JP2011100054A - Planar waveguide element - Google Patents

Abstract

The present invention provides a planar waveguide device capable of reducing crosstalk on the output side and outputting the separated light as light having a single wavelength from a specific output side end face.
In the optical waveguides 5 and 6 in each optical waveguide array, a gradient is formed in the equivalent refractive index distribution in one direction in the direction in which the optical waveguides 5 and 6 are arranged. When the light propagates from the first optical waveguide array to the second optical waveguide array, the connecting portion of the first optical waveguide array and the second optical waveguide array has m as an integer, and the phase of the optical Bloch oscillation caused by the light. Is formed so as to change by (2m−1) × π. The average value of the length of the optical waveguide of each optical waveguide array is such that the light propagating through each optical waveguide array propagates through the optical waveguides 5 and 6 while the optical Bloch oscillation vibrates for ½ period. Approximate length.
[Selection] Figure 1

Description

  The present invention relates to a planar waveguide device, and more particularly to a planar waveguide device that splits wavelength-multiplexed light using optical Bloch oscillation and outputs each of the dispersed light from a desired output side end face. About.

  In wavelength division multiplexing (hereinafter referred to as “WDM”) optical communication, signal light (hereinafter referred to as wavelength) obtained by multiplexing a plurality of lights having different wavelengths such as a wavelength of 1.55 μm or a wavelength of 1.3 μm. (Referred to as multiplexed light) is transmitted by a single optical fiber. With this WDM optical communication, high-capacity and high-speed optical communication is realized.

  The WDM light is finally output from a port designated for each wavelength. For this reason, a spectroscope that separates WDM light before output is required. As a spectroscope, a planar waveguide element (hereinafter referred to as “OBO planar waveguide element”) using optical Bloch Oscillations (hereinafter referred to as “OBO”) is described in Non-Patent Document 1. Proposed in ~ 3.

Hereinafter, an OBO planar waveguide device described in Non-Patent Document 2 will be described as an example of the prior art. FIG. 22 is a perspective view schematically showing the OBO planar waveguide device disclosed in Non-Patent Document 2. As shown in FIG. As shown in FIG. 22, a conventional OBO planar waveguide device 100 includes a substrate 101 made of SiO ₂ (silicon dioxide) and glass, a plurality of substrates 101 arranged side by side on a substrate 101, made of a polymer material, and propagates light. Optical waveguide 102 (optical waveguide array), and a polymer clad layer 103 that prevents propagating light from leaking out of the optical waveguide 102. An input side end face 104 on which light is incident is provided at one end of the plurality of optical waveguides 102, and an output side end face 105 from which light is emitted is provided at the other end opposite to the input side end face 104. . Furthermore, the conventional OBO planar waveguide device 100 includes a heater 106 disposed at one end of the substrate 101 in a direction in which the optical waveguides 102 are arranged, and a heat sink 107 disposed at the other end opposite to the heater 106. I have. The temperature distribution (temperature gradient) of the substrate 101 can be controlled by the heater 106 and the heat sink 107.

  Here, in FIG. 22, a dotted arrow indicates a path 108 of light propagating while vibrating in the X-axis direction in the plurality of optical waveguides 102 in the OBO planar waveguide device 100. In FIG. 22, the direction in which the plurality of optical waveguides 102 are arranged is the X-axis direction, the extending direction of each optical waveguide 102 is the Y-axis direction, and the direction perpendicular to the X-axis direction and the Y-axis direction is the Z-axis direction. .

  Next, a method for manufacturing the OBO planar waveguide device 100 will be described. First, a polymer material to be the optical waveguide 102 is deposited on the substrate 101. A resist is coated on the polymer material to form a resist film, and then a pattern of the optical waveguide 102 is formed on the resist film by electron beam drawing or photolithography. The above-described polymer material is etched using the resist film on which this pattern is formed as a mask. Thereby, the optical waveguide 102 is formed on the substrate 101. Thereafter, a polymer clad layer 103 is deposited on the substrate 101 so as to cover the surface of the substrate 101 where the optical waveguide 102 is formed and the optical waveguide 102. Next, the heater 106 is attached to one side end of the substrate 101 in the X-axis direction. Further, the heat sink 107 is attached to the other side end portion of the substrate 101 in the X-axis direction. Through the above steps, the OBO planar waveguide device 100 can be manufactured. Non-Patent Document 2 does not describe processing of the end of the optical waveguide 102.

  Next, the operation of the OBO planar waveguide device 100 will be described. In the OBO planar waveguide device 100, the temperature difference per unit length in the X-axis direction of the substrate 101 can be controlled by the functions of the heater 106 and the heat sink 107. The difference in equivalent refractive index per unit length in the X-axis direction of the optical waveguide 102 changes according to this temperature difference. OBO appears due to the difference in refractive index, and the OBO planar waveguide device 100 can be used as a variable spectrometer.

  In general, in the OBO planar waveguide device 100 having the optical waveguide 102 made of a polymer material, the refractive index of the optical waveguide 102 at the position where the substrate 101 is at a high temperature is the refractive index of the optical waveguide 102 at the position where the substrate 101 is at a low temperature. Higher than the rate.

  When the OBO planar waveguide device 100 is used, a gradient (temperature difference per unit length) is formed in the temperature distribution in the X-axis direction of the substrate 101 by the functions of the heater 106 and the heat sink 107. Then, WDM light having different wavelengths is input into the OBO planar waveguide device 100 so that the intensity peak of the light is located on the predetermined one input side end face 104. At this time, each light included in the WDM light leaks from the propagating optical waveguide 102 and is coupled to the optical waveguide 102 adjacent to the optical waveguide 102. As a result, the WDM light causes OBO in the X-axis direction while propagating in the Y-axis direction.

  In general, as the wavelength of light increases, the amplitude of OBO increases. That is, according to the nature of OBO, the amplitude of OBO differs for each wavelength of light. In addition, the amplitude of OBO decreases as the difference in equivalent refractive index per unit length of the optical waveguide 102 in the X-axis direction, that is, the gradient of the equivalent refractive index distribution in the X-axis direction of the optical waveguide 102 increases. Has properties.

  Therefore, the WDM light input into the OBO planar waveguide device 100 has a different path 108 that propagates through the OBO planar waveguide device 100. That is, the WDM light is split in the OBO planar waveguide device 10. Further, each of the dispersed light is output from the unique output side end face 105 as single wavelength light.

  Further, the gradient of the equivalent refractive index distribution in the X-axis direction of the optical waveguide 102 is controlled by adjusting the temperature distribution gradient in the X-axis direction of the substrate 101 using the heater 106 and the heat sink 107. By controlling the gradient of the equivalent refractive index distribution, it is possible to freely specify the output side end face 105 of each light by adjusting the amplitude of the OBO of the dispersed light. As described above, the OBO planar waveguide device 100 can be used as a variable spectrometer.

R. Morandotti, U. Peschel, and J. S. Aitchison, `` Experimental Observation of Linear and Nonlinear Optical Bloch Oscillations '', Physical Review Letters, Vol. 83, No. 23, 4756-4759 (1999). T.Pertsch, P.Dannberg, W.Elflein, and A.Brauer, “Optical Bloch Oscillations in Temperature Tuned Waveguide Arrays”, Physical Review letters, Vol.83, No.23, 4752-4755 (1999). U. Peschel, T. Pertsch, and F. Lederer “Optical Bloch oscillations in waveguide arrays”, Optics Letters, Vol. 23, No. 21, 1701-1703 (1998).

  In order to increase the communication speed in the WDM optical communication, a method of multiplexing more light having different wavelengths within a limited wavelength band such as the wavelength 1.55 μm band or the wavelength 1.3 μm band can be adopted. Here, since the total bandwidth of the multiplexed light is constant, in order to implement the above measures, it is necessary to shorten the wavelength interval of the multiplexed light. Then, in the configuration of the OBO planar waveguide device 100 described in Non-Patent Document 2, the difference in OBO amplitude of each light included in the WDM light is reduced due to the nature of OBO.

  As a result, in the plurality of light paths 108 propagating in the OBO planar waveguide device 100, the interval in the vibration direction of the OBO (X-axis direction in FIG. 22) is narrowed. When the difference in the amplitude of the OBO of the multiplexed light becomes shorter than the distance between the centers of the optical waveguides 102, a plurality of lights are output from the same output side end face 105. In this case, each of the dispersed light is not output from the unique output side end face 105 as light having a single wavelength, and crosstalk occurs on the output side of the OBO planar waveguide device 100, so that it does not function sufficiently as a spectroscope.

  The present invention has been made in view of the above-described problems, and reduces crosstalk on the output side even when the wavelength interval between the light contained in the WDM light input into the planar waveguide element is narrowed. Another object of the present invention is to provide a planar waveguide device capable of outputting the separated light as light having a single wavelength from a specific output side end face.

  A planar waveguide device according to the present invention includes a substrate, a clad layer laminated on the substrate, and a guide layer laminated on the clad layer and having a higher refractive index than the clad layer. On the upper portion of the guide layer, a plurality of optical waveguide arrays including a plurality of optical waveguides extending linearly so as to be arranged in parallel are continuously formed in the light propagation direction. Each optical waveguide array includes at least one optical waveguide having an incident side end face on which light is incident. Each optical waveguide array includes at least two optical waveguides each having an emission side end surface from which light is emitted. In the optical waveguide in each optical waveguide array, a gradient is formed in the equivalent refractive index distribution in one direction in the direction in which the optical waveguides are arranged. In an optical waveguide array formed adjacent to each other, an optical waveguide having an incident-side end surface and an optical waveguide having an output-side end surface are connected to each other at a predetermined angle and formed on the light incident side. The emission side end face of the first optical waveguide of the first optical waveguide array thus formed is connected to the incidence side end face of the second optical waveguide of the second optical waveguide array formed on the light emission side. When the light propagates from the first optical waveguide array to the second optical waveguide array, the connecting portion of the first optical waveguide array and the second optical waveguide array has m as an integer, and the phase of the optical Bloch oscillation caused by the light. Is formed so as to change by (2m−1) × π. The average value of the length of the optical waveguide of each optical waveguide array is the length that the light propagating through each optical waveguide array propagates through the optical waveguide while oscillating for 1/2 period in the optical Bloch oscillation. It is almost coincident.

  According to the planar waveguide element described above, the length of the first optical waveguide is substantially equal to the length of the light propagating during the half period of the optical Bloch oscillation of the light incident on the first optical waveguide. When the light has been most dispersed when propagating through the first optical waveguide, the light is incident on the second optical waveguide. When light enters the second optical waveguide, the phase of the optical Bloch oscillation of the light changes by an odd multiple of a half wavelength, so that the light is further dispersed after entering the second optical waveguide. Since the length of the second optical waveguide is almost equal to the length of the optical Bloch oscillation of the light incident on the second optical waveguide that propagates during a half cycle, the propagation of the second optical waveguide is completed. In the case of the most spectroscopic. Therefore, by allowing the wavelength multiplexed light to be incident on the planar waveguide element, crosstalk on the output side can be reduced, and light having a single wavelength can be output from the unique output side end face.

Preferably, in each optical waveguide array, from the low refractive index side to the high refractive index side of the equivalent refractive index distribution of the optical waveguide in the optical waveguide array in a direction orthogonal to the direction in which the optical waveguide extends on the upper surface of the substrate. This is the Y axis in the first optical waveguide array when a coordinate axis consisting of an X axis whose direction is positive and a Y axis whose direction away from the incident side end face is positive in the direction in which the optical waveguide extends. The angle between the Y ₁ axis and the Y ₂ axis that is the Y axis in the second optical waveguide array, θ ₂ , which is counterclockwise with respect to the Y ₁ axis of the Y ₂ axis, and the pitch between the second optical waveguides Is P ₂ , the equivalent refractive index of the second optical waveguide is n, and the average wavelength of light is λ, the relationship of P ₂ × tan θ ₂ = (2m−1) × λ / (2 × n) is satisfied. In the first optical waveguide array formed on the most incident side, all intersections between the straight line extending in the extending direction of the first optical waveguide and the incident side end surface of the first optical waveguide are in the coordinate axis of the first optical waveguide array. located X ₁ axis is X-axis, and all intersections of the exit side end surface of the straight line and the first optical waveguide extending in the extending direction of the first optical waveguide, coordinates in the coordinate axis of the first optical waveguide array At the same Y ₁ coordinate. In the second optical waveguide array, the Y ₂ coordinate on the coordinate axis of the second optical waveguide array at the intersection of the straight line extending in the extending direction of one second optical waveguide and the emission side end surface of the first optical waveguide is From the Y ₂ coordinate on the coordinate axis of the second optical waveguide array at the intersection of the straight line extending in the extending direction of another second optical waveguide adjacent to the low refractive index side of the second optical waveguide and the output side end surface of the first optical waveguide −P ₂ × tan θ _{2 The} coordinates are changed, and all the intersections of the straight line extending in the extending direction of the second optical waveguide and the output side end surface of the second optical waveguide are in the coordinates on the coordinate axis of the second optical waveguide array. It is located on the same Y ₂ coordinates.

  According to the above planar waveguide element, the phase of the optical Bloch oscillation of the light is changed by an odd multiple of a half wavelength when light propagates from the exit end face of the first optical waveguide to the entrance end face of the second optical waveguide. Can be made.

Preferably, in each optical waveguide array, from the low refractive index side to the high refractive index side of the equivalent refractive index distribution of the optical waveguide in the optical waveguide array in a direction orthogonal to the direction in which the optical waveguide extends on the upper surface of the substrate. This is the Y axis in the first optical waveguide array when a coordinate axis consisting of an X axis whose direction is positive and a Y axis whose direction away from the incident side end face is positive in the direction in which the optical waveguide extends. The angle between the Y ₁ axis and the Y ₂ axis that is the Y axis in the second optical waveguide array, θ ₂ that is counterclockwise with respect to the Y ₁ axis of the Y ₂ axis, and the pitch between the first optical waveguides Is P ₁ and the pitch between the second optical waveguides is P ₂ , the relationship of P ₂ = P ₁ × cos | θ ₂ | is satisfied.

  According to the above planar waveguide element, the shape of the equivalent refractive index distribution of the first optical waveguide in the first optical waveguide array is similar to the shape of the equivalent refractive index distribution of the second optical waveguide in the second optical waveguide array. When light propagates from the first optical waveguide to the second optical waveguide, the light intensity distribution does not change significantly, and the light propagation loss occurs at the connecting portion between the first optical waveguide array and the second optical waveguide array. Can be reduced.

Preferably, in each optical waveguide array, from the low refractive index side to the high refractive index side of the equivalent refractive index distribution of the optical waveguide in the optical waveguide array in a direction orthogonal to the direction in which the optical waveguide extends on the upper surface of the substrate. This is the Y axis in the first optical waveguide array when a coordinate axis consisting of an X axis whose direction is positive and a Y axis whose direction away from the incident side end face is positive in the direction in which the optical waveguide extends. The angle between the Y ₁ axis and the Y ₂ axis that is the Y axis in the second optical waveguide array, θ ₂ that is counterclockwise with respect to the Y ₁ axis of the Y ₂ axis, and the pitch between the first optical waveguides Is P ₁ , the equivalent refractive index of the second optical waveguide is n, and the average wavelength of light is λ, the relationship of P ₁ × tan θ ₂ = (2m−1) × λ / (2 × n) is satisfied. In the first optical waveguide array, all intersections of the straight line extending in the extending direction of the first optical waveguide and the incident side end surface of the first optical waveguide are X ₁ axes that are the X axis in the coordinate axis of the first optical waveguide array. The Y ₁ coordinate on the coordinate axis of the first optical waveguide array at the intersection of the straight line located above and extending in the extending direction of the first optical waveguide of the first optical waveguide array and the output side end surface of the first optical waveguide Is the coordinate axis of the first optical waveguide array at the intersection of the straight line extending in the extending direction of the other first optical waveguide adjacent to the low refractive index side of the first optical waveguide and the output side end surface of the first optical waveguide. The coordinates are changed by P ₁ × tan θ ₂ from the Y ₁ coordinate at. In the second optical waveguide array, all the intersections of the straight line extending in the extending direction of the second optical waveguide and the incident side end surface of the second optical waveguide are the same Y ₂ coordinates in the coordinates on the coordinate axis of the second optical waveguide array. Is located.

  According to the above planar waveguide element, the phase of the optical Bloch oscillation of the light is changed by an odd multiple of a half wavelength when light propagates from the exit end face of the first optical waveguide to the entrance end face of the second optical waveguide. Can be made.

Preferably, in each optical waveguide array, from the low refractive index side to the high refractive index side of the equivalent refractive index distribution of the optical waveguide in the optical waveguide array in a direction orthogonal to the direction in which the optical waveguide extends on the upper surface of the substrate. This is the Y axis in the first optical waveguide array when a coordinate axis consisting of an X axis whose direction is positive and a Y axis whose direction away from the incident side end face is positive in the direction in which the optical waveguide extends. The angle between the Y ₁ axis and the Y ₂ axis that is the Y axis in the second optical waveguide array, θ ₂ that is counterclockwise with respect to the Y ₁ axis of the Y ₂ axis, and the pitch between the first optical waveguides the P _1, when the pitch between the second optical waveguide to each other and P _2, the second optical _{waveguide, P 2 = P 1 / cos} | satisfy the relationship | theta _2.

  According to the above planar waveguide element, the shape of the equivalent refractive index distribution of the first optical waveguide in the first optical waveguide array is similar to the shape of the equivalent refractive index distribution of the second optical waveguide in the second optical waveguide array. When light propagates from the first optical waveguide to the second optical waveguide, the light intensity distribution does not change significantly, and the light propagation loss occurs at the connecting portion between the first optical waveguide array and the second optical waveguide array. Can be reduced.

  Preferably, in each optical waveguide array, the width of the optical waveguide becomes wider in one direction in the direction in which the optical waveguides are arranged.

  According to the above planar waveguide element, in each optical waveguide array, a gradient is formed in the equivalent refractive index distribution in one direction in the direction in which the optical waveguides are arranged.

  Preferably, in each optical waveguide array, if the width of the optical waveguide is W and the pitch between the optical waveguides is P, W / P ≧ 0.55 at the incident side end face.

  According to the planar waveguide element described above, optical Bloch oscillation is manifested in an optical waveguide having a large coupling constant, and the optical Bloch due to the difference in wavelength of light propagating through the optical waveguide due to the large coupling constant of the optical waveguide. The amount of change in vibration amplitude increases. Therefore, crosstalk at the output end face of the planar waveguide device can be reduced.

  Preferably, a heater is formed on one side surface of the substrate in a direction in which the optical waveguides are arranged, and a heat sink is formed on the other side surface.

  According to the above planar waveguide element, in each optical waveguide array, a gradient is formed in the equivalent refractive index distribution in one direction in the direction in which the optical waveguides are arranged.

  Preferably, in each optical waveguide array, when the width of the optical waveguide is W and the pitch between the optical waveguides is P, each of the width W and the pitch P satisfies W / P ≧ 0.55 and is substantially constant. It becomes the value of.

  According to the planar waveguide element described above, optical Bloch oscillation is manifested in an optical waveguide having a large coupling constant, and the optical Bloch due to the difference in wavelength of light propagating through the optical waveguide due to the large coupling constant of the optical waveguide. The amount of change in vibration amplitude increases. Therefore, crosstalk at the output end face of the planar waveguide device can be reduced.

Preferably, in the second optical waveguide array formed on the most output side, all the intersections of the straight line extending in the extending direction of the second optical waveguide and the end surface on the output side of the second optical waveguide are formed on the most incident side. The first optical waveguide array is located at the same Y ₁ coordinate in the coordinate axes.

  According to the above planar waveguide element, the input end face and the output end face of the planar waveguide element can be easily manufactured by cleaving the substrate.

  Preferably, if the phase of the optical Bloch oscillation of the light on the emission side end face of the second optical waveguide formed on the most emission side is Y and s is an integer, (2s-5 / 4) π ≦ Y ≦ (2s− 3/4) π.

  According to the above planar waveguide element, crosstalk at the output end face of the planar waveguide element can be reduced.

Preferably, θ ₂ is −20 ° ≦ θ ₂ ≦ 20 °.
According to the above planar waveguide element, it is possible to reduce the propagation loss of light at the connecting portion between the first optical waveguide array and the second optical waveguide array.

  Preferably, the intersection of the virtual center line of the first optical waveguide and the virtual center line of the second optical waveguide corresponding to the first optical waveguide is an interface between the first optical waveguide array and the second optical waveguide array. Located on the top.

  According to the above planar waveguide element, all the emission side end faces of the first optical waveguide are in contact with all the incident side end faces of the second optical waveguide, so that the first optical waveguide array and the second optical waveguide array It is possible to reduce light propagation loss at the connecting portion.

Preferably, the width of the first optical waveguide at the exit end face of the first optical waveguide is L ₁ , and the width of the second optical waveguide at the entrance end face of the second optical waveguide connected to the first optical waveguide is L ₂ . Then, L ₁ ≦ L ₂ .

  According to the planar waveguide element described above, since the entire exit side end face of the first optical waveguide is in contact with the entrance end face of the second optical waveguide, the light at the connecting portion between the first optical waveguide array and the second optical waveguide array Propagation loss can be reduced.

  Preferably, the optical waveguide array is formed of a semiconductor material, the pitch between the optical waveguides is 2.0 μm or less, and the height of the optical waveguide is 0.05 μm or less.

  According to the planar waveguide element described above, optical Bloch oscillation is manifested in an optical waveguide having a large coupling constant, and the optical Bloch due to the difference in wavelength of light propagating through the optical waveguide due to the large coupling constant of the optical waveguide. The amount of change in vibration amplitude increases. Therefore, crosstalk at the output end face of the planar waveguide device can be reduced.

  According to the present invention, since the length of the first optical waveguide is substantially equal to the length of the light propagating during the half period of the optical Bloch oscillation of the light incident on the first optical waveguide, When the light is most dispersed when propagating through the waveguide, it is incident on the second optical waveguide. When light enters the second optical waveguide, the phase of the optical Bloch oscillation of the light changes by an odd multiple of a half wavelength, so that the light is further dispersed after entering the second optical waveguide. Since the length of the second optical waveguide is almost equal to the length of the optical Bloch oscillation of the light incident on the second optical waveguide that propagates during a half cycle, the propagation of the second optical waveguide is completed. In the case of the most spectroscopic. Therefore, by allowing the wavelength multiplexed light to be incident on the planar waveguide element, crosstalk on the output side can be reduced, and light having a single wavelength can be output from the unique output side end face.

It is a top view showing typically the OBO plane waveguide device concerning Embodiment 1 of the present invention. It is sectional drawing seen from the II-II line arrow direction of FIG. It is a top view which shows typically the 1st optical waveguide array in the OBO planar waveguide element concerning the embodiment. It is a top view which shows typically the 2nd optical waveguide array in the OBO planar waveguide element concerning the embodiment. It is a top view which shows typically the connection part of the 1st optical waveguide and 2nd optical waveguide in the embodiment. It is sectional drawing which shows typically the state which apply | coated the resist to the upper surface of the guide layer in the same embodiment. In the embodiment, it is sectional drawing which shows the state which patterned the resist film typically. In the same embodiment, it is sectional drawing which shows typically the state which has etched the guide layer and has formed the optical waveguide. 5 is a graph showing a relationship between a light propagation constant κ ₁ in the X ₁ axis direction and a light propagation constant β ₁ in the Y ₁ axis direction in the first optical waveguide array. 5 is a graph showing a relationship between a light propagation constant κ ₂ in the X ₂ axis direction and a light propagation constant β ₂ in the Y ₂ axis direction in the second optical waveguide array. It is a top view which shows typically the OBO planar waveguide element which concerns on Embodiment 2 of this invention. It is sectional drawing seen from the XII-XII line arrow direction of FIG. It is a top view which shows typically the 1st optical waveguide array in the OBO planar waveguide element concerning the embodiment. It is a top view which shows typically the 2nd optical waveguide array in the OBO planar waveguide element concerning the embodiment. It is a top view which shows typically the connection part of the 1st optical waveguide and 2nd optical waveguide in the embodiment. In the embodiment, it is sectional drawing which shows the state which patterned the resist film typically. In the same embodiment, it is sectional drawing which shows typically the state which has etched the guide layer and has formed the optical waveguide. In the embodiment, it is sectional drawing which shows typically the state in which the upper clad layer was formed. In the same embodiment, it is sectional drawing which shows typically the state in which the heater and the heat sink were formed. It is a top view which shows typically the OBO planar waveguide element which concerns on Embodiment 3 of this invention. It is sectional drawing seen from the XXI-XXI line arrow direction of FIG. It is a perspective view which shows typically the OBO planar waveguide element disclosed in the nonpatent literature 2. FIG.

  Hereinafter, the OBO planar waveguide device according to Embodiment 1 of the present invention will be described in detail with reference to the drawings.

Embodiment 1
FIG. 1 is a plan view schematically showing an OBO planar waveguide device according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view as seen from the direction of arrows II-II in FIG. As shown in FIGS. 1 and 2, in the OBO planar waveguide device 1 according to this embodiment, a Si substrate 2 is used as a substrate. As the lower cladding layer laminated on the Si substrate 2, the SiO ₂ layer 3 having a thickness of about 1 μm was used. Laminated on the SiO ₂ layer 3, as a guide layer having a higher refractive index than SiO ₂ layer 3, and a thickness of a Si layer 4 of about 0.27 [mu] m. In the upper part of the guide layer 4, a plurality of optical waveguides 5 and 6 having a height of about 0.04 μm are formed.

  The plurality of optical waveguides 5 have an incident-side end face 7 on which light is incident and an exit-side end face 8 from which light is emitted. In the present embodiment, all the optical waveguides 5 have the incident side end face 7, but at least one of the plurality of optical waveguides 5 only needs to have the incident side end face 7. . In the present embodiment, all the optical waveguides 5 have the emission side end face 8, but at least two of the plurality of optical waveguides 5 only have to have the emission side end face 8. . The optical waveguide 5 extends linearly so as to be arranged substantially in parallel.

  The plurality of optical waveguides 6 have an incident-side end face 9 on which light is incident and an exit-side end face 10 from which light is emitted. In the present embodiment, all the optical waveguides 6 have the incident side end face 9, but at least two of the plurality of optical waveguides 6 only have to have the incident side end face 9. . In the present embodiment, all the optical waveguides 6 have the emission side end face 10, but at least two of the plurality of optical waveguides 6 only have to have the emission side end face 10. . The optical waveguide 6 extends linearly so as to be arranged substantially in parallel.

  An optical waveguide array including a plurality of optical waveguides 5 and an optical waveguide array including a plurality of optical waveguides 6 are formed continuously in the light propagation direction. In the OBO planar waveguide device 1 of the present embodiment, two optical waveguide arrays are provided, but three or more optical waveguide arrays may be provided. In the optical waveguides 5 and 6 in each optical waveguide array, a gradient is formed in the equivalent refractive index distribution toward one direction in the direction in which the optical waveguides 5 and 6 are arranged.

  In the optical waveguide array formed adjacent to each other, the optical waveguides 5 and 6 included therein are connected to each other with a predetermined angle. The exit side end face 8 of the first optical waveguide 5 of the first optical waveguide array formed on the light incident side and the entrance side end face 9 of the second optical waveguide 6 of the second optical waveguide array formed on the light exit side. And are connected.

  Since the OBO planar waveguide device 1 of the present embodiment includes two optical waveguides, the incident-side end surface 7 of the first optical waveguide 5 formed on the most light incident side is the OBO planar waveguide device 1. Input end face 11. On the other hand, the emission side end face 10 of the second optical waveguide 6 formed on the most light emission side becomes the output end face 12 of the OBO planar waveguide device 1.

  FIG. 3 is a plan view schematically showing the first optical waveguide array in the OBO planar waveguide device according to the present embodiment. FIG. 4 is a plan view schematically showing a second optical waveguide array in the OBO planar waveguide device according to the present embodiment.

Note that the coordinate axis in each optical waveguide array is in the direction orthogonal to the direction in which the optical waveguide extends on the upper surface of the substrate, from the low refractive index side to the high refractive index side of the equivalent refractive index distribution of the optical waveguide in the optical waveguide array. The X-axis is positive in the direction toward the optical axis, the Y-axis is positive in the direction in which the optical waveguide extends, and the direction away from the incident-side end face is Z-axis, and the Z-axis is perpendicular to the X-axis and Y-axis. The X axis, Y axis, and Z axis, which are coordinate axes of the first optical waveguide, are composed of the X ₁ axis, the Y ₁ axis, and the Z ₁ axis. The X axis, Y axis, and Z axis, which are coordinate axes of the second optical waveguide, are composed of the X ₂ axis, the Y ₂ axis, and the Z ₂ axis. Each arrow of X ₁ , X ₂ , Y ₁ , Y ₂ , Z ₁ , Z ₂ shown in the referenced figure indicates the direction of each coordinate axis.

As shown in FIG. 3, in order to form a gradient in the equivalent refractive index distribution of the first optical waveguide 5 in the first optical waveguide array, the width of the first optical waveguide 5 gradually increases toward the + X ₁ axis direction. ing. In other words, in the first optical waveguide array, the width of the first optical waveguide 5 is increased in one direction in the direction in which the first optical waveguides 5 are arranged.

As shown in FIG. 4, to form a gradient in the equivalent refractive index distribution of the second optical waveguide 6 in the second optical waveguide array, the width of the second optical waveguide 6 is widened gradually toward the + X ₂ axial ing. In other words, in the second optical waveguide array, the width of the second optical waveguide 6 is increased in one direction in the direction in which the second optical waveguides 6 are arranged.

In the present embodiment, the pitch P ₁ between the first optical waveguides 5 is constant at 2 μm, and the width of the first optical waveguide 5 is in the range of 0.2 μm to 1.7 μm toward the + X ₁ axis direction. And getting wider. The pitch P ₂ between the second optical waveguides 6 is constant at 1.99 μm, and the width of the second optical waveguide 6 becomes wider in the + X ₂ axis direction in the range of 0.3 μm to 1.8 μm. Yes.

When the light propagates from the first optical waveguide array to the second optical waveguide array, the connecting portion of the first optical waveguide array and the second optical waveguide array has m as an integer, and the phase of the optical Bloch oscillation caused by the light. Is formed so as to change by (2m−1) × π. Specifically, in the OBO planar waveguide device 1 of this embodiment, the angle formed by the Y ₁ axis in the first optical waveguide array and the Y ₂ axis in the second optical waveguide array is the Y ₁ axis of the Y ₂ axis. The first optical waveguide array and the second optical waveguide array are connected to each other by determining θ ₂ that is positive counterclockwise and the formation position of the incident-side end face 9 of the second optical waveguide 6.

The above θ ₂ is P ₂ × tan θ ₂ = (2m−1) where P _{2 is} the pitch between the second optical waveguides 6, n is the equivalent refractive index of the second optical waveguide, and λ is the average wavelength of the light. ) × λ / (2 × n)... Satisfies the relationship of the formula (1). In Formula (1), when P ₂ is 1.99 μm, λ is 1.4 μm, n is 3.48, and m is 0, θ ₂ is −5.8 °. At this time, when light propagates from the output-side end face 8 of the first optical waveguide 5 to the incident-side end face 9 of the second optical waveguide 6, the OBO phase changes by −π.

In the first optical waveguide array formed on the most light incident side, all the intersections between the straight line extending in the extending direction of the first optical waveguide 5 and the incident side end surface 7 of the first optical waveguide 5 are the first optical waveguide. located on the X ₁ axis in the coordinate axis of the waveguide array, and all intersections of the exit-side end surface 8 of the straight line and the first optical waveguide 5 extending in the extending direction of the first optical waveguide 5, the first optical waveguide array Are located at the same Y ₁ coordinate in the coordinate axes.

  The length of the first optical waveguide 5 of the first optical waveguide array is such that the light propagating through the first optical waveguide array propagates through the first optical waveguide 5 while oscillating for half a period in the optical Bloch oscillation. Approximate length. In the present embodiment, the length of each first optical waveguide 5 is constant. Note that the length of light propagating through the optical waveguide while the light vibrates in 1/2 period in the optical Bloch oscillation is referred to as OBO 1/2 period length. In other words, the 1/2 period length of OBO refers to the distance that light propagates in the Y-axis direction while the OBO phase caused by the light propagating through the optical waveguide array changes by π. In the present embodiment, the length of the first optical waveguide 5 is 1000 μm.

FIG. 5 is a plan view schematically showing a connection portion between the first optical waveguide and the second optical waveguide in the present embodiment. As shown in FIG. 5, in the second optical waveguide array, the second optical waveguide array at the intersection of the straight line extending in the extending direction of one second optical waveguide 6 and the emission-side end face 8 of the first optical waveguide 5. The Y ₂ coordinate on the coordinate axis is a straight line extending in the extending direction of the other second optical waveguide 6 adjacent to the low refractive index side of the one second optical waveguide 6 and the emission side end face 8 of the first optical waveguide 5. The coordinates are changed by −P ₂ × tan θ ₂ from the Y ₂ coordinate on the coordinate axis of the second optical waveguide array at the intersection.

In FIG. 5, for convenience of explanation, when the Y ₂ coordinate of the intersection of the straight line extending in the extending direction of one second optical waveguide 6 and the emission-side end face 8 of the first optical waveguide 5 is 0, The Y ₂ coordinate of the intersection of the straight line extending in the extending direction of the other second optical waveguide 6 adjacent to the + X ₂ direction side of the one second optical waveguide 6 and the emission side end face 8 of the first optical waveguide 5 is − P ₂ × tan θ ₂ is obtained.

As shown in FIGS. 1 and 4, all the intersections between the straight line extending in the extending direction of the second optical waveguide 6 and the emission-side end face 10 of the second optical waveguide 6 are coordinates on the coordinate axis of the second optical waveguide array. Are located at the same Y ₂ coordinate.

Therefore, in the second optical waveguide array, the length of the second optical waveguide 6 in the Y ₂ axis direction changes by P ₂ × tan θ _{2 in} the + X ₂ axis direction. In the present embodiment, the length of the second optical waveguide 6 in the second optical waveguide array in the Y ₂ axis direction is reduced by 0.202 μm in the + X ₂ axis direction.

  The average value of the length of the second optical waveguide 6 of the second optical waveguide array is the same as that of the second optical waveguide while the light propagating through the second optical waveguide array oscillates in 1/2 period in the optical Bloch oscillation. The length substantially propagates through the waveguide 6. In the present embodiment, the average length of the second optical waveguide 6 is 1000 μm.

As shown in FIG. 5, in the present embodiment, the pitch P ₂ between the second optical waveguides 6 in the second optical waveguide array and the pitch P between the first optical waveguides 5 in the first optical waveguide array. ₁ satisfies the relationship P ₂ = P ₁ × cos | θ ₂ |.

  With this configuration, the shape of the equivalent refractive index distribution of the first optical waveguide 5 in the first optical waveguide array is similar to the shape of the equivalent refractive index distribution of the second optical waveguide 6 in the second optical waveguide array. When the light propagates from the first optical waveguide 5 to the second optical waveguide 6, the light intensity distribution does not change greatly, and the light at the connection portion between the first optical waveguide array and the second optical waveguide array is not changed. Propagation loss can be reduced.

  In the present embodiment, the intersection 15 between the virtual center line 13 of the first optical waveguide 5 and the virtual center line 14 of the second optical waveguide 6 corresponding to the first optical waveguide 5 is the first light guide. It is located on the interface 16 between the waveguide array and the second optical waveguide array. With this configuration, all the emission-side end faces 8 of the first optical waveguide 5 and all the incident-side end faces 9 of the second optical waveguide 6 are always in contact with each other, so that the first optical waveguide array and the second optical waveguide array are in contact with each other. It is possible to reduce the propagation loss of light at the connecting portion.

Furthermore, in the present embodiment, the width of the first optical waveguide 5 at the emission-side end face 8 of the first optical waveguide 5 is L ₁ , and the incident-side end face 9 of the second optical waveguide 6 connected to the first optical waveguide 5. If the width of the second optical waveguide 6 is L ₂ , then L ₁ ≦ L ₂ . With this configuration, the entire surface of the emission-side end face 8 of the first optical waveguide 5 is in contact with the incident-side end face 9 of the second optical waveguide 6, so that the connecting portion between the first optical waveguide array and the second optical waveguide array It is possible to reduce the propagation loss of light.

Hereinafter, a method for manufacturing the OBO planar waveguide device 1 according to the present embodiment will be described. FIG. 6 is a cross-sectional view schematically showing a state in which a resist is applied to the upper surface of the guide layer in the present embodiment. As shown in FIG. 6, first, an SOI substrate in which a Si substrate 2, a SiO ₂ layer 3 and a Si layer 4 are sequentially laminated is prepared. Next, a resist film 17 is formed on the upper surface of the Si layer 4 by applying a resist with a thickness of 0.3 μm.

  FIG. 7 is a cross-sectional view schematically showing a state in which the resist film is patterned in the present embodiment. As shown in FIG. 7, a resist pattern 18 for forming an optical waveguide array is produced by processing the resist film 17 by direct electron beam lithography or photolithography.

  In this embodiment, when the electron beam direct writing method is performed, the irradiation current of the electron beam is 0.1 nA, and the dose time of the electron beam per dot is 4.5 μsec. Further, when performing the photolithography method, the resist pattern 18 is produced with a transfer time of about 10 seconds.

  FIG. 8 is a cross-sectional view schematically showing a state where an optical waveguide is formed by etching a guide layer in the present embodiment. As shown in FIG. 8, using the resist pattern 18 as a mask, the Si layer 4 is etched using an etching method such as ICP (Inductively Coupled Plasma) etching, reactive ion etching, or reactive ion beam etching. The first optical waveguide array and the second optical waveguide array are manufactured by etching the upper part of the Si layer 4 to a depth of about 0.04 μm.

  In this embodiment, reactive ion etching is performed, a mixed gas of chlorine gas 25 sccm and nitrogen gas 10 sccm is used as an etching gas, an etching pressure is 0.1 Pa, and an RF (Radio Frequency) power is 200 W.

Next, the operation of the OBO planar waveguide device 1 according to this embodiment will be described. As shown in FIG. 3, since the width of the first optical waveguide 5 of the first optical waveguide array gradually increases toward the + X ₁ axis direction, the equivalent refractive index of the first optical waveguide 5 of the first optical waveguide array is increased. A gradient is formed in the distribution.

The wavelength multiplexed light is incident on the OBO planar waveguide device 1 so that the peak of the light intensity distribution 19 is located on the predetermined incident side end face 7. The incident light leaks from the propagating first optical waveguide 5 and is coupled to the adjacent first optical waveguide 5. As a result, the wavelength multiplexed light propagates in the + Y ₁ axis direction and causes OBO in the X ₁ axis direction. The amplitude of OBO increases as the wavelength of light increases. Therefore, the path 20 in the OBO planar waveguide device 1 for wavelength multiplexed light differs depending on the wavelength of the light. As a result, the wavelength multiplexed light is split by the first optical waveguide array.

As shown in FIG. 4, the plurality of lights dispersed by the first optical waveguide array enter the second optical waveguide 6 from the respective incident side end faces 9 of the second optical waveguide array. Width of the second optical waveguide 6, + X ₂ for gradually becomes wider toward the direction, the gradient is formed in the equivalent refractive index distribution of the second optical waveguide 6 in the second optical waveguide array. Each of the incident light leaks from the propagating second optical waveguide 6 and is coupled to the adjacent second optical waveguide 6. As a result, OBO occurs in the X ₂ axis direction while propagating in the Y ₂ axis direction.

Next, an effect obtained by connecting a plurality of optical waveguide arrays will be described. 9, in the first optical waveguide array, a propagation constant kappa ₁ light in the X ₁ axis direction is a graph showing the relationship between the propagation constant beta ₁ of the light in the Y ₁ axis direction. Here, the group velocity v ₁ of light in the X ₁ axis direction coincides with the slope of the graph shown in FIG. 9, and is represented by v ₁ = −∂β ₁ / ∂κ ₁ . In FIG. 3, the + X ₁ axial orientation to the positive direction of v _1.

As shown in FIG. 3, the light incident on the incident side end face 7 of the OBO planar waveguide device 1 is κ = 0 in a state where the light is located at the point a. This light state corresponds to point A in FIG. 9, and v ₁ of light located at point a is zero. This light propagates in the first optical waveguide array, thereby causing OBO in the X ₁ axis direction while propagating in the Y ₁ axis direction. The light propagates while shifting in the + X ₁ axis direction and travels from the point a shown in FIG. 3 to the point b on the emission side end face 8. Since the length of the first optical waveguide 5 is approximately ½ period length of OBO, the state of light located at the point b corresponds to the point B in FIG. 9 and is located at the point b. The OBO phase of light is approximately π.

10, in the second optical waveguide array, and ₂ propagation constant of light κ in X ₂ axial direction, is a graph showing the relationship between the propagation constant beta ₂ of the light in the Y ₂ axially. Here, the group velocity v ₂ of the light in the X ₂ axis direction coincides with the slope of the graph shown in FIG. 10, and is represented by v ₂ = −∂β ₂ / ∂κ ₂ . In FIG. 4, the + X ₂ axial orientation to the positive direction of v _2.

The light emitted from the emission side end face 8 of the first optical waveguide 5 enters the incident side end face 9 of the second optical waveguide 6. When light propagates from the output-side end face 8 of the first optical waveguide 5 to the incident-side end face 9 of the second optical waveguide 6, the angle θ ₂ so that the OBO phase changes by −π and the second optical waveguide 6. The formation position of the incident side end face 9 is determined, and the first optical waveguide array and the second optical waveguide array are connected. As a result, the initial phase of OBO in the second optical waveguide array becomes zero. Therefore, the state of the light located at the point c corresponds to the point C shown in FIG. 10, and v ₂ of the light located at the point c is 0.

The light that propagates the second optical waveguide 6 array, causing OBO in the X ₂ axis direction while propagating in Y ₂ axially. The light propagates while shifting in the + X ₂ axis direction, and travels from the point c shown in FIG. 4 to the point d on the emission side end face 10. Since the average length of the second optical waveguide 5 is approximately ½ period length of OBO, the state of light located at the point d corresponds to the point D in FIG. 10 and is located at the point d. The OBO phase of the incident light is approximately π.

In the present embodiment, it is made incident and a light having a wavelength of lambda _1, a wavelength-multiplexed light including light having a wavelength of lambda ₂ is lambda ₁ is smaller than the wavelength to the incident side end surface 7 of the first optical waveguide 5. For example, λ ₁ is 1550 nm and λ ₂ is 1300 nm. Light having a wavelength of λ ₁ and light having a wavelength of λ ₂ propagates through the first optical waveguide 5 until the phase of OBO changes from 0 to π.

When the OBO amplitude of the light having the wavelength of λ ₁ is A ₁ , the light having the wavelength of λ ₁ is transmitted from the output side end surface 8 at a position shifted by A ₁ from the position of the incident side end surface 7 in the + X ₁ axis direction. Emitted. When the OBO amplitude of light having a wavelength of λ ₂ is A ₂ , light having a wavelength of λ ₂ is transmitted from the output side end surface 8 at a position shifted by A ₂ from the position of the incident side end surface 7 in the + X ₁ axis direction. Emitted. Note that A ₁ > A ₂ from the characteristics of OBO.

The light having the wavelength of λ _{1 and} the light having the wavelength of λ ₂ emitted from the emission side end face 8 of the first optical waveguide 5 are incident on the incident side end face 9 of the second optical waveguide 6 as shown in FIG. However, the incident position differs depending on the wavelength of light. The light having the wavelength of λ ₁ is incident on the position shifted by (A ₁ −A ₂ ) cos (| θ ₂ |) in the + X ₂ axis direction from the incident position of the light having the wavelength of λ ₂ .

As described above, the light having the wavelength of λ _{1 and} the light having the wavelength of λ ₂ incident on the incident-side end surface 9 at different positions are the second optical waveguide until the phase of the OBO changes from approximately 0 to π. 6 is propagated.

When the OBO amplitude of the light having the wavelength of λ ₁ is B ₁ , the light having the wavelength of λ ₁ is transmitted from the output side end surface 10 at a position shifted by B ₁ from the position of the incident side end surface 9 in the + X ₂ axis direction. Emitted. When the OBO amplitude of the light having the wavelength of λ ₂ is B ₂ , the light having the wavelength of λ ₂ is transmitted from the output side end surface 10 at a position shifted by B ₂ from the position of the incident side end surface 9 in the + X ₂ axis direction. Emitted. Therefore, in the X ₂ axis direction, the position of the incident side end face 9 of the light having the wavelength of λ _{1 is different from} the light having the wavelength of λ ₂ by (A ₁ −A ₂ ) cos (| θ ₂ |). As shown in FIG. 1, in the X ₂ axis direction, the position of the emission side end face 10 of light having a wavelength of λ ₁ and light having a wavelength of λ ₂ is (A ₁ −A ₂ ) cos (| θ ₂ |) + (B ₁ −B ₂ ) different.

  By providing a plurality of optical waveguide arrays connected as in the present embodiment, the difference in the path 20 due to the difference in the wavelength of light in the OBO planar waveguide device 1 becomes large. For this reason, the crosstalk at the output end face 12 of the OBO planar waveguide device 1 is reduced, and the light dispersed by the OBO planar waveguide device 1 is a single-wavelength light, respectively. 10 is output.

Note that θ ₂ is preferably −20 ° ≦ θ ₂ ≦ 20 °. By comprising in this way, the propagation loss of the light in the connection part of a 1st optical waveguide array and a 2nd optical waveguide array can be reduced.

  Further, in each optical waveguide array, when the width of the optical waveguide is W and the pitch between the optical waveguides is P, it is preferable that W / P ≧ 0.55 at the incident side end face. With this configuration, optical Bloch oscillation is expressed in an optical waveguide having a large coupling constant. According to the numerical calculation, the OBO amplitude increases in a region where the coupling constant of the optical waveguide is high, and the change amount of the OBO amplitude due to the difference in the wavelength of the light increases accordingly. Therefore, crosstalk at the output end face 12 of the planar waveguide device can be reduced.

  Furthermore, in the present embodiment, it is preferable that the optical waveguide array is formed of a semiconductor material, the pitch between the optical waveguides is 2.0 μm or less, and the height of the optical waveguide is 0.05 μm or less. With this configuration, the coupling constant of the optical waveguide is increased, and the difference in the path 20 due to the difference in the wavelength of light can be increased.

  If the difference between the OBO phase of the light located on the incident side end face and the OBO phase of the light located on the output side end face connected to the incident side end face is (2m−1) × π, The connecting portion between the waveguide arrays may have another structure.

In the second optical waveguide array formed on the most light emission side, all intersections between the straight line extending in the extending direction of the second optical waveguide 6 and the emission-side end surface 10 of the second optical waveguide 6 are the most light incident. in coordinates in the coordinate axis of the first optical waveguide array formed on a side may be located at the same Y ₁ coordinate. In this case, the output end face 12 is parallel to the input end face 11, and the input end face 11 and the output end face 12 are formed so as to be parallel to the crystal face of the Si substrate 2. The end face 12 is easily produced.

  Furthermore, if the phase of the optical Bloch oscillation of the light on the emission side end face 10 of the second optical waveguide 6 formed on the most light emission side is Y and s is an integer, (2s-5 / 4) π ≦ Y ≦ It is preferable that (2s−3 / 4) π. With this configuration, crosstalk at the output end face 12 of the OBO planar waveguide device 1 can be reduced.

Note that the OBO planar waveguide device may be manufactured by removing the substrate and using the cladding layer as a base substrate. In addition, the material of the guide layer is not limited to Si as long as it can transmit light as an optical waveguide and has a higher refractive index than the material constituting the cladding layer. For example, InGaAsP, GaAs, AlGaAs, InP Etc. may be used. The material of the clad layer is not limited to SiO ₂ as long as it has a lower refractive index than the material of the guide layer. For example, Al ₂ O ₃ , InP, AlGaAs, or the like may be used.

  Hereinafter, an OBO planar waveguide device according to Embodiment 2 of the present invention will be described in detail with reference to the drawings. In the second embodiment, the first digit of the reference numeral of the OBO planar waveguide device described in the first embodiment is the same for each portion corresponding to each portion of the OBO planar waveguide device according to the first embodiment. Reference numerals are attached. Accordingly, the corresponding parts to which the reference numerals having the same first digit numbers are assigned have the same structure and function, and therefore the description of those parts will not be repeated unless particularly necessary.

Embodiment 2
FIG. 11 is a plan view schematically showing an OBO planar waveguide device according to Embodiment 2 of the present invention. 12 is a cross-sectional view as seen from the direction of the arrow XII-XII in FIG. As shown in FIGS. 11 and 12, the OBO planar waveguide device 31 according to the second embodiment of the present invention is compared with the OBO planar waveguide device 1 according to the first embodiment in the shape of the optical waveguide and the connection of the optical waveguide array. The structure of the part is different.

In the present embodiment, as shown in FIG. 11, the width of the optical waveguide is substantially constant in each optical waveguide array. Further, as shown in FIG. 12, in order to suppress the propagation loss of the optical waveguide array, an upper cladding layer 51 made of SiO ₂ is provided so as to cover the entire optical waveguide array. In FIG. 11, the illustration of the upper cladding layer 51 is omitted.

In the present embodiment, a temperature gradient is formed in the X-axis direction of the Si substrate 32 as a substrate, the SiO ₂ layer 33 as a lower cladding layer, the Si layer 34 as a guide layer, and the SiO ₂ layer 51 as an upper cladding layer. Therefore, a heater 52 is formed on one side surface of the Si substrate 32, and a heat sink 53 is formed on the other side surface. The heater 52 and the heat sink 53 may be formed so as to cover the side surfaces from the Si substrate 32 to the SiO ₂ layer 51 as the upper clad layer. The output end face 42 of the OBO planar waveguide element 31 is formed substantially parallel to the input end face 41 of the OBO planar waveguide element 31.

  FIG. 13 is a plan view schematically showing the first optical waveguide array in the OBO planar waveguide device according to the present embodiment. FIG. 14 is a plan view schematically showing a second optical waveguide array in the OBO planar waveguide device according to the present embodiment.

Note that the coordinate axis in each optical waveguide array is in the direction orthogonal to the direction in which the optical waveguide extends on the upper surface of the substrate, from the low refractive index side to the high refractive index side of the equivalent refractive index distribution of the optical waveguide in the optical waveguide array. The X-axis is positive in the direction toward the optical axis, the Y-axis is positive in the direction in which the optical waveguide extends, and the direction away from the incident-side end face is Z-axis, and the Z-axis is perpendicular to the X-axis and Y-axis. The X axis, Y axis, and Z axis, which are coordinate axes of the first optical waveguide, are composed of the X ₁ axis, the Y ₁ axis, and the Z ₁ axis. The X axis, Y axis, and Z axis, which are coordinate axes of the second optical waveguide, are composed of the X ₂ axis, the Y ₂ axis, and the Z ₂ axis. Each arrow of X ₁ , X ₂ , Y ₁ , Y ₂ , Z ₁ , Z ₂ shown in the referenced figure indicates the direction of each coordinate axis.

  As shown in FIGS. 13 and 14, the first optical waveguide 35 extends linearly so as to be arranged substantially in parallel. The second optical waveguide 36 extends in a straight line so as to be substantially parallel. The width of the first optical waveguide 35 is constant in the first optical waveguide array. The width of the second optical waveguide 36 is constant in the second optical waveguide array.

The pitch P ₁ between the first optical waveguides 35 is constant at 1.99 μm, and the width of the first optical waveguide 35 is constant at 1.2 μm. The pitch P ₂ between the second optical waveguides 36 is constant at 2 μm, and the width of the second optical waveguide 36 is constant at 1.3 μm.

When the light propagates from the first optical waveguide array to the second optical waveguide array, the connecting portion of the first optical waveguide array and the second optical waveguide array has m as an integer, and the phase of the optical Bloch oscillation caused by the light. Is formed so as to change by (2m−1) × π. Specifically, in the OBO planar waveguide device 1 of this embodiment, the angle formed by the Y ₁ axis in the first optical waveguide array and the Y ₂ axis in the second optical waveguide array is the Y ₁ axis of the Y ₂ axis. The first optical waveguide array and the second optical waveguide array are connected to each other by determining θ ₂ that is positive in the counterclockwise direction and the formation position of the emission side end face 38 of the first optical waveguide 35.

The above θ ₂ is P ₁ × tan θ ₂ = (2m−1) where P _{2 is} the pitch between the second optical waveguides 6, n is the equivalent refractive index of the second optical waveguide, and λ is the average wavelength of light. ) × λ / (2 × n)... Satisfies the relationship of Expression (2). In Formula (2), when P ₁ is 1.99 μm, λ is 1.4 μm, n is 3.48, and m is 0, θ ₂ is −5.8 °. At this time, when light propagates from the output-side end face 38 of the first optical waveguide 35 to the incident-side end face 39 of the second optical waveguide 36, the OBO phase changes by −π.

As shown in FIG. 13, in the first optical waveguide array, all the intersections between the straight line extending in the extending direction of the first optical waveguide 35 and the incident side end face 37 of the first optical waveguide 35 are the first optical waveguide array. It is located on the X ₁ axis in the coordinate axis.

FIG. 15 is a plan view schematically showing a connection portion between the first optical waveguide and the second optical waveguide in the present embodiment. As shown in FIG. 15, the intersection point between the straight line extending in the extending direction of the first optical waveguide 35 of the first optical waveguide array and the emission-side end face 38 of the first optical waveguide 35 in the coordinate axis of the first optical waveguide array. The Y ₁ coordinate is the intersection of the straight line extending in the extending direction of the other first optical waveguide 35 adjacent to the low refractive index side of the first optical waveguide 35 and the exit side end surface 38 of the first optical waveguide 35. The coordinates are changed by P ₁ × tan θ ₂ from the Y ₁ coordinate on the coordinate axis of the first optical waveguide array.

In FIG. 15, for convenience of explanation, when the Y ₁ coordinate of the intersection of the straight line extending in the extending direction of the first optical waveguide 35 and the emission side end surface 38 of the first optical waveguide 35 is set to 0, The Y ₁ coordinate of the intersection of the straight line extending in the extending direction of the other first optical waveguide 35 adjacent to the + X ₁ direction side of the first optical waveguide 35 and the emission side end face 38 of the first optical waveguide 35 is P ₁ × tan θ ₂ .

Therefore, in the first optical waveguide array, the length of the first optical waveguide 35 in the Y ₁ axis direction changes by P ₁ × tan θ _{2 in} the + X ₁ axis direction. In the present embodiment, the length of the first optical waveguide 35 in the first optical waveguide array in the Y ₁ axis direction decreases by 0.202 μm in the + X ₁ axis direction.

  The average value of the length of the first optical waveguide 35 of the first optical waveguide array is such that the light propagating through the first optical waveguide array is oscillated for 1/2 period in the optical Bloch oscillation. The length substantially propagates through the waveguide 35. In the present embodiment, the average length of the first optical waveguide 35 is 1000 μm.

In the second optical waveguide array formed on the most light emission side, all the intersections of the straight line extending in the extending direction of the second optical waveguide 36 and the incident side end face 39 of the second optical waveguide 36 are the second optical waveguide. located on the X ₂ axis in the coordinate axes of the waveguide array, and all intersection of the straight line and the outgoing side end surface 40 of the second optical waveguide 36 extending in the extending direction of the second optical waveguide 36, the first optical waveguide array Are located at the same Y ₁ coordinate in the coordinate axes. Therefore, the output end face 42 is formed so as to be substantially parallel to the input end face 41 of the OBO planar waveguide element 31.

  In addition, the average value of the length of the second optical waveguide 36 of the second optical waveguide array is the same as that of the second optical waveguide while the light propagating through the second optical waveguide array oscillates in 1/2 period in the optical Bloch oscillation. The length substantially propagates along the waveguide 36. In the present embodiment, the average length of the second optical waveguide 36 is 1000 μm.

As shown in FIG. 15, in the present embodiment, the pitch P ₂ between the second optical waveguides 36 in the second optical waveguide array and the pitch P between the first optical waveguides 35 in the first optical waveguide array. ₁ satisfies the relationship P ₂ = P ₁ / cos | θ ₂ |.

  With this configuration, the shape of the equivalent refractive index distribution of the first optical waveguide 35 in the first optical waveguide array is similar to the shape of the equivalent refractive index distribution of the second optical waveguide 36 in the second optical waveguide array. When the light propagates from the first optical waveguide 35 to the second optical waveguide 36, the light intensity distribution does not change greatly, and the light at the connecting portion between the first optical waveguide array and the second optical waveguide array is not changed. Propagation loss can be reduced.

  Hereinafter, a method for manufacturing the OBO planar waveguide device 31 according to this embodiment will be described. FIG. 16 is a cross-sectional view schematically showing a state in which the resist film is patterned in the present embodiment. As shown in FIG. 16, a resist pattern 48 for forming an optical waveguide array is produced by processing a resist film formed on an SOI substrate by direct electron beam drawing or photolithography.

  FIG. 17 is a cross-sectional view schematically showing a state where an optical waveguide is formed by etching a guide layer in the present embodiment. As shown in FIG. 17, using the resist pattern 48 as a mask, the Si layer 34 is etched using an etching method such as ICP etching, reactive ion etching, or reactive ion beam etching. By etching the upper part of the Si layer 34 to a depth of about 0.04 μm, the first optical waveguide array and the second optical waveguide array are manufactured.

FIG. 18 is a cross-sectional view schematically showing a state in which the upper cladding layer is formed in the present embodiment. As shown in FIG. 18, after removing the resist pattern 48, the upper cladding layer and the second optical waveguide array are covered by an evaporation method, a sputtering method, or a CVD (Chemical Vapor Deposition) method so as to cover the first optical waveguide array and the second optical waveguide array. A SiO ₂ layer 51 is deposited.

In the present embodiment, the thickness of the SiO ₂ layer 51 is 200 nm, but is not limited to this value, and may be any other value as long as propagation loss in each optical waveguide array can be suppressed.

FIG. 19 is a cross-sectional view schematically showing a state in which a heater and a heat sink are formed in the present embodiment. As shown in FIG. 19, a tantalum nitride film serving as a heater 52 is formed on the side surface on the + X-axis direction side of the Si substrate 32, the SiO ₂ layer 33, the Si layer 34, and the SiO ₂ layer 51 by using a sputtering method or a vapor deposition method. Form. Further, an aluminum nitride film to be the heat sink 53 is formed on the side surface on the −X axis direction side of the Si substrate 32, the SiO ₂ layer 33, the Si layer 34, and the SiO ₂ layer 51 by using a sputtering method or a vapor deposition method. Thereafter, by cleaving the substrate along the crystal plane of the Si substrate 32, the input end face 41 and the output end face 42 of the OBO planar waveguide device 31 are formed.

Next, the operation of the OBO planar waveguide device 31 according to this embodiment will be described. The heater 52 forms a gradient in the temperature distribution in the X-axis direction of the Si substrate 32, the SiO ₂ layer 33, the Si layer 34, and the SiO ₂ layer 51 in the OBO planar waveguide device 31. The temperature of the Si substrate 32 increases as it approaches the heater 52. In general, since the refractive index of a semiconductor material increases at a high temperature, the refractive index of the first optical waveguide 35 on the heater 52 side is higher than the refractive index of the first optical waveguide 35 located on the heat sink 53 side. Therefore, a gradient is formed in the distribution of the equivalent refractive index of the first optical waveguide 35 in the first optical waveguide array.

  Then, as shown in FIG. 13, the wavelength multiplexed light is incident on the OBO planar waveguide device 31 so that the peak of the light intensity distribution 49 is positioned on the predetermined incident side end face 37. The incident light causes OBO to travel to different paths 50 depending on the wavelength of the light, and the wavelength multiplexed light is split by the first optical waveguide array.

Also in the second optical waveguide array, a gradient is formed in the distribution of the equivalent refractive index of the second optical waveguide 36 as in the first optical waveguide array. Therefore, as shown in FIG. 14, the plurality of lights dispersed in the first optical waveguide array enter the second optical waveguide 36 from the respective incident side end faces 39 of the second optical waveguide array, and in the Y ₂ axis direction. propagation to cause the OBO to X ₂ axis direction while.

In the present embodiment, the light having a wavelength of lambda _1, is incident WDM light including light having a wavelength of lambda ₂ is lambda ₁ is smaller than the wavelength to the incident end face 37 of the first optical waveguide 35. For example, λ ₁ is 1550 nm and λ ₂ is 1300 nm. When the OBO amplitude of the light having the wavelength of λ ₁ is C ₁ , the light having the wavelength of λ ₁ is transmitted from the output side end surface 38 at a position shifted by C ₁ from the position of the incident side end surface 37 in the + X ₁ axis direction. Emitted. When the OBO amplitude of the light having the wavelength of λ ₂ is C ₂ , the light having the wavelength of λ ₂ is transmitted from the output side end surface 38 at a position shifted by C ₂ from the position of the incident side end surface 37 in the + X ₁ axis direction. Emitted.

The light having the wavelength of λ _{1 and} the light having the wavelength of λ ₂ emitted from the emission side end face 38 of the first optical waveguide 35 are incident on the incident side end face 39 of the second optical waveguide 36, as shown in FIG. However, the incident position differs depending on the wavelength of light. Light having a wavelength of λ ₁ is incident at a position shifted by (C ₁ −C ₂ ) / cos (| θ ₂ |) in the + X ₂ axis direction from the incident position of light having a wavelength of λ ₂ .

As described above, the light having the wavelength of λ _{1 and} the light having the wavelength of λ ₂ incident on the incident-side end face 39 at different positions are the second optical waveguide until the phase of OBO changes from approximately 0 to π. 36 is propagated.

When the OBO amplitude of light having a wavelength of λ ₁ is D ₁ , the light having a wavelength of λ ₁ is output from the output side end surface 40 at a position shifted by D ₁ from the position of the incident side end surface 39 in the + X ₂ axis direction. Emitted. When the OBO amplitude of the light having the wavelength of λ ₂ is D ₂ , the light having the wavelength of λ ₂ is transmitted from the output side end surface 40 at a position shifted by D ₂ from the position of the incident side end surface 39 in the + X ₂ axis direction. Emitted. Therefore, in the X ₂ axis direction, the position of the incident side end face 9 of the light having the wavelength of λ _{1 is different from} the light having the wavelength of λ ₂ by (C ₁ −C ₂ ) / cos (| θ ₂ |). As shown in FIG. 11, the position of the emission side end face 40 of the light having the wavelength of λ _{1 and} the light having the wavelength of λ ₂ is (C ₁ −C ₂ ) / cos (| θ ₂ ) in the X ₂ axis direction. |) + (D ₁ −D ₂ ) different.

  In this embodiment, by adjusting the temperature of the heater, the slope of the gradient of the equivalent refractive index distribution of the optical waveguide of each optical waveguide array can be adjusted. Since the amplitude of the OBO changes depending on the slope of the gradient of the equivalent refractive index distribution of the optical waveguide, the output destination of light of each wavelength split in the OBO planar waveguide device 31 can be changed by adjusting the temperature of the heater. Therefore, the OBO planar waveguide element 31 has a function as a variable spectrometer.

  Further, in each optical waveguide array, when the width of the optical waveguide is W and the pitch between the optical waveguides is P, it is preferable that W / P ≧ 0.55 at the incident side end face. With this configuration, optical Bloch oscillation is expressed in an optical waveguide having a large coupling constant. According to the numerical calculation, the OBO amplitude increases in a region where the coupling constant of the optical waveguide is high, and the change amount of the OBO amplitude due to the difference in the wavelength of the light increases accordingly.

  According to the OBO planar waveguide device 31 in the present embodiment, the length of the first optical waveguide 35 propagates while oscillating for a half period in the optical Bloch oscillation of the light incident on the first optical waveguide 35. Since it is almost equal to the length, it is most dispersed when it propagates through the first optical waveguide 35 and then enters the second optical waveguide 36. When the light enters the second optical waveguide 36, the optical Bloch oscillation phase of the light changes by an odd multiple of a half wavelength, so that the light is further separated after entering the second optical waveguide 36. Since the length of the second optical waveguide 36 is approximately equal to the length of the optical Bloch oscillation of light incident on the second optical waveguide 36 that propagates during a half cycle, the second optical waveguide 36 propagates through the second optical waveguide 36. It is most spectroscopic when finished. Therefore, by allowing the wavelength multiplexed light to enter the OBO planar waveguide device 31, crosstalk on the output side can be reduced, and light having a single wavelength can be output from the unique output side end face. Other configurations are the same as those of the OBO planar waveguide device 1 according to the first embodiment, and thus description thereof will not be repeated.

  Hereinafter, the OBO planar waveguide device according to the third embodiment of the present invention will be described in detail with reference to the drawings. In the third embodiment, the first digit of the reference number of the OBO planar waveguide device described in the first embodiment is the same for each portion corresponding to each portion of the OBO planar waveguide device according to the first embodiment. Reference numerals are attached. Accordingly, the corresponding parts to which the reference numerals having the same first digit numbers are assigned have the same structure and function, and therefore the description of those parts will not be repeated unless particularly necessary.

Embodiment 3
FIG. 20 is a plan view schematically showing an OBO planar waveguide device according to Embodiment 3 of the present invention. 21 is a cross-sectional view as seen from the direction of the arrow XXI-XXI in FIG. As shown in FIGS. 20 and 21, the OBO planar waveguide device 61 according to the third embodiment of the present invention covers the entire optical waveguide array as compared with the OBO planar waveguide device 1 according to the first embodiment. An upper clad layer 81 made of SiO ₂ is provided. In FIG. 21, the upper clad layer 81 is not shown.

Further, in order to form a temperature gradient in the X-axis direction of the Si substrate 62 that is the substrate, the SiO ₂ layer 63 that is the lower cladding layer, the Si layer 64 that is the guide layer, and the SiO ₂ layer 81 that is the upper cladding layer, A heater 82 is formed on one side surface of 62, and a heat sink 83 is formed on the other side surface.

  Further, the output end face 72 of the OBO planar waveguide element 61 is formed substantially parallel to the input end face 71. Similar to the OBO planar waveguide device 31 of the second embodiment, the OBO planar waveguide device 61 according to the present embodiment has a function as a variable spectrometer.

  Even when the heater 82 is not operated, the widths of the first optical waveguide 65 and the second optical waveguide 66 are formed so as to gradually increase toward the + X-axis direction. A gradient is formed in the equivalent refractive index distribution of the optical waveguides of the second optical waveguide array. Therefore, even when the heater 82 is not operated, the light propagating through the OBO planar waveguide device 61 causes OBO, and the wavelength multiplexed light is split in the OBO planar waveguide device 61. As described above, the OBO planar waveguide device 61 according to the present embodiment has a function as a variable spectroscope by including the heater 82, and can disperse light even when the heater 82 is not operated. The power consumption can be reduced. Other configurations are the same as those of the OBO planar waveguide devices 1 and 31 of the first embodiment or the second embodiment, and thus description thereof will not be repeated.

  In addition, the said embodiment disclosed this time is an illustration in all the points, Comprising: It does not become a basis of limited interpretation. Therefore, the technical scope of the present invention is not interpreted only by the above-described embodiments, but is defined based on the description of the scope of claims. Further, all modifications within the meaning and scope equivalent to the scope of the claims are included.

  1, 31, 61, 100 Planar waveguide device, 2, 32, 62, 101 Substrate, 3, 33, 63 Clad layer, 4, 34, 64 Guide layer, 5, 35, 65 First optical waveguide, 6, 36 , 66 Second optical waveguide, 7, 9, 37, 39 Incident side end face, 8, 10, 38, 40 Output side end face, 11, 41, 71 Input end face, 12, 42, 72 Output end face, 13 Center line, 14 Center line, 15 intersections, 16 interfaces, 17 resist film, 18, 48 resist pattern, 19, 49 light intensity distribution, 20, 50, 108 light path, 51, 81 upper cladding layer, 52, 82, 106 heater, 53, 83, 107 Heat sink, 102 Optical waveguide, 103 Polymer clad layer, 104 Input side end face, 105 Output side end face

Claims (15)

A substrate,
A clad layer laminated on the substrate;
And a guide layer laminated on the cladding layer and having a higher refractive index than the cladding layer,
On the upper part of the guide layer, a plurality of optical waveguide arrays including a plurality of optical waveguides extending linearly so as to be arranged in parallel are continuously formed in the light propagation direction,
Each of the optical waveguide arrays includes at least one optical waveguide having an incident-side end face on which light is incident,
Each of the optical waveguide arrays includes at least two optical waveguides each having an emission side end surface from which light is emitted;
In each of the optical waveguides in the optical waveguide array, a gradient is formed in the equivalent refractive index distribution in one direction in the direction in which the optical waveguides are arranged,
In the optical waveguide array formed adjacent to each other, the optical waveguide having the incident-side end surface and the optical waveguide having the output-side end surface included therein are connected to each other at a predetermined angle, The end surface of the first optical waveguide of the first optical waveguide array formed on the incident side of the first optical waveguide and the end surface of the second optical waveguide of the second optical waveguide array formed on the output side of the light are connected to each other And
The connecting portion between the first optical waveguide array and the second optical waveguide array is optically generated when the light propagates from the first optical waveguide array to the second optical waveguide array, where m is an integer. It is formed so that the phase of Bloch oscillation changes (2m-1) × π,
The average value of the length of the optical waveguide of each of the optical waveguide arrays is determined by the optical waveguides while the light propagating through the respective optical waveguide arrays vibrates for ½ period in optical Bloch oscillation. A planar waveguide element that approximately matches the length of propagation. In each of the optical waveguide arrays, from the low refractive index side to the high refractive index side of the equivalent refractive index distribution of the optical waveguide in the optical waveguide array in a direction orthogonal to the direction in which the optical waveguide extends on the upper surface of the substrate The first optical waveguide array when a coordinate axis consisting of an X axis with a positive direction toward the positive axis and a Y axis with a positive direction away from the incident side end face is placed in the direction in which the optical waveguide extends. theta ₂ to the counterclockwise positive with respect to Y ₁ axis of the Y ₂ axis with an angle formed between the Y ₂ axis is the Y-axis in the second optical waveguide array and Y ₁ axis is the Y axis in the If the pitch between the second optical waveguides is P ₂ , the equivalent refractive index of the second optical waveguide is n, and the average wavelength of the light is λ, then P ₂ × tan θ ₂ = (2m−1) × λ / ( 2 × n)
In the first optical waveguide array formed closest to the incident side, all the intersections between the straight line extending in the extending direction of the first optical waveguide and the incident side end surface of the first optical waveguide are the first optical waveguide array. located X ₁ axis is the X axis in the coordinate axes of the optical waveguide array, also, all the intersection between the end surface on the outputting side of the first said a straight line extending in the extending direction of the optical waveguide first optical waveguide , Located at the same Y ₁ coordinate in the coordinate axis of the first optical waveguide array,
In the second optical waveguide array, the Y ₂ coordinate on the coordinate axis of the second optical waveguide array at the intersection of the straight line extending in the extending direction of the one second optical waveguide and the output side end surface of the first optical waveguide. However, the second light guide at the intersection of the straight line extending in the extending direction of the other second optical waveguide adjacent to the low refractive index side of the one second optical waveguide and the output side end face of the first optical waveguide. The coordinates are changed by −P ₂ × tan θ ₂ from the Y coordinate on the coordinate axis of the waveguide array, and all the intersections of the straight line extending in the extending direction of the second optical waveguide and the output side end surface of the second optical waveguide are 2. The planar waveguide device according to claim 1, wherein the planar waveguide element is located at the same Y ₂ coordinate in the coordinate axis of the second optical waveguide array. In each of the optical waveguide arrays, from the low refractive index side to the high refractive index side of the equivalent refractive index distribution of the optical waveguide in the optical waveguide array in a direction orthogonal to the direction in which the optical waveguide extends on the upper surface of the substrate The first optical waveguide array when a coordinate axis consisting of an X axis with a positive direction toward the positive axis and a Y axis with a positive direction away from the incident side end face is placed in the direction in which the optical waveguide extends. theta ₂ to the counterclockwise positive with respect to Y ₁ axis of the Y ₂ axis with an angle formed between the Y ₂ axis is the Y-axis in the second optical waveguide array and Y ₁ axis is the Y axis in the _2. The relation of P ₂ = P ₁ × cos | θ ₂ | is satisfied, where P _{1 is} a pitch between the first optical waveguides and P ₂ is a pitch between the second optical waveguides. Planar waveguide element. In each of the optical waveguide arrays, from the low refractive index side to the high refractive index side of the equivalent refractive index distribution of the optical waveguide in the optical waveguide array in a direction orthogonal to the direction in which the optical waveguide extends on the upper surface of the substrate The first optical waveguide array when a coordinate axis consisting of an X axis with a positive direction toward the positive axis and a Y axis with a positive direction away from the incident side end face is placed in the direction in which the optical waveguide extends. theta ₂ to the counterclockwise positive with respect to Y ₁ axis of the Y ₂ axis with an angle formed between the Y ₂ axis is the Y-axis in the second optical waveguide array and Y ₁ axis is the Y axis in the If the pitch between the first optical waveguides is P ₁ , the equivalent refractive index of the second optical waveguide is n, and the average wavelength of the light is λ, then P ₁ × tan θ ₂ = (2m−1) × λ / ( 2 × n)
In the first optical waveguide array, all intersections of the straight line extending in the extending direction of the first optical waveguide and the incident side end surface of the first optical waveguide are the X in the coordinate axis of the first optical waveguide array. located on the X ₁ axis is an axis, also the point of intersection between the said exit side end surface of one said the straight line extending in a first extending direction of the optical waveguide first optical waveguide of the first optical waveguide array The Y ₁ coordinate on the coordinate axis of the first optical waveguide array has a straight line extending in the extending direction of the other first optical waveguide adjacent to the low refractive index side of the first optical waveguide and the first optical waveguide. The coordinates are changed by P ₁ × tan θ ₂ from the Y ₁ coordinate in the coordinate axis of the first optical waveguide array at the intersection point with the emission side end face,
In the second optical waveguide array, all intersections between the straight line extending in the extending direction of the second optical waveguide and the incident side end surface of the second optical waveguide are in coordinates on the coordinate axis of the second optical waveguide array. The planar waveguide device according to claim 1, which is located at the same Y ₂ coordinate. In each of the optical waveguide arrays, from the low refractive index side to the high refractive index side of the equivalent refractive index distribution of the optical waveguide in the optical waveguide array in a direction orthogonal to the direction in which the optical waveguide extends on the upper surface of the substrate The first optical waveguide array when a coordinate axis consisting of an X axis with a positive direction toward the positive axis and a Y axis with a positive direction away from the incident side end face is placed in the direction in which the optical waveguide extends. theta ₂ to the counterclockwise positive with respect to Y ₁ axis of the Y ₂ axis with an angle formed between the Y ₂ axis is the Y-axis in the second optical waveguide array and Y ₁ axis is the Y axis in the P ₁ pitch between the first optical waveguide to each other, when the pitch between the second optical waveguide to each other and P _2, the second optical waveguide, P ₂ = P ₁ / cos | a relationship | theta ₂ The planar waveguide device according to claim 1, wherein the planar waveguide device is satisfied.   2. The planar waveguide device according to claim 1, wherein in each of the optical waveguide arrays, the width of the optical waveguide becomes wider in one direction in a direction in which the optical waveguides are arranged.   In each of the optical waveguide arrays, W / P ≧ 0.55 at the incident side end surface, where W is a width of the optical waveguides and P is a pitch between the optical waveguides. The planar waveguide element as described.   The planar waveguide device according to claim 1, wherein a heater is formed on one side surface of the substrate in a direction in which the optical waveguides are arranged, and a heat sink is formed on the other side surface.   In each of the optical waveguide arrays, if the width of the optical waveguides is W and the pitch between the optical waveguides is P, each of the width and the pitch satisfies W / P ≧ 0.55 and is substantially constant. The planar waveguide device according to claim 1, which has a value of In the second optical waveguide array formed on the most output side, all the intersections of the straight line extending in the extending direction of the second optical waveguide and the output side end surface of the second optical waveguide are the most on the incident side. 2. The planar waveguide device according to claim 1, wherein the planar waveguide device is located at the same Y ₁ coordinate in the coordinate axis of the first optical waveguide array formed in 1.   When the phase of the optical Bloch oscillation of the light on the exit side end face of the second optical waveguide formed on the most exit side is Y and s is an integer, (2s-5 / 4) π ≦ Y ≦ (2s The planar waveguide device according to claim 1, which is −3/4) π. The planar waveguide device according to claim 1, wherein the θ ₂ is −20 ° ≦ θ ₂ ≦ 20 °.   The intersection of the virtual center line of the first optical waveguide and the virtual center line of the second optical waveguide corresponding to the first optical waveguide is the difference between the first optical waveguide array and the second optical waveguide array. The planar waveguide device of claim 1, located on the interface. L _{1 is} the width of the first optical waveguide at the exit end face of the first optical waveguide, and the width of the second optical waveguide at the entrance end face of the second optical waveguide connected to the first optical waveguide. When L _2, is L ₁ ≦ L _2, planar waveguide device according to claim 1.   2. The planar waveguide according to claim 1, wherein the optical waveguide array is formed of a semiconductor material, a pitch between the optical waveguides is 2.0 μm or less, and a height of the optical waveguide is 0.05 μm or less. element.

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