JP2012103505A - Ganged thermo-optic phase shifter and optical interference circuit using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized ganged thermo-optic phase shifter having suppressed heat interference and to provide an optical interference circuit using the same.SOLUTION: A ganged thermo-optic phase shifter comprises: a Mach-Zehnder interferometer comprising two directional couplers 102a and 102b and an arm waveguide 103 connecting them; a phase shifter comprising double cores, thin film heaters 111 installed on the arm waveguide 103, and wiring 112 for supplying power to the heaters 111; and heat insulating grooves 121 formed on both sides of the arm waveguide 103. The double cores and the thin film heaters above them are not aligned along the arm waveguide 103 (in a vertical direction of the paper surface in Figure 1) and are disposed to be shifted from each other so that the double cores and the thin film heaters do not overlap with each other when being translated in a direction perpendicular to a lengthwise direction of the arm waveguide 103. It is important that an amount of shift between the adjacent double cores and thin film heaters 111 is equal to or longer than a length of the thin film heaters 111.

Description

  The present invention relates to a multiple thermo-optical phase shifter and an optical interference circuit using the same, and more particularly to a multiple thermo-optical phase shifter using a thermo-optic effect and an optical interference circuit using the same.

  At present, development of an optical wavelength division multiplexing communication system (WDM system) using a plurality of optical wavelengths is actively performed in order to expand communication capacity. In this optical wavelength division multiplexing communication system, a variable optical attenuator for suppressing variations in light intensity of individual optical wavelengths to be multiplexed is an important optical component.

  FIG. 14 shows an example of a Mach-Zehnder interferometer type variable optical attenuator using an optical waveguide that has been widely used. This is composed of a Mach-Zehnder interferometer comprising two directional couplers 602a and 602b and an arm waveguide 603 connecting them, and a thin film heater for heating the optical waveguide above the arm waveguide 603. 611 is loaded. By passing a current through the thin film heater 611, the arm waveguide 603 is heated, and the optical signal intensity output from the Mach-Zehnder interferometer can be varied by changing the phase of the optical signal propagating through the arm waveguide 603. .

  As a method for manufacturing an optical waveguide used in such a device, as shown in FIG.

Flame hydrolysis deposition on the silicon substrate 701 using (FHD), lower cladding layer 702 was SiO _2-mainly, and, depositing a core layer 703 with the addition of GeO ₂ in SiO _2. Then, after performing high temperature transparency, a core pattern is formed on the core layer 703 using reactive ion etching (RIE), and the upper cladding layer 704 mainly composed of SiO ₂ is formed again using a flame deposition method. The buried optical waveguide is fabricated by depositing and transparentizing at a high temperature.

Kei Watanabe, Yasuaki Hashizume, Yusuke Nasu, Masaki Kohtoku, Mikitaka Itoh, and Yasuyuki Inoue, `` Ultralow power consumption silica-based PLC-VOA / Switch '', JLT, Vol.26 No. 14, July 15, 2008 Takuo Tanemura and Yoshiaki Nakano, "Design and scalability analysis of optical phased-array 1 x N switch on planar lightwave circuit", IEICE Electronics Express, Vol. 5, No. 16, pp. 603-609 Hiroyuki Tsuda, Mitsuhiro Yasumoto, Jiro Ito, Dwight Ritums, Jeff Dawley, David Kudzuma, Yuki Tanaka, and Keiichi Nashimoto, "15 ns, high-speed wavelength tuning over 16 nm using electrically controllable PLZT arrayed waveguide grating", OSA / NFOEC 2007 , PDP47

  However, this conventional Mach-Zehnder interferometer type variable optical attenuator has the following problems.

  The conventional variable attenuator as shown in FIG. 14 changes the phase difference of the optical signal propagating through the two arm waveguides by heating only one of the two arm waveguides. Functions as an attenuator. However, when the distance between the two arm waveguides is very narrow, thermal interference occurs, and the heat for heating one arm waveguide also heats the other arm waveguide, resulting in consumption. Increases power. Further, when a large number of the variable attenuators are arranged in parallel, temperature fluctuation due to thermal interference is given to the adjacent variable attenuators, causing a change in the set attenuation amount.

In order to solve this problem, an optical circuit using a thermo-optic effect has been developed. However, it is necessary to design the arm waveguides in parallel to be separated from each other, resulting in a size disadvantage. (See Non-Patent Document 1)
On the other hand, the thermo-optic phase shifter used in the present variable attenuator is not limited to the variable attenuator as shown in FIG. 14, but the multi-port optical switch shown in FIG. 16 (see Non-Patent Document 2) or FIG. Application to the variable wavelength filter (see Non-Patent Document 3) shown in FIG. Here, in the cited reference of the variable filter, a phase shifter using the electro-optic effect is used, but a similar variable wavelength filter can be realized even using the thermo-optic effect.

  However, in the two circuits as shown in FIGS. 16 and 17, it is necessary to arrange the thermo-optic phase shifters at a high density. However, the conventional technique is applied to give a phase error to the adjacent optical waveguide due to thermal interference. It was difficult. In addition, since a plurality of phase shifters are required, it is difficult to apply the thermo-optic phase shifter from the viewpoint of power consumption.

  The present invention has been made in view of such problems, and the object of the present invention is to provide a compact multiple thermo-optical phase shifter that suppresses thermal interference between adjacent optical waveguides and an optical interference circuit using the same. Is to provide.

  In order to solve the above problems, the invention described in claim 1 is a multiple thermo-optical phase shifter in which thin film heaters are respectively disposed on two or more parallel optical waveguides, and the thin film heater The first region of the optical waveguide in the vicinity has a larger thermo-optic coefficient than the second region other than the first region of the optical waveguide, and at least the first region of the adjacent optical waveguide and the thin film heater Are arranged so as not to overlap at a position perpendicular to the longitudinal direction.

  According to a second aspect of the present invention, in the multiple thermooptic phase shifter according to the first aspect of the present invention, the first region is a buried type optical system including a first core layer, a second core layer, and a cladding layer. A third core layer having the same thermo-optic coefficient as the first core layer, wherein the second core layer has a larger thermo-optic coefficient than the first core layer. A buried optical waveguide comprising a clad layer, wherein the first region and the second region are connected via a spot size converter.

  According to a third aspect of the present invention, in the multiple thermooptic phase shifter according to the first aspect, the first and second regions are embedded optical waveguides comprising a core layer and a cladding layer, and the first The region 1 is characterized in that a plurality of grooves filled with a material having a larger thermo-optic coefficient than the core layer are formed in the core layer.

  According to a fourth aspect of the present invention, in the multiple thermo-optical phase shifter according to the first aspect, the first region is more than the first core layer, the first cladding layer, and the first cladding layer. A buried rib optical waveguide comprising a second clad layer having a low refractive index, wherein the second region comprises a second core layer and a clad layer having the same refractive index as that of the first clad layer. It is a type optical waveguide.

  A fifth aspect of the present invention is a variable optical attenuator having first and second 3 dB couplers, wherein the first and second 3 dB couplers are multiple units according to any one of the first to fourth aspects. They are connected by a thermo-optic phase shifter.

  The invention described in claim 6 is a 1 × M optical switch having a first slab waveguide with one input and N outputs and a second slab waveguide with N inputs and M outputs, wherein the first slab waveguide And the second slab waveguide are connected by the multiple thermo-optical phase shifter according to claim 1 having N optical waveguides having the same optical path length.

  The invention according to claim 7 is a tunable wavelength filter having a first slab waveguide with 1 input and N outputs and a second slab waveguide with N inputs and M outputs, the first slab waveguide and the The second slab waveguide is characterized by being connected by the multiple thermo-optic phase shifter according to claim 1 having N optical waveguides having different optical path lengths.

  The present invention has an effect of suppressing thermal interference between adjacent optical waveguides in a small multiple thermo-optic phase shifter and an optical interference circuit using the same.

It is a figure which shows the circuit structure of the variable optical attenuator array which concerns on the 1st Embodiment of this invention. It is a figure which shows the perspective view of the area | region A of FIG. The top view of the double core part of 1st Embodiment is shown (A) is a figure which shows the perspective view of the multiple phase shifter of the conventional variable optical attenuator, (B) shows the perspective view of the multiple phase shifter of the variable optical attenuator in 1st Embodiment. FIG. It is a figure which shows the circuit structure of the 1 * 5 multiport optical switch which concerns on the 2nd Embodiment of this invention. It is a figure which shows the perspective view of the three arm waveguides of the area | region B of FIG. It is a figure which shows the circuit structure of the variable wavelength filter which concerns on the 3rd Embodiment of this invention. It is a figure which shows the circuit structure of the variable optical attenuator array which concerns on the 4th Embodiment of this invention. It is a figure which shows the upper side figure of the thin film heater 111 and the groove | channel 122. FIG. It is a figure which shows the circuit structure of the 1 * 5 multiport optical switch which concerns on the 5th Embodiment of this invention. It is a figure which shows the circuit structure of the variable wavelength filter which concerns on the 6th Embodiment of this invention. It is a figure which shows the circuit structure of the variable optical attenuator array in the 7th Embodiment of this invention. (A) is a figure which shows the waveguide structure of the 1st area | region right under the heater of the arm waveguide of 7th Embodiment, (B) is 2nd area | regions other than 1st area | region of an arm waveguide. It is a figure which shows a waveguide structure. It is a figure which shows an example of the variable optical attenuator of the Mach-Zehnder interferometer type | mold using the optical waveguide widely used conventionally. It is a figure which shows the preparation process of an optical waveguide. It is a figure which shows the conventional multiport optical switch. It is a figure which shows the conventional variable wavelength filter.

  Hereinafter, embodiments of the present invention will be described in detail.

(First embodiment)
FIG. 1 shows a circuit configuration of a two-channel variable optical attenuator array according to the first embodiment of the present invention. This has a function of adjusting the optical signal intensity input to the circuit from the optical waveguide 101 to a desired value and outputting it.

  The circuit configuration of this embodiment will be described. The variable optical attenuator includes a Mach-Zehnder interferometer composed of two directional couplers 102a and 102b and an arm waveguide 103 connecting them, a double core, a thin film heater 111 installed on the arm waveguide 103, and The phase shifter includes a wiring 112 that supplies power to the heater 111 and heat insulating grooves 121 formed on both sides of the arm waveguide 103.

FIG. 2 is a perspective view of region A in FIG. The optical waveguide constituting the phase shifter has a structure in which a core 202 made of silicon is embedded in a quartz-based core 201 to which GeO ₂ is added. A thin film heater 111 is formed above the optical waveguide composed of these double cores, and functions as a phase shifter by supplying current to the thin film heater 111 via the wiring 112.

  FIG. 3 shows a top view of the double core portion of the present embodiment (note that the thin film heater 111 is not shown here for the sake of clarity). The silicon core 202 has a rectangular parallelepiped silicon core 202a and a silicon core 202b having a tapered structure as a spot size converter for performing spot size conversion of the quartz core 201 and the silicon core 202 on both sides in the longitudinal direction. It has a configuration.

  Next, structural features of the present invention will be described. As shown in FIG. 1, the above-mentioned double core and the thin film heater 111 thereabove are not aligned in the arm waveguide 103 (perpendicular to the longitudinal direction of the arm waveguide 103). It is characterized by being arranged so as not to overlap each other at positions translated in the vertical direction with respect to the longitudinal direction of 103. It is important that the amount of the adjacent double core and the thin film heater 111 is not more than the length of the thin film heater 111. This is because the heat distribution due to the heater heating is distributed perpendicular to the longitudinal direction of the heater, and the influence thereof is reduced. Thereby, thermal interference can be suppressed.

  Here, the variable optical attenuator can be manufactured by the following manufacturing procedure.

An SOI (Silicon on Insulator) substrate in which a SiO ₂ layer and a silicon layer are formed on a silicon substrate is prepared. Next, a silicon core is formed by electron beam exposure and reactive etching. Next, quartz glass to which GeO ₂ is added is deposited so as to cover the silicon core, and a quartz core pattern is formed by photolithography and reactive etching. Next, an upper clad glass mainly composed of SiO ₂ is deposited so as to cover the quartz-based core. Further, a wiring pattern / heater pattern is formed thereon. And the deep groove | channel as a heat insulation groove | channel is produced by the photolithographic technique and reactive ion etching. The core size of the silicon core to be manufactured is 0.5 × 0.3 μm, the refractive index of the quartz core is 1.48, and the core size is 4.5 × 3.5 μm.

  Next, the effect of shifting the double core structure or thin film heater 111 between the arm waveguides 103, which is a feature of this embodiment, will be specifically described.

  In the conventionally proposed variable optical attenuator as shown in FIG. 14, when one arm waveguide is heated, a temperature rise also occurs in the adjacent arm waveguide due to thermal interference. These cause the following problems.

  (1) When a 1-channel variable optical attenuator is considered, power consumption is increased. In this thermo-optic type variable optical attenuator, by heating one arm waveguide, the refractive index is increased via the thermo-optic effect, and an optical path length difference is generated between the two arm waveguides. Operate. Therefore, it is necessary to set the temperature difference between the two arm waveguides to a desired value. At this time, if there is thermal interference, only one arm waveguide is not heated, and the other arm waveguide is also heated by thermal interference. Therefore, in order to obtain a desired temperature difference, compared to the case without thermal interference. And requires more power.

  (2) When a variable optical attenuator having a plurality of channels is considered, the operation state (attenuation amount setting value) of one variable optical attenuator changes the attenuation amount of the adjacent variable optical attenuator. When the electric power to the heater of a certain variable optical attenuator is changed, a temperature gradient is generated between the two arm waveguides of the adjacent variable optical attenuators due to thermal interference corresponding to the electric power. That is, the optical path length difference between two adjacent arm waveguides changes, and the amount of attenuation of the variable optical attenuator including the two arm waveguides changes.

The effects of the present embodiment on these problems will be described with reference to FIG. 4A shows a perspective view of a multiple phase shifter of a conventional variable optical attenuator, and FIG. 4B shows a perspective view of a multiple phase shifter of a variable optical attenuator in the present embodiment. What is important here is the temperature rise to the adjacent core. Therefore, in the conventional structure, when the temperature rise of the adjacent cores 201-2 when the refractive index of the core 201-1 was heated to vary by a desired value and a [Delta] T _A, the refractive index of the core 201-2 The change can be described as:

  here,

Is the thermo-optic coefficient of quartz.

  Next, the refractive index change in the core 201-2 in this embodiment shown in FIG.

Here, ΔT _B indicates the temperature rise of the adjacent core 201-2 when heated so that the refractive index of the silicon core changes by the same amount as the refractive index change of the core 201-1 in FIG. Here, it is important that ΔT _B stays at a temperature increase of about 1/20 compared to ΔT _A. This is because in the double core structure in which the silicon core is embedded, most of the electromagnetic field distribution of light exists in the silicon core having a high refractive index, and the high thermo-optic effect of silicon can be used. . Silicon has a thermo-optic coefficient about 20 times that of quartz glass, and the temperature rise for giving the same refractive index change can be suppressed to 1/20.

  From the above results, in this embodiment, it is possible to reduce thermal interference to 1/20 of the conventional value.

  In this embodiment, the use of a thermo-optic phase shifter having a higher effective thermo-optic effect than the conventional one contributes to a reduction in power consumption.

  In the case of the Mach-Zehnder interferometer as in this embodiment, the arm waveguides between the couplers are arranged in parallel, so that thermal interference always occurs. Therefore, the present embodiment is characterized in that (1) a waveguide having a relatively large thermo-optic effect is provided in the heating region, and (2) a relatively thermo-optic effect is provided at a location that is susceptible to thermal interference. By arranging a small waveguide, thermal interference is suppressed. By using this configuration, the distance between the adjacent waveguides can be shortened, and downsizing can be expected.

(Second Embodiment)
FIG. 5 shows a circuit configuration of a 1 × 5 multi-port optical switch according to the second embodiment of the present invention (wiring to the thin film heater is not shown). This has a function of outputting an optical signal input to the circuit from the input waveguide 301 to a desired output port of the output waveguide 303.

  The circuit configuration of this embodiment will be described. This multi-port optical switch is an optical interference circuit comprising two slab waveguides 311 and 312 and an arrayed waveguide 302 connecting them, and the arrayed waveguide 302 has a dual core as shown in FIGS. A phase shifter including a thin film heater 321 and a heat insulating groove 331 is disposed.

  The operation principle of the circuit of this embodiment will be described. The optical signal incident on the input waveguide 301 is distributed to each arrayed waveguide 302 in the first slab waveguide 311. Next, a desired phase difference is given to the optical signal propagating through the arrayed waveguide 302 by the phase shifter, and the position where the light signal is condensed by the second slab waveguide 312 is determined by the phase difference. An output waveguide 303 is disposed at each condensing position, and output can be performed from any of the five output waveguides.

  Next, structural features of the present embodiment will be described. As shown in FIG. 5, the double core and the thin film heater 321 are shifted in parallel in the longitudinal direction of the arrayed waveguide 302 between a plurality of adjacent arrayed waveguides. As a result, as shown in FIG. 6 showing a perspective view of the three arm waveguides in the region B of FIG. 5, a silicon core is embedded at a position perpendicular to the longitudinal direction of the adjacent array waveguides 302. It is characterized by not.

  Since the manufacturing procedure of this embodiment is the same as that of Embodiment 1, it is omitted.

  Problems and effects to be solved by this embodiment will be briefly described below. In a multi-port optical switch, it is necessary to individually set a phase change amount by a plurality of phase shifters to a desired value. However, in the conventional multiport optical switch shown in FIG. 16, heat generated by the thermo-optic phase shifter for the optical waveguide having the arrayed waveguide changes the phase of the optical signal in the other optical waveguide due to thermal interference. As a result, phase control becomes very complicated. In order to solve this problem, it was necessary to increase the distance between the arrayed waveguides sufficiently, but this increased the size. Therefore, in the present invention, as shown in FIG. 5, silicon having a relatively large thermo-optic effect is disposed only in the heating region, and a region that exerts a large amount of thermal interference on the adjacent optical waveguide is relatively heated. A quartz waveguide with a small optical effect is arranged to suppress thermal interference.

(Third embodiment)
FIG. 7 shows a circuit configuration of a variable wavelength filter according to the third embodiment of the present invention (wiring to the thin film heater is not shown). This has a function of outputting only a specific wavelength among the optical signal wavelengths input to the circuit from the input waveguide 301.

  The circuit configuration of this embodiment will be described. This variable wavelength filter is an optical interference circuit composed of two slab waveguides 311 and 312 and an arrayed waveguide 302 having different lengths for connecting them, and the arrayed waveguide 302 has a structure as shown in FIGS. A phase shifter including a double core, a thin film heater 321 and a heat insulating groove 331 is disposed.

  The operation principle of the circuit of this embodiment will be described. The optical signal incident on the input waveguide is distributed to each arrayed waveguide 302 in the first slab waveguide 311. Next, the optical signal propagating through the arrayed waveguide 302 propagates through the arrayed waveguides 302 having different lengths, and is collected at different positions depending on the wavelength in the second slab waveguide 312. Further, since the condensing position can be changed by changing the phase of the optical signal propagating through the arrayed waveguide with a phase shifter, it is possible to extract only a specific wavelength.

  Since the manufacturing procedure of this embodiment is the same as that of the second embodiment, it is omitted.

  Problems and effects to be solved by this embodiment will be briefly described below. In order to output a desired wavelength in the variable wavelength filter of this embodiment, it is necessary to individually set the phase change amounts by the plurality of phase shifters to a desired value. However, in the conventional variable wavelength filter shown in FIG. 17, the heat generated in the thermo-optic phase shifter for the optical waveguide having the arrayed waveguide changes the phase of the optical signal in the other optical waveguide due to thermal interference. As a result, phase control becomes very complicated. In order to solve this problem, it was necessary to increase the distance between the arrayed waveguides sufficiently, but this increased the size. Therefore, in the present invention, as shown in FIG. 7, silicon having a relatively large thermo-optic effect is disposed only in the heating region, and a region that exerts a large amount of thermal interference on the adjacent optical waveguide is relatively heated. A quartz waveguide with a small optical effect is arranged to suppress thermal interference.

(Fourth embodiment)
FIG. 8 shows a circuit configuration of a variable optical attenuator array according to the fourth embodiment of the present invention. This has a function of adjusting the optical signal intensity input to the circuit from the optical waveguide 101 to a desired value and outputting it.

  The circuit configuration of this embodiment will be described. This variable optical attenuator is a Mach-Zehnder interferometer comprising two directional couplers 102a and 102b and an arm waveguide 103 that connects them, and a groove 122 that divides the core is formed in the arm waveguide 103. And filled with silicone resin. FIG. 9 shows a top view of the thin film heater 111 and the groove 122. Here, the silicone resin assumed in this example has a thermo-optical effect of about -37 times that of quartz glass, and can give a large phase change with a slight heating (compared to quartz glass). it can. A thin film heater 111 for heating the silicone resin is formed around the groove 122 for filling the silicone resin, and can be operated as a thermo-optic phase shifter. Electric power is supplied from the wiring 112 to the thin film heater 111.

  Next, structural features of the present invention will be described. As shown in FIG. 8, the phase shifter including the thin film heater 111 is not aligned with the arm waveguide 103 (in a direction perpendicular to the longitudinal direction of the arm waveguide 103). It is characterized by being arranged so as not to overlap each other at the position translated in the direction perpendicular to the direction. Thereby, thermal interference can be suppressed.

  Next, a manufacturing procedure of the variable optical attenuator will be described. A buried optical waveguide is manufactured by a typical optical waveguide manufacturing method shown in FIG. Thereafter, a wiring pattern and a heater pattern are formed on the upper clad layer. And the groove | channel for filling a silicone resin is produced by the photolithographic technique and reactive ion etching. Finally, a silicone resin is applied in the vicinity of the groove 122, and the silicone resin is filled into the groove 122 and cured.

  The effect of this embodiment is almost the same as that of the first embodiment, but the degree of the effect is different. Silicone resin has a thermo-optic effect about -37 times that of quartz glass. On the other hand, the silicone resin is filled in the groove 122 shown in FIG. 9, and the groove width is 15 μm, and the distance between the grooves is 50 μm. At that time, the effective thermo-optic coefficient ratio in comparison with the quartz waveguide can be given by the following equation.

  here,

Is the thermo-optic coefficient of the silicone resin normalized by the thermo-optic coefficient of quartz glass, L _silicone is the ratio of the propagation direction of light of the silicone resin in the heating area, and L _SiO2 is the ratio of the propagation direction of light of the quartz glass in the heating area. Show. In the present embodiment in which the parameters of the groove 122 are as shown in FIG. 9, L _silicone is 15/50, and L _SiO2 is 35/50. Moreover, since the thermo-optic effect of silicone resin is about -37 times that of quartz glass,

Becomes -37. Therefore, the effective thermo-optic coefficient ratio normalized by the quartz glass in this embodiment is −10.4. Therefore, also in this embodiment, an effect can be expected by the same description as in the first embodiment, and the thermal interference can be suppressed to about 1 / 10.4 times that of the conventional configuration shown in FIG.

(Fifth embodiment)
FIG. 10 shows a circuit configuration of a 1 × 5 multiport optical switch according to the fifth embodiment of the present invention. This has a function of outputting the optical signal intensity input to the circuit from the input waveguide 301 to a desired port.

  The circuit configuration of this embodiment will be described. This multi-port optical switch is an optical interference circuit including two slab waveguides 311 and 312 and an arrayed waveguide 302 connecting them, and the phase shifter shown in FIG.

  Since the operation principle of the circuit of this embodiment is the same as that of the second example, it is omitted.

  Since the manufacturing procedure of this embodiment is the same as that of the fourth embodiment, it is omitted.

  Next, structural features of the present embodiment will be described. The phase shifter composed of the optical waveguide and the groove 332 filled with silicone and the thin film heater 321 is moved in parallel in the longitudinal direction of the array waveguide 302 between a plurality of adjacent array waveguides as shown in FIG. It is characterized by being shifted.

  The features and effects of this embodiment are as follows. As shown in FIG. 10, a silicone resin having a relatively large thermo-optic effect is used only in the heating region, and in a region that exerts a large amount of thermal interference on the adjacent optical waveguide, quartz having a relatively small thermo-optic effect. A waveguide is disposed to suppress thermal interference.

(Sixth embodiment)
FIG. 11 shows a circuit configuration of a variable wavelength filter according to the sixth embodiment of the present invention. This has a function of outputting only a specific wavelength among the optical signal wavelengths input to the circuit from the input waveguide 301.

  The circuit configuration of this embodiment will be described. This variable wavelength filter is an optical interference circuit comprising two slab waveguides 311 and 312 and an array waveguide 302 having different lengths for connecting them, and the phase shifter shown in FIG. 9 is arranged in the array waveguide. ing.

  Since the operation principle of the circuit of this embodiment is the same as that of the third example, it is omitted.

  Since the manufacturing procedure of this embodiment is the same as that of the fourth embodiment, it is omitted.

  The features and effects of this embodiment are as follows. As shown in FIG. 11, a silicone resin having a relatively large thermo-optic effect is used only in the heating region, and in a region that exerts a large amount of thermal interference on an adjacent optical waveguide, quartz having a relatively small thermo-optic effect. A waveguide is disposed to suppress thermal interference.

(Seventh embodiment)
FIG. 12 shows a circuit configuration of a variable optical attenuator array in the seventh embodiment of the present invention. This has a function of adjusting the optical signal intensity input to the circuit from the optical waveguide 101 to a desired value and outputting it.

  Since the circuit configuration of this embodiment is the same as that of the first embodiment, only the differences will be described. The main difference is the difference in the waveguide directly under the heater.

The first region directly under the heater of the arm waveguide has a buried rib waveguide structure as shown in FIG. 13A, and the other second region has a structure as shown in FIG. 13B. This is a buried channel waveguide structure. The first region includes a lower clad layer 502 made of silica-based glass on a silicon substrate 501, a rib waveguide 503 made of silicon, a core 504 of a second waveguide made of silica-based glass to which GeO ₂ is added, silica-based An upper cladding layer 505 made of glass is laminated. The second region includes a lower clad layer 502 made of silica glass on a silicon substrate 501, a core 506 made of silica glass to which GeO ₂ is added, and an upper clad layer 505 made of silica glass covering the periphery thereof. It is a laminated one. The refractive index of the silica-based glass to which GeO ₂ of the cores 504 and 506 of the _second waveguide is added is 1.48, and the size is manufactured as shown in FIGS. 13 (A) and 13 (B).

  In the first region, the electromagnetic field distribution of light is concentrated in the rib waveguide 503 made of silicon having a high refractive index, and silicon has a thermo-optic coefficient about 20 times that of silica. Therefore, thermal interference can be suppressed based on the same principle as in the first embodiment.

  By using two types of waveguides as in this embodiment, a multi-port switch and a variable wavelength filter can be produced as in the second and third embodiments.

  In the second, third, fifth, and sixth embodiments, the heater heating region is arranged at a position parallel to the longitudinal direction of the waveguide every four waveguides. However, the value of 4 is a value designed based on the interval (circuit size) of the arrayed waveguides, and may be another value depending on the requirement.

DESCRIPTION OF SYMBOLS 101 Input waveguide 102a, 102b Directional coupler 103 Arm waveguide 111 Thin film heater 112 Wiring 121 Heat insulation groove 122 Silicon filled groove 201, 201-1 and 201-2 Quartz core 202 Silicon core 202a Rectangular silicon core 202b Tapered silicon core 301 Input waveguide 302 Array waveguide 303 Output waveguide 311, 312 Slab waveguide 321 Thin film heater 331 Heat insulation groove 332 Silicon-filled groove 401 Quartz-based core 402 Silicon core 501 Silicon substrate 502 Lower cladding layer 503 Rib waveguides 504, 506 Second waveguide core 505 Upper cladding layer 601 Input waveguides 602a, 602b Directional coupler 603 Arm waveguide 611 Thin film heater 621 Heat insulation groove 701 Silicon substrate 702 Lower cladding layer 703 Core layer 704 Upper cladding layer 801 Input waveguide 802 Array waveguide 803 Output waveguide 811, 812 Slab waveguide 821 Thin film heater

Claims (7)

A multiple thermo-optic phase shifter in which thin film heaters are respectively disposed on two or more parallel optical waveguides,
The first region of the optical waveguide in the vicinity of the thin film heater has a larger thermo-optic coefficient than the second region other than the first region of the optical waveguide,
The multiple thermo-optical phase shifter, wherein at least the first region of the optical waveguide and the thin film heater which are adjacent to each other are arranged so as not to overlap at a position in the longitudinal direction. The first region is a buried optical waveguide composed of a first core layer, a second core layer, and a clad layer, and the second core layer has a thermo-optic coefficient higher than that of the first core layer. big,
The second region is a buried optical waveguide composed of a third core layer and a cladding layer having the same thermo-optic coefficient as the first core layer,
The multiple thermal optical phase shifter according to claim 1, wherein the first region and the second region are connected via a spot size converter. The first and second regions are embedded optical waveguides composed of a core layer and a cladding layer,
2. The multiple thermo-optic phase according to claim 1, wherein the first region has a plurality of grooves formed in the core layer filled with a material having a larger thermo-optic coefficient than the core layer. Shifter. The first region is a buried rib optical waveguide composed of a first core layer, a first cladding layer, and a second cladding layer having a refractive index lower than that of the first cladding layer,
2. The multiple thermooptic according to claim 1, wherein the second region is a buried optical waveguide including a second core layer and a clad layer having the same refractive index as the first clad layer. Phase shifter. A variable optical attenuator having first and second 3 dB couplers,
The variable optical attenuator, wherein the first and second 3 dB couplers are connected by the multiple thermo-optic phase shifter according to claim 1. A 1 × M optical switch having a first slab waveguide with 1 input and N output and a second slab waveguide with N input and M output,
The first slab waveguide and the second slab waveguide are connected by the multiple thermo-optic phase shifter according to claim 1 having N optical waveguides having the same optical path length. 1 x M optical switch. A variable wavelength filter having a first slab waveguide with 1 input and N output and a second slab waveguide with N input and M output,
The first slab waveguide and the second slab waveguide are connected by the multiple thermo-optic phase shifter according to claim 1 having N optical waveguides having different optical path lengths. Variable wavelength filter.

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