Optical Device and Optical Communication Device

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 Art

[0002] A phase shifter is incorporated in an optical modulator and an optical receiver in an optical communication apparatus used for high-speed optical communication. The phase shifter raises the temperature in the optical waveguide by heater heat, the refractive index in the optical waveguide changes due to the temperature rise, and the phase of the signal light passing through the optical waveguide is shifted according 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 taken along line G-G of the phase shifter 200 shown in FIG. 17. The phase shifter 200 shown in FIG. 17 includes an 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 disposed on the Si substrate 201 and the periphery of the heater electrode 204 disposed on the optical waveguide 203.

[0004] The dielectric 202 is formed of, for example, SiO2 or the like. The optical waveguide 203 is formed of, for example, Si and is a waveguide through which signal light passes. The heater electrode 204 is formed of a resistive metal such as Ti, generates heater heat according to a drive current, and raises the temperature in the optical waveguide 203. The electrode pad 205 has an input-side electrode pad 205A connected to the heater electrode 204 and inputting current to the heater electrode 204, and an output-side electrode pad 205B outputting current from the heater electrode 204.

[0005] In the phase shifter 200, heater heat is generated according to the drive current applied to the heater electrode 204, and the temperature in the optical waveguide 203 is raised by this heater heat. Further, the refractive index in the optical waveguide 203 changes according to the thermo-optical effect of Si due to the temperature rise. Further, the phase shifter 200 shifts the phase of the signal light passing through the optical waveguide 203 according to the change in the refractive index.

[0006] In the phase shifter 200 shown in FIG. 17, most of the heater heat generated by the heater electrode 204 diffuses into the dielectric 202 and the Si substrate 201, and only a part of the heater heat acting on the optical waveguide 203. As a result, the heating efficiency to the optical waveguide 203 is poor, and the power consumption increases.

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

[0008] The phase shifter 200A shown in FIG. 19 has, in addition to the Si substrate 201, the dielectric 202, the optical waveguide 203, the heater electrode 204, and the electrode pad 205, a cavity 206 and two trenches 207 (207A, 207B). The cavity 206 is composed of a cavity formed in a portion of the Si substrate 201 where the dielectric 202 under the optical waveguide 103 is laminated. The trench 207 is composed of a cavity formed in the dielectric 202 surrounding the heater electrode 204 and the optical waveguide 203. Each trench 207 is arranged in parallel so as to sandwich the left and right side surfaces of the heater electrode 204 disposed in the dielectric 202 above the optical waveguide 103 from both sides.

[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 the heater heat generated by the heater electrode 204 into the dielectric 202. The cavity 206 suppresses the diffusion of the heater heat generated by the heater electrode 204 into the Si substrate 201. That is, the phase shifter 200A suppresses the diffusion of the heater heat generated by the heater electrode 204 into 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, while improving the heating efficiency to the optical waveguide 203, the power consumption of the phase shifter 200A can be suppressed.

[0010] However, in the conventional phase shifter 200A, the dielectric 202 covering the optical waveguide 203 by the two trenches 207 and the cavity 206 floats in the air on the Si substrate 201. Moreover, since the dimension L of the phase shifter 200A is about several hundred microns, stress concentrates on the portions X of the dielectric 202 and the optical waveguide 203 at both ends of the trench 207 due to the cavities of the two trenches 207 and the cavity 206. When stress concentrates on the portions X of the dielectric 202 and the optical waveguide 203 at both ends of the trench 207, cracks occur in the portion X. As a result, the optical loss of the optical waveguide 203 increases due to the cracks in the portion X.

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

[0012] FIG. 21 is a schematic plan view showing an example of the conventional phase shifter 200B, FIG. 22 is a schematic cross-sectional view taken along line J-J shown in FIG. 21 of the phase shifter 200B, and FIG. 23 is a schematic cross-sectional view taken along line K-K shown in FIG. 21 of the phase shifter 200B. In addition, the same components as those of the phase shifter 200A shown in FIG. 19 are denoted by the same reference numerals, and the description of the overlapping components and operations is omitted.

[0013] The phase shifter 200B shown in FIG. 21 includes two trenches 207 having a plurality of segment-shaped divided trenches 210, and a bridge 202B formed of a dielectric 202 connecting the divided trenches 210. One trench 207A has, for example, four planar rectangular divided trenches 210 of the same dimension. Similarly, the other trench 207B also has four divided trenches 210.

[0014] In the phase shifter 200B, since the trench 207 is constituted by a plurality of divided trenches 210, the concentration of the stress described above is dispersed by the plurality of bridges 202B between the divided trenches 210. As a result, by suppressing the concentration of stress due to the cavity as compared with the phase shifter 200A shown in FIG. 19, and by suppressing the occurrence of cracks in the portion X, the occurrence of optical loss in the optical waveguide 203 can be suppressed.

Prior Art Documents

Patent Documents

[0015]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0016] In the conventional phase shifter 200B, since the region of the portion 202A of the dielectric 202 between the divided trench 210 and the heater electrode 204 becomes narrow, the heater heat of the heater electrode 204 concentrates in the portion 202A and the temperature locally becomes high. On the other hand, in the phase shifter 200B, since the region of the bridge 202B of the dielectric 202 between the divided trenches 210 becomes wide, the heater heat of the heater electrode 204 diffuses and the temperature becomes low.

[0017]

[0018] On one side, an object is to provide an optical device or the like capable of ensuring long-term reliability.

Means for Solving the Problems

[0019] One aspect of the optical device includes a substrate, a dielectric layer stacked on the substrate, an optical waveguide surrounded by the dielectric layer, a heater electrode disposed on the optical waveguide and surrounded by the dielectric layer, and a trench. The trench includes a plurality of segmented split trenches formed as 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 region of the dielectric between the end of the split trench and the side surface of the heater electrode gradually widens.

Advantages 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

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

Embodiments for Carrying Out the Invention

[0022] Hereinafter, 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 by this embodiment. Also, the following examples may be appropriately combined within a range that does not cause contradictions.

Examples

[0023] FIG. 1 is an explanatory diagram showing an example of the optical communication device 1 of this embodiment. The optical communication device 1 shown in FIG. 1 is connected to an output-side optical fiber 2A(2) and an input-side optical fiber 2B(2). 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. The DSP 3 executes processes such as encoding of transmission data, for example, generates an electrical signal including the transmission data, and outputs the generated electrical signal to the optical modulator 5. Further, the DSP 3 acquires an electrical signal including received data from the optical receiver 6, and executes processes such as decoding of the acquired electrical signal to obtain the received data.

[0024] The light source 4 includes, for example, a laser diode or the like, 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 by the 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 or the like. The optical modulator 5 generates an optical transmission signal by modulating the light supplied from the light source 4 when the light propagates through the waveguide with the electrical signal input to the modulation unit. 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 the 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. Note that the optical receiver 6 also includes a phase shifter 10 or the like.

[0026] FIG. 2 is a schematic plan view showing an example of the phase shifter 10 of Example 1, FIG. 3 is a schematic cross-sectional view taken along line A-A shown in FIG. 2 of the phase shifter 10, and FIG. 4 is a schematic cross-sectional view taken along line B-B shown in FIG. 2 of the phase shifter 10. The phase shifter 10 shown in FIG. 2 includes an 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 disposed on the Si substrate 11 and the periphery of the heater electrode 14 disposed 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 a resistive metal such as Ti, generates heater heat according to the drive current, and raises the temperature in the optical waveguide 13 with the heater heat. The electrode pad 17 has an input-side electrode pad 17A for inputting current to the heater electrode 14 and an output-side electrode pad 17B for outputting current from the heater electrode 14. The cavity portion 16 is composed of a cavity formed in a portion of the Si substrate 11 where the dielectric 12 covering under the optical waveguide 13 is laminated.

[0028] Each trench 15 has a plurality of segmental split trenches 150 each composed of a plurality of cavities formed in a portion of the dielectric 12 parallel to the heater electrode 14. Incidentally, the two trenches 15 are trenches arranged in parallel in the dielectric 12 on the left and right side surfaces of the heater electrode 14. The two trenches 15 have a first trench 15A and a second trench 15B. The first trench 15A has four split trenches 150 of substantially the same fan shape. Similarly, the second trench 15B also has four split trenches 150 of the same dimensions.

[0029] Each divided trench 150 has a central portion 151 which is a trench in the middle portion of the divided trench 150, and a tip portion 152 which is a trench at both end portions of the divided trench 150. The tip portion 152 is a substantially fan-shaped trench whose trench width gradually narrows from the central portion 151 toward the tip portion 152. Incidentally, the tip portion 152 is a trench in which the distance from the tip portion 152 to the optical waveguide 13 continuously changes. The dielectric 12 has a first portion 12A which is a portion between the central portion 151 of the divided trench 150 and the heater electrode 14, and a second portion 12B which is a portion between the tip portion 152 of the divided trench 150 and the heater electrode 14. Further, the dielectric 12 has a bridge 12C which is a portion between the divided 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 on the heater electrode 14 side of the tip portion 152 and the side surface of the heater electrode 14. The bridge 12C is a portion of the dielectric 12 between adjacent divided trenches 150.

[0030] Since the trench width W2 of the tip portion 152 of each divided trench 150 is continuously and gradually narrowed 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 continuously and gradually widens. Therefore, in the second portion 12B, the heater heat of the heater electrode 14 diffuses and the temperature becomes low. As a result, by moderating the temperature gradient between the bridge 12C and the second portion 12B between the divided trenches 150, variation of the material of the heater electrode 14 due to thermomigration can be suppressed.

[0031] In the phase shifter 10, stress concentration is dispersed by a plurality of bridges 12C between the divided trenches 150. As a result, by suppressing the concentration of stress due to cavities compared to the phase shifter 200B shown in FIG. 19, generation of cracks in the optical waveguide 13 can be suppressed.

[0032] In the phase shifter 10 of Example 1, since the trench width W2 at the tip 152 of each divided trench 150 is gradually narrowed compared to the trench width W1 at the central portion 151, the region of the second portion 12B between the tip 152 and the heater electrode 14 gradually widens. Then, the heater heat of the heater electrode 14 diffuses in the second portion 12B and the temperature decreases. As a result, by moderating the temperature gradient between the bridge 12C and the second portion 12B, variation in 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 portion 16 formed of a cavity in the Si substrate 11 on which the dielectric 12 below the heater electrode 14 is laminated. As a result, heat transfer of the heater heat of the heater electrode 14 to the Si substrate 11 can be suppressed in the cavity portion 16. While improving the heating efficiency, it is possible to reduce the power consumption.

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

[0035] In addition, each divided trench 150 of Example 1 has a substantially fan shape in which the shape of the tip 152 gradually narrows the trench width from the central portion 151 toward the tip 152. However, when the trench width of the tip 152 in the divided trench 150 is narrowed, the etching process during the manufacture of the divided trench 150 becomes difficult, which is a factor deteriorating the yield. Therefore, in order to simplify the etching process during the manufacture of the divided trench 150, the shape of the tip 152 may be made the same as the trench width of the central portion 151, and the embodiment thereof will be described below as Example 2.

Example

[0036] FIG. 5 is a schematic plan view showing an example of the phase shifter 10A of Example 2. 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 are omitted. The difference between the phase shifter 10A shown in FIG. 5 and the phase shifter 10 is that the trench width W2 of the tip portion 152A in the divided trench 150A is the same as the trench width W1 of the central portion 151. The divided trench 150A has a structure in which the trench width W2 of the tip portion 152A remains the same as the trench width W1 of the central portion 151 and gradually separates from the heater electrode 14 toward the tip portion 152A from the central portion 151.

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

[0038] Furthermore, since each divided trench 150A gradually separates from the heater electrode 14 toward the tip portion 152A from the central portion 151, the second portion 12B is made wider than the first portion 12A. And the area of the second portion 12B gradually becomes wider. In the second portion 12B, the heater heat of the heater electrode 14 diffuses and the temperature becomes lower. As a result, by moderating the temperature gradient between the second portion 12B and the bridge 12C, variation in the material of the heater electrode 14 due to thermomigration can be suppressed.

[0039] The divided trench 150A of Example 2 is formed such 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 the same. As a result, since the trench widths of the central portion 151 and the tip portion 152A are the same width, the etching process during the manufacture of the divided trench 150A can be simplified.

[0040] In addition, each divided trench 150A of Example 2 is exemplified as having the shape of the tip portion 152A shown in FIG. 5, but is not limited thereto, and the embodiment thereof will be described below as Example 3.

Example

[0041] FIG. 6 is a schematic plan view showing an example of the phase shifter 10B of Embodiment 3. In addition, the same components as those of the phase shifter 10 of Embodiment 1 are denoted by the same reference numerals, and the overlapping components and operations are omitted. The difference between the phase shifter 10B shown in FIG. 6 and the phase shifter 10A shown in FIG. 5 is that the end of the tip 152B of the divided trench 150B is formed in a curved shape 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 152B of each divided 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 divided trench 150B gradually moves away from the heater electrode 14 from the central portion 151 toward the tip 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, in the second portion 12B, the heater heat of the heater electrode 14 diffuses and the temperature becomes lower. As a result, by moderating the temperature gradient between the second portion 12B and the bridge 12C, variation of the material of the heater electrode 14 due to thermomigration can be suppressed.

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

[0045] In addition, in the phase shifter 10B of Embodiment 3, the temperature changes abruptly at the connection portion X2 that connects the wide electrode pad 17 and the heater electrode 14 on the narrow optical waveguide 13. Therefore, an embodiment for eliminating such a situation will be described below as Embodiment 4.

Embodiment

[0046] FIG. 7 is a schematic plan view showing an example of the phase shifter 10C of Example 4. In addition, the same components as those of the phase shifter 10B of Example 3 are denoted by the same reference numerals, and the description of the overlapping components and operations is omitted. The difference between the phase shifter 10C shown in FIG. 7 and the phase shifter 10B shown in FIG. 6 is that a joint portion 14A is provided on the heater electrode 14 in which the width of the heater electrode 14 connected to the electrode pad 17 gradually widens from the heater electrode 14 toward the electrode pad 17.

[0047] The heater electrode 14 is provided with a joint portion 14A at a connection portion connected to the input-side electrode pad 17A. Further, the heater electrode 14 is provided with a joint portion 14A at a connection portion connected to the output-side electrode pad 17B.

[0048] The heater electrode 14 of Example 4 has a joint portion 14A that gradually widens toward the electrode pad 17 to be connected. As a result, it is possible to avoid a situation in which the temperature at the connection portion X2 changes rapidly at the joint portion 14A between the heater electrode 14 and the electrode pad 17.

Example

[0049] FIG. 8 is a schematic plan view showing an example of the phase shifter 10D of Example 5, FIG. 9 is a schematic cross-sectional view taken along line C-C shown in FIG. 8 of the phase shifter 10D, and FIG. 10 is a schematic cross-sectional view taken along line D-D shown in FIG. 8 of the phase shifter 10D. In addition, the same components as those of the phase shifter 10 of Example 1 are denoted by the same reference numerals, and the description of the overlapping components and operations is omitted. The difference between the phase shifter 10D shown in FIG. 8 and the phase shifter 10 of Example 1 is that the pitch dimensions and shapes of the divided trenches 150C in the first trench 15A and the second trench 15B are different. The shape of the divided trench 150C is, for example, rectangular. Further, the number of divided trenches 150C on the first trench 15A side and the number of divided trenches 150C on the second trench 15B side are made the same.

[0050] The divided trenches 150C in the first trench 15A and the divided trenches 150C in the second trench 15B are arranged so that the bridges 12C in the first trench 15A and the bridges 12C in the second trench 15B do not face each other with the heater electrode 14 therebetween.

[0051] With respect to the heater electrode 14, the phase shifter 10D is configured such that the start position S of the first trench 15A and the start position S of the second trench 15B are the same. Further, with respect to the heater electrode 14, the phase shifter 10D is configured such that the end position E of the first trench 15A and the end position E of the second trench 15B are the same.

[0052] The phase shifter 10D arranges the divided trenches 150C in the first trench 15A and the second trench 15B so that the bridges 12C in the first trench 15A and the bridges 12C in the second trench 15B do not face each other with the heater electrode 14 therebetween. Since the bridges 12C are dispersed, the locations where the heater heat from the heater electrode 14 diffuses increase as compared with the phase shifter 10 of the first embodiment. As a result, by moderating the temperature gradient between the bridge 12C and the second part 12B, variation in the material of the heater electrode 14 due to thermomigration can be suppressed. Moreover, the long-term reliability of the phase shifter 10D can be ensured.

[0053] With respect to the heater electrode 14, the phase shifter 10D is configured such that 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. As a result, the process for forming the first trench 15A and the second trench 15B on the dielectric 12 can be simplified.

[0054] Note that the phase shifter 10D of the fifth embodiment has been exemplified in the case where the start positions S of the divided trenches 150C in the first trench 15A and the second trench 15B are the same and the end positions E of the divided trenches 150C in the first trench 15A and the second trench 15B are the same. However, the present invention is not limited thereto, and the implementation form will be described below as the sixth embodiment.

Example

[0055] FIG. 11 is a schematic plan view showing an example of the phase shifter 10E of Example 6. The same components as those of the phase shifter 10D of Example 5 are denoted by the same reference numerals, and the description of the overlapping components and operations is omitted. The difference between the phase shifter 10E shown in FIG. 11 and the phase shifter 10D lies in that, with reference to the heater electrode 14, the start position S1 of the divided trench 150D in the first trench 15A is different from the start position S2 of the divided trench 150D in the second trench 15B. Further, with reference to the heater electrode 14, the end position E1 of the divided trench 150D in the first trench 15A is different from the end position E2 of the divided trench 150D in the second trench 15B.

[0056] That is, the phase shifter 10E is made such that 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. Further, the phase shifter 10E is made such that the number of divided trenches 150D arranged in series in the first trench 15A is different from the number of divided trenches 150D arranged in series in the second trench 15B.

[0057] Then, each divided trench 150D in the first trench 15A and the second trench 15B is 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-side electrode pad 17A and the output-side electrode pad 17B to the first side surface of the heater electrode 14, for example, the right side surface of the heater electrode 14 arranged in parallel with the second trench 15B. The first side surface of the heater electrode 14 is, for example, the right side surface.

[0059] Furthermore, even when the number of divided trenches 150D in the first trench 15A is different from the number of divided trenches 150D in the second trench 15B, the relative positions of the electrode pad 17 and the divided trenches 150D are made the same on the input side and the output side, that is, symmetric left and right on 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 Example 6, the first distance L1 from the start position S1 to the end position E1 of the first trench 15A is made 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 when 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 part 12B is moderated. And the variation of the material of the heater electrode 14 due to thermomigration can be suppressed. Moreover, the long-term reliability of the phase shifter 10E can be ensured.

[0061] In addition, in the phase shifter 10E of Example 6, the case where the input-side electrode pad 17A and the output-side electrode pad 17B are arranged on the same right side surface of the heater electrode 14 is illustrated. However, it is not limited to the right side surface, and it may be the left side surface and can be appropriately changed. Also, the input-side electrode pad 17A may be arranged on the first side surface (right side surface) of the heater electrode 14, and the output-side electrode pad 17B1 may be arranged on the left side surface, which is the second side surface opposite to the first side surface of the heater electrode 14. The embodiment thereof will be described below as Example 7.

Example

[0062] FIG. 12 is a schematic plan view showing an example of the phase shifter 10F of Example 7. The same components as those of the phase shifter 10E of Example 6 are denoted by the same reference numerals, and the description of the overlapping components and operations is omitted. The difference between the phase shifter 10F shown in FIG. 12 and the phase shifter 10E shown in FIG. 11 is that the input-side electrode pad 17A is arranged on the first side surface of the heater electrode 14, and the output-side electrode pad 17B1 is arranged on the second side surface of the heater electrode 14. When the first side surface is the right side surface of the heater electrode 14, the second side surface is the left side surface of the heater electrode 14. That is, when the positions of the first trench 15A and the second trench 15B are different on the left and right side surfaces 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-side electrode pad 17A is arranged on the first side surface side of the heater electrode 14 and the output-side electrode pad 17B1 is arranged on the second side surface side of the heater electrode 14, the first trench 15A is arranged on the first side surface side and the second trench 15B is arranged on the second side surface side. As a result, in the phase shifter 10F, the dimension of the electrode pad 17 corresponding to approximately one unit can be reduced from the overall length of the phase shifter 10E.

[0064] The input-side electrode pad 17A of Example 7 is connected to the first side surface of the heater electrode 14, and the output-side electrode pad 17B1 is connected to the 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] Although the case where the single-direction optical waveguide 13 is arranged is illustrated for the phase shifter 10F of Example 7, a bidirectional optical waveguide 13 having a folding portion may be arranged, and the embodiment thereof will be described below as Example 8.

Example

[0066] FIG. 13 is a schematic plan view showing an example of the phase shifter 10G of Example 8. The same components as those of the phase shifter 10F of Example 7 are denoted by the same reference numerals, and the description of the overlapping components and operations is omitted. The difference between the phase shifter 10G shown in FIG. 13 and the phase shifter 10F is that a bidirectional optical waveguide 13 having a folding portion 13C is arranged, and a first trench 15A and a second trench 15B are arranged on both side surfaces of the heater electrode 14 on the bidirectional optical waveguide 13.

[0067] The bidirectional optical waveguide 13 includes an optical waveguide 13A on the forward path side, a folding portion 13C, and an optical waveguide 13B on the return path side. The optical waveguide 13A on the forward path side is an optical waveguide connected to an input end for inputting signal light. The folding portion 13C includes a first S-shaped curved portion 13C1, a U-shaped curved portion 13C3, and a second S-shaped curved portion 13C2. The first S-shaped curved portion 13C1 is an optical waveguide that optically couples between the optical waveguide 13A on the forward path side and the U-shaped curved portion 13C3. The U-shaped curved portion 13C3 is an optical waveguide that optically couples between the first S-shaped curved portion 13C1 and the second S-shaped curved portion 13C2. The second S-shaped curved portion 13C2 is an optical waveguide that optically couples between the U-shaped curved portion 13C3 and the optical waveguide 13B on the return path side. Further, the optical waveguide 13B on the return path side is connected to an output end and outputs the signal light from the second S-shaped curved portion 13C2 to the output end.

[0068] The length of the optical waveguide 13A on the forward path side is, for example, about 10 μm to 500 μm, and the length of the optical waveguide 13B on the return path side is also, for example, about 10 μm to 500 μm. Further, the diameter dimension of the folding portion 13C is, for example, about 5 μm to 20 μm.

[0069] The heater electrode 14 is arranged in the dielectric 12 on the optical waveguide 13A on the forward path side and the optical waveguide 13B on the return path side. As a result, the heater heat of the single heater electrode 14 is transmitted to the optical waveguide 13A on the forward path side and the optical waveguide 13B on the return path side, so that the refractive indices of the optical waveguide 13A on the forward path side and the optical waveguide 13B on the return path side change.

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

[0071] The first trench 15A of Example 8 is arranged in parallel with the forward-path optical waveguide 13A under the heater electrode 14, and the second trench 15B is arranged in parallel with the return-path optical waveguide 13B under the heater electrode 14. As a result, since the refractive indices of the forward-path optical waveguide 13A and the return-path optical waveguide 13B can be changed, a significant improvement in the phase shift efficiency can be achieved.

[0072] Furthermore, the forward-path optical waveguide 13A and the return-path optical waveguide 13B are arranged under the heater electrode 14. As a result, by making it possible to change the refractive index of the forward-path optical waveguide 13A and the return-path optical waveguide 13B with a single heater electrode 14, the power consumption can be significantly reduced.

[0073] Note that the phase shifter 10G of Example 8 illustrates the case where the folded portion 13C of the optical waveguide 13 is arranged at the tip of the output-side electrode pad 17B1. However, the folded portion 13C may be arranged inside the output-side electrode pad 17B1, and the embodiment thereof will be described below as Example 9.

Example

[0074] FIG. 14 is a schematic plan view showing an example of the phase shifter 10H of Example 9, FIG. 15 is a schematic cross-sectional view taken along line E-E shown in FIG. 14 of the phase shifter 10H, and FIG. 16 is a schematic cross-sectional view taken along line F-F shown in FIG. 14 of the phase shifter 10H. Note that the same components as those of the phase shifter 10G of Example 8 are denoted by the same reference numerals, and the description of the overlapping components and operations is omitted.

[0075] The difference between the phase shifter 10H shown in FIG. 14 and the phase shifter 10G shown in FIG. 13 is that a folding portion 13C that couples the forward optical waveguide 13A and the return optical waveguide 13B is disposed below the electrode pad 17B2 on the output side. In the phase shifter 10H, two optical waveguides 13, for example, a first S-shaped curved portion 13C1 and a second S-shaped curved portion 13C2, are disposed below the heater electrode 14.

[0076] In Example 9, the forward optical waveguide 13A and the return optical waveguide 13B are disposed below the heater electrode 14, and the folding portion 13C is disposed below the electrode pad 17B2 on the output side. As a result, even when a bidirectional optical waveguide 13 is employed, since the folding portion 13C is disposed below the electrode pad 17B2 on the output side, the overall length of the phase shifter 10H can be shortened as compared with the phase shifter 10G shown in FIG. 13.

[0077] Note that, in the phase shifters 10D (10E, 10G, 10H) of Examples 5 to 9, the case where the shape of the divided trench 150C (150D, 150E) is rectangular is illustrated, but the shape is not limited to a rectangle, and the shape of the divided trench 150 (150A, 150B) of Examples 1 to 4 may be employed and can be changed as appropriate.

Description of Reference Numerals

[0078] 1 Optical communication device 3 DSP 4 Light source 5 Optical modulator 6 Optical receiver 10 Phase shifter 11 Si substrate 12 Dielectric 12A First part 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 pad 17A Input-side electrode pad 17B Output-side electrode pad 150 Dividing trench 151 Central part 152 Tip part

Claims

1. A substrate, a dielectric layer laminated on the substrate, an optical waveguide surrounded by the dielectric layer, a heater electrode disposed on the optical waveguide and surrounded by the dielectric layer, and a plurality of segmented split trenches formed as cavities in the dielectric layer, the split trenches being arranged in parallel with the heater electrode. The split trenches, have a central portion and a tip portion of the split trench, With the trench width of the central portion and the trench width of the tip portion being the same, compared to the first portion of the dielectric between the central portion and the side surface of the heater electrode, the second portion of the dielectric between the tip portion and the side surface of the heater electrode is arranged in parallel with the heater electrode so as to gradually widen. An optical device characterized by this.

2. The optical device according to claim 1, characterized in that the substrate on which the dielectric layer is laminated below the heater electrode has a cavity portion formed as a cavity.

3. The trench, a first trench arranged in parallel on one side surface of the optical waveguide, a second trench arranged in parallel on the other side surface of the optical waveguide, a first bridge connecting a plurality of split trenches arranged in series in the first trench, and a second bridge connecting a plurality of split trenches arranged in series in the second trench. The optical device according to claim 1, characterized by having this.

4. The heater electrode, has a joint portion that gradually widens from the heater electrode toward the electrode pad at a portion connected to the electrode pad. The optical device according to claim 1, characterized by this.

5. An input-side electrode pad that is connected to the heater electrode and inputs current to the heater electrode, An output-side electrode pad that is connected to the heater electrode and outputs current from the heater electrode, and having, The input-side electrode pad, Is connected to one side surface of the heater electrode, The output-side electrode pad, Is connected to the other side surface of the heater electrode. The optical device according to claim 1, characterized in that.

6. The optical waveguide, Has an upstream-side optical waveguide, a return-path-side optical waveguide, and a folding-back portion that optically couples the upstream-side optical waveguide and the return-path-side optical waveguide, The first trench, Is arranged in parallel with the upstream-side optical waveguide, and The second trench, Is arranged in parallel with the return-path-side optical waveguide. The optical device according to claim 3, characterized in that.

7. An input-side electrode pad that is connected to the heater electrode and inputs current to the heater electrode, An output-side electrode pad that is connected to the heater electrode and outputs current from the heater electrode, and having, The upstream-side optical waveguide and the return-path-side optical waveguide, Are arranged below the heater electrode, The folding-back portion, Is arranged below the output-side electrode pad. The optical device according to claim 6, characterized in that.

8. A processor that executes signal processing for an electrical signal, A light source that generates light, An optical communication device having an optical modulator that modulates light generated from the light source using the electrical signal output from the processor, The phase shifter in the optical modulator, 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 having a plurality of segmented split trenches formed as cavities in the dielectric, the split trenches being arranged in parallel with the heater electrode, The split trench, Has a central portion of the split trench and a tip portion of the split trench, With the trench width of the central portion and the trench width of the tip portion being the same, compared to the first portion of the dielectric between the central portion and the side surface of the heater electrode, the second portion of the dielectric between the tip portion and the side surface of the heater electrode is arranged in parallel with the heater electrode so as to gradually widen. An optical communication device characterized by this.

9. A light source that generates light, An optical communication device having an optical receiver that demodulates a received optical signal using the light from the light source, The phase shifter in the optical receiver, A substrate, A dielectric 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 having a plurality of segmented split trenches formed as cavities in the dielectric, the split trenches being arranged in parallel with the heater electrode, The split trench, Has a central portion of the split trench and a tip portion of the split trench, With the trench width of the central portion and the trench width of the tip portion being the same, compared to the first portion of the dielectric between the central portion and the side surface of the heater electrode, the second portion of the dielectric between the tip portion and the side surface of the heater electrode is arranged in parallel with the heater electrode so as to gradually widen. An optical communication device characterized by this.

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