Optical devices and optical communication devices

Abstract

To provide an optical device and the like that can secure long-term reliability.SOLUTION: An optical device comprises: a substrate; a dielectric body that is laminated on the substrate; an optical waveguide that is surrounded by the dielectric body; a heater electrode that is arranged on the optical waveguide, and surrounded by the dielectric body; and a trench. The trench is provided with a plurality of segment-like division trenches that is formed by a cavity in the dielectric body, and the division trench is arranged in parallel with the heater electrode. The division trench is arranged in parallel with the heater electrode so that an area of the dielectric body present between an end of the division trench and a lateral face of the heater electrode becomes gradually wider.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an optical device and an optical communication apparatus. [Background technology]

[0002] Optical modulators and optical receivers in optical communication devices used for high-speed optical communication have built-in phase shifters. The phase shifter uses heater heat to increase the temperature inside the optical waveguide, which changes the refractive index inside the optical waveguide due to the increase in temperature, and shifts the phase of the signal light passing through the optical waveguide in response to the change in the refractive index.

[0003] Fig. 17 is a schematic plan view showing an example of a conventional phase shifter 200, and Fig. 18 is a schematic cross-sectional view of the phase shifter 200 taken along line GG shown in Fig. 17. The phase shifter 200 shown in Fig. 17 has a Si substrate 201, a dielectric 202, an optical waveguide 203, a heater electrode 204, and an electrode pad 205. The dielectric 202 is laminated on the Si substrate 201, and surrounds the periphery of the optical waveguide 203 arranged on the Si substrate 201 and the periphery of the heater electrode 204 arranged on the optical waveguide 203.

[0004] The dielectric 202 is made of, for example, SiO2. The optical waveguide 203 is made of, for example, Si, and is a waveguide through which signal light passes. The heater electrode 204 is made of, for example, a resistive metal such as Ti, and generates heater heat in response to a drive current to increase the temperature inside the optical waveguide 203. The electrode pad 205 is connected to the heater electrode 204 and has an input-side electrode pad 205A that inputs a current to the heater electrode 204, and an output-side electrode pad 205B that outputs a current from the heater electrode 204.

[0005] The phase shifter 200 generates heater heat in response to a drive current to the heater electrode 204, and this heater heat increases the temperature inside the optical waveguide 203. Furthermore, the refractive index inside the optical waveguide 203 changes in response to the thermo-optic effect of Si caused by the temperature increase. Furthermore, the phase shifter 200 shifts the phase of the signal light passing through the optical waveguide 203 in response to the change in the refractive index.

[0006] 17, most of the heater heat generated in the heater electrode 204 is diffused to the dielectric 202 and the Si substrate 201, and only a part of the heater heat acts on the optical waveguide 203. As a result, the heating efficiency to the optical waveguide 203 is poor, and power consumption is large.

[0007] Therefore, there is a phase shifter that improves the heating efficiency of the optical waveguide 203. Fig. 19 is a schematic plan view showing an example of a conventional phase shifter 200A, and Fig. 20 is a schematic cross-sectional view of the phase shifter 200A taken along line HH shown in Fig. 19. Note that the same components as those in the phase shifter 200 shown in Fig. 17 are denoted by the same reference numerals, and explanations of the overlapping components and operations will be omitted.

[0008] 19 includes a Si substrate 201, a dielectric 202, an optical waveguide 203, a heater electrode 204, and an electrode pad 205, as well as a cavity 206 and two trenches 207 (207A, 207B). The cavity 206 is formed in a portion of the Si substrate 201 where the dielectric 202 is laminated below the optical waveguide 103. The trench 207 is formed in the dielectric 202 surrounding the heater electrode 204 and the optical waveguide 203. The trenches 207 are arranged in parallel to sandwich the left and right side surfaces of the heater electrode 204 arranged in the dielectric 202 on the optical waveguide 103.

[0009] Each trench 207 forms a cavity in a portion of the dielectric 202 that is parallel to the heater electrode 204, thereby suppressing the diffusion of heater heat generated in the heater electrode 204 to the dielectric 202. The cavity 206 suppresses the diffusion of heater heat generated in the heater electrode 204 to the Si substrate 201. In other words, the phase shifter 200A suppresses the diffusion of heater heat generated in the heater electrode 204 to the dielectric 202 and the Si substrate 201 other than the optical waveguide 203 by the two trenches 207 and the cavity 206. As a result, the power consumption of the phase shifter 200A can be suppressed while improving the heating efficiency to the optical waveguide 203.

[0010] However, in the conventional phase shifter 200A, the dielectric 202 covering the optical waveguide 203 is suspended in the air above the Si substrate 201 by the two trenches 207 and the cavity 206. Moreover, since the dimension L of the phase shifter 200A is about several hundreds of microns, the two trenches 207 and the cavity 206 cause stress to concentrate on the dielectric 202 and the portion X of the optical waveguide 203 at both ends of the trench 207. When stress concentrates on the dielectric 202 and the portion X of the optical waveguide 203 at both ends of the trench 207, a crack occurs at the portion X. As a result, the crack at the portion X increases the optical loss of the optical waveguide 203.

[0011] Therefore, there is a need for a phase shifter 200B that can improve the heating efficiency of the optical waveguide 203 while suppressing the occurrence of cracks in the optical waveguide 203.

[0012] Fig. 21 is a schematic plan view showing an example of a conventional phase shifter 200B, Fig. 22 is a schematic cross-sectional view of the phase shifter 200B taken along line JJ shown in Fig. 21, and Fig. 23 is a schematic cross-sectional view of the phase shifter 200B taken along line KK shown in Fig. 21. Note that the same components as those in the phase shifter 200A shown in Fig. 19 are denoted by the same reference numerals, and descriptions of the overlapping components and operations will be omitted.

[0013] 21 has two trenches 207 each having a plurality of segment-shaped dividing trenches 210, and a bridge 202B formed of a dielectric 202 connecting the dividing trenches 210. One trench 207A has, for example, four dividing trenches 210 each having a rectangular shape in plan view and the same dimensions. Similarly, the other trench 207B also has four dividing trenches 210.

[0014] In the phase shifter 200B, the trench 207 is formed of a plurality of dividing trenches 210, and therefore the above-mentioned concentration of stress is dispersed by a plurality of bridges 202B between the dividing trenches 210. As a result, compared to the phase shifter 200A shown in Fig. 19, the concentration of stress due to cavities is suppressed, and the occurrence of cracks in the portion X is suppressed, thereby suppressing the occurrence of optical loss in the optical waveguide 203. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] Japanese Patent Application Publication No. 01-158413 [Patent Document 2] JP 2016-142995 A [Patent Document 3] JP 2004-037524 A [Patent Document 4] U.S. Patent No. 5,117,470 Summary of the Invention [Problem to be solved by the invention]

[0016] In the conventional phase shifter 200B, the area of ​​the portion 202A of the dielectric 202 between the dividing trench 210 and the heater electrode 204 is narrowed, so that the heater heat of the heater electrode 204 is concentrated in the portion 202A, causing a local increase in temperature. On the other hand, in the phase shifter 200B, the area of ​​the bridge 202B of the dielectric 202 between the dividing trenches 210 is widened, so that the heater heat of the heater electrode 204 is diffused, causing a decrease in temperature.

[0017] However, in the conventional phase shifter 200B, the heater heat of the heater electrode 204 is diffused by the bridge 202B between the dividing trenches 210, so that when a large current is passed through the heater electrode 204, a steep temperature gradient occurs between the bridge 202B and the portion 202A. If the temperature gradient becomes steep between the bridge 202B and the portion 202A, the material (Ti) of the heater electrode 204 may be mutated due to thermomigration, and the heater electrode 204 may be broken. As a result, the long-term reliability of the phase shifter 200B is deteriorated.

[0018] In one aspect, an object of the present invention is to provide an optical device or the like that can ensure long-term reliability. [Means for solving the problem]

[0019] An optical device according to one embodiment includes a substrate, a dielectric layered on the substrate, an optical waveguide surrounded by the dielectric, a heater electrode disposed on the optical waveguide and surrounded by the dielectric, and a trench. The trench includes a plurality of segment-shaped split trenches formed by cavities in the dielectric, and the split trenches are arranged in parallel with the heater electrode. The split trenches are arranged in parallel with the heater electrode such that the area of ​​the dielectric between the end of the split trench and the side of the heater electrode gradually becomes wider. Effect of the Invention

[0020] According to one aspect, the long-term reliability of the optical device can be ensured. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is an explanatory diagram showing an example of an optical communication device according to this embodiment. [Diagram 2] FIG. 2 is a schematic plan view illustrating an example of the phase shifter of the first embodiment. [Diagram 3] FIG. 3 is a schematic cross-sectional view of the phase shifter taken along line AA in FIG. [Figure 4] FIG. 4 is a schematic cross-sectional view of the phase shifter taken along line BB in FIG. [Diagram 5] FIG. 5 is a schematic plan view illustrating an example of a phase shifter according to the second embodiment. [Figure 6] FIG. 6 is a schematic plan view illustrating an example of a phase shifter according to the third embodiment. [Figure 7] FIG. 7 is a schematic plan view illustrating an example of a phase shifter according to the fourth embodiment. [Figure 8] FIG. 8 is a schematic plan view illustrating an example of a phase shifter according to the fifth embodiment. [Figure 9] FIG. 9 is a schematic cross-sectional view of the phase shifter taken along line CC shown in FIG. [Figure 10] FIG. 10 is a schematic cross-sectional view of the phase shifter taken along line DD in FIG. [Figure 11] FIG. 11 is a schematic plan view showing an example of a phase shifter according to the sixth embodiment. [Figure 12] FIG. 12 is a schematic plan view illustrating an example of a phase shifter according to the seventh embodiment. [Figure 13] FIG. 13 is a schematic plan view showing an example of a phase shifter according to the eighth embodiment. [Figure 14] FIG. 14 is a schematic plan view showing an example of a phase shifter according to the ninth embodiment. [Figure 15] FIG. 15 is a schematic cross-sectional view of the phase shifter taken along line EE shown in FIG. [Figure 16] FIG. 16 is a schematic cross-sectional view of the phase shifter taken along line FF shown in FIG. [Figure 17] FIG. 17 is a schematic plan view showing an example of a conventional phase shifter. [Figure 18] FIG. 18 is a schematic cross-sectional view of the phase shifter taken along line GG shown in FIG. [Figure 19] FIG. 19 is a schematic plan view showing an example of a conventional phase shifter. [Figure 20] FIG. 20 is a schematic cross-sectional view of the phase shifter taken along line HH shown in FIG. [Figure 21] FIG. 21 is a schematic plan view showing an example of a conventional phase shifter. [Figure 22] FIG. 22 is a schematic cross-sectional view of the phase shifter taken along line JJ shown in FIG. [Figure 23] FIG. 23 is a schematic cross-sectional view of the phase shifter taken along line KK shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, the embodiments of the optical device and the like disclosed in the present application will be described in detail with reference to the drawings. Note that the present invention is not limited to these embodiments. In addition, the following examples may be appropriately combined as long as no contradiction occurs. EXAMPLES

[0023] FIG. 1 is an explanatory diagram showing an example of an optical communication device 1 according to the present embodiment. The optical communication device 1 shown in FIG. 1 is connected to an optical fiber 2A(2) on the output side and an optical fiber 2B(2) on the input side. The optical communication device 1 includes a DSP (Digital Signal Processor) 3, a light source 4, an optical modulator 5, and an optical receiver 6. The DSP 3 is an electrical component that executes digital signal processing. For example, the DSP 3 executes processing such as encoding transmission data, generates an electrical signal including the transmission data, and outputs the generated electrical signal to the optical modulator 5. The DSP 3 also acquires an electrical signal including reception data from the optical receiver 6, and executes processing such as decoding the acquired electrical signal to obtain reception data.

[0024] The light source 4 includes, for example, a laser diode, and generates light of a predetermined wavelength and supplies it to the optical modulator 5 and the optical receiver 6. The optical modulator 5 is an optical device that modulates the light supplied from the light source 4 with an electrical signal output from the DSP 3, and outputs the obtained optical transmission signal to the optical fiber 2A. The optical modulator 5 is an optical modulator including a phase shifter 10, etc. When the light supplied from the light source 4 propagates through the waveguide, the optical modulator 5 generates an optical transmission signal by modulating the light with an electrical signal input to the modulation section. The phase shifter 10 shifts the phase of the signal light passing through the optical waveguide.

[0025] The optical receiver 6 receives an optical signal from the optical fiber 2B and demodulates the received optical signal using light supplied from the light source 4. Then, the optical receiver 6 converts the demodulated received optical signal into an electrical signal and outputs the converted electrical signal to the DSP 3. The optical receiver 6 also includes a phase shifter 10 and the like.

[0026] Fig. 2 is a schematic plan view showing an example of the phase shifter 10 of the first embodiment, Fig. 3 is a schematic cross-sectional view of the phase shifter 10 taken along line AA shown in Fig. 2, and Fig. 4 is a schematic cross-sectional view of the phase shifter 10 taken along line BB shown in Fig. 2. The phase shifter 10 shown in Fig. 2 has a Si substrate 11, a dielectric 12, an optical waveguide 13, a heater electrode 14, two trenches 15 (15A, 15B), a cavity 16, and an electrode pad 17.

[0027] The dielectric 12 is laminated on the Si substrate 11 and surrounds the periphery of the optical waveguide 13 arranged on the Si substrate 11 and the periphery of the heater electrode 14 arranged on the optical waveguide 13. The dielectric 12 is formed of, for example, SiO2 or the like. The optical waveguide 13 in the dielectric 12 is formed of, for example, Si, and is a waveguide through which signal light passes. The heater electrode 14 in the dielectric 12 is formed of, for example, a resistive metal such as Ti, generates heater heat in response to a drive current, and increases the temperature in the optical waveguide 13 with the heater heat. The electrode pad 17 has an input-side electrode pad 17A that inputs a current to the heater electrode 14, and an output-side electrode pad 17B that outputs a current from the heater electrode 14. The cavity 16 is formed of a cavity formed in a portion of the Si substrate 11 where the dielectric 12 that covers the lower part of the optical waveguide 13 is laminated.

[0028] Each trench 15 has a plurality of segment-shaped divided trenches 150 consisting of a plurality of cavities formed in a portion of the dielectric 12 that is in parallel with the heater electrode 14. The two trenches 15 are trenches that are arranged in parallel in the dielectric 12 on the left and right side surfaces of the heater electrode 14. The two trenches 15 include a first trench 15A and a second trench 15B. The first trench 15A has four divided trenches 150 of approximately sector shape and the same dimensions. Similarly, the second trench 15B also has four divided trenches 150 of the same dimensions.

[0029] Each of the split trenches 150 has a central portion 151 which is a trench in the middle of the split trench 150, and tip portions 152 which are trenches at both ends of the split trench 150. The tip portion 152 is a trench having a generally fan-shaped shape in which the trench width gradually narrows from the central portion 151 toward the tip portion 152. The tip portion 152 is a trench in which the distance from the tip portion 152 to the optical waveguide 13 changes continuously. The dielectric 12 has a first portion 12A which is a portion between the central portion 151 of the split trench 150 and the heater electrode 14, and a second portion 12B which is a portion between the tip portion 152 of the split trench 150 and the heater electrode 14. Furthermore, the dielectric 12 has a bridge 12C which is a portion between the split trenches 150. The first portion 12A is a portion of the dielectric 12 between the wall surface on the heater electrode 14 side of the central portion 151 and the side surface of the heater electrode 14. The second portion 12B is a portion of the dielectric 12 between the wall surface of the tip portion 152 on the heater electrode 14 side and the side surface of the heater electrode 14. The bridge 12C is a portion of the dielectric 12 between adjacent dividing trenches 150.

[0030] Since the trench width W2 of the tip portion 152 of each dividing trench 150 is gradually narrowed continuously compared to the trench width W1 of the central portion 151, the width of the second portion 12B of the dielectric 22 between the tip portion 152 and the heater electrode 14 is gradually widened continuously. Therefore, the heater heat of the heater electrode 14 is diffused in the second portion 12B, and the temperature of the second portion 12B is lowered. As a result, the temperature gradient between the bridge 12C between the dividing trenches 150 and the second portion 12B is made gentle, thereby suppressing the mutation of the material of the heater electrode 14 due to thermomigration.

[0031] In the phase shifter 10, stress concentration is dispersed by the multiple bridges 12C between the dividing trenches 150. As a result, stress concentration due to cavities is suppressed compared to the phase shifter 200B shown in FIG.

[0032] In the phase shifter 10 of the first embodiment, the trench width W2 of the tip 152 of each dividing trench 150 is gradually narrowed compared to the trench width W1 of the central portion 151, so that the area of ​​the second portion 12B between the tip 152 and the heater electrode 14 is gradually widened. Then, the heater heat of the heater electrode 14 in the second portion 12B is diffused and the temperature is lowered. As a result, the temperature gradient between the bridge 12C and the second portion 12B is made gentle, so that the mutation of the material of the heater electrode 14 due to thermomigration can be suppressed. Moreover, the long-term reliability of the phase shifter 10 can be ensured.

[0033] The phase shifter 10 has a cavity 16 formed as a cavity in the Si substrate 11 on which the dielectric 12 is laminated below the heater electrode 14. As a result, the cavity 16 can suppress the transfer of heater heat from the heater electrode 14 to the Si substrate 11. This allows the power consumption to be reduced while improving the heating efficiency.

[0034] Tip portion 152 is formed such that second portion 12B of dielectric 12 between tip portion 152 and heater electrode 14 is wider than first portion 12A of dielectric 12 between central portion 151 and heater electrode 14. As a result, heater heat of heater electrode 14 is diffused in second portion 12B, lowering the temperature.

[0035] In addition, each dividing trench 150 in Example 1 has a tip 152 in a generally fan shape with the trench width gradually narrowing from the center 151 toward the tip 152. However, narrowing the trench width of the tip 152 in the dividing trench 150 makes the etching process in manufacturing the dividing trench 150 difficult, which causes a decrease in yield. Therefore, in order to simplify the etching process in manufacturing the dividing trench 150, the shape of the tip 152 may be made the same as the trench width of the center 151, and this embodiment will be described below as Example 2. EXAMPLES

[0036] 5 is a schematic plan view showing an example of a phase shifter 10A according to the second embodiment. The same components as those of the phase shifter 10 according to the first embodiment are denoted by the same reference numerals, and the overlapping components and operations are omitted. The phase shifter 10A shown in FIG. 5 differs from the phase shifter 10 in that the trench width W2 of the tip portion 152A in the division trench 150A is set to be the same as the trench width W1 of the central portion 151. The division trench 150A has a structure in which the trench width W2 of the tip portion 152A is gradually separated from the heater electrode 14 from the central portion 151 toward the tip portion 152A while keeping the trench width W1 of the central portion 151 the same.

[0037] The second portion 12B of the dielectric 12 between the tip 152A of each dividing trench 150A and the heater electrode 14 is made wider than the first portion 12A of the dielectric 12 between the central portion 151 and the heater electrode 14.

[0038] Furthermore, since each dividing trench 150A is gradually separated from the heater electrode 14 from the center portion 151 toward the tip portion 152A, the second portion 12B is made wider than the first portion 12A. The area of ​​the second portion 12B gradually becomes wider. In the second portion 12B, the heater heat of the heater electrode 14 is diffused and the temperature becomes lower. As a result, by making the temperature gradient between the second portion 12B and the bridge 12C gentle, it is possible to suppress the mutation of the material of the heater electrode 14 due to thermomigration.

[0039] The dividing trench 150A of the second embodiment is formed so that the second portion 12B is wider than the first portion 12A while the trench width W1 of the central portion 151 and the trench width W2 of the tip portion 152A are kept the same. As a result, the trench widths of the central portion 151 and the tip portion 152A are the same, and therefore the etching process during the manufacture of the dividing trench 150A can be simplified.

[0040] In the second embodiment, each dividing trench 150A has the shape of the tip portion 152A shown in FIG. 5, but the present invention is not limited to this. An embodiment of the present invention will be described below as a third embodiment. EXAMPLES

[0041] Fig. 6 is a schematic plan view showing an example of a phase shifter 10B of Example 3. The same components as those of the phase shifter 10 of Example 1 are denoted by the same reference numerals, and the overlapping components and operations will not be described. The phase shifter 10B shown in Fig. 6 differs from the phase shifter 10A shown in Fig. 5 in that the end of the tip 152B of the dividing trench 150B is curved while the trench width W2 of the tip 152B is the same as the trench width W1 of the central portion 151.

[0042] The second portion 12B between the tip portion 152B of each dividing trench 150B and the heater electrode 14 is made wider than the first portion 12A of the dielectric 12 between the central portion 151 and the heater electrode 14.

[0043] Furthermore, since each dividing trench 150B is gradually separated from the heater electrode 14 from the central portion 151 toward the tip portion 152B, the second portion 12B is made wider than the first portion 12A. And, since the area of ​​the second portion 12B gradually becomes wider, the heater heat of the heater electrode 14 is diffused in the second portion 12B, and the temperature becomes lower. As a result, by making the temperature gradient between the second portion 12B and the bridge 12C gentle, it is possible to suppress mutation of the material of the heater electrode 14 due to thermomigration.

[0044] The dividing trench 150B of Example 3 is formed so that the second portion 12B is wider than the first portion 12A while the trench width W1 of the central portion 151 and the trench width W2 of the tip portion 152B are kept the same. As a result, the trench widths of the central portion 151 and the tip portion 152B are the same, and therefore the etching process during the manufacture of the dividing trench 150B can be simplified.

[0045] In the phase shifter 10B of the third embodiment, the temperature changes suddenly at the connection part X2 that connects the wide electrode pad 17 and the narrow heater electrode 14 on the optical waveguide 13. Therefore, an embodiment for solving such a situation will be described below as a fourth embodiment. EXAMPLES

[0046] Fig. 7 is a schematic plan view showing an example of a phase shifter 10C according to the fourth embodiment. The same components as those of the phase shifter 10B according to the third embodiment are denoted by the same reference numerals, and the description of the overlapping components and operations will be omitted. The phase shifter 10C shown in Fig. 7 differs from the phase shifter 10B shown in Fig. 6 in that the heater electrode 14 is provided with a joint 14A in which the width of the heater electrode 14 connected to the electrode pad 17 gradually increases from the heater electrode 14 toward the electrode pad 17.

[0047] The heater electrode 14 is provided with a joint 14A at a connection site where it is connected to the input-side electrode pad 17A, and further provided with a joint 14A at a connection site where it is connected to the output-side electrode pad 17B.

[0048] The heater electrode 14 of the fourth embodiment has a joint 14A that gradually widens toward the connected electrode pad 17. As a result, it is possible to prevent a sudden change in temperature of the connection part X2 at the joint 14A between the heater electrode 14 and the electrode pad 17. EXAMPLES

[0049] FIG. 8 is a schematic plan view showing an example of a phase shifter 10D of the fifth embodiment, FIG. 9 is a schematic cross-sectional view of the phase shifter 10D taken along the line CC shown in FIG. 8, and FIG. 10 is a schematic cross-sectional view of the phase shifter 10D taken along the line DD shown in FIG. 8. The same components as those in the phase shifter 10 of the first embodiment are denoted by the same reference numerals, and the description of the overlapping components and operations is omitted. The phase shifter 10D shown in FIG. 8 is different from the phase shifter 10 of the first embodiment in that the pitch dimensions and shapes of the split trenches 150C in the first trench 15A and the second trench 15B are different. The shape of the split trench 150C is, for example, rectangular. Furthermore, the number of split trenches 150C on the first trench 15A side is the same as the number of split trenches 150C on the second trench 15B side.

[0050] Each divided trench 150C in the first trench 15A and each divided trench 150C in the second trench 15B are arranged so that the bridge 12C in the first trench 15A and the bridge 12C in the second trench 15B do not face each other across the heater electrode 14.

[0051] In the phase shifter 10D, the start position S of the first trench 15A and the start position S of the second trench 15B are the same with respect to the heater electrode 14. Furthermore, in the phase shifter 10D, the end position E of the first trench 15A and the end position E of the second trench 15B are the same with respect to the heater electrode 14.

[0052] In the phase shifter 10D, the divided trenches 150C in the first trench 15A and the second trench 15B are arranged so that the bridge 12C in the first trench 15A and the bridge 12C in the second trench 15B do not face each other across the heater electrode 14. Since the bridges 12C are dispersed, the number of locations to which the heater heat from the heater electrode 14 is diffused increases compared to the phase shifter 10 of the first embodiment. As a result, the temperature gradient between the bridges 12C and the second portions 12B is made gentle, thereby suppressing the mutation of the material of the heater electrode 14 due to thermomigration. Moreover, the long-term reliability of the phase shifter 10D can be ensured.

[0053] In the phase shifter 10D, the start position S of the first trench 15A and the start position S of the second trench 15B are the same and the end position E of the first trench 15A and the end position E of the second trench 15B are the same with respect to the heater electrode 14. As a result, the process for forming the first trench 15A and the second trench 15B on the dielectric 12 can be simplified.

[0054] In the phase shifter 10D of the fifth embodiment, the start positions S of the dividing trenches 150C in the first trench 15A and the second trench 15B are the same, and the end positions E of the dividing trenches 150C in the first trench 15A and the second trench 15B are the same. However, the present invention is not limited to this, and an embodiment thereof will be described below as a sixth embodiment. EXAMPLES

[0055] FIG. 11 is a schematic plan view showing an example of a phase shifter 10E according to a sixth embodiment. The same components as those of the phase shifter 10D according to the fifth embodiment are denoted by the same reference numerals, and the description of the overlapping components and operations will be omitted. The phase shifter 10E shown in FIG. 11 differs from the phase shifter 10D in that the start position S1 of the dividing trench 150D in the first trench 15A is different from the start position S2 of the dividing trench 150D in the second trench 15B with respect to the heater electrode 14. Furthermore, the end position E1 of the dividing trench 150D in the first trench 15A is different from the end position E2 of the dividing trench 150D in the second trench 15B with respect to the heater electrode 14.

[0056] That is, in the phase shifter 10E, the first distance L1 from the start position S1 to the end position E1 of the first trench 15A is longer than the second distance L2 from the start position S2 to the end position E2 of the second trench 15B. Furthermore, in the phase shifter 10E, the number of dividing trenches 150D arranged in series in the first trench 15A is different from the number of dividing trenches 150D arranged in series in the second trench 15B.

[0057] Then, the dividing trenches 150D in the first trench 15A and the second trench 15B are arranged so that the bridge 12C in the first trench 15A and the bridge 12C in the second trench 15B do not face each other with the heater electrode 14 interposed therebetween.

[0058] The phase shifter 10E connects the input electrode pad 17A and the output electrode pad 17B to a first side surface of the heater electrode 14, for example, the right side surface of the heater electrode 14 arranged in parallel in the second trench 15B. The first side surface of the heater electrode 14 is, for example, the right side surface.

[0059] Furthermore, even if the number of dividing trenches 150D in the first trench 15A is different from the number of dividing trenches 150D in the second trench 15B, the relative positions of the electrode pads 17 and the dividing trenches 150D are the same on the input side and the output side, that is, symmetrical on the left and right in the drawing of Fig. 11. As a result, by optimizing the pattern, the temperature distribution can be improved in the same way on the input side and the output side.

[0060] In the phase shifter 10E of the sixth embodiment, the first distance L1 from the start position S1 to the end position E1 of the first trench 15A is longer than the second distance L2 from the start position S2 to the end position E2 of the second trench 15B. As a result, even if the first distance L1 of the first trench 15A is different from the second distance L2 of the second trench 15B, the temperature gradient between the bridge 12C and the second portion 12B is gentle. Thus, the material of the heater electrode 14 can be prevented from being changed by thermomigration. Moreover, the long-term reliability of the phase shifter 10E can be ensured.

[0061] In the phase shifter 10E of the sixth embodiment, the input electrode pad 17A and the output electrode pad 17B are disposed on the same right side surface of the heater electrode 14. However, this is not limited to the right side surface, and may be the left side surface, and can be changed as appropriate. The input electrode pad 17A may be disposed on the first side surface (right side surface) of the heater electrode 14, and the output electrode pad 17B1 may be disposed on the left side surface, which is the second side surface opposite to the first side surface of the heater electrode 14. This embodiment will be described below as the seventh embodiment. EXAMPLES

[0062] FIG. 12 is a schematic plan view showing an example of a phase shifter 10F according to the seventh embodiment. The same components as those of the phase shifter 10E according to the sixth embodiment are denoted by the same reference numerals, and the description of the overlapping components and operations will be omitted. The phase shifter 10F shown in FIG. 12 differs from the phase shifter 10E shown in FIG. 11 in that the input electrode pad 17A is arranged on the first side of the heater electrode 14, and the output electrode pad 17B1 is arranged on the second side of the heater electrode 14. When the first side is the right side of the heater electrode 14, the second side is the left side of the heater electrode 14. In other words, when the positions of the first trench 15A and the second trench 15B are different on the left and right sides of the heater electrode 14, the overall length of the phase shifter 10F including the electrode pad 17 can be shortened.

[0063] Since the input electrode pad 17A is disposed on the first side surface of the heater electrode 14 and the output electrode pad 17B1 is disposed on the second side surface of the heater electrode 14, the first trench 15A is disposed on the first side surface and the second trench 15B is disposed on the second side surface. As a result, in the phase shifter 10F, the dimension of approximately one electrode pad 17 can be reduced from the overall length of the phase shifter 10E.

[0064] The input side electrode pad 17A of the seventh embodiment is connected to a first side surface of the heater electrode 14, and the output side electrode pad 17B1 is connected to a second side surface of the heater electrode 14. In the phase shifter 10F, the overall length of the phase shifter 10F can be shortened.

[0065] In the phase shifter 10F of the seventh embodiment, a unidirectional optical waveguide 13 is illustrated, but a bidirectional optical waveguide 13 having a folded portion may also be arranged, and this embodiment will be described below as the eighth embodiment. EXAMPLES

[0066] Fig. 13 is a schematic plan view showing an example of a phase shifter 10G according to the eighth embodiment. The same components as those of the phase shifter 10F according to the seventh embodiment are denoted by the same reference numerals, and the description of the overlapping components and operations will be omitted. The phase shifter 10G shown in Fig. 13 differs from the phase shifter 10F in that a bidirectional optical waveguide 13 having a folded portion 13C is arranged, and a first trench 15A and a second trench 15B are arranged on both sides of a heater electrode 14 on the bidirectional optical waveguide 13.

[0067] The bidirectional optical waveguide 13 has an outgoing optical waveguide 13A, a turn-back portion 13C, and a return-side optical waveguide 13B. The outgoing optical waveguide 13A is an optical waveguide that connects to an input end that inputs a signal light. The turn-back portion 13C has a first S-shaped curve portion 13C1, a U-shaped curve portion 13C3, and a second S-shaped curve portion 13C2. The first S-shaped curve portion 13C1 is an optical waveguide that optically couples the outgoing optical waveguide 13A and the U-shaped curve portion 13C3. The U-shaped curve portion 13C3 is an optical waveguide that optically couples the first S-shaped curve portion 13C1 and the second S-shaped curve portion 13C2. The second S-curve portion 13C2 is an optical waveguide that optically couples the U-curve portion 13C3 and the return optical waveguide 13B. Furthermore, the return optical waveguide 13B is an optical waveguide that is connected to the output end and outputs the signal light from the second S-curve portion 13C2 to the output end.

[0068] The length of the outgoing optical waveguide 13A is, for example, about 10 μm to 500 μm, and the length of the returning optical waveguide 13B is, for example, about 10 μm to 500 μm. Furthermore, the diameter of the folded portion 13C is, for example, about 5 μm to 20 μm.

[0069] The heater electrode 14 is disposed within the dielectric 12 on the outgoing optical waveguide 13A and the returning optical waveguide 13B. As a result, the heater heat of the single heater electrode 14 is transmitted to the outgoing optical waveguide 13A and the returning optical waveguide 13B, thereby changing the refractive indexes of the outgoing optical waveguide 13A and the returning optical waveguide 13B.

[0070] With only the outgoing optical waveguide 13A, the phase of the passing signal light can be shifted up to 90 degrees, but by adding the returning optical waveguide 13B, the phase of the passing signal light can be shifted up to 180 degrees. As a result, by making it possible to change the optical refractive index of the outgoing optical waveguide 13A and the returning optical waveguide 13B with a single heater electrode 14, power consumption can be significantly reduced.

[0071] The first trench 15A of the eighth embodiment is arranged in parallel with the outgoing optical waveguide 13A below the heater electrode 14, and the second trench 15B is arranged in parallel with the returning optical waveguide 13B below the heater electrode 14. As a result, the refractive indexes of the outgoing optical waveguide 13A and the returning optical waveguide 13B can be changed, and the phase shift efficiency can be significantly improved.

[0072] Furthermore, the outgoing optical waveguide 13A and the returning optical waveguide 13B are disposed below the heater electrode 14. As a result, the optical refractive indexes of the outgoing optical waveguide 13A and the returning optical waveguide 13B can be changed by the single heater electrode 14, thereby making it possible to significantly reduce power consumption.

[0073] In the phase shifter 10G of the eighth embodiment, the folded portion 13C of the optical waveguide 13 is disposed at the tip of the electrode pad 17B1 on the output side. However, the folded portion 13C may be disposed within the electrode pad 17B1 on the output side, and such an embodiment will be described below as a ninth embodiment. EXAMPLES

[0074] Fig. 14 is a schematic plan view showing an example of a phase shifter 10H of the ninth embodiment, Fig. 15 is a schematic cross-sectional view of the phase shifter 10H taken along line EE shown in Fig. 14, and Fig. 16 is a schematic cross-sectional view of the phase shifter 10H taken along line FF shown in Fig. 14. Note that the same components as those in the phase shifter 10G of the eighth embodiment are denoted by the same reference numerals, and explanations of the same components and operations will be omitted.

[0075] The phase shifter 10H shown in Fig. 14 differs from the phase shifter 10G shown in Fig. 13 in that a folded portion 13C is disposed below the output electrode pad 17B2, which couples the outgoing optical waveguide 13A and the return optical waveguide 13B. The phase shifter 10H has two optical waveguides 13, for example, a first S-shaped curve portion 13C1 and a second S-shaped curve portion 13C2, disposed below the heater electrode 14.

[0076] In the ninth embodiment, the outgoing optical waveguide 13A and the returning optical waveguide 13B are disposed below the heater electrode 14, and the folded-back portion 13C is disposed below the output-side electrode pad 17B2. As a result, even when a bidirectional optical waveguide 13 is employed, the folded-back portion 13C is disposed below the output-side electrode pad 17B2, so that the overall length of the phase shifter 10H can be shortened compared to the phase shifter 10G shown in FIG.

[0077] In the phase shifters 10D (10E, 10G, 10H) of Examples 5 to 9, the shape of the dividing trench 150C (150D, 150E) is rectangular, but this is not limited to a rectangular shape and may be the shape of the dividing trench 150 (150A, 150B) of Examples 1 to 4, and can be modified as appropriate. [Explanation of symbols]

[0078] 1 Optical communication devices 3. DSP 4 light source 5 Optical Modulator 6 Optical Receiver 10 Phase Shifter 11. Silicon substrate 12 Dielectrics 12A First Section 12B Second Part 12C Bridge 13 Optical waveguide 14 Heater electrode 14A Junction 15. Trench 15A First Trench 15B Second Trench 16 Cavity 17 Electrode Pads 17A Input electrode pad 17B Output electrode pad 150 Split Trench 151 Central part 152 Tip

Claims

1. A substrate; a dielectric layer laminated on the substrate; an optical waveguide surrounded by the dielectric; a heater electrode disposed on the optical waveguide and surrounded by the dielectric; a trench including a plurality of segment-shaped dividing trenches formed as cavities in the dielectric, the dividing trenches being arranged in parallel with the heater electrode; The dividing trench is A trench includes a center portion of the dividing trench and a tip portion of the dividing trench, an optical device arranged in parallel with the heater electrode such that, while the trench width of the central portion and the trench width of the tip portion are the same, a second portion of the dielectric between the tip portion and a side surface of the heater electrode is gradually wider than a first portion of the dielectric between the central portion and the side surface of the heater electrode.

2. 2. The optical device according to claim 1, further comprising a cavity formed in the substrate on which the dielectric layer is laminated and below the heater electrode.

3. The trench is A first trench is arranged in parallel on one side of the optical waveguide; a second trench disposed in parallel on the other side of the optical waveguide; a first bridge connecting a plurality of dividing trenches arranged in series in the first trench; 2. The optical device according to claim 1, further comprising: a second bridge connecting a plurality of dividing trenches arranged in series within the second trench.

4. The heater electrode is 2. The optical device according to claim 1, further comprising a junction portion at a portion connected to an electrode pad, the junction portion gradually widening from the heater electrode toward the electrode pad.

5. an input electrode pad connected to the heater electrode for inputting a current to the heater electrode; an output electrode pad connected to the heater electrode and outputting a current from the heater electrode; The input electrode pad is Connected to one side of the heater electrode; The output electrode pad is 2. The optical device according to claim 1, further comprising a connection to the other side of the heater electrode.

6. The optical waveguide is a forward optical waveguide, a return optical waveguide, and a turn-back portion that optically couples the forward optical waveguide and the return optical waveguide, The first trench comprises: The optical waveguide is arranged in parallel with the outgoing optical waveguide. The second trench comprises:

4. The optical device according to claim 3, wherein the optical waveguide is arranged in parallel with the return optical waveguide.

7. An input side electrode pad connected to the heater electrode and inputting a current to the heater electrode; an output electrode pad connected to the heater electrode and outputting a current from the heater electrode; The outgoing optical waveguide and the return optical waveguide are A heater electrode is disposed below the heater electrode. The folded portion is 7. The optical device according to claim 6, wherein the output electrode pad is disposed below the output electrode pad.

8. A processor that performs signal processing on the electrical signal; A light source that generates light; an optical modulator that modulates light generated from the light source using an electrical signal output from the processor, The phase shifter in the optical modulator comprises: A substrate; a dielectric layer laminated on the substrate; an optical waveguide surrounded by the dielectric; a heater electrode disposed on the optical waveguide and surrounded by the dielectric; a trench including a plurality of segment-shaped dividing trenches formed as cavities in the dielectric, the dividing trenches being arranged in parallel with the heater electrode; The dividing trench is A trench includes a center portion of the dividing trench and a tip portion of the dividing trench, an optical communication device arranged in parallel with the heater electrode such that, with the trench width of the central portion and the trench width of the tip portion being the same, a second portion of the dielectric between the tip portion and a side surface of the heater electrode is gradually wider than a first portion of the dielectric between the central portion and the side surface of the heater electrode.

9. A light source that generates light; an optical receiver that demodulates a received optical signal using light from the light source, The phase shifter in the optical receiver includes: A substrate; a dielectric layer laminated on the substrate; an optical waveguide surrounded by the dielectric; a heater electrode disposed on the optical waveguide and surrounded by the dielectric; a trench including a plurality of segment-shaped dividing trenches formed as cavities in the dielectric, the dividing trenches being arranged in parallel with the heater electrode; The dividing trench is A trench includes a center portion of the dividing trench and a tip portion of the dividing trench, an optical communication device arranged in parallel with the heater electrode such that, with the trench width of the central portion and the trench width of the tip portion being the same, a second portion of the dielectric between the tip portion and a side surface of the heater electrode is gradually wider than a first portion of the dielectric between the central portion and the side surface of the heater electrode.

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