Optical device, optical transmitter and optical receiver

Abstract

To provide an optical device and the like which reduce element size.SOLUTION: The optical device comprises a first rib type optical waveguide arranged on a substrate and including a first slab area of first conductivity and a second slab area of second conductivity. The optical device further comprises: a second rib type optical waveguide arranged on the substrate and including a third slab area of first conductivity and a fourth slab area of second conductivity; and a turn-around waveguide arranged on the substrate and connecting the first rib type optical waveguide and the second rib type optical waveguide. The optical device comprises: a first electrode wire electrically connecting the first slab area and the third slab area; and a second electrode wire electrically connecting the second slab area and the fourth slab area. The first electrode wire electrically connects the first slab area and the third slab area while crossing over at least one of the second slab area and the fourth slab area.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical device, an optical transmitter, and an optical receiver. [Background technology]

[0002] In recent years, the demand for optical fiber communications has increased along with the increase in communication capacity. Therefore, the development of optical devices, typified by silicon photonics, has been actively pursued. Known examples of such optical devices include optical attenuators such as variable optical attenuators (VOAs), which attenuate the intensity of signal light propagating through an optical waveguide in response to an electrical signal.

[0003] Fig. 26 is a schematic plan view showing an example of an optical device 100, Fig. 27 is a schematic cross-sectional view taken along line AA in Fig. 26, and Fig. 28 is a schematic cross-sectional view taken along line BB in Fig. 26. A VOA 110, which is the optical device 100, has a Si substrate 121, a rib-type optical waveguide 102 formed on the Si substrate 121, and lower electrodes 103 connected to both sides of the rib-type optical waveguide 102. Furthermore, the VOA 110 has a cladding layer 122 formed on the Si substrate 121 and surrounding the rib-type optical waveguide 102 and the two lower electrodes 103.

[0004] The rib-type optical waveguide 102 has, for example, a rib waveguide 102A forming a Si core, and a first slab region 102D and a second slab region 102E on either side of the waveguide 102A. The rib-type optical waveguide 102 has an optical input section 102B and an optical output section 102C. The optical input section 102B is an input stage of the rib-type optical waveguide 102 that inputs signal light to the rib waveguide 102A. The optical output section 102C is an output stage of the rib-type optical waveguide 102 that outputs signal light from the rib waveguide 102A. A P-doped region 102F is formed at the outer end of the first slab region 102D, and an N-doped region 102G is formed at the outer end of the second slab region 102E. The rib waveguide 102A, the first slab region 102D, and the second slab region 102E are undoped regions. The rib optical waveguide 102 has a PIN diode structure with the P-doped region 102F, the undoped region, and the N-doped region 102G.

[0005] The lower electrode 103 has a first lower electrode 103A electrically connected to the P-doped region 102F via a contact layer 111A (111), and a second lower electrode 103B electrically connected to the N-doped region 102G via a contact layer 111B (111).

[0006] Upper-layer electrode 104 is an electrode disposed on an upper layer compared to lower-layer electrode 103, and constitutes input pad 105 and ground pad 106. Upper-layer electrode 104 has first upper-layer electrode 104A electrically connected to first lower-layer electrode 103A via via 107A (107), and second upper-layer electrode 104B electrically connected to second lower-layer electrode 103B via via 107B (107). Input pad 105 is formed by exposing a portion of first upper-layer electrode 104A through an opening in cladding layer 122. Ground pad 106 is formed by exposing a portion of second upper-layer electrode 104B through an opening in cladding layer 122.

[0007] In optical device 100, input pad 105 is located near the center of VOA 110, and power is supplied from input pad 105 to first lower-layer electrode 103A (as a signal electrode) via via 107A and first upper-layer electrode 104A. In optical device 100, ground pad 106 is located near the center of VOA 110, and power is supplied from second lower-layer electrode 103B (as a ground electrode) to ground pad 106 via via 107B and second upper-layer electrode 104B.

[0008] When a positive voltage is applied to first lower-layer electrode 103A from input pad 105, a current flows from first lower-layer electrode 103A to second lower-layer electrode 103B. Then, a current flows through rib-type optical waveguide 102 disposed between first lower-layer electrode 103A and second lower-layer electrode 103B. As a result, the signal light guided through rib-type optical waveguide 102 is absorbed by free carrier absorption of the current flowing through rib-type optical waveguide 102, thereby attenuating the intensity of the signal light. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Special Publication No. 2004-506935 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-188886 [Patent Document 3] US Patent Application Publication No. 2015 / 0346520 [Patent Document 4] US Patent Application Publication No. 2012 / 0080672 Summary of the Invention [Problem to be solved by the invention]

[0010] In the optical device 100, in order to reduce the driving power of the VOA, it is necessary to increase the lengths of the lower electrode 103 and the PIN region in the VOA. Therefore, in the optical device 100, the VOA has a linear structure as shown in Fig. 26, which increases the size of the element. Furthermore, in the optical device 100, the size of the element is not limited to the PIN region, and in fact, reduction in element size is required even in the PIP region or NIN region.

[0011] In one aspect, an object is to provide an optical device or the like that is capable of reducing the element size. [Means for solving the problem]

[0012] An optical device according to one embodiment includes a first rib-type optical waveguide disposed on a substrate and having a first slab region having a first conductivity type and a second slab region having a second conductivity type. The optical device also includes a second rib-type optical waveguide disposed on the substrate and having a third slab region having the first conductivity type and a fourth slab region having the second conductivity type, and a folded waveguide disposed on the substrate and connecting the first rib-type optical waveguide and the second rib-type optical waveguide. The optical device also includes a first electrode line electrically connecting the first slab region and the third slab region, and a second electrode line electrically connecting the second slab region and the fourth slab region. The first electrode line electrically connects the first slab region and the third slab region across at least one of the second slab region and the fourth slab region. [Effects of the Invention]

[0013] According to one aspect, the size of the element is reduced. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic plan view showing an example of an optical device according to a first embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view taken along line AA shown in FIG. [Figure 3] FIG. 3 is a schematic cross-sectional view taken along line BB shown in FIG. [Figure 4] FIG. 4 is a schematic cross-sectional view taken along line CC shown in FIG. [Figure 5] FIG. 5 is a schematic plan view illustrating an example of an optical device according to a second embodiment. [Figure 6] FIG. 6 is a schematic cross-sectional view taken along line AA shown in FIG. [Figure 7] FIG. 7 is a schematic cross-sectional view taken along line BB shown in FIG. [Figure 8] FIG. 8 is a schematic cross-sectional view taken along line CC shown in FIG. [Figure 9] FIG. 9 is a schematic plan view illustrating an example of an optical device according to a third embodiment. [Figure 10] FIG. 10 is a schematic cross-sectional view taken along the line AA shown in FIG. [Figure 11] FIG. 11 is a schematic cross-sectional view taken along line BB shown in FIG. [Figure 12] FIG. 12 is a schematic cross-sectional view taken along line CC shown in FIG. [Figure 13] FIG. 13 is a schematic plan view showing an example of an optical device according to a fourth embodiment. [Figure 14] FIG. 14 is a schematic cross-sectional view taken along line AA shown in FIG. [Figure 15] FIG. 15 is a schematic cross-sectional view taken along line BB shown in FIG. [Figure 16] FIG. 16 is a schematic cross-sectional view taken along line CC shown in FIG. [Figure 17] FIG. 17 is a schematic plan view illustrating an example of an optical device according to a fifth embodiment. [Figure 18] FIG. 18 is a schematic cross-sectional view taken along line AA shown in FIG. [Figure 19] FIG. 19 is a schematic cross-sectional view taken along line BB shown in FIG. [Figure 20] FIG. 20 is a schematic cross-sectional view taken along line CC shown in FIG. [Figure 21] FIG. 21 is an explanatory diagram showing an example of an optical transceiver that employs the optical device of this embodiment. [Figure 22]FIG. 22 is a schematic plan view showing an example of the optical device of Comparative Example 1. As shown in FIG. [Figure 23] FIG. 23 is a schematic cross-sectional view taken along line AA shown in FIG. [Figure 24] FIG. 24 is a schematic cross-sectional view taken along line BB shown in FIG. [Figure 25] FIG. 25 is a schematic plan view showing an example of an optical device of Comparative Example 2. As shown in FIG. [Figure 26] FIG. 26 is a schematic plan view showing an example of an optical device. [Figure 27] FIG. 27 is a schematic cross-sectional view taken along line AA shown in FIG. [Figure 28] FIG. 28 is a schematic cross-sectional view taken along line BB shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0015] In optical devices, reducing the driving power of the optical device requires increasing the length of the lower layer electrodes and PIN regions in the optical device, which results in an increase in element size. Therefore, the optical device of Comparative Example 1, in which the lower layer electrodes and PIN regions are divided, can be considered as a method for reducing the element size of the optical device.

[0016] [Comparative Example 1] Fig. 22 is a schematic plan view showing an example of an optical device 200 of Comparative Example 1, Fig. 23 is a schematic cross-sectional view taken along line AA in Fig. 22, and Fig. 24 is a schematic cross-sectional view taken along line BB in Fig. 22. The optical device 200 is, for example, an optical attenuator such as a VOA (Variable Optical Attenuator). The optical device 200 has a first VOA 210A with a linear structure, a second VOA 210B with a linear structure, and a folded waveguide 220 that optically connects the first VOA 210A and the second VOA 210B. The optical device 200 is a VOA with a folded structure.

[0017] 22 includes a Si substrate 231, a first rib-type optical waveguide 210A1 formed on the Si substrate 231, and a first lower electrode 214A and a second lower electrode 214B electrically connected to both sides of the first rib-type optical waveguide 210A1. The first VOA 210A is formed on the Si substrate 231 and includes a cladding layer 232 surrounding the first rib-type optical waveguide 210A1, the first lower electrode 214A, and the second lower electrode 214B.

[0018] The first rib type optical waveguide 210A1 is formed of, for example, Si. The first rib type optical waveguide 210A1 has a first rib waveguide 211A that forms a core. The first rib waveguide 211A has a linear structure with the same width. The first rib type optical waveguide 210A1 has an optical input section 211A1 and an optical output section 211A2. The optical input section 211A1 is an input stage of the first rib type optical waveguide 210A1 that inputs signal light to the first rib waveguide 211A. The optical output section 211A2 is an output stage of the first rib type optical waveguide 210A1 that outputs signal light from the first rib waveguide 211A.

[0019] The first rib-type optical waveguide 210A1 has a first slab region 212A formed on one outer side of the first rib waveguide 211A and a second slab region 212B formed on the other outer side of the first rib waveguide 211A. The first rib-type optical waveguide 210A1 has a P-doped region 213A formed in the first slab region 212A and an N-doped region 213B formed in the second slab region 212B. The P-doped region 213A is a region outside the first slab region 212A that is P-doped and electrically connected to the first lower electrode 214A. The N-doped region 213B is a region outside the second slab region 212B that is N-doped and electrically connected to the second lower electrode 214B.

[0020] In the first rib type optical waveguide 210A1, the first rib waveguide 211A, the first slab region 212A, and the second slab region 212B are undoped regions. The first rib type optical waveguide 210A1 has a PIN diode structure with, for example, a P-doped region 213A, an undoped region, and an N-doped region 213B.

[0021] Lower electrode 214 includes first lower electrode 214A electrically connected to P-doped region 213A via contact layer 231A (231) and second lower electrode 214B electrically connected to N-doped region 213B via contact layer 231B (231). First lower electrode 214A is made of a material having electrical resistance, for example, a metal such as aluminum or a semiconductor material such as Si. Second lower electrode 214B is also made of a material having electrical resistance, for example, a metal such as aluminum or a semiconductor material such as Si or Ge.

[0022] Upper-layer electrode 215 is an electrode disposed on an upper layer compared to lower-layer electrode 214, and constitutes first input pad 216A and first ground pad 217A. Upper-layer electrode 215 has first upper-layer electrode 215A electrically connected to first lower-layer electrode 214A via via 218A (218), and second upper-layer electrode 215B electrically connected to second lower-layer electrode 214B via via 218B (218). First input pad 216A is constituted by exposing a portion of first upper-layer electrode 215A at an opening in cladding layer 232. First ground pad 217A is constituted by exposing a portion of second upper-layer electrode 215B at an opening in cladding layer 232.

[0023] The cladding layer 232 is formed of, for example, SiO2. The first input pad 216A is an electrode pad connected to the first lower-layer electrode 214A as a signal electrode via a via 218A. The first ground pad 217A is an electrode pad connected to the second lower-layer electrode 214B as a ground electrode via a via 218B.

[0024] The second VOA 210B has a Si substrate 231, a second rib-type optical waveguide 210B1 formed on the Si substrate 231, and a third lower electrode 214C and a fourth lower electrode 214D electrically connected to both sides of the second rib-type optical waveguide 210B1. The second VOA 210B has a cladding layer 232 formed on the Si substrate 231 and surrounding the second rib-type optical waveguide 210B1, the third lower electrode 214C, and the fourth lower electrode 214D.

[0025] The second rib type optical waveguide 210B1 is formed of, for example, Si. The second rib type optical waveguide 210B1 has a second rib waveguide 211B that forms a core. The second rib waveguide 211B has a linear structure with the same width. The second rib type optical waveguide 210B1 has an optical input section 211B1 and an optical output section 211B2. The optical input section 211B1 is an input stage of the second rib type optical waveguide 210B1 that inputs signal light to the second rib waveguide 211B. The optical output section 211B2 is an output stage of the second rib type optical waveguide 210B1 that outputs signal light from the second rib waveguide 211B.

[0026] The second rib-type optical waveguide 210B1 has a third slab region 212C formed on one outer side of the second rib waveguide 211B and a fourth slab region 212D formed on the other outer side of the second rib waveguide 211B. The second rib-type optical waveguide 210B1 has a P-doped region 213C formed in the third slab region 212C and an N-doped region 213D formed in the fourth slab region 212D. The P-doped region 213C is a region outside the third slab region 212C that is P-doped and electrically connected to the third lower electrode 214C. The N-doped region 213D is a region outside the fourth slab region 212D that is N-doped and electrically connected to the fourth lower electrode 214D.

[0027] In the second rib type optical waveguide 210B1, the second rib waveguide 211B, the third slab region 212C, and the fourth slab region 212D are undoped regions. The second rib type optical waveguide 210B1 has a PIN diode structure with, for example, a P-doped region 213C, an undoped region, and an N-doped region 213D.

[0028] Lower electrode 214 includes third lower electrode 214C electrically connected to P-doped region 213C via contact layer 231A and fourth lower electrode 214D electrically connected to N-doped region 213D via contact layer 231B. Third lower electrode 214C is made of a material having electrical resistance, such as a metal such as aluminum or a semiconductor material such as Si. Fourth lower electrode 214D is also made of a material having electrical resistance, such as a metal such as aluminum or a semiconductor material such as Si or Ge.

[0029] Upper-layer electrode 215 is an electrode disposed on an upper layer compared to lower-layer electrode 214, and constitutes second input pad 216B and second ground pad 217B. Upper-layer electrode 215 has third upper-layer electrode 215C electrically connected to third lower-layer electrode 214C through via 218A, and fourth upper-layer electrode 215D electrically connected to fourth lower-layer electrode 214D through via 218B. Second input pad 216B is constituted by exposing a portion of third upper-layer electrode 215C at an opening in cladding layer 232. Second ground pad 217B is constituted by exposing a portion of fourth upper-layer electrode 215D at an opening in cladding layer 232.

[0030] The second input pad 216B is an electrode pad that connects to the third lower layer electrode 214C as a signal electrode through a via 218A. The second ground pad 217B is an electrode pad that connects to the fourth lower layer electrode 214D as a ground electrode through a via 218B.

[0031] The folded waveguide 220 is formed of, for example, Si. The folded waveguide 220 has a third rib waveguide 221 forming a core. The third rib waveguide 221 is a folded optical waveguide that optically connects the first rib waveguide 211A of the first rib type optical waveguide 210A1 and the second rib waveguide 211B of the second rib type optical waveguide 210B1. The folded waveguide 220 has a fifth slab region 222A formed on one outer side of the third rib waveguide 221 and a sixth slab region 222B formed on the other outer side of the third rib waveguide 221.

[0032] In the first VOA 210A, a first input pad 216A is located near the center of the first VOA 210A, and power is fed from the first input pad 216A to the first lower electrode 214A via a via 218A. In the first VOA 210A, a first ground pad 217A is located near the center of the first VOA 210A, and power is fed from the second lower electrode 214B to the first ground pad 217A via a via 218A.

[0033] When a voltage is applied to first lower electrode 214A from first input pad 216A, a current flows from first lower electrode 214A to second lower electrode 214B. Then, a current flows to first rib waveguide 211A in first rib optical waveguide 210A1 arranged between first lower electrode 214A and second lower electrode 214B. As a result, in first VOA 210A, the signal light guided through first rib waveguide 211A is absorbed by free carrier absorption of the current flowing through first rib waveguide 211A, resulting in attenuation of the intensity of the signal light.

[0034] In the second VOA 210B, a second input pad 216B is located near the center of the second VOA 210B, and power is fed from the second input pad 216B to the third lower electrode 214C via a via 218A. In the second VOA 210B, a second ground pad 217B is located near the center of the second VOA 210B, and power is fed from the fourth lower electrode 214D to the second ground pad 217B via a via 218B.

[0035] When a voltage is applied to third lower electrode 214C from second input pad 216B, a current flows from third lower electrode 214C to fourth lower electrode 214D. Then, a current flows to second rib waveguide 211B in second rib optical waveguide 210B1 arranged between third lower electrode 214C and fourth lower electrode 214D. As a result, in second VOA 210B, the signal light guided through second rib waveguide 211B is absorbed by free carrier absorption of the current flowing through second rib waveguide 211B, resulting in attenuation of the intensity of the signal light.

[0036] The optical device 200 of Comparative Example 1 has a folded structure, which is divided into a first VOA 210A and a second VOA 210B, and the first VOA 210A and the second VOA 210B are optically connected by a folded waveguide 220. As a result, the element size of the optical device 200 can be reduced.

[0037] However, the optical device 200 of Comparative Example 1 has a first connection line electrically connecting the first input pad 216A and the second input pad 216B and a second connection line electrically connecting the first ground pad 217A and the second ground pad 217B. The first connection line and the second connection line are generated in a layer above the lower-layer electrode 214, which results in a two-layer structure. This results in a complex wiring pattern. Therefore, an optical device 200A of Comparative Example 2, in which the wiring pattern is simplified, will be described.

[0038] Comparative Example 2 25 is a schematic plan view showing an example of an optical device 200A of Comparative Example 2. Note that the same components as those of the optical device 200 of Comparative Example 1 are given the same reference numerals, and redundant descriptions of the components and operations will be omitted.

[0039] The optical device 200 of Comparative Example 1 differs from the optical device 200A of Comparative Example 2 in that a first folded lower electrode 214E and a second folded lower electrode 214F are provided in addition to the folded waveguide 220A.

[0040] Folded waveguide 220A is disposed on the periphery of fifth slab region 222A and has first folded bottom electrode 214E electrically connecting first bottom electrode 214A and third bottom electrode 214C. Folded waveguide 220A is disposed on the periphery of sixth slab region 222B and has second folded bottom electrode 214F electrically connecting second bottom electrode 214B and fourth bottom electrode 214D.

[0041] Optical device 200A has first folded lower-layer electrode 214E electrically connecting first lower-layer electrode 214A and third lower-layer electrode 214C, and second folded lower-layer electrode 214F electrically connecting second lower-layer electrode 214B and fourth lower-layer electrode 214D. As a result, wiring layers for first and second connecting lines are not required, simplifying the wiring pattern on a layer different from lower-layer electrode 214. Moreover, optical device 200A requires only two pads, second input pad 216B and second ground pad 217B, thereby preventing the wiring from becoming complicated.

[0042] However, in optical device 200A, the distance from first lower-layer electrode 214A via first folded lower-layer electrode 214E to third lower-layer electrode 214C and the distance from second lower-layer electrode 214B via second folded lower-layer electrode 214F to fourth lower-layer electrode 214D are long. That is, in optical device 200A, the length of lower-layer electrode 214 is long, and an area for arranging lower-layer electrode 214 is required. Furthermore, in optical device 200A, the length of lower-layer electrode 214 increases, resulting in increased electrical resistance and therefore increased power consumption. Therefore, there is a demand for an optical device that can reduce power consumption by shortening lower-layer electrode 214.

[0043] Hereinafter, examples of optical devices and the like disclosed in the present application will be described in detail with reference to the drawings. Note that the disclosed technology is not limited to these examples. Furthermore, the examples shown below may be combined as appropriate within the scope of not causing any contradiction. [Example]

[0044] FIG. 1 is a schematic plan view showing an example of an optical device 1 according to a first embodiment, FIG. 2 is a schematic cross-sectional view taken along line AA in FIG. 1, FIG. 3 is a schematic cross-sectional view taken along line BB in FIG. 1, and FIG. 4 is a schematic cross-sectional view taken along line CC in FIG. 1. The optical device 1 is, for example, an optical attenuator such as a VOA (Variable Optical Attenuator). The optical device 1 has a first VOA 2A with a linear structure, a second VOA 2B with a linear structure, and a folded waveguide 3 optically connecting the first VOA 2A and the second VOA 2B. The optical device 1 is a VOA with a folded structure.

[0045] The first VOA 2A has a Si substrate 41, a first rib-type optical waveguide 2A1 formed on the Si substrate 41, and a first lower-layer electrode 14A and a second lower-layer electrode 14B electrically connected to both sides of the first rib-type optical waveguide 2A1. The first VOA 2A is formed on the Si substrate 41 and has a cladding layer 42 surrounding the first rib-type optical waveguide 2A1, the first lower-layer electrode 14A, and the second lower-layer electrode 14B.

[0046] The first rib type optical waveguide 2A1 is formed of, for example, Si. The first rib type optical waveguide 2A1 has a first rib waveguide 11A that forms a core. The first rib waveguide 11A has a linear structure with the same width. The first rib type optical waveguide 2A1 has an optical input section 11A1 and an optical output section 11A2. The optical input section 11A1 is an input stage of the first rib type optical waveguide 2A1 that inputs signal light to the first rib waveguide 11A. The optical output section 11A2 is an output stage of the first rib type optical waveguide 2A1 that outputs signal light from the first rib waveguide 11A.

[0047] The first rib-type optical waveguide 2A1 has a first slab region 12A formed on one outer side of the first rib waveguide 11A and a second slab region 12B formed on the other outer side of the first rib waveguide 11A. The first rib-type optical waveguide 2A1 has a P-doped region 13A formed in the first slab region 12A and an N-doped region 13B formed in the second slab region 12B. The P-doped region 13A is a region outside the first slab region 12A that is P-doped and electrically connected to the first lower electrode 14A. The P-doped region 13A has P-type conductivity. The N-doped region 13B is a region outside the second slab region 12B that is N-doped and electrically connected to the second lower electrode 14B. The N-doped region 13B is a region having N-type conductivity.

[0048] In the first rib type optical waveguide 2A1, the first rib waveguide 11A, the first slab region 12A, and the second slab region 12B are undoped regions. The first rib type optical waveguide 2A1 has a PIN diode structure, for example, with a P-doped region 13A, an undoped region, and an N-doped region 13B.

[0049] The lower electrode 14 includes a first lower electrode 14A electrically connected to the P-doped region 13A via a contact layer 19A (19) and a second lower electrode 14B electrically connected to the N-doped region 13B via a contact layer 19B (19). The first lower electrode 14A is a signal electrode to which a voltage is applied. The first lower electrode 14A is made of a material having electrical resistance, such as a metal such as aluminum or a semiconductor material such as silicon. The second lower electrode 14B is a ground electrode. The second lower electrode 14B is also made of a material having electrical resistance, such as a metal such as aluminum or a semiconductor material such as silicon or germanium. The cladding layer 42 is formed of, for example, silicon dioxide.

[0050] The upper-layer electrode 15 is an electrode disposed on an upper layer compared to the lower-layer electrode 14, and constitutes an input pad 16 and a ground pad 17. The upper-layer electrode 15 has a first upper-layer electrode wire 15A electrically connected to the first lower-layer electrode 14A via a via 18A (18), and a second upper-layer electrode wire 15B electrically connected to the second lower-layer electrode 14B via a via 18B (18). The input pad 16 is formed by exposing a portion of the first upper-layer electrode wire 15A at an opening in the cladding layer 42. The ground pad 17 is formed by exposing a portion of the second upper-layer electrode wire 15B at an opening in the cladding layer 42.

[0051] The second VOA 2B has a Si substrate 41, a second rib type optical waveguide 2B1 formed on the Si substrate 41, and a third lower electrode 14C and a fourth lower electrode 14D electrically connected to both sides of the second rib type optical waveguide 2B1. The second VOA 2B has a cladding layer 42 formed on the Si substrate 41 and surrounding the second rib type optical waveguide 2B1, the third lower electrode 14C, and the fourth lower electrode 14D.

[0052] The second rib type optical waveguide 2B1 is formed of, for example, Si. The second rib type optical waveguide 2B1 has a second rib waveguide 11B that forms a core. The second rib waveguide 11B has a linear structure with the same width. The second rib type optical waveguide 2B1 has an optical input section 11B1 and an optical output section 11B2. The optical input section 11B1 is an input stage of the second rib type optical waveguide 2B1 that inputs signal light to the second rib waveguide 11B. The optical output section 11B2 is an output stage of the second rib type optical waveguide 2B1 that outputs signal light from the second rib waveguide 11B.

[0053] The second rib-type optical waveguide 2B1 has a third slab region 12C formed on one outer side of the second rib waveguide 11B and a fourth slab region 12D formed on the other outer side of the second rib waveguide 11B. The second rib-type optical waveguide 2B1 has a P-doped region 13C formed in the third slab region 12C and an N-doped region 13D formed in the fourth slab region 12D. The P-doped region 13C is a region outside the third slab region 12C that is P-doped and electrically connected to the third lower electrode 14C. The P-doped region 13C has P-type conductivity. The N-doped region 13D is a region outside the fourth slab region 12D that is N-doped and electrically connected to the fourth lower electrode 14D. The N-doped region 13D is a region having N-type conductivity.

[0054] In the second rib optical waveguide 2B1, the second rib waveguide 11B, the third slab region 12C, and the fourth slab region 12D are undoped regions. The second rib optical waveguide 2B1 has a PIN diode structure with, for example, a P-doped region 13C, an undoped region, and an N-doped region 13D.

[0055] The lower-layer electrode 14 includes a third lower-layer electrode 14C electrically connected to the P-doped region 13C via a contact layer 19A and a fourth lower-layer electrode 14D electrically connected to the N-doped region 13D via a contact layer 19B. The third lower-layer electrode 14C is a signal electrode connected to an input pad 16 to which a voltage is applied. The third lower-layer electrode 14C is made of a material having electrical resistance, such as a metal such as aluminum or a semiconductor material such as silicon. The fourth lower-layer electrode 14D is a ground electrode connected to a ground pad 17. The fourth lower-layer electrode 14D is also made of a material having electrical resistance, such as a metal such as aluminum or a semiconductor material such as silicon or germanium.

[0056] The third lower-layer electrode 14C is electrically connected to the first upper-layer electrode wire 15A via a via 18C (18). The first upper-layer electrode wire 15A electrically connects the input pad 16 to the first lower-layer electrode 14A, and also electrically connects the input pad 16 to the third lower-layer electrode 14C across the first slab region 12A and the second slab region 12B. In other words, the input pad 16 is connected to the first lower-layer electrode 14A via the first upper-layer electrode wire 15A and the via 18A, and is also connected to the third lower-layer electrode 14C via the first upper-layer electrode wire 15A and the via 18C.

[0057] The fourth lower-layer electrode 14D is electrically connected to the second upper-layer electrode wire 15B via a via 18D (18). The second upper-layer electrode wire 15B electrically connects the ground pad 17 to the second lower-layer electrode 14B, and also electrically connects the ground pad 17 to the fourth lower-layer electrode 14D across the third slab region 12C and the fourth slab region 12D. In other words, the ground pad 17 is connected to the second lower-layer electrode 14B via the second upper-layer electrode wire 15B and the via 18B, and is also connected to the fourth lower-layer electrode 14D via the second upper-layer electrode wire 15B and the via 18D.

[0058] The folded waveguide 3 is made of, for example, Si. The folded waveguide 3 has a third rib waveguide 31 forming a core. The third rib waveguide 31 is a folded optical waveguide that optically connects the first rib waveguide 11A of the first rib type optical waveguide 2A1 and the second rib waveguide 11B of the second rib type optical waveguide 2B1. The folded waveguide 3 has a fifth slab region 22A formed on one outer side of the third rib waveguide 31 and a sixth slab region 22B formed on the other outer side of the third rib waveguide 31.

[0059] In the optical device 1 of Example 1, the first upper-layer electrode wire 15A connected to the input pad 16 straddles the first slab region 12A and the second slab region 12B in the first rib-type optical waveguide 2A1 and connects to the third lower-layer electrode 14C in the second rib-type optical waveguide 2B1. In the optical device 1, the second upper-layer electrode wire 15B connected to the ground pad 17 straddles the third slab region 12C and the fourth slab region 12D in the second rib-type optical waveguide 2B1 and connects the second lower-layer electrode 14B and the fourth lower-layer electrode 14D in the first rib-type optical waveguide 2A1. As a result, since the connection is made with an upper-layer electrode 15 different from the lower-layer electrode 14, the electrode length can be shortened compared to Comparative Example 2. The element size can be reduced. Furthermore, the elimination of the folded electrodes reduces the electrode area, and the elimination of the folded electrodes allows electrical continuity to each PN region without increasing electrical resistance. Moreover, the upper layer electrode 15 connects the P-doped regions 13A and 13C together and the N-doped regions 13B and 13D together, allowing the electrode area to be reduced.

[0060] Furthermore, in the optical device 1, the first upper-layer electrode wire 15A and the second upper-layer electrode wire 15B are arranged in parallel. That is, in the optical device 1, the positions in the light propagation direction of the vias 18A and 18C that are electrically connected to the P-doped regions 13A and 13C are different from the positions in the light propagation direction of the vias 18B and 18D that are electrically connected to the N-doped regions 13B and 13D. As a result, the positions of the vias 18A and 18C are different from the positions of the vias 18B and 18D, so the area required for wiring in the vertical direction of the figure of the upper electrode 15 can be reduced. This allows the wiring pattern to be simplified while the device size can be reduced.

[0061] In the optical device 1 of Example 1, the second upper-layer electrode wire 15B connected to the ground pad 17 is disposed across the third slab region 12C and the fourth slab region 12D of the second rib-type optical waveguide 2B1. However, the present invention is not limited to this, and an embodiment thereof will be described below as Example 2. [Example]

[0062] Fig. 5 is a schematic plan view showing an example of an optical device 1A of Example 2, Fig. 6 is a schematic cross-sectional view taken along line AA in Fig. 5, Fig. 7 is a schematic cross-sectional view taken along line BB in Fig. 5, and Fig. 8 is a schematic cross-sectional view taken along line CC in Fig. 5. Note that the same components as those in the optical device 1 of Example 1 are denoted by the same reference numerals, and descriptions of the overlapping components and operations will be omitted. The optical device 1 of Example 1 differs from the optical device 1A of Example 2 in that a fifth lower-layer electrode wire 14E electrically connects second lower-layer electrode 14B connected to ground pad 17 and fourth lower-layer electrode 14D1 without spanning second rib-type optical waveguide 2B2.

[0063] Furthermore, the first rib-type optical waveguide 2A2 has a P-doped region 13A and a first slab region 12A formed outside the folded structure, and an N-doped region 13B and a second slab region 12B formed inside the folded structure.

[0064] The lower electrode 14 includes a first lower electrode 14A electrically connected to the P-doped region 13A via a contact layer 19A, and a second lower electrode 14B electrically connected to the N-doped region 13B via a contact layer 19B. The first lower electrode 14A is a signal electrode for applying a voltage, and the second lower electrode 14B is a ground electrode.

[0065] In contrast, the second rib-type optical waveguide 2B2 has a P-doped region 13C1 and a third slab region 12C1 formed outside the folded structure, and an N-doped region 13D1 and a fourth slab region 12D1 formed inside the folded structure.

[0066] The lower electrode 14 includes a third lower electrode 14C1 electrically connected to the P-doped region 13C1 via a contact layer 19C1 (19) and a fourth lower electrode 14D1 electrically connected to the N-doped region 13D1 via a contact layer 19D1 (19). The third lower electrode 14C1 is made of a material having electrical resistance, such as a metal such as aluminum or a semiconductor material such as silicon. The fourth lower electrode 14D1 is also made of a material having electrical resistance, such as a metal such as aluminum or a semiconductor material such as silicon or germanium.

[0067] The upper-layer electrode 15 has a first upper-layer electrode wire 15A1 electrically connected to the first lower-layer electrode 14A via a via 18A and electrically connected to the third lower-layer electrode 14C1 via a via 18C1. The first upper-layer electrode wire 15A1 is disposed across the first slab region 12A, the second slab region 12B, the fourth slab region 12D1, and the third slab region 12C1. The input pad 16 is formed by exposing a portion of the first upper-layer electrode wire 15A1 through an opening in the cladding layer 42. That is, the input pad 16 is connected to the first lower-layer electrode 14A via the first upper-layer electrode wire 15A1 and the via 18A, and is connected to the third lower-layer electrode 14C1 via the first upper-layer electrode wire 15A1 and the via 18C1.

[0068] Upper-layer electrode 15 has second upper-layer electrode wire 15B1 electrically connected to second lower-layer electrode 14B via via 18A. Ground pad 17A is formed by exposing a portion of second upper-layer electrode wire 15B1 at an opening in cladding layer 42. In other words, ground pad 17A is connected to second lower-layer electrode 14B via second upper-layer electrode wire 15B1 and via 18B, and is also connected to fourth lower-layer electrode 14D1 via second upper-layer electrode wire 15B1, via 18C, and fifth lower-layer electrode wire 14E.

[0069] In the optical device 1A of Example 2, the first upper-layer electrode wire 15A1 connected to the input pad 16 is connected to the third lower-layer electrode 14C1 across the first slab region 12A, the second slab region 12B, the fourth slab region 12D1, and the third slab region 12C1. In the optical device 1A, the second lower-layer electrode 14B is connected to the fourth lower-layer electrode 14D1 using the fifth lower-layer electrode wire 14E connected to the second upper-layer electrode wire 15B1 connected to the ground pad 17A. As a result, the electrode wire between the second lower-layer electrode 14B and the fourth lower-layer electrode 14D1 is shortened, and a folded electrode is not required compared to Comparative Example 2, thereby shortening the electrode length. Moreover, the wiring pattern can be simplified and the element size can be reduced.

[0070] For ease of explanation, in the optical device 1A, the outside of the folded structure of the first rib optical waveguide 2A2 is designated as a P-doped region 13A, and the inside of the folded structure is designated as an N-doped region 13B. Furthermore, the example shows a case where the outside of the folded structure of the second rib optical waveguide 2B2 is designated as a P-doped region 13C1, and the inside of the folded structure is designated as an N-doped region 13D1. However, this is not limited to this, and the outside of the folded structure of the first rib optical waveguide 2A2 is designated as an N-doped region, and the inside of the folded structure is designated as a P-doped region. Furthermore, the outside of the folded structure of the second rib optical waveguide 2B2 may be designated as an N-doped region, and the inside of the folded structure may be designated as a P-doped region, and other appropriate modifications can be made. In this case, the first lower electrode connected to the P-doped region of the first rib optical waveguide 2A2 faces the third lower electrode connected to the P-doped region of the second rib optical waveguide 2B2. As a result, the second upper electrode wire and the fifth lower electrode wire electrically connect the first lower electrode connected to the P-doped region of the first rib optical waveguide 2A2 and the third lower electrode connected to the P-doped region of the second rib optical waveguide 2B2. The electrode wire between the first lower electrode and the fourth lower electrode can be shortened.

[0071] In the optical device 1A of the second embodiment, it is effective to increase the width of the optical waveguide in order to increase the extinction ratio of the VOA, but in the folded waveguide, it is necessary to narrow the width of the waveguide in order to prevent the generation of higher-order modes. Therefore, an embodiment that addresses this situation will be described below as a third embodiment. [Example]

[0072] FIG. 9 is a schematic plan view showing an example of an optical device 1B of Example 3, FIG. 10 is a schematic cross-sectional view taken along line AA in FIG. 9, FIG. 11 is a schematic cross-sectional view taken along line BB in FIG. 9, and FIG. 12 is a schematic cross-sectional view taken along line CC in FIG. 9. The same components as those in the optical device 1A of Example 2 are denoted by the same reference numerals, and descriptions of the same components and operations will be omitted. The optical device 1A of Example 2 differs from the optical device 1B of Example 3 in that the core widths of the first rib waveguide 11A3 and the second rib waveguide 11B3 are increased. Another difference is that the first rib waveguide 11A3 and the third rib waveguide 31, and the second rib waveguide 11B3 and the third rib waveguide 31 are optically connected by tapered waveguides 31A.

[0073] The tapered waveguide 31A has a first tapered waveguide 31A1 arranged between the first rib waveguide 11A3 and the third rib waveguide 31, and a second tapered waveguide 31A2 arranged between the second rib waveguide 11B3 and the third rib waveguide 31. The first tapered waveguide 31A1 has a structure in which the core width gradually decreases continuously from the first rib waveguide 11A3 to the third rib waveguide 31. The second tapered waveguide 31A2 has a structure in which the core width gradually increases continuously from the third rib waveguide 31 to the second rib waveguide 11B3.

[0074] The upper-layer electrode 15 also has a first upper-layer electrode wire 15A1 and a second upper-layer electrode wire 15B2. The second upper-layer electrode wire 15B2 is electrically connected to the second lower-layer electrode 14B through a via 18B and is electrically connected to the fourth lower-layer electrode 14D1 through a via 18D1. The ground pad 17B is formed by exposing a portion of the second upper-layer electrode wire 15B2 at an opening in the cladding layer 42. That is, the ground pad 17B is connected to the second lower-layer electrode 14B through the second upper-layer electrode wire 15B2 and the via 18B and is connected to the fourth lower-layer electrode 14D1 through the second upper-layer electrode wire 15B2 and the via 18D1.

[0075] In the optical device 1B of the third embodiment, the core widths of the first rib waveguide 11A3 and the second rib waveguide 11B3 are increased. The optical device 1B includes a first tapered waveguide 31A1 whose core width between the first rib waveguide 11A3 and the third rib waveguide 31 continuously changes, and a second tapered waveguide 31A2 whose core width between the second rib waveguide 11B3 and the third rib waveguide 31 continuously changes. By increasing the length of the tapered waveguide 31A while increasing the extinction ratio of the VOA, it is possible to suppress an increase in optical loss due to the conversion of the waveguide width. Furthermore, since the third rib waveguide 31 is narrower than the first rib waveguide 11A3 and the second rib waveguide 11B3, it is possible to suppress the generation of higher-order modes in the folded waveguide 3.

[0076] In the optical device 1B of Example 3, the wiring pattern of the upper layer electrode 15 connected to the input pad 16 and the ground pad 17B is complicated, but it may be configured with the lower layer electrode 14 connected to the input pad 16C and the ground pad 17C without using the upper layer electrode. Such an embodiment will be described below as Example 4. [Example]

[0077] FIG. 13 is a schematic plan view showing an example of an optical device 1C of Example 4, FIG. 14 is a schematic cross-sectional view taken along line AA in FIG. 13, FIG. 15 is a schematic cross-sectional view taken along line BB in FIG. 13, and FIG. 16 is a schematic cross-sectional view taken along line CC in FIG. 13. Note that the same components as those in the optical device 1B of Example 3 are designated by the same reference numerals, and descriptions of the overlapping components and operations will be omitted. The optical device 1B of Example 3 differs from the optical device 1C of Example 4 in that it includes a third lower-layer electrode wire 14F that electrically connects the first lower-layer electrode 14A and the third lower-layer electrode 14C1. Another difference is that it includes a fifth lower-layer electrode wire 14E that electrically connects the second lower-layer electrode 14B and the fourth lower-layer electrode 14D.

[0078] The second lower-layer electrode 14B of the first rib-type optical waveguide 2A4 has a divided structure including a second input-side lower-layer electrode 14B11 and a second output-side lower-layer electrode 14B12. The fourth lower-layer electrode 14D of the second rib-type optical waveguide 2B4 has a divided structure including a fourth output-side lower-layer electrode 14D11 and a fourth input-side lower-layer electrode 14D12.

[0079] Third lower-layer electrode wire 14F is an electrode wire that electrically connects first lower-layer electrode 14A and third lower-layer electrode 14C1. Input pad 16C is configured by exposing a portion of third lower-layer electrode wire 14F at an opening in cladding layer 42. In other words, input pad 16C is connected to first lower-layer electrode 14A via third lower-layer electrode wire 14F, and also connected to third lower-layer electrode 14C1 via third lower-layer electrode wire 14F.

[0080] The fifth lower-layer electrode wire 14E includes a first lower-layer electrode wire 14E11 and a second lower-layer electrode wire 14E12. The first lower-layer electrode wire 14E11 electrically connects the second input lower-layer electrode 14B11 and the fourth output lower-layer electrode 14D11. The second lower-layer electrode wire 14E12 electrically connects the second output lower-layer electrode 14B12 and the fourth input lower-layer electrode 14D12. The ground pad 17C is formed by exposing a portion of the second lower-layer electrode wire 14E12 through an opening in the cladding layer 42. That is, the ground pad 17C is connected to the second output lower-layer electrode 14B12 via the second lower-layer electrode wire 14E12 and also to the fourth input lower-layer electrode 14D12 via the second lower-layer electrode wire 14E12.

[0081] The third lower layer electrode wire 14F is disposed between the first lower layer electrode wire 14E11 and the second lower layer electrode wire 14E12, and electrically connects the first lower layer electrode 14A and the third lower layer electrode 14C1. Furthermore, the third lower layer electrode wire 14F straddles the first slab region 12A, the second slab region 12B, the fourth slab region 12D1, and the third slab region 12C1, and electrically connects the first lower layer electrode 14A and the third lower layer electrode 14C1.

[0082] In optical device 1C of Example 4, first lower-layer electrode 14A and third lower-layer electrode 14C1 are connected using third lower-layer electrode wire 14F connected to input pad 16C. In optical device 1C, second lower-layer electrode wire 14E12 connected to ground pad 17C is used to connect second output-side lower-layer electrode 14B12 and fourth input-side lower-layer electrode 14D12, and second input-side lower-layer electrode 14B11 and fourth output-side lower-layer electrode 14D11. As a result, connections are made using lower-layer electrodes 14 without using upper-layer electrodes 15, which simplifies the wiring pattern and reduces the device size.

[0083] In the optical device 1C of Example 4, the second lower electrode 14B and the fourth lower electrode 14D have a split structure, and the N-doped regions 13B and 13D1 connected to the second lower electrode 14B and the fourth lower electrode 14D are semiconductors, resulting in high electrical resistance. As a result, when the electrical resistance value of the N-doped regions increases, power consumption increases. Therefore, an embodiment that addresses this situation will be described below as Example 5. [Example]

[0084] Fig. 17 is a schematic plan view showing an example of an optical device 1D of Example 5, Fig. 18 is a schematic cross-sectional view taken along line AA shown in Fig. 17, Fig. 19 is a schematic cross-sectional view taken along line BB shown in Fig. 17, and Fig. 20 is a schematic cross-sectional view taken along line CC shown in Fig. 17. Note that the same components as those in optical device 1C of Example 4 are given the same reference numerals, and descriptions of the overlapping components and operations will be omitted. The optical device 1C of Example 4 differs from optical device 1D of Example 5 in that first lower-layer electrode wire 14E11 and second lower-layer electrode wire 14E12 are electrically connected by third upper-layer electrode wire 15C.

[0085] The upper-layer electrode 15 has a third upper-layer electrode wire 15C that electrically connects the first lower-layer electrode wire 14E11 and the second lower-layer electrode wire 14E12 across the third lower-layer electrode wire 14F. The third upper-layer electrode wire 15C is electrically connected to the first lower-layer electrode wire 14E11 through a via 18E1 and to the second lower-layer electrode wire 14E12 through a via 18E2.

[0086] Ground pad 17C is connected to second output lower-layer electrode 14B12 and fourth input lower-layer electrode 14D12 via second lower-layer electrode wire 14E12. Ground pad 17C is connected to second input lower-layer electrode 14B11 and fourth output lower-layer electrode 14D11 via third upper-layer electrode wire 15C and first lower-layer electrode wire 14E11. As a result, first lower-layer electrode wire 14E11 and second lower-layer electrode wire 14E12 are electrically connected by third upper-layer electrode wire 15C, thereby reducing the electrical resistance of N-doped regions 13B and 13D1 and suppressing power consumption.

[0087] In the optical device 1D of Example 5, the first lower electrode wire 14E11 and the second lower electrode wire 14E12 are electrically connected by the third upper electrode wire 15C, which reduces the electrical resistance of the N-doped regions 13B and 13D1, thereby reducing power consumption.

[0088] For ease of explanation, the optical device 1 is illustrated as having a PIN diode structure with a P-doped region, an undoped region, and an N-doped region. However, the optical device can also be applied to a PIP diode structure with a P-doped region, an undoped region, and a P-doped region. The optical device can also be applied to an NIN diode structure with an N-doped region, an undoped region, and an N-doped region.

[0089] Furthermore, although a VOA has been exemplified as the optical device 1, the optical device is not limited to a VOA and can also be applied to a high-order filter.

[0090] Next, an optical transceiver 50 employing the optical device 1 (1A, 1B, 1C, 1D) of the first to fifth embodiments will be described. FIG. 21 is an explanatory diagram showing an example of an optical transceiver 50 employing the optical device 1 (1A, 1B, 1C, 1D) of the present embodiment. The optical transceiver 50 shown in FIG. 21 is connected to an output optical fiber FC and an input optical fiber FC. The optical transceiver 50 includes a DSP (Digital Signal Processor) 51, an optical transmitter 53, and an optical receiver 54. The DSP 51 is an electrical component that performs digital signal processing. For example, the DSP 51 performs processing such as encoding transmission data, generates an electrical signal including the transmission data, and outputs the generated electrical signal to the optical transmitter 53. The DSP 51 also acquires an electrical signal including reception data from the optical receiver 54 and performs processing such as decoding the acquired electrical signal to obtain the reception data.

[0091] The optical transmitter 53 modulates the supplied light with the electrical signal output from the DSP 51 and outputs the obtained transmission light to the optical fiber FC. The optical transmitter 53 has an optical modulation unit 53A that generates transmission light by modulating the supplied light with the electrical signal input to the optical modulator as the light propagates through the waveguide.

[0092] The optical receiver 54 has an optical receiving section 54A that receives an optical signal from the optical fiber FC and demodulates the received light using the supplied light. The optical receiver 54 then converts the demodulated received light into an electrical signal and outputs the converted electrical signal to the DSP 51. The optical transmitter 53 and the optical receiver 54 each have, for example, an optical device 1 (1A, 1B, 1C, 1D) built in that attenuates light.

[0093] For convenience of explanation, the optical transceiver 50 has been illustrated as having a built-in optical transmitter 53 and an optical receiver 54, but the optical transceiver 50 may have a built-in optical transmitter 53 or an optical receiver 54. For example, the optical device 1 (1A, 1B, 1C, 1D) may be applied to the optical transceiver 50 having a built-in optical transmitter 53 or the optical transceiver 50 having a built-in optical receiver 54, and modifications can be made as appropriate.

[0094] In the embodiment, the rib-type optical waveguide may be a PLC (Planar Lightwave Circuit) in which both the core and clad are made of SiO2, an InP waveguide, or a GaAs waveguide. The core may be Si or Si3N4, the lower clad may be SiO2, and the upper clad may be SiO2 or air.

[0095] Furthermore, the components of each unit shown in the figure do not necessarily have to be physically configured as shown in the figure. In other words, the specific form of distribution and integration of each unit is not limited to that shown in the figure, and all or part of them can be functionally or physically distributed and integrated in any unit depending on various loads, usage conditions, etc.

[0096] Furthermore, the various processing functions performed by each device may be executed in whole or in part on a CPU (Central Processing Unit) (or a microcomputer such as an MPU (Micro Processing Unit), MCU (Micro Controller Unit), or DSP). Needless to say, the various processing functions may be executed in whole or in part on a program analyzed and executed by a CPU (or a microcomputer such as an MPU, MCU, or DSP), or on hardware using wired logic.

[0097] In addition, the following supplementary notes are disclosed regarding the above-described embodiment.

[0098] (Supplementary Note 1) A first rib-type optical waveguide disposed on a substrate, the first rib-type optical waveguide having a first slab region having a first conductivity and a second slab region having a second conductivity; a second rib-type optical waveguide disposed on the substrate, the second rib-type optical waveguide having a third slab region having the first conductivity type and a fourth slab region having the second conductivity type; a folded waveguide disposed on the substrate and connecting between the first rib-type optical waveguide and the second rib-type optical waveguide; a first electrode line electrically connecting the first slab region and the third slab region; a second electrode line electrically connecting the second slab region and the fourth slab region; The first electrode wire is An optical device comprising: an optical waveguide having a first slab region and a third slab region electrically connected to each other across at least one of the second slab region and the fourth slab region.

[0099] (Supplementary Note 2) The second electrode wire is 2. The optical device described in claim 1, wherein the second slab region and the fourth slab region are electrically connected across at least one of the first slab region and the third slab region.

[0100] (Supplementary Note 3) The second electrode wire is 2. The optical device of claim 1, wherein the second slab region and the fourth slab region are electrically connected in a state where the second slab region and the fourth slab region face each other.

[0101] (Supplementary Note 4) The optical device according to Supplementary Note 1, wherein the first electrode wire and the second electrode wire are arranged in a state of running parallel to each other.

[0102] (Supplementary Note 5) A first electrode electrically connecting the first slab region; a second electrode electrically connecting the second slab regions; a third electrode electrically connected to the third slab region; a fourth electrode electrically connected to the fourth slab region; The first electrode wire is electrically connecting the first electrode and the third electrode to electrically connect the first slab region and the third slab region; The second electrode wire is 2. The optical device of claim 1, wherein the second electrode and the fourth electrode are electrically connected to each other, and the second slab region and the fourth slab region are electrically connected to each other.

[0103] (Note 6) The first electrode, the second electrode, the third electrode, and the fourth electrode are formed of a first layer; The first electrode wire and the second electrode wire are 6. The optical device according to claim 5, characterized in that it is made up of a second layer different from the first layer.

[0104] (Note 7) The first electrode, the second electrode, the third electrode, the fourth electrode, and the second electrode line are formed in a first layer; The first electrode wire is 6. The optical device according to claim 5, characterized in that it is made up of a second layer different from the first layer.

[0105] (Supplementary Note 8) The second electrode is a second input electrode electrically connecting the input regions of the second slab region; a second output electrode electrically connecting the output regions of the second slab region; The fourth electrode is a fourth output electrode electrically connecting the output regions of the fourth slab region; a fourth input electrode electrically connecting the input regions of the fourth slab region; The second electrode wire is a second input electrode line electrically connecting the second input electrode and the fourth output electrode; a second output electrode wire electrically connecting the second output electrode and the fourth input electrode; The first electrode wire is An optical device as described in Appendix 5, characterized in that it is arranged between the second input electrode line and the second output electrode line, and electrically connects the first electrode and the third electrode.

[0106] (Supplementary Note 9) The optical device according to Supplementary Note 8, further comprising an electrode wire electrically connecting the second input electrode wire and the second output electrode wire.

[0107] (Supplementary Note 10) The first rib-type optical waveguide is a first P-doped region as the first slab region and a first N-doped region as the second slab region; The second rib-type optical waveguide comprises: a second P-doped region as the third slab region and a second N-doped region as the fourth slab region; 2. The optical device according to claim 1, comprising:

[0108] (Supplementary Note 11) The first rib-type optical waveguide is a first P-doped region as the first slab region and a second P-doped region as the second slab region; The second rib-type optical waveguide comprises: a third P-doped region as the third slab region; and a fourth P-doped region as the fourth slab region. 2. The optical device according to claim 1, comprising:

[0109] (Supplementary Note 12) The first rib-type optical waveguide is a first N-doped region as the first slab region and a second N-doped region as the second slab region; The second rib-type optical waveguide comprises: a third N-doped region as the third slab region; and a fourth N-doped region as the fourth slab region. 2. The optical device according to claim 1, comprising:

[0110] (Supplementary Note 13) An optical modulation unit that optically modulates light using a transmission signal and transmits transmission light; an optical device disposed in the optical modulation unit, The optical device is a first rib-type optical waveguide disposed on a substrate and having a first slab region having a first conductivity and a second slab region having a second conductivity; a second rib-type optical waveguide disposed on the substrate, the second rib-type optical waveguide having a third slab region having the first conductivity type and a fourth slab region having the second conductivity type; a folded waveguide disposed on the substrate and connecting between the first rib-type optical waveguide and the second rib-type optical waveguide; a first electrode line electrically connecting the first slab region and the third slab region; a second electrode line electrically connecting the second slab region and the fourth slab region; The first electrode wire is The first slab region and the third slab region are electrically connected across at least one of the second slab region and the fourth slab region. 1. An optical transmitter comprising:

[0111] (Supplementary Note 14) An optical receiving unit that receives a reception signal from the received light using light; an optical device disposed in the optical receiving section, The optical device is a first rib-type optical waveguide disposed on a substrate and having a first slab region having a first conductivity and a second slab region having a second conductivity; a second rib-type optical waveguide disposed on the substrate, the second rib-type optical waveguide having a third slab region having the first conductivity type and a fourth slab region having the second conductivity type; a folded waveguide disposed on the substrate and connecting between the first rib-type optical waveguide and the second rib-type optical waveguide; a first electrode line electrically connecting the first slab region and the third slab region; a second electrode line electrically connecting the second slab region and the fourth slab region; The first electrode wire is The first slab region and the third slab region are electrically connected across at least one of the second slab region and the fourth slab region. 1. An optical receiver comprising: [Explanation of symbols]

[0112] 1 Optical Devices 2A1 First rib-type optical waveguide 2B1 Second rib-type optical waveguide 3. Folded waveguide 12A First slab region 12B Second slab region 12C Third Slab Region 12D Fourth Slab Region 13A P-doped region 13B N-doped region 13C P-doped region 13D N-doped region 14 Lower electrode 14A First Lower Electrode 14B Second lower electrode 14B11 Second input side lower layer electrode 14B12 Second output side lower layer electrode 14C Third lower electrode 14D Fourth lower electrode 14D11 Fourth output side lower layer electrode 14D12 Fourth input side lower layer electrode 14E11 First lower electrode wire 14E12 Second lower electrode wire 14F Third lower layer electrode wire 15 Upper layer electrode 15A First upper electrode wire 15B Second upper electrode wire 15C Third upper electrode wire

Claims

1. a first rib-type optical waveguide disposed on a substrate and having a first slab region having a first conductivity and a second slab region having a second conductivity; a second rib-type optical waveguide disposed on the substrate, the second rib-type optical waveguide having a third slab region having the first conductivity type and a fourth slab region having the second conductivity type; a folded waveguide disposed on the substrate and connecting between the first rib-type optical waveguide and the second rib-type optical waveguide; a first electrode line electrically connecting the first slab region and the third slab region; a second electrode line electrically connecting the second slab region and the fourth slab region; The first electrode wire is An optical device comprising: an optical waveguide having a first slab region and a third slab region electrically connected to each other across at least one of the second slab region and the fourth slab region.

2. The second electrode wire is 2. The optical device according to claim 1, wherein the second slab region and the fourth slab region are electrically connected across at least one of the first slab region and the third slab region.

3. The second electrode wire is 2. The optical device according to claim 1, wherein the second slab region and the fourth slab region are electrically connected together in a state where the second slab region and the fourth slab region face each other.

4. 2. The optical device according to claim 1, wherein the first electrode wire and the second electrode wire are arranged in a state where they run side by side.

5. a first electrode electrically connecting the first slab regions; a second electrode electrically connecting the second slab regions; a third electrode electrically connected to the third slab region; a fourth electrode electrically connected to the fourth slab region; The first electrode wire is electrically connecting the first electrode and the third electrode to electrically connect the first slab region and the third slab region; The second electrode wire is 2. The optical device of claim 1, wherein the second electrode and the fourth electrode are electrically connected to each other, and the second slab region and the fourth slab region are electrically connected to each other.

6. the first electrode, the second electrode, the third electrode, and the fourth electrode are formed of a first layer; The first electrode wire and the second electrode wire are 6. The optical device according to claim 5, further comprising a second layer different from the first layer.

7. the first electrode, the second electrode, the third electrode, the fourth electrode, and the second electrode line are formed on a first layer; The first electrode wire is 6. The optical device according to claim 5, further comprising a second layer different from the first layer.

8. The second electrode is a second input electrode electrically connecting the input regions of the second slab region; a second output electrode electrically connecting the output regions of the second slab region; The fourth electrode is a fourth output electrode electrically connecting the output regions of the fourth slab region; a fourth input electrode electrically connecting the input regions of the fourth slab region; The second electrode wire is a second input electrode line electrically connecting the second input electrode and the fourth output electrode; a second output electrode line electrically connecting the second output electrode and the fourth input electrode, The first electrode wire is 6. The optical device according to claim 5, wherein the first electrode is disposed between the second input electrode line and the second output electrode line, and electrically connects the first electrode and the third electrode.

9. 9. The optical device according to claim 8, further comprising an electrode wire that electrically connects the second input electrode wire and the second output electrode wire.

10. an optical modulation unit that optically modulates light using a transmission signal and transmits the transmission light; an optical device disposed in the optical modulation unit, The optical device is a first rib-type optical waveguide disposed on a substrate and having a first slab region having a first conductivity and a second slab region having a second conductivity; a second rib-type optical waveguide disposed on the substrate, the second rib-type optical waveguide having a third slab region having the first conductivity type and a fourth slab region having the second conductivity type; a folded waveguide disposed on the substrate and connecting between the first rib-type optical waveguide and the second rib-type optical waveguide; a first electrode line electrically connecting the first slab region and the third slab region; a second electrode line electrically connecting the second slab region and the fourth slab region; The first electrode wire is The first slab region and the third slab region are electrically connected across at least one of the second slab region and the fourth slab region.

1. An optical transmitter comprising:

11. an optical receiving unit that receives a reception signal from the received light using light; an optical device disposed in the optical receiving section, The optical device is a first rib-type optical waveguide disposed on a substrate and having a first slab region having a first conductivity and a second slab region having a second conductivity; a second rib-type optical waveguide disposed on the substrate, the second rib-type optical waveguide having a third slab region having the first conductivity type and a fourth slab region having the second conductivity type; a folded waveguide disposed on the substrate and connecting between the first rib-type optical waveguide and the second rib-type optical waveguide; a first electrode line electrically connecting the first slab region and the third slab region; a second electrode line electrically connecting the second slab region and the fourth slab region; The first electrode wire is The first slab region and the third slab region are electrically connected across at least one of the second slab region and the fourth slab region.

1. An optical receiver comprising:

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