductor manufacturing technique such as photolithography or electron beam drawing.

  The cladding layer 15 has a function of confining light propagating through the core layer 12 inside the core layer 12. From this point of view, the phase refractive index of the cladding layer 15 is preferably smaller than the phase refractive index of the core layer 12.

  The phase refractive index is a refractive index that affects the phase speed of light, and is a value obtained by dividing the speed of light in vacuum by the speed of light (phase speed) in a substance.

  As shown in FIG. 3A, the resonance wavelength modulation layer 16 is arranged in a region where the diffraction grating 13 is provided in the longitudinal direction of the resonance portion 14 (X direction in FIG. 3A), and is vertically long. It has the shape of In addition, as shown in FIG. 3B, the resonance wavelength modulation layer 16 is disposed on the resonance portion 15 via the cladding layer 15.

  The width W of the resonant wavelength modulation layer 16 changes linearly in the direction in which light propagates. Specifically, the width W of the resonant wavelength modulation layer 16 increases linearly as the light propagation direction X increases. The center in the width direction of the resonant wavelength modulation layer 16 is preferably disposed on the cladding layer 15 so as to coincide with the center in the width direction of the core layer 12. The resonant wavelength modulation layer 16 preferably has a symmetrical shape with respect to the center line in the width direction. In the optical device 10, the resonant wavelength modulation layer 16 has an isosceles triangular shape, and the direction of the base is orthogonal to the longitudinal direction X of the core layer 12.

  The resonant wavelength modulation layer 16 of the optical device 10 can be formed using conventional semiconductor manufacturing techniques such as photolithography or electron beam drawing.

  Here, the resonance wavelength of the part where the diffraction grating 13 of the resonance part 14 is formed is expressed by the following equation (1).

  λm = 2neΛ / m (1)

  Here, ne is the equivalent phase refractive index of the core layer 12, Λ is the period of the diffraction grating 13, and m is the order of the diffraction grating.

  The equivalent phase refractive index ne is influenced by the phase refractive index of the resonant wavelength modulation layer 16 together with the phase refractive index of the core layer 12 and the phase refractive index of 15 of the cladding layer. Since the width W of the core layer 12 covered with the resonant wavelength modulation layer 16 changes in the light propagation direction X, the equivalent phase refractive index ne is equal to the region where the resonant wavelength modulation layer 16 is disposed. , And changes in the light propagation direction X.

  FIG. 4A is a diagram showing the relationship between the equivalent phase refractive index and the position in the light propagation direction in the resonance part. FIG. 4B is a diagram showing the relationship between the resonance wavelength and the position in the light propagation direction in the resonance part.

  The equivalent phase refractive index ne in the resonance unit 14 increases as the width W of the resonance wavelength modulation layer 16 increases. And the resonance wavelength in the resonance part 14 increases with the increase in equivalent phase refractive index ne from the relationship shown in Formula (1). That is, the resonance wavelength in the resonance unit 14 increases along the core layer 12.

  Thus, the optical device 10 has a resonance wavelength band with a predetermined width, and can resonate light having a wavelength included in this band.

  For example, the input light Pi having the wavelength λ <b> 1 input to the optical resonator 10 is propagated through the core layer 12 at the diffraction grating portion at the position of the width of the resonant wavelength modulation layer 16 having the resonant wavelength that resonates with the wavelength λ <b> 1. After being resonated, it is output as output light Po.

  Similarly, the input light Pi having a wavelength λ2 different from the wavelength λ1 resonates at the diffraction grating portion at the position of the width of the resonant wavelength modulation layer 16 having a resonant wavelength that resonates with the wavelength λ2 while propagating through the core layer 12. Is output as output light Po.

  FIG. 5 is an electric field intensity distribution diagram in a direction perpendicular to the propagation direction of light in the waveguide mode of light propagating through the core layer of the optical device.

  The electric field intensity of the waveguide mode of light propagating through the core layer 12 has a distribution as shown in FIG. 5 in the direction Z (see FIG. 3B) perpendicular to the light propagation direction X. . The zero position on the horizontal axis Z in FIG. 5 corresponds to the center of the core layer 12.

  The electric field intensity in the waveguide mode is distributed to the cladding layer 15 and the resonance wavelength modulation layer 16 beyond the core layer 12 in the Z direction. Thus, since the electric field intensity of the waveguide mode is distributed over the resonance wavelength modulation layer 16, the influence of the phase refractive index of the resonance wavelength modulation layer 16 is exerted on the equivalent phase refractive index ne. become.

  When the distance between the resonant wavelength modulation layer 16 and the core layer 15 is short, the influence of the phase refractive index of the resonant wavelength modulation layer 16 on the equivalent phase refractive index ne increases. Then, as the distance between the resonance wavelength modulation layer 16 and the core layer 15 is closer, the change width of the resonance wavelength is greatly changed with respect to the change of the width W of the resonance wavelength modulation layer 16. In such a case, in order to obtain a resonance wavelength band having an accurate width, the change rate of the resonance wavelength is reduced by reducing the rate of change of the width W of the resonance wavelength modulation layer 16 in the longitudinal direction X of the core layer. It may be required to be small. However, reducing the change rate of the width W of the resonant wavelength modulation layer 16, that is, reducing the slopes of the two hypotenuses of the resonant wavelength modulation layer 16 is a sub-nanometer in manufacturing the resonant wavelength modulation layer 16. It may be required to produce a structure that changes on the order of.

  Therefore, in order to obtain a resonance wavelength band of a predetermined width, the distance between the resonance wavelength modulation layer 16 and the core layer 15 should be separated to such an extent that the resonance wavelength modulation layer 16 can be manufactured. preferable.

  From this point of view, the resonant wavelength modulation layer 16 is arranged in the tail portion (see FIG. 5) of the electric field intensity distribution C in the direction Z perpendicular to the propagation direction X of the waveguide mode of light propagating through the core layer 12. It is preferred that Here, the tail portion of the electric field intensity distribution C is a position where the sign of the second derivative changes with respect to the distance in the direction Z perpendicular to the propagation direction X of the electric field intensity of the waveguide mode of light propagating through the core layer 12. The portion W is located on the opposite side of the core layer 12 with respect to P. The position P is an inflection point of the electric field strength. More specifically, since the electric field intensity distribution C extends from the core layer 12 to the substrate 11 side and the resonance wavelength modulation layer 16 side, the portion W is a region opposite to the substrate 11 with respect to the position P. It is in.

  On the other hand, when the distance between the resonant wavelength modulation layer 16 and the core layer 15 is increased, the influence of the phase refractive index of the resonant wavelength modulation layer 16 on the equivalent phase refractive index ne is reduced. As the distance between the resonance wavelength modulation layer 16 and the core layer 15 increases, the change width of the resonance wavelength decreases with respect to the change in the width W of the resonance wavelength modulation layer 16. Accordingly, if the distance between the resonant wavelength modulation layer 16 and the core layer 15 is too large, the change width of the resonance wavelength becomes small with respect to the change in the width W of the resonant wavelength modulation layer 16, There is a possibility that a resonance wavelength band having a width cannot be obtained.

  Therefore, in order to obtain a resonance wavelength band of a predetermined width, the distance between the resonance wavelength modulation layer 16 and the core layer 15 is such that the influence of the phase refractive index of the resonance wavelength modulation layer 16 on the equivalent phase refractive index ne is small. It is preferable that it is not too much.

  From this point of view, the position of the resonant wavelength modulation layer 16 in the Z direction is such that the electric field intensity value is 1/10000 or more and 1/10 or less with respect to the peak value of the electric field intensity distribution C. It is preferably arranged in the region V (refer to FIG. 5) having a value of 1/1000 or more and 1/100 or less, and further having an electric field strength value of 1/500 or more and 1/200 or less.

  For example, when the resonance unit 14 and the resonance wavelength modulation layer 16 are formed using silicon and the cladding layer is formed using silicon oxide, the distance between the resonance wavelength modulation layer 16 and the core layer 15 is From the viewpoint described above, it is preferably 50 nm to 500 nm, particularly 150 nm to 300 nm, more preferably 175 nm to 225 nm. In this way, the optical device 10 can obtain, for example, a range of 1 nm to 20 nm as the resonance wavelength band.

  Next, the relationship between the phase refractive index of the resonant wavelength modulation layer 16 and the phase refractive indexes of the core layer 12 and the cladding layer 15 will be described below.

  When the phase refractive index of the resonant wavelength modulation layer 16 is larger than the phase refractive index of the core layer 12, the light propagating through the core layer 12 moves toward the resonant wavelength modulation layer 16, and thus propagates through the core layer 12. There is a risk that the light to be reduced.

  From such a viewpoint, it is preferable that the phase refractive index of the resonant wavelength modulation layer 16 is the same as or smaller than the phase refractive index of the core layer 12. In particular, if the phase refractive index of the resonant wavelength modulation layer 16 is set to the same value as the phase refractive index of the core layer 12, there is an advantage that the optical characteristics of the optical device 10 can be easily designed. Further, if the phase refractive index of the resonant wavelength modulation layer 16 is too small than the phase refractive index of the core layer 12, the influence of the resonant wavelength modulation layer 16 on the equivalent phase refractive index ne may be reduced.

  The phase refractive index ne of the resonant wavelength modulation layer 16 is preferably larger than the phase refractive index of the cladding layer 15. On the other hand, when the phase refractive index ne of the resonant wavelength modulation layer 16 is smaller than that of the cladding layer 15, the influence of the resonant wavelength modulation layer 16 on the equivalent phase refractive index ne is reduced.

  The thickness of the resonant wavelength modulation layer 16 is preferably smaller than the thickness of the core layer 12, although it depends on the magnitude of the phase refractive index of the resonant wavelength modulation layer 16. If the thickness of the resonant wavelength modulation layer 16 is thicker than that of the core layer 12, the light propagating through the core layer 12 moves toward the resonant wavelength modulation layer 16, so that the light propagating through the core layer 12 decreases. This is because there is a fear.

  When the phase refractive index of the resonant wavelength modulation layer 16 is large, the equivalent phase refractive index ne can be changed even if the resonant wavelength modulation layer 16 is thin. On the other hand, when the phase refractive index of the resonant wavelength modulation layer 16 is small, the equivalent phase refractive index ne may not be changed sufficiently unless the resonant wavelength modulation layer 16 is thickened.

  The above is the description of the relationship between the phase refractive index of the resonant wavelength modulation layer 16 and the phase refractive indexes of the core layer 12 and the cladding layer 15.

  The optical device 10 is designed so as to obtain a desired resonance wavelength band in consideration of the above viewpoint. For example, when the lower limit value λ1 and the upper limit value λ2 of the wavelength to be resonated by the optical device 10 are determined, the corresponding equivalent phase refractive indexes n1 and n2 are determined using the equation (1). Then, the widths W1 and W2 of the resonant wavelength modulation layer 16 from which the equivalent phase refractive indexes n1 and n2 are obtained are determined, and the dimensions of the resonant wavelength modulation layer 16 are designed to include these widths W1 and W2. . Note that the slope of the oblique side of the resonant wavelength modulation layer 16 can also be determined by the longitudinal dimension of the resonant wavelength modulation layer 16 or the optical device 10.

  As a material for forming the optical device 10, a compound semiconductor, silicon, or an oxide thereof can be used. In particular, when the optical device 10 is formed using silicon or an oxide thereof, a plurality of optical devices can be manufactured on a silicon substrate using a conventional silicon semiconductor manufacturing technique, and other silicon can be manufactured. There is an advantage that it is easy to manufacture in combination with a semiconductor element.

  According to the optical device 10 of the present embodiment described above, since the resonance wavelength of the resonance unit in the direction in which light propagates can be changed, each light having a different wavelength can resonate.

  Further, since the optical device 10 can process the diffraction grating 13 and the resonant wavelength modulation layer 16 using a semiconductor manufacturing technology such as conventional photolithography or electron beam drawing, an optical device with stable quality can be obtained. It can be manufactured.

  Next, modifications 1 to 3 of the optical device of the first embodiment described above will be described below with reference to the drawings.

  FIG. 6A is a diagram illustrating a first modification of the optical device according to the first embodiment.

  In the optical device 10 of Modification 1, the shape of the resonant wavelength modulation layer 16 is different from that of the first embodiment described above.

  In the present modification, the width W of the resonant wavelength modulation layer 16 changes nonlinearly in the longitudinal direction of the core layer 12. Specifically, the shape of the hypotenuse of the resonant wavelength modulation layer, which was the shape of an isosceles triangle in the first embodiment, is a shape that is convexly convex inward in the width direction.

  Thus, the width W of the resonant wavelength modulation layer 16 may change, for example, in a parabolic shape or a hyperbolic shape in the longitudinal direction of the core layer 12. Further, the width W of the resonant wavelength modulation layer 16 may change so as to be convexly curved outward in the width direction.

  FIG. 6B is a diagram illustrating Modification Example 2 of the optical device according to the first embodiment.

  In this modification, the width W of the resonant wavelength modulation layer 16 decreases and then increases again in the longitudinal direction of the core layer 12.

  Specifically, the resonant wavelength modulation layer 16 has a shape in which two isosceles triangles face each other at the apex angle. That is, the width W of the resonant wavelength modulation layer 16 decreases linearly in the longitudinal direction of the core layer 12 to zero, and then increases linearly again.

  FIG. 6C is a diagram illustrating a third modification of the optical device according to the first embodiment. FIG. 6C is a cross-sectional view corresponding to FIG.

  In this modification, a groove 15 a is formed in the upper part of the cladding layer 15, and the groove 15 a part is the resonance wavelength modulation layer 16. The resonant wavelength modulation layer 16 is filled with, for example, air, and the phase refractive index of the resonant wavelength modulation layer 16 becomes the phase refractive index of air.

  The groove 15a may be filled with a material other than air to form the resonance wavelength modulation layer 16.

  In the first embodiment and the modification described above, the diffraction grating 13 is provided on both sides of the core layer 12 in the longitudinal direction. However, the diffraction grating 13 is located on the resonance wavelength modulation layer 16 side of the core layer 12. It may be provided on the surface and the surface on the substrate 11 side.

  Next, a second embodiment of the above-described optical device will be described below with reference to FIGS. 7 (A) and (B). For points that are not particularly described in the second embodiment, the description in detail regarding the first embodiment is applied as appropriate. Moreover, the same code | symbol is attached | subjected to the same component.

  FIG. 7A is a plan view showing a second embodiment of the optical device disclosed in this specification, and FIG. 7B is a cross-sectional view taken along line X4-X4 of FIG.

  In the optical device 10 of the present embodiment, the resonating unit 14 includes the core layer 12 and a plurality of ring-type optical waveguides 17 arranged so as to be coupled with light propagating along the core layer 12 along the core layer 12. . The optical device 10 also includes a resonant wavelength modulation layer 16 disposed on the plurality of ring optical waveguides 17.

  As shown in FIG. 7B, the core layer 12 and the plurality of ring type optical waveguides 17 are embedded in the cladding layer 15, and between the plurality of ring type optical waveguides 17 and the resonant wavelength modulation layer 16. A cladding layer 16 is disposed.

  The present embodiment is different from the first embodiment described above in that the resonating unit 14 has a plurality of ring optical waveguides 17 instead of a diffraction grating.

  The plurality of ring-type optical waveguides 17 are spaced apart so as not to be optically coupled to each other. Each ring optical waveguide 17 has the same dimensions. The ring-type optical waveguide 17 only needs to have a closed optical waveguide shape. In the example shown in FIG. 7A, the ring optical waveguide 17 has a circular shape.

  As shown in FIG. 7A, the width W of the resonant wavelength modulation layer 16 changes linearly in the direction in which light propagates. The resonance wavelength modulation layer 16 is disposed so as to cover all the ring type optical waveguides 17 in the longitudinal direction of the resonance part 14 (X direction in FIG. 7A), and has a vertically long shape. Yes. The center in the width direction of the resonant wavelength modulation layer 16 is preferably disposed on the cladding layer 15 so as to coincide with the center in the width direction of each of the plurality of ring type optical waveguides 17.

  Adjacent ring optical waveguides 17 are different in the ratio of the length of the portion of the optical waveguide covered with the resonant wavelength modulation layer 16 to the entire length of each ring optical waveguide 17.

  More specifically, in the example shown in FIG. 7A, five ring-type optical waveguides 17 are arranged along the core layer 12, and each part of the optical waveguide is covered with the resonant wavelength modulation layer 16. Are shown as S1, S2, S3, S4 and S5 in order from the left. As described above, the circumferences of the five ring optical waveguides 17 are the same.

  The ratio of the length of the portion S1 of the ring optical waveguide 17 positioned first from the left side to the circumference of the ring optical waveguide 17 is the ratio of the portion S2 of the adjacent ring optical waveguide 17 The ratio of the length to the circumference of the ring optical waveguide 17 is different. That is, the length of the portion S1 is different from the length of the portion S2, and the length of the portion S2 is longer.

  Similarly, the ratio of the length of the portion S2 of the ring-shaped optical waveguide 17 located second from the left side to the circumferential length of the ring-shaped optical waveguide 17 is the portion S3 of the adjacent ring-shaped optical waveguide 17 Is different from the ratio of the length of the ring type optical waveguide 17 to the circumference of the ring type optical waveguide 17. That is, the length of the portion S2 is different from the length of the portion S3, and the length of the portion S3 is longer.

  Similarly, the length of the portion S3 and the length of the portion S4 are different, the length of the portion S4 and the length of the portion S4 are different, and the length becomes longer in the order of S3, S4, and S5. Yes.

  As described above, in the optical device 10, the lengths of the ring-type optical waveguides 17 covered with the resonant wavelength modulation layer 16 are different from each other. The ratio of the length of the covered optical waveguide portion is different.

  Here, the resonance wavelength of the portion of the resonance unit 14 where the ring optical waveguide 17 is formed is expressed by the following equation (2).

  λm = nae2πR / m (2)

  Here, nae is the average equivalent phase refractive index of the ring optical waveguide 17, R is the radius of the ring optical waveguide 17, and m is the order of the diffraction grating.

  The equivalent phase refractive index of the ring-type optical waveguide 17 is, together with the phase refractive index of the ring-type optical waveguide 17 and the phase refractive index of 15 of the cladding layer, in the portion covered with the resonant wavelength modulation layer 16. It is influenced by the phase refractive index. On the other hand, the equivalent phase refractive index of the ring type optical waveguide 17 is affected only by the phase refractive index of the ring type optical waveguide 17 and the cladding layer 15 in the portion not covered with the resonant wavelength modulation layer 16. The average equivalent phase refractive index nae of the ring type optical waveguide 17 includes an equivalent phase refractive index of a portion covered with the resonant wavelength modulation layer 16 and an equivalent phase refractive index of a portion not covered with the resonant wavelength modulation layer 16. The averaged equivalent phase refractive index is obtained. In each ring-type optical waveguide 17, the lengths of the optical waveguide portions S 1, S 2, S 3, S 4, and S 5 covered with the resonance wavelength modulation layer 16 are different. The influence of the modulation layer 16 on the equivalent phase refractive index is different. Therefore, the average equivalent phase refractive index nae of each ring type optical waveguide 17 is also different.

  The average equivalent phase refractive index nae in the ring type optical waveguide 17 increases as the lengths of the portions S1, S2, S3, S4, and S5 of the optical waveguide covered with the resonant wavelength modulation layer 16 increase. And the resonance wavelength in the resonance part 14 increases with the increase in average equivalent phase refractive index nae from the relationship shown in Formula (2).

  Thus, the optical device 10 has a resonance wavelength band with a predetermined width, and can resonate light having a wavelength included in this band.

  For example, the input light Pi having the wavelength λ1 input to the optical resonator 10 is resonated at the portion of the ring optical waveguide 17 having the resonance wavelength that resonates with the wavelength λ1 while propagating through the core layer 12, and then the output light. Output as Po.

  Similarly, the input light Pi having a wavelength λ2 different from the wavelength λ1 is resonated at the portion of the ring optical waveguide 17 having a resonance wavelength that resonates with the wavelength λ2 while propagating through the core layer 12, and then the output light Po. Is output as

  In the example shown in FIG. 7A, the optical device 10 has five ring-type optical waveguides, but the number and radius of the ring-type optical waveguides are appropriately set according to the wavelength band to be resonated. Can do.

  According to the optical device 10 of the present embodiment described above, the same effects as the optical device of the first embodiment are exhibited.

  Next, a modification of the optical device of the second embodiment described above will be described below with reference to the drawings.

  FIG. 8 is a diagram illustrating a modification of the optical device according to the second embodiment.

  In the optical device 10 of this modification, the ring optical waveguide 17 has a racetrack shape, and is optically coupled to the core layer 12 at the linear optical waveguide portion. Thus, when optically coupling with the core layer 12 in the linear optical waveguide portion, there is an advantage that the coupling efficiency can be increased even if the distance between the core layer 12 and the ring optical waveguide 17 is increased. is there.

  Next, a preferred first embodiment of the above-described optical device manufacturing method will be described below with reference to the drawings.

  First, as shown in FIGS. 9A and 9B, a substrate 30 having a support layer 31, an insulating layer 32, and a semiconductor layer 33 is prepared. In the present embodiment, an SOI (Silicon on Insulator) substrate is used as the substrate 30. The support layer 31 is a silicon substrate, the insulating layer is a silicon oxide layer, and the semiconductor layer 33 is a single crystal silicon layer. The thickness of the semiconductor layer 33 can be set to 220 nm, for example.

  The substrate 30 may be prepared by forming the insulating layer 32 and the semiconductor layer 33 on the support layer 31 instead of using an SOI substrate.

  Next, as shown in FIGS. 10A and 10B, the semiconductor layer 33 is patterned to form the resonance part 14 having the core layer 12 and the diffraction grating 13. As the patterning, an electron beam drawing method and a dry etching method can be used. The width of the core layer can be set to 450 nm, for example.

  Next, as shown in FIGS. 11A and 11B, a material for forming the cladding layer 15 is laminated on the insulating layer 32 so as to embed the resonance part 14, and is integrated with the insulating layer 32. A clad layer 15 is formed. In the present embodiment, the same silicon oxide as the forming material of the insulating layer 32 is used as the forming material of the cladding layer 15. The thickness of the portion of the cladding layer 15 on the resonance unit 14 can be set to 200 nm, for example.

  Next, as shown in FIGS. 12A and 12B, the resonant wavelength modulation layer 16 is laminated on the cladding layer 15. The thickness of the resonant wavelength modulation layer 16 can be set to, for example, 50 nm. As a material for forming the resonant wavelength modulation layer 16, for example, polysilicon can be used.

  Then, the resonant wavelength modulation layer 16 is patterned to obtain the optical device shown in FIGS. As patterning of the resonant wavelength modulation layer 16, for example, an i-line exposure method and a dry etching method can be used. The length of the bottom side of the resonant wavelength modulation layer 16 patterned into an isosceles triangle shape can be set to, for example, 500 nm. In FIGS. 3A and 3B, the support layer 31 becomes the substrate 11. Finally, a clad layer having a thickness of about 1000 nm may be formed on the entire element surface using the same material as the clad layer 15 so as to cover the clad layer 15 and the resonant wavelength modulation layer 16.

  Next, a second preferred embodiment of the above-described optical device manufacturing method will be described below with reference to the drawings.

  First, as shown in FIGS. 13A and 13B, a substrate 30 having a support layer 31, an insulating layer 32, and a semiconductor layer 33 is prepared. In the present embodiment, an SOI (Silicon on Insulator) substrate is used as the substrate 30. The support layer 31 is a silicon substrate, the insulating layer is a silicon oxide layer, and the semiconductor layer 33 is a single crystal silicon layer. The thickness of the semiconductor layer 33 can be set to 220 nm, for example.

  The substrate 30 may be prepared by forming the insulating layer 32 and the semiconductor layer 33 on the support layer 31 instead of using an SOI substrate.

  Next, as shown in FIGS. 14A and 14B, the semiconductor layer 33 is patterned to form the resonance part 14 having the core layer 12 and the plurality of ring-type optical waveguides 17. As the patterning, an electron beam drawing method and a dry etching method can be used. The width of the core layer can be set to 450 nm, for example. The diameter of the ring type optical waveguide 17 can be set to 16 μm, for example. In addition, the width of the ring-type optical waveguide 17 can be the same as the width of the core layer, for example.

  Next, as shown in FIGS. 15A and 15B, a material for forming the cladding layer 15 is laminated on the insulating layer 32 so as to embed the resonance portion 14, and integrated with the insulating layer 32. A clad layer 15 is formed. In the present embodiment, the same silicon oxide as the forming material of the insulating layer 32 is used as the forming material of the cladding layer 15. The thickness of the portion of the cladding layer 15 on the resonance unit 14 can be set to 200 nm, for example.

  Next, as shown in FIGS. 16A and 16B, the resonant wavelength modulation layer 16 is laminated on the cladding layer 15. The thickness of the resonant wavelength modulation layer 16 can be set to, for example, 50 nm. As a material for forming the resonant wavelength modulation layer 16, for example, polysilicon can be used.

  Then, the resonant wavelength modulation layer 16 is patterned to obtain the optical device shown in FIGS. As patterning of the resonant wavelength modulation layer 16, for example, an i-line exposure method and a copper plating etching method can be used. The length of the bottom side of the resonant wavelength modulation layer 16 patterned in the shape of an isosceles triangle can be set to 18 μm, for example. In FIGS. 7A and 7B, the support layer 31 becomes the substrate 11. Finally, a clad layer having a thickness of about 1000 nm may be formed on the entire element surface using the same material as the clad layer 15 so as to cover the clad layer 15 and the resonant wavelength modulation layer 16.

  The above-described optical device disclosed in this specification can be incorporated into an optical modulator, for example.

  FIG. 17A is a diagram illustrating a first embodiment of an optical modulator disclosed in this specification.

  The optical modulator 20 of the present embodiment is a Mach-Zehnder interferometric optical modulator, and is a second optical waveguide 21 having a first core layer 21a that propagates light and a second core layer 22a that propagates light. And an optical waveguide 22. The first core layer 21 a and the second core layer 22 a are embedded in the cladding layer 25. In the optical modulator 20, the first electrode 23 that applies the first modulation signal to the first optical waveguide 22 and the second electrode 24 that applies the second modulation signal to the second optical waveguide 22 include the cladding layer 25. Is placed on top.

  In the first optical waveguide 21 to which an electric field is applied by the first electrode 23, the refractive index changes in accordance with the magnitude and direction of the electric field. Therefore, the optical path length changes in response to the change in the refractive index. 1 The phase of propagating light propagating through the optical waveguide 21 changes. Similarly, the phase of propagating light changes in the second optical waveguide 22 to which an electric field is applied by the second electrode 24.

  The optical modulator 20 branches the input light Pi, sends it to the first optical waveguide 21 and the second optical waveguide 22, multiplexes the light propagated through the first optical waveguide 21 and the second optical waveguide 22, and modulates them. The emitted light is output as output light Po.

  Further, the first optical waveguide device 10 described above is disposed in the first optical waveguide 21.

  That is, in the optical modulator 20, the first optical waveguide 21 extends along the first core layer 21 a with the resonance unit 14 that resonates light propagating through the first core layer 21 a while changing the width. And a resonance wavelength modulation layer 16 that changes the resonance wavelength of the resonance part in the direction in which the light propagates. The resonance part 14 is formed by a part of the first core layer 21a and the diffraction gratings 13 provided on both sides in the longitudinal direction of a part of the first core layer 21a.

  According to the optical modulator 20 described above, since a large phase change can be caused to the optical signal propagating through the first optical waveguide 21, the amount of phase change per unit optical waveguide can be increased. The length can be shortened. In addition, since the device 10 can change the resonance wavelength of the resonance unit in the direction in which the light propagates, each of the light having different wavelengths can resonate. Therefore, the input light Pi input to the optical modulator 20 is a predetermined value. Even if it has a wavelength band, the light can be resonated and modulated.

  In the optical modulator 20, the resonance unit 12 and the resonance wavelength modulation layer 16 are arranged only in the first optical waveguide 21. However, the resonance unit 12 and the resonance wavelength modulation layer 16 are arranged also in the second optical waveguide 22. May be.

  Next, a second embodiment of the above-described optical modulator will be described below with reference to FIG. For the points that are not particularly described in the second embodiment of the optical modulator, the description in detail regarding the above-described first embodiment of the optical modulator is applied as appropriate. Moreover, the same code | symbol is attached | subjected to the same component.

  FIG. 17B is a diagram illustrating a second embodiment of the optical modulator disclosed in this specification.

  In the optical modulator 20 of the present embodiment, the structure of the resonance part disposed in the first optical waveguide 21 is different.

  That is, the optical device 10 of the second embodiment described above is arranged in the first optical waveguide 21.

  In the optical modulator 20 of the present embodiment, the first optical waveguide 21 is disposed on the plurality of ring optical waveguides 17 disposed along the first core layer 21 a and the plurality of ring optical waveguides 17. And a resonant wavelength modulation layer 16. A clad layer 25 is disposed between the plurality of ring optical waveguides 17 and the resonant wavelength modulation layer 16. The adjacent ring optical waveguides 17 in the plurality of ring optical waveguides 16 have different ratios of the length of the portion of the optical waveguide covered with the resonant wavelength modulation layer 16 to the entire length of the ring optical waveguide.

  The resonating unit 14 is formed by a part of the first core layer 21a and a plurality of ring-type optical waveguides 17 arranged along a part of the first core layer 21a.

  In the present invention, the optical device and the optical modulator of the above-described embodiment can be appropriately changed without departing from the gist of the present invention. In addition, the configuration requirements of one embodiment can be applied to other embodiments as appropriate.

  For example, extending the resonance wavelength modulation layer while changing its width along the core layer includes extending the resonance wavelength modulation layer along the core layer while changing its width stepwise.

  Further, the resonance part may be formed using a photonic crystal.

  In the above-described embodiment, the resonant wavelength modulation layer is disposed above the core layer. However, the resonant wavelength modulation layer may be disposed anywhere on the top, bottom, left, or right of the core layer.

  All examples and conditional words mentioned herein are intended for educational purposes to help the reader deepen and understand the inventions and concepts contributed by the inventor. All examples and conditional words mentioned herein are to be construed without limitation to such specifically stated examples and conditions. Also, such exemplary mechanisms in the specification are not related to showing the superiority and inferiority of the present invention. While embodiments of the present invention have been described in detail, it should be understood that various changes, substitutions or modifications can be made without departing from the spirit and scope of the invention.

  Regarding the above-described embodiments, the following additional notes are disclosed.

(Appendix 1)
A resonating portion having a core layer that propagates light, and resonating light propagating through the core layer;
A resonant wavelength modulation layer extending in width along the core layer;
An optical device comprising:

(Appendix 2)
The optical device according to appendix 1, wherein a thickness of the resonant wavelength modulation layer is thinner than a thickness of the core layer.

(Appendix 3)
The optical device according to appendix 1 or 2, wherein a phase refractive index of the resonant wavelength modulation layer is the same as or smaller than a phase refractive index of the core layer.

(Appendix 4)
Comprising a cladding layer positioned between the core layer and the resonant wavelength modulation layer;
The optical device according to any one of Supplementary notes 1 to 3, wherein a phase refractive index of the resonant wavelength modulation layer is larger than a phase refractive index of the cladding layer.

(Appendix 5)
The optical device according to any one of Supplementary notes 1 to 4, wherein the resonance unit includes a diffraction grating provided in the core layer.

(Appendix 6)
The optical device according to any one of appendices 1 to 4, wherein the resonance unit includes a plurality of ring-type optical waveguides arranged along the core layer.

(Appendix 7)
The resonance wavelength modulation layer according to any one of appendices 1 to 6, wherein the resonance wavelength modulation layer is disposed at a tail portion of an electric field intensity distribution in a direction perpendicular to a propagation direction of a waveguide mode of light propagating through the core layer. Optical device.

(Appendix 8)
The tail portion of the electric field intensity distribution is at a position where the sign of the second derivative with respect to the distance in the direction perpendicular to the propagation direction of the electric field intensity of the waveguide mode of light propagating through the core layer changes, The optical device according to appendix 7, which is located on the opposite side to the core layer.

(Appendix 9)
The optical device according to appendix 7 or 8, wherein a distance between the core layer and the resonance wavelength modulation layer is 50 nm or more and 500 nm or less.

(Appendix 10)
The optical device according to any one of appendices 1 to 9, wherein the width of the resonant wavelength modulation layer changes linearly in a direction in which light propagates.

(Appendix 11)
The core layer,
A plurality of ring optical waveguides disposed along the core layer;
A resonant wavelength modulation layer disposed on the plurality of ring-type optical waveguides;
A clad layer disposed between the plurality of ring optical waveguides and the resonant wavelength modulation layer;
With
An optical device in which the ring-type optical waveguides adjacent to each other differ in the ratio of the length of the portion of the optical waveguide covered with the resonance wavelength modulation layer to the entire length of the optical waveguide.

(Appendix 12)
A first optical waveguide having a core layer for propagating light;
A second optical waveguide having a core layer for propagating light;
With
The first optical waveguide or the second optical waveguide is
A resonating unit for resonating light propagating through the core layer;
A resonance wavelength modulation layer that extends while changing in width along the core layer, and changes a resonance wavelength of the resonance unit in a direction in which light propagates;
An optical modulator.

(Appendix 13)
A first optical waveguide having a core layer for propagating light;
A second optical waveguide having a core layer for propagating light;
With
The first optical waveguide or the second optical waveguide is
A plurality of ring optical waveguides disposed along the core layer;
A resonant wavelength modulation layer disposed on the plurality of ring waveguides;
A clad layer disposed between the plurality of ring optical waveguides and the resonant wavelength modulation layer;
Have
An optical modulator in which the ring-type optical waveguides adjacent to each other are different in the ratio of the length of the portion of the optical waveguide covered with the resonant wavelength modulation layer to the entire length of the optical waveguide.

DESCRIPTION OF SYMBOLS 10 Optical device 11 Substrate 12 Core layer 13 Diffraction grating 14 Resonance part 15 Cladding layer 16 Resonance wavelength modulation layer 17 Ring optical waveguide 20 Optical modulator 21 First optical waveguide 21a First core layer 22 Second optical waveguide 22a Second core layer 23 First electrode 24 Second electrode 25 Clad layer 30 Substrate 31 Support layer 32 Insulating layer 33 Semiconductor layer C Electric field intensity distribution P Inflection point W Tail part

Claims (8)

A resonating portion having a core layer that propagates light, and resonating light propagating through the core layer;
A resonant wavelength modulation layer extending in width along the core layer;
An optical device comprising:   The optical device according to claim 1, wherein a thickness of the resonant wavelength modulation layer is thinner than a thickness of the core layer.   The optical device according to claim 1, wherein a phase refractive index of the resonant wavelength modulation layer is the same as or smaller than a phase refractive index of the core layer.   The optical device according to claim 1, wherein the resonance unit includes a diffraction grating provided in the core layer.   The optical device according to any one of claims 1 to 3, wherein the resonance unit includes a plurality of ring-type optical waveguides arranged along the core layer. The core layer,
A plurality of ring optical waveguides disposed along the core layer;
A resonant wavelength modulation layer disposed on the plurality of ring-type optical waveguides;
A clad layer disposed between the plurality of ring optical waveguides and the resonant wavelength modulation layer;
With
An optical device in which the ring-type optical waveguides adjacent to each other differ in the ratio of the length of the portion of the optical waveguide covered with the resonance wavelength modulation layer to the entire length of the optical waveguide. A first optical waveguide having a core layer for propagating light;
A second optical waveguide having a core layer for propagating light;
With
The first optical waveguide or the second optical waveguide is
A resonating unit for resonating light propagating through the core layer;
A resonance wavelength modulation layer that extends while changing in width along the core layer, and changes a resonance wavelength of the resonance unit in a direction in which light propagates;
An optical modulator. A first optical waveguide having a core layer through which light propagates;
A second optical waveguide having a core layer through which light propagates;
With
The first optical waveguide or the second optical waveguide is
A plurality of ring optical waveguides disposed along the core layer;
A resonant wavelength modulation layer disposed on the plurality of ring waveguides;
A clad layer disposed between the plurality of ring optical waveguides and the resonant wavelength modulation layer;
Have
An optical modulator in which the ring-type optical waveguides adjacent to each other are different in the ratio of the length of the portion of the optical waveguide covered with the resonant wavelength modulation layer to the entire length of the optical waveguide.

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