Optical device, optical transmitter, and optical receiver

Abstract

To provide an optical device or the like capable of securing an optical input / output function of a GC in which influence of a support substrate is suppressed.SOLUTION: The optical device includes a first cladding layer, an optical waveguide disposed on the first cladding layer, and a second cladding layer disposed on the optical waveguide. The optical device includes a material layer disposed on the second cladding layer, a grating coupler disposed in the optical waveguide, and a reflective layer disposed between the grating coupler and the material layer.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] FIG. 5 is a cross-sectional view showing an example of a conventional optical device 100. The optical device 100 shown in FIG. 5 is, for example, a modulator element that modulates light propagating through an optical waveguide. The optical device 100 has a Si substrate 101, a first cladding layer 102, an optical waveguide 103, a second cladding layer 104, an electrode layer 106, and a GC (Grating Coupler) 105 that has an optical input / output function. The optical device 100 is, for example, an optical device that has an optical input / output function, such as the GC 105 that inputs and outputs light to and from the optical waveguide 103.

[0003] The first cladding layer 102 is, for example, a BOX layer made of SiO2 or the like, formed on the Si substrate 101. The optical waveguide 103 is, for example, a Si waveguide, formed on the first cladding layer 102. The optical waveguide 103 has an arm waveguide 103C of the optical modulator element, an input waveguide 103A, and an output waveguide 103B. The arm waveguide 103C is a waveguide that forms the main body of the optical modulator element. The input waveguide 103A is a waveguide that connects to the input stage of the arm waveguide 103C. The output waveguide 103B is a waveguide that connects to the output stage of the arm waveguide 103C.

[0004] The second cladding layer 104 is an upper cladding layer made of, for example, SiO2, formed on the optical waveguide 103 and the first cladding layer 102. The electrode layer 106 is an electrode used in an optical modulation element that applies an electric signal, such as a high-frequency signal, to the arm waveguide 103C in the optical waveguide 103 and modulates the light guided through the optical waveguide 103 by changing the refractive index of the optical waveguide 103 in response to the electric signal.

[0005] The GC 105 is a coupler that inputs light from the optical fiber 107 through the etched surface 111A of the diffraction grating 111 arranged in the optical waveguide 103, and outputs light from the etched surface 111A to the optical fiber 107. The optical fiber 107 has a first optical fiber 107A and a second optical fiber 107B. The first optical fiber 107A is an optical fiber that connects to a light source of a test device that emits light. The second optical fiber 107B is an optical fiber that connects to a power meter of the test device that measures the optical power of the light modulated by the optical modulator element.

[0006] The GC 105 includes a first GC 105A and a second GC 105B. The first GC 105A has an etched surface 111A of a diffraction grating 111 disposed in the input waveguide 103A, and is a GC that inputs light from the first optical fiber 107A to the input waveguide 103A. The second GC 105B has an etched surface 111A of a diffraction grating 111 disposed in the output waveguide 103B, and is a GC that outputs light from the output waveguide 103B to the second optical fiber 107B.

[0007] Next, a method for evaluating the optical device 100 will be described. The output end of the first optical fiber 107A, which is connected to a test device, is placed on the surface of the second cladding layer 104, and the first optical fiber 107A and the etched surface 111A of the diffraction grating 111 of the first GC 105A are brought into close proximity. Furthermore, the input end of the second optical fiber 107B, which is connected to a test device, is placed on the surface of the second cladding layer 104, and the second optical fiber 107B and the etched surface 111A of the diffraction grating 111 of the second GC 105B are brought into close proximity. A light source connected to the first optical fiber 107A inputs light to the first GC 105A via the first optical fiber 107A. The first GC 105A outputs the light input from the first optical fiber 107A to the arm waveguide 103C via the input waveguide 103A.

[0008] The arm waveguide 103C guides the light input from the input waveguide 103A, modulates the guided light in response to an electrical signal from the electrode layer 106, and outputs the modulated light to the output waveguide 103B. The second GC 105B outputs the modulated light from the output waveguide 103B to the second optical fiber 107B. A power meter connected to the second optical fiber 107B measures the optical power of the modulated light from the second optical fiber 107B. As a result, the test equipment can evaluate the optical loss in the optical waveguide 103 based on the measurement result of the power meter. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] U.S. Patent Application Publication No. 2021 / 0217908 [Patent Document 2] US Patent Application Publication No. 2013 / 0279844 [Patent Document 3] International Publication No. 2020 / 255191 Summary of the Invention [Problem to be solved by the invention]

[0010] In the conventional optical device 100, the arm waveguide 103C is a Si waveguide, which results in a small electro-optic effect and a high driving voltage. Therefore, in order to reduce the driving voltage, optical devices are known in which the arm waveguide 103C is an LN waveguide, for example, which has a high electro-optic effect. However, when optical waveguides made of various materials are integrated in an optical device, a support substrate is required, and therefore it is necessary to ensure the optical input / output function of the GC while suppressing the influence of the support substrate.

[0011] In one aspect, an object of the present invention is to provide an optical device or the like that can ensure the optical input / output function of a GC while suppressing the influence of a support substrate. [Means for solving the problem]

[0012] An optical device according to one embodiment includes a first cladding layer, an optical waveguide disposed on the first cladding layer, a second cladding layer disposed on the optical waveguide, and a material layer disposed on the second cladding layer, and further includes a grating coupler disposed in the optical waveguide and a reflective layer disposed between the grating coupler and the material layer. [Effects of the Invention]

[0013] According to one aspect, for example, it is possible to ensure the optical input / output function of the GC while suppressing the influence of material layers such as a support substrate. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a cross-sectional view showing an example of an optical device according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing an example of an optical device according to a second embodiment. [Figure 3] FIG. 3 is an explanatory diagram illustrating an example of an optical transceiver according to this embodiment. [Figure 4] FIG. 4 is a cross-sectional view showing an example of an optical device of the comparative example. [Figure 5] FIG. 5 is a schematic cross-sectional view showing an example of a conventional optical device. DETAILED DESCRIPTION OF THE INVENTION

[0015] <Comparative Example> The present applicant has proposed an optical device having optical input / output functions, which includes a support substrate on which optical waveguides made of various materials, for example, LN material with a high electro-optic effect, are integrated. FIG. 4 is a cross-sectional schematic diagram showing an example of an optical device 200 as a comparative example. Note that the same components as those of the optical device 100 shown in FIG. 5 are designated by the same reference numerals, and redundant descriptions of the components and operations will be omitted. The optical device 200 shown in FIG. 4 is an optical device having optical input / output functions, which includes a support substrate on which optical waveguides made of LN material with a high electro-optic effect are integrated. The optical device 200 includes a first cladding layer 102A (102), a first optical waveguide 103X, a second cladding layer 104A (104), a support substrate 211, a third cladding layer 213, a second optical waveguide 212, and an electrode layer 214.

[0016] The first cladding layer 102A is, for example, a BOX layer made of a material such as SiO2. The first optical waveguide 103X is, for example, a Si waveguide formed on the first cladding layer 102A. The second cladding layer 104A is, for example, a cladding layer made of a material such as SiO2, formed on the first cladding layer 102A and the first optical waveguide 103X. The support substrate 211 is a substrate bonded to the second cladding layer 104A.

[0017] The third cladding layer 213 is a cladding layer formed under the first cladding layer 102A and made of a material such as SiO2. The second optical waveguide 212 is formed on a portion of the third cladding layer 213 and is, for example, an LN waveguide with a high electro-optic effect. The electrode layer 214 is disposed on the surface of the third cladding layer 213 and below the second optical waveguide 212.

[0018] The first optical waveguide 103X has an input waveguide 103A1 and an output waveguide 103B1. The second optical waveguide 212 is an arm waveguide 212A of an optical modulator element, which is disposed on a different layer from the first optical waveguide 103X and is indirectly connected to the input waveguide 103A1 and indirectly connected to the output waveguide 103B1. The electrode layer 214 is an electrode used in the optical modulator element that applies an electric signal, such as a high-frequency signal, to the arm waveguide 212A and modulates the light guided through the arm waveguide 212A by changing the refractive index of the arm waveguide 212A in response to the electric signal. As a result, the arm waveguide 212A of the optical modulator element is an LN waveguide, and therefore requires a low driving voltage.

[0019] The GC 105 includes a first GC 105A and a second GC 105B. The first GC 105A has an etched surface 111A of a diffraction grating 111 disposed in a Si input waveguide 103A1, and is a GC that inputs light from the first optical fiber 107A to the input waveguide 103A1. The second GC 105B has an etched surface 111A of a diffraction grating 111 disposed in a Si output waveguide 103B1, and is a GC that outputs light from the output waveguide 103B1 to the second optical fiber 107B.

[0020] The etched surface 111A of the first GC 105A is the surface that enters the output end of the first optical fiber 107A through the support substrate 211. The etched surface 111A of the second GC 105B is the surface that exits the input end of the second optical fiber 107B through the support substrate 211.

[0021] Next, a method for manufacturing the optical device 200 will be described. In the optical device 200, when a Si waveguide serving as the first optical waveguide 103X and an LN waveguide serving as the second optical waveguide 212 are arranged, a support substrate 211 is attached onto the second cladding layer 104A (104) on the first optical waveguide 103X (103) shown in FIG. 5. After the support substrate 211 is attached onto the second cladding layer 104A (104), the Si substrate 101 and a portion of the first cladding layer 102 are removed. Then, an LN substrate serving as the second optical waveguide 212 is attached to the first cladding layer 102A below the first optical waveguide 103X.

[0022] The LN substrate is then polished to a submicron thickness and patterned by lithography and etching to form the second optical waveguide 212. Then, a SiO2 film is formed on the second optical waveguide 212 to form the third cladding layer 213. An electrode layer 214 located below the second optical waveguide 212 is formed on the surface of the third cladding layer 213.

[0023] Next, a method for evaluating optical device 200 will be described. The output end of first optical fiber 107A, which is connected to a test device, is placed on the surface of support substrate 211, and first optical fiber 107A and etched surface 111A of diffraction grating 111 of first GC 105A are brought close to each other. The input end of second optical fiber 107B, which is connected to a test device, is placed on the surface of support substrate 211, and second optical fiber 107B and etched surface 111A of diffraction grating 111 of second GC 105B are brought close to each other.

[0024] A light source connected to the first optical fiber 107A inputs light to the first GC 105A disposed on the support substrate 211 via the first optical fiber 107A. The first GC 105A outputs the light input from the first optical fiber 107A to the input waveguide 103A1. The arm waveguide 212A guides the light indirectly transferred from the input waveguide 103A1 and modulates the guided light in accordance with an electrical signal such as a high-frequency signal. The arm waveguide 212A then indirectly transfers the modulated light to the output waveguide 103B1.

[0025] The second GC 105B outputs the modulated light from the output waveguide 103B1 to a second optical fiber 107B disposed on the support substrate 211. A power meter connected to the second optical fiber 107B measures the optical power of the modulated light from the second optical fiber 107B. As a result, the test device can evaluate the optical loss in the first optical waveguide 103X and the second optical waveguide 212 based on the measurement result of the power meter.

[0026] However, in the optical device 200, the thick support substrate 211 is provided on the first GC 105A and the second GC 105B, which increases the loss of optical coupling between the optical fiber 107 and the GC 105. As a result, the loss of light input and output using the first GC 105A and the second GC 105B increases, which reduces the measurement accuracy of the test equipment.

[0027] Therefore, an embodiment of an optical device that can ensure the optical input / output function of GC while suppressing the influence of the support substrate 211 will be described below as an example. [Example]

[0028] Fig. 1 is a cross-sectional schematic diagram showing an example of an optical device 1 according to Example 1. The optical device 1 shown in Fig. 1 is an optical device such as an optical modulator element that can ensure optical input / output functions while suppressing the influence of a support substrate on which optical waveguides made of different materials, such as a Si waveguide as a first optical waveguide 12 and an LN waveguide as a second optical waveguide 16, are integrated.

[0029] The optical device 1 includes a first cladding layer 11, a first optical waveguide 12, a second cladding layer 13, a support substrate 14, a third cladding layer 17, a second optical waveguide 16, a first electrode layer 18, and a second electrode layer 19. The first cladding layer 11 is, for example, a BOX layer formed of a material such as SiO2. The first optical waveguide 12 is, for example, a Si waveguide formed on the first cladding layer 11. The first optical waveguide 12 includes an input waveguide 12A and an output waveguide 12B.

[0030] The second cladding layer 13 is a cladding layer made of a material such as SiO2, and is formed on the first cladding layer 11 and the first optical waveguide 12. The support substrate 14 is a material layer bonded onto the second cladding layer 13.

[0031] The third cladding layer 17 is a cladding layer formed under the first cladding layer 11 and made of a material such as SiO2. The second optical waveguide 16 is formed on a part of the third cladding layer 17 and is, for example, an LN waveguide with a high electro-optic effect. The first electrode layer 18 is disposed on the surface of the third cladding layer 17 and is disposed under the second optical waveguide 16.

[0032] The second electrode layer 19 is an electrode layer serving as a reflective layer formed on the second clad layer 13 between the first optical waveguide 12 and the support substrate 14. The second electrode layer 19 is made of an electrode material such as aluminum or titanium. The second electrode layer 19 includes an input-side electrode layer 19A and an output-side electrode layer 19B. The input-side electrode layer 19A is an input-side reflective layer formed on the second clad layer 13 between the input waveguide 12A in the first optical waveguide 12 and the support substrate 14. The output-side electrode layer 19B is an output-side reflective layer formed on the second clad layer 13 between the output waveguide 12B of the first optical waveguide 12 and the support substrate 14.

[0033] The second optical waveguide 16 is an arm waveguide 16A of an optical modulator element, which is disposed on a different layer from the first optical waveguide 12 and is indirectly connected to the input waveguide 12A and indirectly connected to the output waveguide 12B. The first electrode layer 18 is an electrode used in an optical modulator element that applies an electric signal, such as a high-frequency signal, to the arm waveguide 16A and modulates the light guided through the arm waveguide 16A by changing the refractive index of the arm waveguide 16A in response to the electric signal. As a result, the arm waveguide 16A of the optical modulator element is an LN waveguide, and therefore requires a small driving voltage.

[0034] GC15 is a coupler that inputs light from the optical fiber 2 to the first optical waveguide 12 and outputs light from the first optical waveguide 12 to the optical fiber 2. The optical fiber 2 has a first optical fiber 2A and a second optical fiber 2B. The first optical fiber 2A is an optical fiber that connects to a light source of the test equipment that emits light. The second optical fiber 2B is an optical fiber that connects to a power meter of the test equipment that measures the optical power of the received light.

[0035] The GC 15 includes a first GC 15A and a second GC 15B. The first GC 15A has an etched surface 15A11 of a diffraction grating 15A1 disposed in the input waveguide 12A of the first optical waveguide 12, and is a GC that inputs light from the first optical fiber 2A to the input waveguide 12A. The etched surface 15A11 of the diffraction grating 15A1 of the first GC 15A faces the surface of the support substrate 14. The second GC 15B has an etched surface 15B11 of a diffraction grating 15B1 disposed in the output waveguide 12B of the first optical waveguide 12, and is a GC that outputs light from the output waveguide 12B to the second optical fiber 2B. The etched surface 15B11 of the diffraction grating 15B1 of the second GC 15B faces the surface of the support substrate 14.

[0036] The input-side electrode layer 19A is a reflector that reflects light from the first optical fiber 2A into the second cladding layer 13 that is located between the support substrate 14 and the etched surface 15A11 of the diffraction grating 15A1 of the first GC 15A in the input waveguide 12A. The output-side electrode layer 19B is a reflector that reflects light toward the second optical fiber 2B into the second cladding layer 13 that is located between the support substrate 14 and the etched surface 15B11 of the diffraction grating 15B1 of the second GC 15B in the output waveguide 12B.

[0037] The first GC 15A receives light from the first optical fiber 2A through the surface opposite the etched surface 15A11 of the diffraction grating 15A1, and transmits the received light through the diffraction grating 15A1. The first GC 15A then transmits the light transmitted through the diffraction grating 15A1 to the input electrode layer 19A. The input electrode layer 19A reflects the light transmitted through the diffraction grating 15A1 and transmits the reflected light to the etched surface 15A11 of the diffraction grating 15A1. As a result, the input waveguide 12A receives light from the first optical fiber 2A on the surface of the third cladding layer 17, and the received light is reflected by the input electrode layer 19A and inputs it through the etched surface 15A11 of the diffraction grating 15A1 of the first GC 15A. In other words, the coupling loss between the first optical fiber 2A and the first GC 15A can be significantly reduced compared to the comparative example.

[0038] The second GC 15B outputs the modulated light from the output waveguide 12B to the output electrode layer 19B through the etched surface 15B11 of the diffraction grating 15B1. The output electrode layer 19B reflects the modulated light from the second GC 15B to the diffraction grating 15B1. The diffraction grating 15B1 of the second GC 15B transmits the modulated light from the output electrode layer 19B and outputs the transmitted light to the second optical fiber 2B. As a result, the output waveguide 12B reflects the light from the etched surface 15B11 of the diffraction grating 15B1 of the second GC 15B at the output electrode layer 19B and inputs the reflected light to the second optical fiber 2B on the surface of the third cladding layer 17. In other words, the coupling loss between the second optical fiber 2B and the second GC 15B can be significantly reduced compared to the comparative example.

[0039] Next, a method for manufacturing the optical device 1 will be described. After forming a second electrode layer 19 in the second clad layer 13 on the GC 15 of the first optical waveguide 12, SiO2 is deposited on the second electrode layer 19 and the second clad layer 13. As a result, an input-side electrode layer 19A is formed in the second clad layer 13 between the etched surface 15A11 of the diffraction grating 15A1 of the first GC 15A and the support substrate 14. Also, an output-side electrode layer 19B is formed in the second clad layer 13 between the etched surface 15B11 of the diffraction grating 15B1 of the second GC 15B and the support substrate 14. The second electrode layer 19 is formed in the same electrode formation process as the electrodes used for other VOAs (Variable Optical Attenuators), phase shifters, etc. used in the optical device 1.

[0040] Furthermore, in the optical device 1, when a Si waveguide serving as the first optical waveguide 12 and an LN waveguide serving as the second optical waveguide 16 are arranged, a support substrate 14 is attached onto the second clad layer 13 on the first optical waveguide 12. After the support substrate 14 is attached onto the second clad layer 13 of the optical device 1, the Si substrate 101 and a portion of the first clad layer 102 shown in FIG. 5 are removed. Then, an LN substrate serving as the second optical waveguide 16 is attached to the first clad layer 11 below the first optical waveguide 12.

[0041] The LN substrate is then polished to a submicron thickness and patterned by lithography and etching to form the second optical waveguide 16. Then, a SiO2 film is formed on the second optical waveguide 16 to form the third cladding layer 17. A first electrode layer 18 located below the second optical waveguide 16 is formed on the surface of the third cladding layer 17.

[0042] Next, we will explain the method for evaluating the optical device 1. The output end of the first optical fiber 2A, which is connected to a test device, is placed on the surface of the third cladding layer 17 opposite the etched surface 15A11 of the diffraction grating 15A1 of the first GC 15A, and the first optical fiber 2A and the etched surface 15A11 of the first GC 15A are brought close to each other. The input end of the second optical fiber 2B, which is connected to a test device, is placed on the surface of the third cladding layer 17 opposite the etched surface 15B11 of the diffraction grating 15B1 of the second GC 15B, and the second optical fiber 2B and the etched surface 15B11 of the second GC 15B are brought close to each other.

[0043] The light source connected to the first optical fiber 2A inputs light from the first optical fiber 2A on the surface of the third cladding layer 17 to the first GC 15A. The first GC 15A transmits the light from the first optical fiber 2A through the third cladding layer 17 and the first cladding layer 11 from the surface opposite the etched surface 15A11 of the diffraction grating 15A1, and outputs the transmitted light to the input electrode layer 19A. The input electrode layer 19A reflects the light transmitted through the diffraction grating 15A1 to the etched surface 15A11 of the diffraction grating 15A1. As a result, the first GC 15A inputs light from the first optical fiber 2A on the surface of the third cladding layer 17 to the input waveguide 12A.

[0044] The arm waveguide 16A, which is the second optical waveguide 16, guides the light indirectly transferred from the input waveguide 12A and modulates the guided light in response to an electrical signal such as a high-frequency signal. The arm waveguide 16A then indirectly transfers the modulated light to the output waveguide 12B. The second GC 15B outputs the modulated light from the output waveguide 12B to the output electrode layer 19B from the etched surface 15B11 of the diffraction grating 15B1. The output electrode layer 19B reflects the light output from the etched surface 15B11 of the diffraction grating 15B1 back to the etched surface 15B11 of the diffraction grating 15B1. The second GC 15B transmits the light input from the etched surface 15B11 of the diffraction grating 15B1 and outputs the transmitted light to the second optical fiber 2B. As a result, the second GC 15B outputs the light from the output waveguide 12B to the second optical fiber 2B on the surface of the third cladding layer 17.

[0045] The power meter connected to the second optical fiber 2B measures the optical power of the modulated light from the second optical fiber 2B. As a result, the test device can evaluate the optical loss in the first optical waveguide 12 and the second optical waveguide 16 based on the measurement result of the power meter.

[0046] In the optical device 1 of Example 1, an input-side electrode layer 19A is disposed in the second cladding layer 13 between the etched surface 15A11 of the first GC 15A and the support substrate 14. In the optical device 1, an output-side electrode layer 19B is disposed in the second cladding layer 13 between the etched surface 15B11 of the second GC 15B and the support substrate 14. That is, even in the optical device 1 having the support substrate 14, the reflection function of the second electrode layer 19 can be used to input and output light from the etched surface of the GC 15. As a result, the optical input / output function of the GC 15 can be ensured while suppressing the influence of material layers such as the support substrate 14. Furthermore, by reducing the loss of light input and output in the GC 15, the accuracy of optical power measurement can be improved.

[0047] In the optical device 1, an input-side electrode layer 19A is provided between the first GC 15A and the support substrate 14, and the input-side electrode layer 19A reflects light from the first optical fiber 2A toward the surface opposite to the support substrate 14, causing the light to enter the first GC 15A. As a result, the first optical fiber 2A can be brought close to the surface of the third cladding layer 17 opposite to the support substrate 14, thereby realizing low-loss light input to the first GC 15A and improving the light measurement accuracy of the optical device 1.

[0048] In the optical device 1, the output-side electrode layer 19B is provided between the second GC 15B and the support substrate 14, and the output-side electrode layer 19B reflects light from the second GC 15B in the direction of the surface opposite to the support substrate 14, and inputs it to the second optical fiber 2B. As a result, the second optical fiber 2B can be brought close to the surface of the third cladding layer 17 opposite to the support substrate 14, thereby realizing low-loss optical output for the second GC 15B and improving the light measurement accuracy of the optical device 1.

[0049] For convenience of explanation, the optical device 1 is exemplified as an optical modulator element having a support substrate 14. However, any optical device having a support substrate 14 may be used, and the optical device may also be applied to, for example, an optical receiver element.

[0050] In the optical device 1 of Example 1, the second electrode layer 19 is in a floating state between the GC 15 and the support substrate 14. As a result, the second electrode layer 19 becomes a noise source for the high-frequency signal applied to the arm waveguide 16A, which is the adjacent second optical waveguide 16, and there is a risk that the characteristics of the high-frequency signal of the optical modulator element will be deteriorated. Therefore, an embodiment that addresses this situation will be described below as Example 2. [Example]

[0051] 2 is a cross-sectional schematic diagram showing an example of an optical device 1A of Example 2. Note that the same components as those in the optical device 1 of Example 1 are denoted by the same reference numerals, and explanations of the overlapping components and operations will be omitted. The optical device 1A of Example 2 differs from the optical device 1 of Example 1 in that the second electrode layer 19 is electrically connected to the surface electrode 21, which is a ground electrode.

[0052] The second electrode layer 19 is electrically connected to a surface electrode 21 disposed on the surface of the third cladding layer 17 through a connection via 22 that connects the first cladding layer 11, the second cladding layer 13, and a portion of the third cladding layer 17. The second electrode layer 19 has an input-side electrode layer 19A1 and an output-side electrode layer 19B1. The surface electrode 21 has a first surface electrode 21A and a second surface electrode 21B. The surface electrode 21 is in the same layer as the first electrode layer 18 and can be formed in the same process as the first electrode layer 18. The connection via 22 has a first connection via 22A and a second connection via 22B.

[0053] The first surface electrode 21A is electrically connected to the first connecting via 22A and the input electrode layer 19A1. Even if a high-frequency signal applied to the first electrode layer 18 is transmitted to the input electrode layer 19A1, the signal is grounded from the input electrode layer 19A1 to the first surface electrode 21A via the first connecting via 22A. As a result, the floating state of the input electrode layer 19A1 is eliminated, thereby suppressing the influence of the high-frequency signal from the first electrode layer 18 on the input waveguide 12A1.

[0054] The second surface electrode 21B is electrically connected to the second connection via 22B and the output-side electrode layer 19B1. Even if a high-frequency signal applied to the first electrode layer 18 is transmitted to the output-side electrode layer 19B1, the signal is grounded from the output-side electrode layer 19B1 to the second surface electrode 21B via the second connection via 22B. As a result, the floating state of the output-side electrode layer 19B1 is eliminated, thereby suppressing the influence of the high-frequency signal from the first electrode layer 18 on the output waveguide 12B1.

[0055] In the optical device 1A of the second embodiment, the input-side electrode layer 19A1 and the first surface electrode 21A are electrically connected by a first connecting via 22A, and the output-side electrode layer 19B1 and the second surface electrode 21B are electrically connected by a second connecting via 22B. A high-frequency signal from the first electrode layer 18 is grounded to the first surface electrode 21A and the second surface electrode 21B. As a result, the floating state of the second electrode layer 19 is eliminated, thereby suppressing deterioration of the high-frequency characteristics of the optical modulator element.

[0056] For the sake of convenience, the optical device 1 (1A) is shown as an example having a support substrate 14 on which optical waveguides made of different materials are integrated. However, this embodiment is applicable to any optical device having a support substrate 14 that is a material layer and an optical input / output function such as GC, regardless of whether optical waveguides made of different materials are integrated.

[0057] FIG. 3 is an explanatory diagram illustrating an example of an optical transceiver 70 according to this embodiment. The optical transceiver 70 shown in FIG. 3 includes a DSP (Digital Signal Processor) 71 and an optical transmitter / receiver 72. The optical transmitter / receiver 72 includes an optical transmitter 72A that transmits an optical signal and an optical receiver 72B that receives the optical signal. The optical transmitter 72A includes an optical device 1 (1A) such as an optical modulator element 72A1 that modulates light in response to an electrical signal from the DSP 71. The optical receiver 72B includes an optical device 1 (1A) such as an optical receiver element 72B1 that converts the optical signal into an electrical signal. The DSP 71 digitally converts each electrical signal input from the optical receiver 72B.

[0058] Furthermore, the optical device 1 (1A) is exemplified as a digital coherent transceiver, but is not limited to a digital coherent system, and may be an optical receiver or optical transmitter of another system, and can be changed as appropriate.

[0059] 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.

[0060] 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 or MCU), or on hardware using wired logic. [Explanation of symbols]

[0061] 1 Optical Devices 11 First cladding layer 12 First optical waveguide 13 Second cladding layer 14 Support substrate 15 Grating coupler 15A First GC 15B Second GC 15A1 Diffraction grating 19 Second electrode layer 19A Input electrode layer 19B Output electrode layer 21 Surface electrode 22 Connection vias

Claims

1. a first cladding layer; and an optical waveguide disposed on the first cladding layer; a second cladding layer disposed on the optical waveguide; a material layer disposed on the second cladding layer; a grating coupler disposed in the optical waveguide; a reflective layer disposed between the grating coupler and the material layer; An optical device comprising:

2. The grating coupler comprises:

2. The optical device according to claim 1, further comprising a diffraction grating disposed in the optical waveguide opposite the material layer.

3. The grating coupler comprises: transmits light incident from the surface opposite to the etched surface of the diffraction grating; The reflective layer is reflecting light transmitted through the grating coupler; The grating coupler comprises:

3. The optical device according to claim 2, wherein the light reflected by said reflective layer is input through an etched surface of said diffraction grating.

4. The grating coupler comprises: outputting light from the etched surface of the diffraction grating; The reflective layer is reflecting the light output from the etched surface to the grating coupler; The grating coupler comprises:

3. The optical device according to claim 2, wherein the light reflected by the reflective layer is transmitted and output from a surface opposite to the etched surface of the diffraction grating.

5. another optical waveguide made of a material different from that of the optical waveguide, disposed under the first clad layer; an electrode layer for applying an electric signal to the other optical waveguide; 10. The optical device of claim 1, further comprising:

6. The grating coupler comprises: a first grating coupler disposed at an input stage of the optical waveguide; a second grating coupler disposed at an output stage of the optical waveguide; The reflective layer is an input-side reflective layer disposed between the first grating coupler and the material layer; an output-side reflective layer disposed between the second grating coupler and the material layer; 2. The optical device according to claim 1, wherein:

7. 6. The optical device according to claim 5, further comprising a ground electrode electrically connected to the reflective layer.

8. the ground electrode disposed on the surface of the first clad layer; a connection via arranged in communication with the first clad layer from above to below, and electrically connecting the ground electrode and the reflective layer; 8. The optical device according to claim 7, wherein:

9. An optical transmitter incorporating an optical device having an optical circuit including an optical modulation unit that optically modulates light using a transmission signal and transmits transmission light, The optical device is a first cladding layer; and an optical waveguide disposed on the first cladding layer; a second cladding layer disposed on the optical waveguide; a material layer disposed on the second cladding layer; a grating coupler disposed in the optical waveguide; a reflective layer disposed between the grating coupler and the material layer; An optical transmitter comprising:

10. An optical receiver incorporating an optical device having an optical circuit including an optical receiving unit that receives a reception signal from received light using light, The optical device is a first cladding layer; and an optical waveguide disposed on the first cladding layer; a second cladding layer disposed on the optical waveguide; a material layer disposed on the second cladding layer; a grating coupler disposed in the optical waveguide; a reflective layer disposed between the grating coupler and the material layer; An optical receiver comprising:

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