JP2008180943A - Planar waveguide element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a planar waveguide element capable of outputting a signal wave from a proper output port as the signal wave of a single wavelength even when the wavelength spacing of wavelength multiplexed signal waves which are inputted into the planar waveguide element is narrowed. <P>SOLUTION: The OBO planar waveguide element 1 includes an SOI substrate 10, optical waveguides 30 of three or more which are arranged side by side on the SOI substrate 10 and can propagate the signal wave 99 and a heater 40 which heats the SOI substrate 10. Therein, at least one optical waveguide 30 can input the signal wave 99 to an inputting terminal part 31, and at least two optical waveguides 30 arranged on the side nearer to the heater 40 than the optical waveguide 30 can output the signal wave 99 from an outputting terminal part 32. Further, on the terminal part of the side opposite to the side of the inputting terminal part 31, a first HR coating 60A which reflects the signal wave 99 so as to propagate the same to the side getting near to the heater 40 is formed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a planar waveguide device, and more specifically, uses optical Bloch oscillation to demultiplex a wavelength-multiplexed signal wave, and each of the demultiplexed signal waves to a desired output port. The present invention relates to a planar waveguide device that outputs from the above.

  In wavelength division multiplexing (hereinafter referred to as “WDM”) optical communication, a multiplexed signal wave consisting of a signal wave with a wavelength of 1.55 μm and a signal wave with a wavelength of 1.3 μm is a single optical fiber. It is transmitted with. Therefore, according to WDM optical communication, high-capacity and high-speed optical communication can be realized.

  In WDM optical communication, an element that demultiplexes multiplexed signal waves is required so that each signal wave is output from a designated port. As a branching element that performs such a function, there is a planar waveguide element (hereinafter referred to as “OBO planar waveguide element”) using optical Bloch oscillations (hereinafter referred to as “OBO”). It has been proposed (see, for example, non-patent documents 1 to 3).

Hereinafter, the OBO planar waveguide device disclosed in Non-Patent Document 2 will be described as an example of the prior art. FIG. 23 is a schematic perspective view showing a conventional OBO planar waveguide device disclosed in Non-Patent Document 2. As shown in FIG. Referring to FIG. 23, a conventional OBO planar waveguide device 100 is composed of a substrate 110 made of SiO ₂ (silicon dioxide) and glass, arranged side by side on the substrate 110, made of a polymer material, and light (signal wave). Are provided with a plurality of optical waveguides 130 and a polymer clad layer 120 that prevents the propagating signal waves from leaking out of the optical waveguides. An input port 131 through which signal waves are incident is provided at one end of the plurality of optical waveguides 130, and an output port 132 through which signal waves are emitted is provided at the other end opposite to the input port 131. Furthermore, the conventional OBO planar waveguide device 100 includes a heater 140 disposed at one end of the substrate 110 in a direction in which the optical waveguides 130 are arranged, and a heat sink 150 disposed at the other end opposite to the heater 140. It has more. The heater 140 and the heat sink 150 can control the temperature distribution (temperature gradient) of the substrate 110.

  Here, with reference to FIG. 23, dotted arrows indicate signal wave paths 190 that propagate while oscillating in the X-axis direction in the plurality of optical waveguides 130 in the OBO planar waveguide device 100. In FIG. 23, the direction in which the plurality of optical waveguides 130 are arranged is the X-axis direction, the extending direction of each optical waveguide 130 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, referring to FIG. 23, a substrate 110 made of SiO ₂ and glass is prepared, and a polymer material to be an optical waveguide 130 is deposited on the substrate 110. Then, after applying a resist on the polymer material to form a resist film, the pattern of the optical waveguide 130 is formed on the resist film by electron beam drawing or photolithography. Further, the above-described polymer material is etched using the resist film on which this pattern is formed as a mask. Thereby, the optical waveguide 130 is formed on the substrate 110. Thereafter, a polymer clad layer 120 is deposited on the substrate 110 so as to cover the surface of the substrate 110 where the optical waveguide 130 is formed and the optical waveguide 130. Furthermore, the heater 140 is attached to one side end of the substrate 110 in the X-axis direction, and the heat sink 150 is attached to the other side end. Through the above steps, the OBO planar waveguide device 100 can be manufactured. Non-Patent Document 2 does not describe processing of the end portion of the optical waveguide 130.

  Next, the operation of the OBO planar waveguide device 100 will be described. Referring to FIG. 23, in OBO planar waveguide device 100, the temperature difference per unit length in the X-axis direction of substrate 110 can be controlled by the function of heater 140 and heat sink 150. The difference in refractive index per unit length of the optical waveguide 130 in the X-axis direction 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 demultiplexer.

  This will be specifically described below. In the OBO planar waveguide device 100 having the optical waveguide 130 made of a polymer material, the refractive index of the optical waveguide 130 at a position where the substrate 110 is at a high temperature is higher than the refractive index of the optical waveguide 130 at a position where the substrate 110 is at a low temperature. Is also relatively low.

  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 110 by the functions of the heater 140 and the heat sink 150. Then, a plurality of signal waves having different wavelengths are input into the OBO planar waveguide device 100 so that the intensity peak of the signal wave is positioned at one predetermined input port 131. At this time, each of the plurality of signal waves leaks from the traveling optical waveguide 130 and is coupled to the adjacent optical waveguide 130. As a result, the plurality of signal waves cause OBO in the X-axis direction while propagating in the Y-axis direction.

  The multiplexed signal wave is a superposition of a plurality of signal waves having different wavelengths. In general, the amplitude of the OBO increases as the wavelength of the signal wave increases. That is, according to the nature of OBO, the amplitude of OBO differs for each wavelength of the signal wave. In addition, OBO has a property that its amplitude decreases as the difference in refractive index per unit length in the X-axis direction of the optical waveguide 130, that is, the gradient of the refractive index distribution in the X-axis direction of the optical waveguide 130 increases. Have. Therefore, in the multiplexed signal wave input to the OBO planar waveguide device 100, the path 190 propagating in the OBO planar waveguide device 100 differs depending on the wavelength. That is, the multiplexed signal wave is demultiplexed in the OBO planar waveguide device 100. Each of the demultiplexed signal waves is output from the unique output port 132 as a single wavelength signal wave.

Further, the difference in refractive index per unit length in the X-axis direction of the optical waveguide 130 is controlled by adjusting the gradient of the temperature distribution in the X-axis direction of the substrate 110 using the heater 140 and the heat sink 150. By controlling the difference in refractive index, the amplitude of the OBO of the demultiplexed signal wave can be adjusted, and the output port 132 of each signal wave can be freely specified. As described above, the OBO planar waveguide device 100 can be used as a variable demultiplexer.
R. Morandotti, U. Peschel, J. et al. S. Aitchison, "Experimental Observation of Linear and Nonlinear Optical Block Oscillations", Physical Review Letters, Vol. 83, No. 23, 4756-4759 (1999). T.A. Pertsch, P.M. Dannberg, W.D. Elflein, A.M. Brauer, "Optical Bloch Oscillations in Temperature Tuned Waveguide Arrays", Physical Review letters, Vol. 83, No. 23, 4752-4755 (1999). U. Peschel, T .; Pertsch, F.A. Lederer, “Optical Bloch Oscillations in Waveguide Arrays”, Optics Letters, Vol. 23, No. 21, 1701-1703 (1998).

  In WDM optical communication, in order to increase the capacity and speed, it is possible to adopt a method of multiplexing more signal waves having different wavelengths within the wavelength band of 1.55 μm or 1.3 μm. . Here, since the entire bandwidth of the multiplexed signal wave is constant, in order to implement the above countermeasure, it is necessary to narrow the wavelength interval of the multiplexed signal wave. Then, in the configuration of the OBO planar waveguide device 100 described in Non-Patent Document 2, the difference in OBO amplitude of each of the multiplexed signal waves is reduced due to the nature of OBO. As a result, in the plurality of signal wave paths 190 propagating in the OBO planar waveguide device 100, the interval in the vibration direction (X-axis direction in FIG. 23) of the OBO is narrowed. When the difference in the amplitude of the OBO of the multiplexed signal wave becomes shorter than the distance between the centers of the optical waveguides 130, a plurality of signal waves are output from the same output port 132. In this case, each of the demultiplexed signal waves is not output as a single wavelength signal wave from the unique output port 132, and the OBO planar waveguide device 100 does not function sufficiently as a demultiplexer.

  The present invention solves the above-mentioned problem, and even if the wavelength interval of the wavelength-multiplexed signal wave input into the planar waveguide element is narrow, the signal wave of a single wavelength is transmitted from a unique output port. An object of the present invention is to provide a planar waveguide element capable of outputting a signal wave.

  A planar waveguide device according to the present invention includes a substrate having a low refractive index layer, a high refractive index layer disposed on the low refractive index layer and having a higher refractive index than the low refractive index layer, and a substrate. Three or more optical waveguides arranged side by side and capable of propagating signal waves, and a heating member arranged at one end of the substrate in the direction in which the optical waveguides are arranged to heat the substrate. Then, at least one of the three or more optical waveguides can input a signal wave to an end portion in the extending direction of the optical waveguide. Furthermore, at least two of the three or more optical waveguides arranged on the side closer to the heating member than the optical waveguide having an end portion to which a signal wave can be input are end portions in the extending direction of the optical waveguide. A signal wave can be output from the unit. And, in the end portion in the extending direction of the optical waveguide opposite to the end portion where the signal wave can be input in the three or more optical waveguides, the signal wave is propagated to the side closer to the heating member. A reflective first reflecting portion is formed.

  In the planar waveguide device of the present invention, when a plurality of multiplexed signal waves having different wavelengths are input to the optical waveguide, the signal wave propagates in the extending direction of the optical waveguide, and then the end of the optical waveguide device. It is reflected by the first reflecting portion formed in the portion and further propagates so as to approach the heating member. At this time, based on the nature of OBO, when the multiplexed signal wave is reflected by the first reflection unit, the distance between the paths of propagation of the multiplexed signal waves is widened in the direction in which the signal wave travels. As a result, according to the planar waveguide device of the present invention, a signal wave is output from a specific output port as a single wavelength signal wave even if the wavelength interval of the input wavelength multiplexed signal wave is narrowed. It becomes possible to do.

  Preferably, in the planar waveguide element, the first reflection unit may be configured such that, when the signal wave is reflected by the first reflection unit, the phase of the OBO of the signal wave after the reflection is the phase of the OBO of the signal wave before the reflection. It arrange | positions so that (pi) may change. Further, in the extending direction of the optical waveguide, the distance from the end portion where the signal wave can be input to the first reflecting portion is a half period length of OBO (Optical Bloch Oscillations) generated by the signal wave. It has become. Note that the ½ period length indicates the distance that the signal wave propagates in the extending direction of the optical waveguide during the ½ period of the OBO generated by the signal.

  As a result, the signal wave input to the optical waveguide propagates in the extending direction of the optical waveguide, and when it reaches the first reflecting portion, the phase of the OBO changes by π and is reflected by the first reflecting portion. The phase of the OBO of the signal wave changes by π. As a result, the signal wave reflected at the first reflecting portion propagates to the side closer to the heating member.

Preferably, in the planar waveguide element, when a coordinate axis having a positive direction away from the end where the signal wave can be input is placed in the direction in which the optical waveguide having the end where the signal wave can be input extends, The first reflection position, which is the coordinate on the coordinate axis of the intersection of the straight line extending in the extending direction of one of the three or more optical waveguides and the first reflecting portion, is the heating member side of the one optical waveguide. compared to (2m + 1) × λ / 4n w by monotonically increasing or monotonically decreasing in the first reflection position in the optical waveguide adjacent to the opposite side of the. Here, m is an integer greater than or equal to 0, λ is the wavelength of the signal wave, and n _w is the equivalent refractive index of the optical waveguide.

Thus, when the signal wave is reflected by the first reflecting portion, the phase of the OBO of the signal wave after reflection changes by π with respect to the phase of the OBO of the signal wave before reflection. Incidentally, the error of the first reflecting position to decrease monotonically increasing or is preferably within 10% ± for values of (2m + 1) × λ / 4n w.

  Preferably, in the planar waveguide element, the optical waveguide disposed closer to the heating member than the optical waveguide having an end capable of inputting a signal wave is opposite to the first reflecting portion in the extending direction of the optical waveguide. A second reflection portion that reflects the signal wave so as to propagate to the side closer to the heating member is further formed at the end portion on the side.

  As a result, when a plurality of multiplexed signal waves having different wavelengths are input to the optical waveguide, the signal waves propagate in the extending direction of the optical waveguide, are reflected by the first reflecting portion, and then further It is reflected at the reflecting portion and propagates so as to approach the heating member. For this reason, in the direction in which the signal wave travels, the distance between the paths of propagation of the multiplexed signal waves further increases. As a result, even if the wavelength interval of the input wavelength-multiplexed signal wave is narrowed, it becomes easier to output the signal wave from the unique output port as a single wavelength signal wave.

  Preferably, in the planar waveguide element, the first reflecting portion and the second reflecting portion are configured such that when the signal wave is reflected by the first reflecting portion and the second reflecting portion, the OBO phase of the reflected signal wave is before reflection. The signal waves are arranged so as to change by π with respect to the phase of the OBO. Furthermore, in the extending direction of the optical waveguide, the distance from the end where the signal wave can be input to the first reflecting part and the distance from the first reflecting part to the second reflecting part are both OBO ( Optical Bloch Oscillations) (1/2 period length).

  As a result, the signal wave input to the optical waveguide propagates in the extending direction of the optical waveguide, and when it reaches the first reflecting portion, the phase of the OBO changes by π and is reflected by the first reflecting portion. The phase of the OBO of the signal wave changes by π. Furthermore, when the signal wave reflected by the first reflecting portion propagates in the extending direction of the optical waveguide and reaches the second reflecting portion, the phase of the OBO changes by π, and at the second reflecting portion When reflected, the phase of the OBO of the signal wave changes by π. As a result, both signal waves reflected by the first reflecting portion and the second reflecting portion propagate to the side approaching the heating member.

Preferably, in the planar waveguide element, when a coordinate axis having a positive direction away from the end where the signal wave can be input is placed in the direction in which the optical waveguide having the end where the signal wave can be input extends, The first reflection position, which is the coordinate on the coordinate axis of the intersection of the straight line extending in the extending direction of one of the three or more optical waveguides and the first reflecting portion, is the heating member side of the one optical waveguide. and as compared with the first reflection position in the optical waveguide adjacent to the opposite side, decreasing (2m + 1) × λ / 4n w by monotonous increase or monotonous. Furthermore, the second reflection position, which is a coordinate on the coordinate axis of the intersection of the straight line extending in the extending direction of one of the three or more optical waveguides and the second reflecting portion, is the heating of the one optical waveguide. the member side than the second reflection position in the optical waveguide adjacent to the opposite side, decreasing (2m + 1) × λ / 4n w by monotonous increase or monotonous. Here, m is an integer greater than or equal to 0, λ is the wavelength of the signal wave, and n _w is the equivalent refractive index of the optical waveguide.

As a result, when the signal wave is reflected by the first reflection unit and when the signal wave is reflected by the second reflection unit, the phase of the OBO of the signal wave after reflection is the same as that of the OBO of the signal wave before reflection. Π changes with respect to phase. Incidentally, the error of the first reflecting position and a second reflecting position decreases monotonically increasing or is preferably within 10% ± for values of (2m + 1) × λ / 4n w.

  Preferably, in the planar waveguide element, the first reflection unit may be configured such that, when the signal wave is reflected by the first reflection unit, the phase of the OBO of the signal wave after the reflection is the phase of the OBO of the signal wave before the reflection. Arranged so as not to change. Further, the second reflection unit is arranged such that when the signal wave is reflected by the second reflection unit, the phase of the OBO of the signal wave after reflection changes by π with respect to the phase of the OBO of the signal wave before reflection. The In the extending direction of the optical waveguide, the distance from the end where the signal wave can be input to the first reflecting part, and the distance from the first reflecting part to the second reflecting part are both the OBO where the signal wave is generated. It is a quarter cycle length. Note that the ¼ period length indicates a distance in which a signal wave propagates in the extending direction of the optical waveguide during a ¼ period of OBO generated by the signal.

  As a result, the signal wave input to the optical waveguide propagates in the extending direction of the optical waveguide, and when it reaches the first reflecting portion, the phase of the OBO changes by π / 2, and at the first reflecting portion The phase of the OBO of the signal wave does not change when reflected. Therefore, the signal wave reflected at the first reflecting portion propagates to the side approaching the heating member. Further, the signal wave reflected by the first reflecting portion propagates in the extending direction of the optical waveguide, and when it reaches the second reflecting portion, the phase of the OBO changes by π from the time when it is input to the optical waveguide. And the phase of the OBO of the signal wave changes by π when reflected by the second reflecting portion. Therefore, the signal wave reflected at the second reflecting portion propagates to the side approaching the heating member. As a result, both signal waves reflected by the first reflecting portion and the second reflecting portion propagate to the side approaching the heating member. Further, in the extending direction of the optical waveguide, the distance from the end where the signal wave can be input to the first reflecting part, and the distance from the first reflecting part to the second reflecting part is 1 / OBO of the signal wave. Compared with the case where the length is two periods, the length of the optical waveguide element can be shortened in the extending direction of the optical waveguide, and the thermal resistivity of the substrate can be increased in the direction in which the optical waveguides are arranged. As a result, it becomes easy to give a temperature gradient to the optical waveguide element in the direction in which the optical waveguides are arranged, and energy (for example, electric power) consumed in the heating member can be reduced.

Preferably, in the planar waveguide element, when a coordinate axis having a positive direction away from the end where the signal wave can be input is placed in the direction in which the optical waveguide having the end where the signal wave can be input extends, The first reflection position, which is the coordinate on the coordinate axis, of the intersection of the straight line extending in the extending direction of each of the three or more optical waveguides and the first reflecting portion is constant. Furthermore, the second reflection position, which is a coordinate on the coordinate axis of the intersection of the straight line extending in the extending direction of one of the three or more optical waveguides and the second reflecting portion, is the heating of the one optical waveguide. the member side than the second reflection position in the optical waveguide adjacent to the opposite side, decreasing (2m + 1) × λ / 4n w by monotonous increase or monotonous. Here, m is an integer greater than or equal to 0, λ is the wavelength of the signal wave, and n _w is the equivalent refractive index of the optical waveguide.

Thereby, when the signal wave is reflected by the first reflection part, the phase of the OBO of the signal wave after reflection does not change with respect to the phase of the OBO of the signal wave before reflection, and the signal wave is reflected by the second reflection part. At the time of reflection, the phase of OBO of the signal wave after reflection changes by π with respect to the phase of OBO of the signal wave before reflection. The first reflection position is constant, and monotonically increasing or decreasing error of the second reflection position is preferably within 10% ± for values of (2m + 1) × λ / 4n w.

  Preferably, in the planar waveguide element, the first reflection unit may be configured such that, when the signal wave is reflected by the first reflection unit, the phase of the OBO of the signal wave after the reflection is the phase of the OBO of the signal wave before the reflection. Arranged so as not to change. Further, in the extending direction of the optical waveguide, the distance from the end portion where the signal wave can be input to the first reflecting portion is ¼ period length of OBO generated by the signal wave.

  As a result, the signal wave input to the optical waveguide propagates in the extending direction of the optical waveguide, and when it reaches the first reflecting portion, the phase of the OBO changes by π / 2, and at the first reflecting portion The phase of the OBO of the signal wave does not change when reflected. Therefore, the signal wave reflected at the first reflecting portion propagates to the side approaching the heating member. As a result, the signal wave reflected at the first reflecting portion propagates to the side closer to the heating member. Further, in the extending direction of the optical waveguide, the distance from the end where the signal wave can be input to the first reflecting portion is set to be 1/2 the length of the OBO generated by the signal wave. The length of the optical waveguide element can be shortened in the extending direction, and the thermal resistivity of the substrate can be increased in the direction in which the optical waveguides are arranged. As a result, it becomes easy to give a temperature gradient to the optical waveguide element in the direction in which the optical waveguides are arranged, and energy (for example, electric power) consumed in the heating member can be reduced.

  Preferably, in the planar waveguide element, when a coordinate axis having a positive direction away from the end where the signal wave can be input is placed in the direction in which the optical waveguide having the end where the signal wave can be input extends, The first reflection position, which is a coordinate on the coordinate axis of the intersection of the straight line extending in the extending direction of each of the three or more optical waveguides and the first reflection portion, is constant.

Thereby, when the signal wave is reflected by the first reflecting portion, the phase of the OBO of the signal wave after reflection does not change with respect to the phase of the OBO of the signal wave before reflection. Incidentally, the error of the first reflection position is constant, it is preferably within ± 10% of (2m + 1) × λ / 4n w.

  In the planar waveguide element, preferably, the first reflecting portion and the second reflecting portion are HR (High Reflection) coating. Thereby, in the 1st reflective part and the 2nd reflective part, a signal wave can be reflected by high reflectance, for example, reflectance 90% or more. The HR coating refers to a multilayer coating that exhibits high reflectivity or total reflection with respect to a signal wave.

  In the planar waveguide element, preferably, the first reflecting portion and the second reflecting portion are photonic crystals. The frequency band of the signal wave is located within the photonic band gap of the photonic crystal. Thereby, a 1st reflection part and a 2nd reflection part can be formed easily, and manufacture of a planar waveguide element becomes easy. Here, in order for the frequency band of the signal wave to be located in the photonic band gap, a condition is necessary that the signal wave propagating through the optical waveguide causes Bragg reflection in the photonic crystal. That is, a structure having a periodic refractive index distribution at about half the wavelength of the signal wave in the optical waveguide is required.

  As is clear from the above explanation, even if the wavelength interval of the wavelength-multiplexed signal wave input into the planar waveguide element is narrow, the signal wave is transmitted from the specific output port as a single wavelength signal wave. A planar waveguide element capable of outputting can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
FIG. 1 is a schematic plan view showing a configuration of a planar waveguide device according to the first embodiment which is an embodiment of the present invention. FIG. 2 is a schematic side view showing the configuration of the planar waveguide device according to the first embodiment which is an embodiment of the present invention. FIG. 3 is an enlarged schematic partial plan view showing the vicinity of the HR coating shown in FIG. With reference to FIGS. 1-3, the structure of the planar waveguide element in Embodiment 1 is demonstrated.

Referring to FIGS. 1 and 2, OBO planar waveguide device 1 which is a planar waveguide device in the first embodiment is arranged side by side on SOI (silicon on insulator) substrate 10 as a substrate and SOI substrate 10. Three or more optical waveguides 30 through which the signal wave 99 can propagate, and a heater 40 as a heating member that is disposed at one end of the SOI substrate 10 in the direction in which the optical waveguides 30 are arranged, and heats the SOI substrate 10 And a heat sink 50 disposed at the other end opposite to the heater 40 in the direction in which the optical waveguides 30 are arranged, and cooling the SOI substrate 10 by releasing the heat of the SOI substrate 10 to the outside. ing. SOI substrate 10 includes a Si substrate 11 made of Si (silicon), and the SiO ₂ layer 12 as a low refractive index layer made of SiO ₂ (silicon dioxide) is disposed on the SiO ₂ layer 12, from the SiO ₂ layer 12 And a Si layer 13 made of Si (silicon) as a high refractive index layer having a large refractive index.

The Si substrate 11 has a thickness of 600 μm. However, if the element can be divided and the mechanical strength of the divided element is sufficiently maintained, the thickness of the Si substrate 11 is not limited to 600 μm, and is 50 μm or more and 800 μm or less. I just need it. The SiO ₂ layer 12 has a thickness of 1 μm. However, if the signal wave propagating through the optical waveguide does not leak into the Si substrate, the thickness of the SiO ₂ layer 12 is not limited to 1 μm and may be 0.3 μm or more. Furthermore, the Si layer 13 has a thickness of 0.19 μm. However, the thickness of the Si layer 13 is not limited to 0.19 μm as long as a signal wave propagating through a certain optical waveguide can be combined with an adjacent optical waveguide to develop OBO, and the thickness of the Si layer 13 is not limited to 0.19 μm. What is necessary is just 25 micrometers or less.

Further, among the three or more optical waveguides 30, in the input optical waveguide 30 </ b> A, signal waves having wavelengths λ ₁ to λ _k are multiplexed on the input end portion 31 that is an end portion in the extending direction of the optical waveguide 30. The input signal wave 99 can be input. This input end 31 can function as an input port of the OBO planar waveguide device 1. Of the three or more optical waveguides 30 disposed on the side closer to the heater 40 than the input optical waveguide 30A, the output optical waveguide 30B is an end portion in the extending direction of the optical waveguide 30. A signal wave 99 demultiplexed from the end 32 can be output. The output end 32 can function as an output port of the OBO planar waveguide device 1.

  In the three or more optical waveguides 30, the signal wave 99 is propagated to the side closer to the heater 40 at the end in the extending direction of the optical waveguide 30 on the side opposite to the input end 31 side. A first HR (High Reflection) coating 60 </ b> A is formed as a first reflecting portion that reflects light.

  Further, the signal wave 99 is applied to the heater 40 at the end of the optical waveguide 30 disposed closer to the heater 40 than the input optical waveguide 30A on the opposite side of the first HR coating 60A in the extending direction of the optical waveguide 30. 2nd HR coating 60B as a 2nd reflection part which reflects so that it may propagate to the side which approaches is formed.

  More specifically, a plurality of optical waveguides 30 are provided on the Si layer 13. The direction in which the plurality of optical waveguides 30 are arranged is the X-axis direction, the direction in which the optical waveguide 30 extends is the Y-axis direction, and the direction perpendicular to each of the X-axis direction and the Y-axis direction is the Z-axis direction. Are linear, and are arranged in parallel to each other in the X-axis direction. Light as the signal wave 99 can propagate through each of the plurality of optical waveguides 30.

  In order to control the gradient of the temperature distribution generated in the X-axis direction of the SOI substrate 10, a heater 40 is provided so as to come into contact with one side end surface of the substrate 10 and contact with the other side end surface of the SOI substrate 10. Thus, a heat sink 50 is provided. The heater 40 is connected to the power supply device 81 via a conducting wire 82. Further, an HR coating 60 is applied to the reflection end portion 33 which is the end portion of the optical waveguide 30 other than the input end portion 31 functioning as an input port and the output end portion 32 functioning as an output port.

  Further, when the signal wave 99 is reflected by the first HR coating 60A and the second HR coating 60B, the first HR coating 60A and the second HR coating 60B have the OBO phase of the reflected signal wave 99 of the signal wave 99 before reflection. It arrange | positions so that (pi) may change with respect to the phase of OBO. Further, in the Y-axis direction, the distance from the input end 31 to the first HR coating 60A and the distance from the first HR coating 60A to the second HR coating 60B are both OBO (Optical Bloch Oscillations; The period length is half of the Bloch vibration. Note that the ½ period length indicates the distance that the signal wave propagates in the extending direction of the optical waveguide during the ½ period of the OBO generated by the signal.

More specifically, referring to FIG. 1 and FIG. 3, the Y coordinate axis in which the direction away from the input end 31 is positive in the direction in which the input optical waveguide 30A having the input end 31 extends is defined. In this case, the second reflection, which is the coordinate on the Y coordinate axis, of the intersection of the second HR coating 60B with the straight line extending in the extending direction through one optical waveguide 30 among the three or more optical waveguides 30. position, the heater 40 side of the first optical waveguide 30 that as compared with the second reflection position in the optical waveguide 30 adjacent to the opposite side, has decreased monotonically by (2m + 1) × λ / 4n w. Here, m is an integer greater than or equal to 0, λ is the wavelength of the signal wave 99, and n _w is the equivalent refractive index of the optical waveguide 30.

The first reflection position, which is the coordinate on the Y coordinate axis of the intersection of the first HR coating 60A with the straight line extending in the extending direction through one of the three or more optical waveguides 30, is the heater 40 side of the optical waveguide 30 as compared to the first reflection position in the optical waveguide 30 adjacent to the opposite side, has increased monotonically by (2m + 1) × λ / 4n w.

  In the present embodiment, the case where the second reflection position monotonously decreases and the first reflection position monotonously increases will be described. However, the optical waveguide element of the present invention is not limited to this, and the first reflection position and the first reflection position The two reflection positions may be monotonously increased or monotonously decreased.

More specifically, in the present embodiment, the OBO planar waveguide device 1 is configured under the conditions of λ = 1.55 μm, n _w = 3.5, and m = 0, and on the input end portion 31 side. The Y coordinate (second reflection position) of the end (end face) of a certain optical waveguide 30 is adjusted so as to monotonously decrease by 111 nm toward the heater 40 side. On the other hand, the Y coordinate (first reflection position) of the end portion of the optical waveguide 30 on the side opposite to the input end portion 31 is adjusted so as to monotonically increase by 111 nm toward the heater 40 side.

  Further, in the Y-axis direction, while the signal wave 99 propagates from one end (end face) of the optical waveguide 30 to the other end (end face), the optical waveguide travels by a half period length of OBO. The length of 30 is adjusted. That is, in the present embodiment, the OBO planar waveguide device 1 is configured under the condition that the length of the optical waveguide 30 is 1.5 mm.

  As described above, since the first reflection position and the second reflection position of each optical waveguide 30 are displaced by 111 nm, the lengths of the optical waveguides 30 are not strictly 1.5 mm. However, the amount of displacement is 111 nm (0.000111 mm), which is extremely small with respect to 1.5 mm which is the length of the optical waveguide 30. Therefore, substantially the above-described configuration makes it possible to achieve both the above-described conditions regarding the Y coordinate of the end portion and the conditions regarding the length with respect to the optical waveguide 30. The error between the first reflection position and the second reflection position is preferably within ± 10% with respect to 111 nm. Further, the length error of the optical waveguide 30 is preferably within ± 10% with respect to 1.5 mm.

  As described above, in the OBO planar waveguide device 1 of the present embodiment, the HR coating 60 is applied to the reflection end portion 33 which is the end surface of the optical waveguide 30 other than the input end portion 31 and the output end portion 32. Furthermore, the conventional OBO planar waveguide described with reference to FIG. 23 is adjusted in that the position of the end face (end portion) of the optical waveguide 30 and the length of the optical waveguide 30 in the Y-axis direction are adjusted as described above. Different from the waveguide element 100.

  Next, a method for manufacturing the planar waveguide device in the present embodiment will be described. 4, FIG. 5, FIG. 7 and FIG. 8 are schematic cross-sectional views for explaining the method for manufacturing the OBO planar waveguide device in the first embodiment. FIGS. 6, 9 and 10 are schematic plan views for explaining the method for manufacturing the OBO planar waveguide device in the first embodiment.

First, a substrate preparation process for preparing a substrate is performed. Specifically, referring to FIG. 4, SOI substrate 10 in which Si substrate 11, SiO ₂ layer 12, and 0.3 μm thick Si layer 13 are laminated in this order is prepared.

  Next, an optical waveguide forming step in which an optical waveguide is formed on the SOI substrate 10 is performed. Specifically, first, as shown in FIG. 4, a resist is applied on the Si layer 13 of the SOI substrate 10 to form a resist film 91. Thereafter, as shown in FIGS. 5 and 6, the resist film 91 is processed by electron beam direct writing or photolithography to form an optical waveguide 30 in which the position and length of the end face are adjusted in the Y-axis direction. The resist pattern is formed. The resist film 91 can be processed under the conditions that, for example, in direct electron beam drawing, the electron beam irradiation current is 0.1 nA and the electron beam dose time per dot is 4.5 μsec. In photolithography, a resist pattern can be formed under conditions where the transfer time is about 10 seconds.

  Thereafter, using the resist film 91 processed into a resist pattern as a mask, as shown in FIG. 7, an etching method such as ICP (Inductively Coupled Plasma) etching, reactive ion etching, or reactive ion beam etching is adopted. The middle of the Si layer 13 is etched. More specifically, for example, reactive ion etching using etching gas as a mixed gas of chlorine gas 25 sccm and nitrogen gas 10 sccm, etching pressure 0.1 Pa, and RF (Radio Frequency) power 200 W. Is done. Then, by removing the resist film 91, the optical waveguide 30 is obtained.

  Next, a temperature adjusting member forming step for forming a heater and a heat sink is performed on the SOI substrate 10 on which the optical waveguide 30 is formed. Specifically, as shown in FIG. 8, a heater 40 made of, for example, a tantalum nitride film is formed at one side end in the X-axis direction of the SOI substrate 10 using a sputtering method or a vapor deposition method. Further, a heat sink 50 made of an aluminum nitride film is formed at the other side end in the X-axis direction of the SOI substrate 10 by using a sputtering method or a vapor deposition method.

  Next, in the optical waveguide 30 formed on the SOI substrate 10, a reflection portion forming step of forming a reflection portion at the reflection end portion 33 other than the input end portion 31 and the output end portion 32 is performed. To be implemented. Specifically, first, as shown in FIG. 9, a resist is applied again on the SOI substrate 10 on which the optical waveguide 30 is formed to form a resist film 91. Thereafter, as shown in FIG. 9, the resist film 91 is processed by direct electron beam drawing or photolithography. Thus, a resist pattern having an opening 91A corresponding to the shape of the first HR coating 60A and the second HR coating 60B as the reflection portion, that is, the end portion to be the reflection end portion 33 of the end portion of the optical waveguide 30 is exposed. Is formed.

  Thereafter, referring to FIG. 10, an Al (aluminum) film 92 is formed by sputtering or vapor deposition so as to cover the resist film 91 processed into a resist pattern. Then, the Al film 92 formed on the resist film 91 is removed from the SOI substrate 10 together with the resist film 91 by using a lift-off method. Thereby, referring to FIG. 1 and FIG. 2, the HR coating 60 made of Al is applied to the reflection end portion 33 of the optical waveguide 30.

  Next, a power supply device connection step is performed in which a power supply device that enables heating of the SOI substrate 10 by the heater 40 is connected to the heater by supplying power to the heater 40. Specifically, referring to FIG. 1 and FIG. 2, power supply device 81 is arranged, and power supply device 81 and heater 40 are connected by conductive wire 82.

  Through the above steps, the OBO planar waveguide device 1 in the present embodiment can be manufactured.

  Next, the operation of the OBO planar waveguide device 1 in the present embodiment will be described. With reference to FIGS. 1 and 2, one end of the SOI substrate 10 in the X-axis direction is heated by the heater 40 supplied with power from the power supply device 81. On the other hand, the heat of the SOI substrate 10 is released from the other end in the X-axis direction of the SOI substrate 10 by the function of the heat sink 50, so that the other end is relative to the one end. To be cooled. As a result, a gradient occurs in the temperature distribution in the X-axis direction of the SOI substrate 10. That is, the temperature of the SOI substrate 10 gradually increases as it approaches the heater 40 in the X-axis direction. In general, the refractive index of a semiconductor material such as Si increases as the temperature increases. Therefore, the refractive index of the optical waveguide 30 on the heater 40 side of the SOI substrate 10 is relatively higher than the refractive index of the optical waveguide 30 on the heat sink 50 side of the SOI substrate 10.

In this state, a plurality of signal waves having different wavelengths (wavelengths: λ _{1 to} λ _k ) are guided by the OBO plane so that the intensity peak of the signal wave 99 is positioned at the input end 31 which is a predetermined one input port. It is input into the waveguide element 1. As a result, the plurality of signal waves included in the signal wave 99 leak from the traveling optical waveguide 30 and are coupled to the adjacent optical waveguide 30. As a result, the plurality of signal waves included in the signal wave 99 cause OBO in the X-axis direction while propagating in the Y-axis direction. The amplitude of OBO increases as the wavelength of the signal wave increases. Therefore, as shown in FIG. 1, when a plurality of signal waves propagate through the OBO planar waveguide device 1, the propagation path varies depending on the wavelength. That is, the signal wave 99 is demultiplexed in the OBO planar waveguide device 1.

  Here, OBO has a property that its amplitude decreases as the difference in refractive index per unit length in the X-axis direction of the optical waveguide 30, that is, the gradient of the refractive index in the X-axis direction of the optical waveguide 30 increases. is doing. Therefore, by changing the temperature gradient of the SOI substrate 10 in the X-axis direction, a signal wave can be output to the output end 32 that is a desired output port.

  Next, the reflection of the signal wave 99 by the HR coating 60 which is a reflection part in the present embodiment will be described. FIG. 11 is a diagram for explaining the relationship between the propagation constant κ of the signal wave in the X-axis direction and the propagation constant β of the signal wave in the Y-axis direction. FIG. 12 is a diagram illustrating a path of a signal wave corresponding to FIG.

In general, the relationship between the propagation constant κ of the signal wave in the X-axis direction and the propagation constant β of the signal wave in the Y-axis direction is as shown in FIG. 11, and the group velocity (v _g ) of the signal wave in the X-axis direction is It is represented by the formula (1).

That is, the value of v _g signal wave 99 propagating through OBO planar waveguide device 1 is consistent with the slope of the graph of FIG. 11. Therefore, the v _g of OBO planar waveguide device 1, the orientation of the heater 40 side is positive from the heat sink 50 side in the X-axis direction.

Here, with reference to FIG. 12, the signal wave 99 entering the input end portion 31 of the OBO planar waveguide device 1 at the point a in FIG. Therefore, the state of the signal wave 99 at the point a in FIG. 12 corresponds to point A in FIG. 11, v _g signal wave 99 at the input end 31 is zero. Next, when the temperature of the SOI substrate 10 has a gradient that rises from the heat sink 50 toward the heater 40 due to heat generated by the heater 40, the signal wave 99 that propagates through the OBO planar waveguide device 1 is in the Y-axis direction. OBO occurs in the X-axis direction while propagating to. For this reason, the signal wave 99 travels to the heater 40 side so as to reach the point b starting from the point a in FIG. Progression from point a to point b corresponds to the change of the state of the signal wave from point A to point B in FIG. Further, in the signal wave 99 propagated to the point c in FIG. 12, the state of the signal wave in FIG. 11 corresponds to the point C, and the phase of the OBO of the signal wave 99 changes from 0 to π during propagation. Therefore, in the reflective end 33, _{v g} is 0.

Next, the signal wave 99 is reflected by the first HR coating 60A. At this time, as described above, the OBO phase of the reflected signal wave 99 changes by π. As a result, as shown in FIG. 11, the state of the signal wave changes from point C to point A. Therefore, v _g is 0 signal wave, the value of the subsequent v _g becomes positive. Accordingly, the signal wave 99 reflected by the first HR coating 60A travels again toward the heater 40.

Thereafter, as shown in FIG. 1, the signal wave 99 propagating through the OBO planar waveguide device 1 is repeatedly reflected by the HR coating 60 and is output from the output end portion 32 which is an output port. Here, while the signal wave 99 propagates through the OBO planar waveguide device 1, as shown in FIG. 11, the state of the signal wave 99 changes from the point A to the point C and from the point C in the HR coating 60. The change to point A is repeated. Therefore, the signal wave 99 propagating in the OBO planar waveguide device 1 repeats OBO in the range of v _g ≧ 0 in the X-axis direction.

  Based on the nature of OBO, the intervals of the plurality of signal waves having different wavelengths in the multiplexed signal wave 99 increase in the interval in the X-axis direction each time reflection is repeated by the HR coating 60.

  As described above, when the number of times the multiplexed signal wave 99 is reflected by the HR coating 60 is increased, the interval between the wavelengths of the multiplexed signal wave 99 input into the OBO planar waveguide device 1 is narrowed. However, a signal wave can be output from the output end 32 as a unique output port as a single wavelength signal wave.

  Further, when the temperature gradient in the X-axis direction of the SOI substrate 10 is adjusted using the heater 40 and the heat sink 50, the refractive index difference per unit length in the X-axis direction is controlled. Therefore, by using the heater 40 and the heat sink 50, the amplitude of the OBO of the demultiplexed signal wave 99 is adjusted to freely specify the wavelength of the signal wave 99 output from the output end 32 that is an output port. be able to.

  In this embodiment, Al is used as a material for the HR coating. However, if the reflectance of the multiplexed signal wave in the wavelength band of 1.3 μm or 1.55 μm is 90% or more, Even if Ag (silver), Rh (rhodium), Au (gold), or Cu (copper) is used as the material for the HR coating, the same effect as described above can be obtained.

  Further, in the present embodiment, the case where the HR coating is employed as the reflecting portion in order to reflect the signal wave has been described, but the reflection of the multiplexed signal wave having the wavelength band of 1.3 μm or the wavelength of 1.55 μm is reflected. If the rate is 90% or more, as will be described later, a photonic crystal (Photonic Crystal; hereinafter referred to as “PhC”) that does not allow a signal wave to enter can be employed as the reflecting portion.

(Embodiment 2)
Next, Embodiment 2 which is another embodiment of the planar waveguide device of the present invention will be described. FIG. 13 is a schematic plan view showing the configuration of the planar waveguide device according to the second embodiment. FIG. 14 is a schematic side view showing the configuration of the planar waveguide device according to the second embodiment. FIG. 15 is an enlarged schematic partial plan view showing the vicinity of PhC in FIG. With reference to FIGS. 13 to 15, the configuration of the planar waveguide device in the second embodiment will be described.

  Referring to FIGS. 13 and 14, OBO planar waveguide device 1 in the second embodiment has basically the same configuration as OBO planar waveguide device 1 in the first embodiment. However, the OBO planar waveguide device 1 according to the second embodiment is different from the first embodiment in the configuration of the reflection portion formed at the end of the optical waveguide 30.

  That is, in the optical waveguide 30 of the OBO planar waveguide device 1 according to the second embodiment, as shown in FIG. 13, at the end portions other than the input end portion 31 that is an input port and the output end portion 32 that is an output port. A certain end 33 for reflection is provided with PhC 70. The structure of this PhC 70 is determined so that the frequency band of the multiplexed signal wave 99 is located in the photonic band gap. For example, when a signal wave 99 in the 1.55 μm band is input to the OBO planar waveguide device 1, a PhC 70 in which holes (circular holes) having a diameter of 175 nm are arranged so as to have a lattice constant of 400 nm is formed. For this reason, the signal wave 99 cannot travel to the end portion of the optical waveguide 30 having the PhC 70. Therefore, as shown in FIG. 13, when the signal wave 99 propagating in the OBO planar waveguide device 1 tries to travel from a region where there is no PhC 70 at the end of the optical waveguide 30 to a certain region, at the end of the optical waveguide 30 The light is reflected at the boundary surface (PhC boundary surface 34) between the region with and without the PhC 130.

  That is, the first reflection that reflects the signal wave 99 so as to propagate toward the heater 40 on the end in the extending direction of the optical waveguide 30 on the side opposite to the input end 31 in the optical waveguide 30. A first PhC 70A as a part is formed. Further, the signal wave 99 approaches the heater 40 at the end opposite to the first PhC 70A in the extending direction of the optical waveguide 30 of the optical waveguide 30 disposed on the side closer to the heater 40 than the input optical waveguide 30A. A second PhC 70B is formed as a second reflecting portion that reflects so as to propagate to the side. Here, the frequency band of the signal wave 99 is located in the photonic band gap of the PhC 70.

  The first PhC 70A is arranged such that when the signal wave 99 is reflected by the first PhC 70A, the phase of the OBO of the signal wave 99 after reflection does not change with respect to the phase of the OBO of the signal wave 99 before reflection. The 2PhC 70B is arranged such that when the signal wave 99 is reflected by the second PhC 70B, the phase of the OBO of the signal wave 99 after reflection changes by π with respect to the phase of the OBO of the signal wave 99 before reflection. Further, in the Y-axis direction, the distance from the input end 31 to the first PhC 70A and the distance from the first PhC 70A to the second PhC 70B are both ¼ period length of OBO generated by the signal wave 99. Note that the ¼ period length indicates a distance in which a signal wave propagates in the extending direction of the optical waveguide during a ¼ period of OBO generated by the signal.

More specifically, referring to FIG. 13 and FIG. 15, the Y coordinate axis in which the direction away from the input end 31 is positive in the direction in which the input optical waveguide 30 </ b> A having the input end 31 extends m. Is the second coordinate which is the intersection of the straight line extending in the extending direction through one optical waveguide 30 and the second PhC 70B (PhC interface 34) in the Y coordinate axis. reflection position, the heater 40 side of the first optical waveguide 30 that as compared with the second reflection position in the optical waveguide 30 adjacent to the opposite side, has increased monotonically by (2m + 1) × λ / 4n w. Here, m is an integer greater than or equal to 0, λ is the wavelength of the signal wave 99, and n _w is the equivalent refractive index of the optical waveguide 30. The first reflection position, which is the coordinate on the Y coordinate axis, of the intersection of the straight line extending in the extending direction through each of the optical waveguides 30 and the first PhC 70A (PhC boundary surface 34) is constant.

  In the present embodiment, the case where the second reflection position monotonously increases will be described. However, the optical waveguide element of the present invention is not limited to this, and the second reflection position may monotonously decrease.

More specifically, in the present embodiment, the OBO planar waveguide device 1 is configured under the conditions of λ = 1.55 μm, n _w = 3.5, and m = 0, and on the input end portion 31 side. The Y coordinate (second reflection position) of the PhC boundary surface 34 of the second PhC 70B formed at the end of a certain optical waveguide 30 is adjusted so as to increase monotonically by 111 nm toward the heater 40 side. On the other hand, the Y coordinate (first reflection position) of the PhC boundary surface 34 of the first PhC 70A formed at the end of the optical waveguide 30 on the side opposite to the input end 31 is constant.

  Further, while the signal wave 99 propagates from one end portion (PhC boundary surface 34) of the optical waveguide 30 to the other end portion (PhC boundary surface 34) in the Y-axis direction, it travels by a quarter period length of OBO. Thus, the length of the optical waveguide 30 is adjusted. That is, in this embodiment, the OBO planar waveguide device 1 is configured under the condition that the length of the optical waveguide 30 is 0.75 mm.

  As described above, the second reflection position of each optical waveguide 30 is displaced by 111 nm. However, as in the case of the first embodiment, the amount of displacement is extremely large with respect to the length of the optical waveguide 30. Since it is very small, substantially the above-described configuration makes it possible to satisfy both the above-described conditions relating to the Y coordinate of the PhC interface and the conditions relating to the length of the optical waveguide.

  According to the OBO planar waveguide device 1 in the second embodiment, the distance that the signal wave reflected by the reflecting portion propagates in the OBO planar waveguide device 1 before being reflected next is the same as that in the first embodiment. Shorter than Thus, the OBO planar waveguide device 1 of the second embodiment can be reduced in size as compared with the OBO planar waveguide device 1 of the first embodiment. Further, in the OBO planar waveguide device 1 according to the second embodiment, the element length in the Y-axis direction is shortened, so that the thermal resistivity in the X-axis direction of the SOI substrate 10 is increased. For this reason, it becomes easy to give a gradient to the temperature distribution of the SOI substrate 10 in the X-axis direction. As a result, power consumption in the heater 40 of the OBO planar waveguide device 1 is reduced.

  Next, a method for manufacturing the planar waveguide device in the second embodiment will be described. 16, FIG. 17, FIG. 19 and FIG. 20 are schematic cross-sectional views for explaining the method of manufacturing the OBO planar waveguide device in the second embodiment. FIG. 18 is a schematic plan view for explaining the method for manufacturing the OBO planar waveguide device according to the second embodiment.

  Referring to FIGS. 16 to 20, the method for manufacturing the planar waveguide element in the second embodiment is basically the same as the method for manufacturing the planar waveguide element in the first embodiment. However, the manufacturing method of the planar waveguide device in the second embodiment is different from that in the first embodiment due to the difference in the configuration of the reflecting portion.

  That is, first, after the SOI substrate 10 is prepared in the substrate preparation step, an optical waveguide forming step in which an optical waveguide is formed on the SOI substrate 10 is performed. Specifically, first, as shown in FIG. 16, a resist film 91 is formed by applying a resist on the Si layer 13 of the SOI substrate 10 prepared in the substrate preparation step. Thereafter, as shown in FIGS. 17 and 18, the resist film 91 is processed by direct electron beam drawing or photolithography to form an optical waveguide 30 in which the position and length of the end face are adjusted in the Y-axis direction. The resist pattern is formed. Here, in the present embodiment, as shown in FIG. 18, an opening 91 </ b> B corresponding to a hole (circular hole) constituting PhC is formed in the resist film 91.

  Thereafter, using the resist film 91 processed into a resist pattern as a mask, an etching method such as ICP etching, reactive ion etching, or reactive ion beam etching is employed as shown in FIG. Halfway is etched. Thereby, the optical waveguide 30 having PhC 70 at the reflection end portion 33 is formed.

  Next, as in the case of the first embodiment, a temperature adjusting member forming step for forming a heater and a heat sink and a power supply device connecting step are performed on the SOI substrate 10 on which the optical waveguide 30 is formed. Through the above steps, the OBO planar waveguide device 1 in the present embodiment can be manufactured.

  In the second embodiment, unlike the case of the first embodiment, steps such as formation of a resist pattern, sputtering, and lift-off for forming the HR coating can be omitted. As a result, the OBO planar waveguide device 1 of the second embodiment has an advantage that the manufacturing process can be simplified as compared with the OBO planar waveguide device 1 of the first embodiment.

Next, the operation of the OBO planar waveguide device 1 in the second embodiment will be described. Referring to FIGS. 13 and 14, first, as in the case of the first embodiment, a gradient is formed in the temperature distribution in the X-axis direction of SOI substrate 10 by the functions of heater 40 and heat sink 50. In this state, a plurality of signal waves having different wavelengths (wavelengths: λ _{1 to} λ _k ) are guided by the OBO plane so that the intensity peak of the signal wave 99 is positioned at the input end 31 which is a predetermined one input port. It is input into the waveguide element 1. A plurality of signal waves included in the signal wave 99 are demultiplexed in the OBO planar waveguide device 1 by causing OBO in the X-axis direction while propagating in the Y-axis direction. Further, by changing the temperature gradient of the SOI substrate 10 in the X-axis direction, a signal wave can be output from the output end 32 that is a desired output port.

  Here, the reflection of the signal wave 99 on the PhC 70 which is the reflection portion in the present embodiment will be described. FIG. 21 is a diagram for explaining the relationship between the propagation constant κ of the signal wave in the X-axis direction and the propagation constant β of the signal wave in the Y-axis direction. FIG. 22 is a diagram illustrating a path of a signal wave corresponding to FIG.

As with the first embodiment, the value of v _g signal wave 99 propagating through OBO planar waveguide device 1 is consistent with the slope of the graph of FIG. 21. Here, with reference to FIG. 22, the signal wave 99 that has entered the input end 31 of the OBO planar waveguide device 1 at the point a in FIG. Therefore, the state of the signal wave 99 at the point a in FIG. 22 corresponds to point A in FIG. 21, v _g signal wave 99 at the input end 31 is zero. Next, when the temperature of the SOI substrate 10 has a gradient that rises from the heat sink 50 toward the heater 40 due to heat generated by the heater 40, the signal wave 99 that propagates through the OBO planar waveguide device 1 is in the Y-axis direction. OBO occurs in the X-axis direction while propagating to. For this reason, the signal wave 99 travels to the heater 40 side so as to reach the point b starting from the point a in FIG. The progression from the point a to the point b corresponds to the state of the signal wave changing from the point A to the point B in FIG. 21, and the phase of the OBO of the signal wave 99 changes from 0 to π / 2 during propagation. Change.

  Next, the signal wave that has reached the PhC interface 34 of the first PhC 70A is reflected by the PhC interface 34. At this time, the OBO phase of the reflected signal wave 99 does not change. For this reason, the state of the signal wave in FIG. 21 does not change from point B.

Next, the signal wave travels from the point b to the point c in FIG. 22 toward the heater 40 side toward the PhC boundary surface 34 of the second PhC 70B. Point c in FIG. 22 corresponds to point C in FIG. 21, and the phase of the OBO of the signal wave changes from π / 2 to π during propagation. Therefore, the _{v g} signal wave 99 at PhC boundary 34 of the 2PhC70B becomes 0.

Next, the signal wave that has reached the PhC interface 34 of the second PhC 70B is reflected by the PhC interface 34. At this time, the OBO phase of the reflected signal wave 99 changes by π. Thereby, as shown in FIG. 21, the state of the signal wave changes from the C point to the A point. Therefore, next _{v g} is 0 signal wave 99, the value of the subsequent _{v g} becomes positive. Therefore, the signal wave 99 reflected by the second PhC 70B travels again to the heater 40 side.

Thereafter, as shown in FIG. 13, the signal wave 99 propagating through the OBO planar waveguide device 1 repeats reflection at the PhC boundary surface 34 of PhC 70 and is output from the output end 32 which is an output port. Here, while the signal wave 99 propagates through the OBO planar waveguide device 1, as shown in FIG. 21, the state of the signal wave changes from the point A to the point C via the point B and the PhC boundary surface. The change from point C to point A at 34 is repeated. Therefore, the signal wave 99 propagating in the OBO planar waveguide device 1 repeats OBO in the range of v _g ≧ 0 in the X-axis direction.

  Based on the nature of the OBO, the intervals of the plurality of signal waves having different wavelengths in the multiplexed signal wave 99 increase in intervals in the X-axis direction each time reflection is repeated on the PhC boundary surface 34.

  As described above, when the number of times the multiplexed signal wave 99 is reflected by the PhC boundary surface 34 is increased, the interval between the wavelengths of the multiplexed signal wave 99 input into the OBO planar waveguide device 1 is narrowed. Even so, the signal wave can be output from the output end 32 as a unique output port as a single-wavelength signal wave.

  In the present embodiment, the case where a photonic crystal (PhC) is used as a reflecting portion to reflect a signal wave has been described. However, a wavelength 1.3 μm band or a wavelength 1.55 μm band is multiplexed. If the reflectance of the signal wave is 90% or more, the HR coating can be adopted as the reflecting portion as in the first embodiment.

  In the first embodiment and the second embodiment, not only the first HR coating 60A or the first PhC 70A as the first reflecting part but also the second HR coating 60B or the second PhC 70B as the second reflecting part is formed. However, only the first HR coating 60 </ b> A or the first PhC 70 </ b> A as the first reflecting portion may be formed in consideration of the use of the planar waveguide element and the like.

  The embodiment disclosed this time is to be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The planar waveguide device according to the present invention uses an optical Bloch oscillation to demultiplex a wavelength-multiplexed signal wave and outputs each of the demultiplexed signal waves from a desired output port. Can be applied particularly advantageously.

FIG. 3 is a schematic plan view showing the configuration of the planar waveguide device in the first embodiment. FIG. 3 is a schematic side view showing the configuration of the planar waveguide element in the first embodiment. It is a schematic partial plan view which expands and shows the vicinity of HR coating of FIG. FIG. 5 is a schematic cross-sectional view for illustrating the method for manufacturing the OBO planar waveguide device in the first embodiment. FIG. 5 is a schematic cross-sectional view for illustrating the method for manufacturing the OBO planar waveguide device in the first embodiment. FIG. 6 is a schematic plan view for illustrating the method for manufacturing the OBO planar waveguide device in the first embodiment. FIG. 5 is a schematic cross-sectional view for illustrating the method for manufacturing the OBO planar waveguide device in the first embodiment. FIG. 5 is a schematic cross-sectional view for illustrating the method for manufacturing the OBO planar waveguide device in the first embodiment. FIG. 6 is a schematic plan view for illustrating the method for manufacturing the OBO planar waveguide device in the first embodiment. FIG. 6 is a schematic plan view for illustrating the method for manufacturing the OBO planar waveguide device in the first embodiment. It is a figure for demonstrating the relationship between the propagation constant (beta) of the signal wave in a X-axis direction, and the propagation constant (beta) of the signal wave in a Y-axis direction. It is a figure which shows the course of the signal wave corresponding to FIG. FIG. 6 is a schematic plan view showing a configuration of a planar waveguide element in a second embodiment. FIG. 5 is a schematic side view showing the configuration of a planar waveguide device in a second embodiment. It is a schematic partial top view which expands and shows the PhC vicinity of FIG. 12 is a schematic cross-sectional view for illustrating the method for manufacturing the OBO planar waveguide device in the second embodiment. FIG. 12 is a schematic cross-sectional view for illustrating the method for manufacturing the OBO planar waveguide device in the second embodiment. FIG. FIG. 10 is a schematic plan view for illustrating the method for manufacturing the OBO planar waveguide device in the second embodiment. 12 is a schematic cross-sectional view for illustrating the method for manufacturing the OBO planar waveguide device in the second embodiment. FIG. 12 is a schematic cross-sectional view for illustrating the method for manufacturing the OBO planar waveguide device in the second embodiment. FIG. It is a figure for demonstrating the relationship between the propagation constant (beta) of the signal wave in a X-axis direction, and the propagation constant (beta) of the signal wave in a Y-axis direction. It is a figure which shows the course of the signal wave corresponding to FIG. It is a schematic perspective view which shows the conventional OBO planar waveguide element.

Explanation of symbols

1 OBO planar waveguide element, 10 SOI substrate, 11 Si substrate, 12 SiO ₂ layer, 13 Si layer, 30 optical waveguide, 30 A input optical waveguide, 30 B output optical waveguide, 31 input end, 32 output end Part, 33 reflection end part, 34 PhC interface, 40 heater, 50 heat sink, 60 HR coating, 60A first HR coating, 60B second HR coating, 70 PhC, 70A first PhC, 70B second PhC, 81 power supply, 82 conductor 91 resist film, 91A opening, 91B opening, 92 Al film, 99 signal wave.

Claims (14)

A substrate having a low refractive index layer and a high refractive index layer disposed on the low refractive index layer and having a higher refractive index than the low refractive index layer;
Three or more optical waveguides arranged side by side on the substrate and capable of transmitting signal waves;
A heating member that is disposed at one end of the substrate in the direction in which the optical waveguides are arranged, and that heats the substrate;
At least one of the three or more optical waveguides is capable of inputting the signal wave to an end in the extending direction of the optical waveguide,
At least two of the three or more optical waveguides arranged closer to the heating member than the optical waveguide having an end portion to which the signal wave can be input is an extending direction of the optical waveguide. The signal wave can be output from the end of
The signal wave is propagated to the side closer to the heating member at the end in the extending direction of the optical waveguide opposite to the end where the signal wave can be input in the three or more optical waveguides. A planar waveguide element in which a first reflecting portion that reflects in this manner is formed. The first reflection unit is arranged such that when the signal wave is reflected by the first reflection unit, the phase of the signal wave after reflection changes by π with respect to the phase of the signal wave before reflection,
In the extending direction of the optical waveguide, the distance from the end where the signal wave can be input to the first reflection part is a half period of OBO (Optical Bloch Oscillations) generated by the signal wave. The planar waveguide device of claim 1, wherein the planar waveguide device is long. When three or more light guides are provided in the direction in which the optical waveguide having the end where the signal wave can be input extends in the direction in which the direction away from the end where the signal wave can be input is positive The first reflection position, which is a coordinate on the coordinate axis of the intersection of the straight line extending in the extending direction of one optical waveguide of the waveguides and the first reflection portion, is opposite to the heating member side of the one optical waveguide. compared to the first reflection position in the optical waveguide adjacent to the (2m + 1) × λ / 4n w by decreasing monotonically increasing or, planar waveguide device according to claim 2.
Here, m is an integer greater than or equal to 0, λ is the wavelength of the signal wave, and n _w is the equivalent refractive index of the optical waveguide.   The end of the optical waveguide disposed closer to the heating member than the optical waveguide having an end to which the signal wave can be input is opposite to the first reflecting portion in the extending direction of the optical waveguide. 2. The planar waveguide device according to claim 1, further comprising a second reflecting portion configured to reflect the signal wave so as to propagate to the side closer to the heating member. When the signal wave is reflected by the first reflection part and the second reflection part, the first reflection part and the second reflection part have a phase of the signal wave after reflection of the signal wave before reflection. Arranged to change by π with respect to phase,
In the extending direction of the optical waveguide, the distance from the end where the signal wave can be input to the first reflecting part and the distance from the first reflecting part to the second reflecting part are both the signal wave. 5. The planar waveguide device according to claim 4, wherein the planar waveguide device has a half period length of OBO (Optical Bloch Oscillations) caused by the above. When three or more light guides are provided in the direction in which the optical waveguide having the end where the signal wave can be input extends in the direction in which the direction away from the end where the signal wave can be input is positive The first reflection position, which is a coordinate on the coordinate axis of the intersection of the straight line extending in the extending direction of one optical waveguide of the waveguides and the first reflection portion, is opposite to the heating member side of the one optical waveguide. compared to the first reflection position in the optical waveguide adjacent to, decreased (2m + 1) × λ / 4n w by monotonically increasing or,
The second reflection position, which is a coordinate on the coordinate axis of the intersection of the straight line extending in the extending direction of one of the three or more optical waveguides and the second reflecting portion, is the heating of the one optical waveguide. the member side than the second reflection position in the optical waveguide adjacent to the opposite side, (2m + 1) × λ / 4n w by decreasing monotonically increasing or, planar waveguide device according to claim 5.
Here, m is an integer greater than or equal to 0, λ is the wavelength of the signal wave, and n _w is the equivalent refractive index of the optical waveguide. The first reflection unit is arranged so that the phase of the signal wave after reflection does not change with respect to the phase of the signal wave before reflection when the signal wave is reflected by the first reflection unit,
The second reflection unit is arranged such that when the signal wave is reflected by the second reflection unit, the phase of the signal wave after reflection changes by π with respect to the phase of the signal wave before reflection,
In the extending direction of the optical waveguide, the distance from the end where the signal wave can be input to the first reflecting part and the distance from the first reflecting part to the second reflecting part are both the signal wave. 5. The planar waveguide device according to claim 4, wherein the planar waveguide device has a quarter period length of OBO (Optical Bloch Oscillations). When three or more light guides are provided in the direction in which the optical waveguide having the end where the signal wave can be input extends in the direction in which the direction away from the end where the signal wave can be input is positive The first reflection position, which is the coordinate on the coordinate axis of the intersection of the straight line extending in the extending direction of each of the waveguides and the first reflection portion, is constant
The second reflection position, which is a coordinate on the coordinate axis of the intersection of the straight line extending in the extending direction of one of the three or more optical waveguides and the second reflecting portion, is the heating of the one optical waveguide. the member side than the second reflection position in the optical waveguide adjacent to the opposite side, (2m + 1) × λ / 4n w by decreasing monotonically increasing or, planar waveguide device according to claim 7.
Here, m is an integer greater than or equal to 0, λ is the wavelength of the signal wave, and n _w is the equivalent refractive index of the optical waveguide. The first reflection unit is arranged so that the phase of the signal wave after reflection does not change with respect to the phase of the signal wave before reflection when the signal wave is reflected by the first reflection unit,
In the extending direction of the optical waveguide, the distance from the end where the signal wave can be input to the first reflecting portion is a quarter period of OBO (Optical Bloch Oscillations) generated by the signal wave. The planar waveguide device of claim 1, wherein the planar waveguide device is long.   The three or more optical waveguides are arranged in a direction in which the optical waveguide having an end portion to which the signal wave can be input extends in a direction in which the direction away from the end portion to which the signal wave can be input is positive. 10. The planar waveguide device according to claim 9, wherein a first reflection position, which is a coordinate on the coordinate axis, of an intersection of a straight line extending in each extending direction of the waveguide and the first reflection portion is constant.   11. The planar waveguide device according to claim 1, wherein the first reflecting portion is an HR coating.   The planar waveguide device according to any one of claims 4 to 8, wherein the first reflecting portion and the second reflecting portion are HR coatings. The first reflecting portion is a photonic crystal,
11. The planar waveguide device according to claim 1, wherein a frequency band of the signal wave is located in a photonic band gap of the photonic crystal. The first reflecting portion and the second reflecting portion are photonic crystals,
9. The planar waveguide device according to claim 4, wherein a frequency band of the signal wave is located in a photonic band gap of the photonic crystal.

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