Optical integrated device, optical transmitter, and optical transceiver

Abstract

To provide an optical integrated device and the like that can reduce the workload required for implementing a chip including an optical waveguide having an electro-optic effect.SOLUTION: An optical integrated device comprises a first chip including a step portion, and a second chip mounted on the step portion and optically connected to the first chip. The first chip includes an optical waveguide including a material having a high electro-optic effect compared to a material of the second chip. The optical integrated device has a first inclined surface that is formed on a wall surface on a side on which the optical waveguide and the second chip are optically connected in the step portion, and a second inclined surface that is formed on an end surface of the second chip on a side on which it is mounted within the step portion, and that abuts on the first inclined surface facing the first inclined surface.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] FIG. 14 is a schematic plan view illustrating an example of an optical integrated device 200, and FIG. 15 is a schematic cross-sectional view illustrating an example of the optical integrated device 200. For ease of explanation, the schematic cross-sectional view is a schematic cross-sectional view of the optical integrated device 200 illustrated in FIG. 14. The optical integrated device 200 includes an optical modulator chip 210, a micro lens array (MLA) 221, a polarization rotator (PR) 222, a polarized beam combiner (PBC) 223, and an optical fiber array 230. The optical modulator chip 210 is, for example, a thin-film LiNbO (TF-LN) modulator chip. The optical modulator chip 210 includes a TF-LN optical waveguide 211, a TF-LN optical modulator 212, an input section 213, a first output section 214A, and a second output section 214B. On a chip end surface 210A of the optical modulator chip 210, an input section 213, a first output section 214A, and a second output section 214B are arranged.

[0003] The optical waveguide 211 in the optical modulator chip 210 has an input waveguide 211A, a folded waveguide 211B, a first output waveguide 211C1, and a second output waveguide 211C2. The input waveguide 211A is a TF-LN waveguide that extends linearly from the input section 213 of the optical modulator chip 210 in the longitudinal direction of the optical modulator chip 210. The folded waveguide 211B is a TF-LN waveguide that folds back from the input waveguide 211A and connects to the input stage of the optical modulator 212. The first output waveguide 211C1 is a TF-LN waveguide that connects the output stage of the optical modulator 212 and the first output section 214A of the optical modulator chip 210. The second output waveguide 211C2 is a TF-LN waveguide that connects the output stage of the optical modulator 212 and the second output section 214B of the optical modulator chip 210.

[0004] The optical modulator 212 has an optical waveguide and an electrode for applying an electric signal to the optical waveguide, and optically modulates the light passing through the optical waveguide by applying the electric signal from the electrode. The optical fiber array 230 has an input optical fiber 231A for inputting light and an output optical fiber 231B for outputting light.

[0005] The MLA 221 is an optical component connected to a chip end surface 210A of the optical modulator chip 210, which optically couples the TF-LN optical waveguide 211 and the optical fiber array 230. The MLA 221 is connected to an input-side optical fiber 231A in the optical fiber array 230, and inputs light from the input-side optical fiber 231A to the input waveguide 211A. The MLA 221 outputs TE polarized signal light from the optical modulator 212 to the PR 222 and the PBC 223. The PR 222 rotates the polarization of the signal light from the optical modulator 212 by 90 degrees through the MLA 221, and outputs the TM polarized signal light after the polarization rotation to the PBC 223. The PBC 223 polarization-multiplexes the TE polarized signal light obtained from the optical modulator 212 via the MLA 221 and the TM polarized signal light after polarization rotation, and outputs the polarization-multiplexed signal light to the output optical fiber 231B in the optical fiber array 230. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent No. 06510258 [Patent Document 2] US Patent Application Publication No. 2013 / 0163916 [Patent Document 3] Japanese Patent Application Publication No. 8-327841 [Patent Document 4] Japanese Patent Application Laid-Open No. 2012-98472 Summary of the Invention [Problem to be solved by the invention]

[0007] In the optical integrated device 200, the optical axes of the optical waveguide 211 on the chip end face 210A of the optical modulator chip 210 and the MLA 221 are aligned, and the optical modulator chip 210 and the MLA 221 are fixed together with adhesive A. Then, an alignment process is required to align the optical axes of the PR 222, PBC 223, and optical fiber array 230 with the MLA 221.

[0008] However, since the optical waveguide 211 in the optical modulator chip 210 is a TF-LN optical waveguide having an electro-optic effect, the optical mode field diameter is small and high-precision alignment work is required. Therefore, the workload required for mounting a chip having an optical waveguide having an electro-optic effect is large.

[0009] In one aspect, an object of the present invention is to provide an optical integrated device or the like that can reduce the workload required for mounting a chip that includes an optical waveguide having an electro-optic effect. [Means for solving the problem]

[0010] An optical integrated device according to one embodiment includes a first chip having a stepped portion and a second chip mounted on the stepped portion and optically connected to the first chip, the first chip having an optical waveguide containing a material with a larger electro-optic effect than the material of the second chip. The optical integrated device includes a first inclined surface formed on a wall surface of the stepped portion on the side where the optical waveguide and the second chip are optically connected, and a second inclined surface formed on an end surface of the second chip on the side mounted in the stepped portion, facing the first inclined surface and abutting the first inclined surface. [Effects of the Invention]

[0011] According to one aspect, it is possible to reduce the workload required for mounting a chip having an optical waveguide with an electro-optic effect. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a plan view schematically illustrating an example of an optical integrated device according to a first embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view showing an example of an optical integrated device. [Figure 3] FIG. 3 is a plan view schematically illustrating an example of an optical integrated device according to the second embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view showing an example of an optical integrated device. [Figure 5] FIG. 5 is a plan view schematically illustrating an example of an optical integrated device according to the third embodiment. [Figure 6] FIG. 6 is a schematic cross-sectional view showing an example of an optical integrated device. [Figure 7] FIG. 7 is a schematic plan view showing an example of an optical integrated device according to the fourth embodiment. [Figure 8A] FIG. 8A is a schematic cross-sectional view taken along line AA shown in FIG. [Figure 8B] FIG. 8B is a schematic cross-sectional view taken along line BB shown in FIG. [Figure 9] FIG. 9 is a plan view schematically illustrating an example of an optical integrated device according to the fifth embodiment. [Figure 10A] FIG. 10A is a schematic cross-sectional view taken along line AA shown in FIG. [Figure 10B] FIG. 10B is a schematic cross-sectional view taken along line BB shown in FIG. [Figure 11] FIG. 11 is an explanatory diagram showing an example of an optical transceiver according to this embodiment. [Figure 12] FIG. 12 is a schematic plan view showing an example of an optical integrated device of the comparative example. [Figure 13] FIG. 13 is a schematic cross-sectional view showing an example of an optical integrated device of a comparative example. [Figure 14] FIG. 14 is a schematic plan view showing an example of an optical integrated device. [Figure 15] FIG. 15 is a schematic cross-sectional view showing an example of an optical integrated device. DETAILED DESCRIPTION OF THE INVENTION

[0013] First, an optical integrated device of a comparative example that can reduce the workload required for mounting a chip having an optical waveguide with an electro-optic effect will be described.

[0014] FIG. 12 is a schematic plan view illustrating an example of an optical integrated device 100 of a comparative example, and FIG. 13 is a schematic cross-sectional view illustrating an example of the optical integrated device 100 of the comparative example. For ease of explanation, the schematic cross-sectional view is a schematic cross-sectional view of the optical integrated device 100. The optical integrated device 100 includes a first chip 102 having a first optical waveguide 111 with an electro-optic effect, a second chip 103 having an optical circuit 124 and a second optical waveguide 123, and an optical fiber array 104. The first chip 102 is, for example, a chip having an electro-optic effect, such as TF-LN (Thin-Film LiNbO). The first chip 102 is a thin-film LN substrate with a submicron thickness. The second chip 103 is, for example, a silicon photonics (SiPh) chip. The optical fiber array 104 includes an input optical fiber 104A for inputting light and an output optical fiber 104B for outputting light.

[0015] The first chip 102 includes a first optical waveguide 111 made of a TF-LN material, an optical modulator 112 made of a TF-LN material, a step portion 113 formed on the chip end surface 102A1, an input portion 114, a first output portion 115A, and a second output portion 115B. The step portion 113 is formed on the chip end surface 102A1 of the first chip 102 and has a terrace structure for mounting the second chip 103. The input portion 114 is disposed on an inclined surface 113A of the step portion 113 and is a portion through which light from the second optical waveguide 123 of the second chip 103 is input. The inclined surface 113A faces a bonding surface 103A of the second chip 103, which will be described later. The first output section 115A and the second output section 115B are disposed on the inclined surface 113A of the step section 113, and are sections that output the signal light from the optical modulator 112 to the second optical waveguide 123 of the second chip 103.

[0016] The first optical waveguide 111 has an input waveguide 111A, a folded waveguide 111B, a first output waveguide 111C1, and a second output waveguide 111C2. The input waveguide 111A is a linear TF-LN optical waveguide that extends from the input section 114 in the longitudinal direction of the first chip 102 and connects to the folded waveguide 111B. The folded waveguide 111B is a folded TF-LN waveguide that connects the input waveguide 111A and the input stage of the optical modulator 112. The first output waveguide 111C1 is a TF-LN waveguide that connects the output stage of the optical modulator 112 and the first output section 115A. The second output waveguide 111C2 is a TF-LN waveguide that connects the output stage of the optical modulator 112 and the second output section 115B.

[0017] The second chip 103 has a first input section 121A, a second input section 121B, a third input section 121C, a first output section 122A, a second output section 122B, a second optical waveguide 123, and an optical circuit 124. The optical circuit 124 has a PR (Polarization Rotator) 124A formed of a Si material and a PBC (Polarization Beam Combiner) 124B formed of a Si material. The first input section 121A is disposed on a surface that connects to the optical fiber array 104, and is a section that inputs light from an optical fiber 104A on the input side within the optical fiber array 104. The first output section 122A is disposed on a bonding surface 103A that faces the inclined surface 113A of the first chip 102, and is a section that outputs light from the first input section 121A to the first chip 102. The second input unit 121B is disposed on the bonding surface 103A opposite the inclined surface 113A of the first chip 102, and is a portion that inputs light from the optical modulator 112 in the first chip 102 to the PR 124A. The third input unit 121C is disposed on the bonding surface 103A opposite the inclined surface 113A of the first chip 102, and is a portion that inputs light from the optical modulator 112 in the first chip 102 to the PBC 124B. The second output unit 122B is disposed on the surface that connects to the optical fiber array 104, and is a portion that outputs signal light from the PBC 124B to the output optical fiber 104B in the optical fiber array 104.

[0018] The second optical waveguide 123 has an input waveguide 123A, a first input waveguide 123B1, a second input waveguide 123B2, and an output waveguide 123C. The input waveguide 123A is a Si waveguide connecting the first input unit 121A and the first output unit 122A. The first input waveguide 123B1 is a Si waveguide connecting the second input unit 121B and the PR 124A. The second input waveguide 123B2 is a Si waveguide connecting the third input unit 121C and the PBC 124B. The output waveguide 123C is a Si waveguide connecting the second output unit 122B and the PBC 124B.

[0019] PR124A is a polarization rotation unit that rotates the TE polarized signal light from the first input waveguide 123B1 by 90 degrees to convert it into TM polarized signal light and outputs the TM polarized signal light to PBC 124B. PBC 124B is a polarization multiplexing unit that polarization multiplexes the TE polarized signal light from the second input waveguide 123B2 and the TM polarized signal light after polarization rotation from PR124A and outputs the polarization multiplexed signal light to output waveguide 123C.

[0020] A stepped portion 113 having a terrace structure is provided in a portion near chip end surface 102A1 of first chip 102, for example, to mount second chip 103 face-down. Note that step portion 113 is formed, for example, by etching the surface of first chip 102, and therefore the wall surface of step portion 113 is inclined surface 113A. As described above, first output portion 122A, first input portion 121A, and second input portion 121B are arranged on inclined surface 113A.

[0021] When the second chip 103 is mounted face-down in the stepped portion 113 of the first chip 102, the first optical waveguide 111 of the first chip 102 and the second optical waveguide 123 of the second chip 103 are optically coupled by butt coupling using adhesive A. As a result, the input portion 114 in the first chip 102 and the first output portion 122A in the second chip 103 are optically connected. Furthermore, the first output portion 115A in the first chip 102 and the second input portion 121B of the second chip 103 are optically connected, and the second output portion 115B in the first chip 102 and the third input portion 121C of the second chip 103 are optically connected.

[0022] Furthermore, the second chip 103 is connected to the optical fiber array 104 with adhesive A, thereby optically connecting the first input section 121A to the input side optical fiber 104A and optically connecting the second output section 122B to the output side optical fiber 104B.

[0023] In the optical integrated device 100, a second chip 103 having an optical circuit 124 is mounted on a step portion 113 in a first chip 102 having an electro-optic effect. Then, in the optical integrated device 100, a first optical waveguide 111 on an inclined surface 113A of the first chip 102 is optically coupled to a second optical waveguide 123 on a bonding surface 103A of the second chip 103 by butt coupling. As a result, it is no longer necessary to mount the components PR124A and PBC124B individually, which reduces the number of components and significantly reduces the workload required for mounting the first chip 102 having an electro-optic effect.

[0024] In the optical integrated device 100, the wall surface of the step portion 113 of the first chip 102 is an inclined surface 113A, which creates a gap between the inclined surface 113A of the first chip 102 and the bonding surface 103A of the second chip 103. Then, adhesive A is applied to this gap to optically couple the second optical waveguide 123 and the first optical waveguide 111. However, in the optical integrated device 100, the gap between the inclined surface 113A and the bonding surface 103A is large. Therefore, light emitted from the bonding surface 103A of the second chip 103 diverges in the adhesive A applied to this gap, reducing the optical coupling efficiency between the second optical waveguide 123 and the first optical waveguide 111.

[0025] Therefore, an embodiment of an optical integrated device that can improve the optical coupling efficiency between the second optical waveguide 123 and the first optical waveguide 111 will be described below as Example 1. Note that the disclosed technology is not limited to this Example. Furthermore, the Examples shown below may be combined as appropriate within a range that does not cause contradictions. [Example]

[0026] FIG. 1 is a plan view showing an example of an optical integrated device 1 according to a first embodiment, and FIG. 2 is a cross-sectional view showing the example of the optical integrated device 1. For ease of explanation, the cross-sectional view is a cross-sectional view of the optical integrated device 1. The optical integrated device 1 includes a first chip 2 having a first optical waveguide 11 with an electro-optic effect, a second chip 3 having an optical circuit 24 and a second optical waveguide 23, and an optical fiber array 4. The first chip 2 is a chip having an electro-optic effect, such as TF-LN (Thin-Film LiNbO). The first chip 2 is a thin-film substrate of LN with a submicron thickness. The second chip 3 is a silicon photonics (SiPh) chip, for example. The optical fiber array 4 includes an input optical fiber 4A for inputting light and an output optical fiber 4B for outputting light.

[0027] The first chip 2 includes a first optical waveguide 11 made of a TF-LN material, an optical modulator 12 made of a TF-LN material, a stepped portion 13 formed on the chip end face 2A1, an input portion 14, a first output portion 15A, and a second output portion 15B. The stepped portion 13 is formed on the chip end face 2A1 of the first chip 2 and has a terrace structure for mounting the second chip 3. The input portion 14 is disposed on a first inclined surface 13A of the stepped portion 13 and is a portion that inputs light from the second optical waveguide 23 of the second chip 3. The first inclined surface 13A is a surface that is inclined relative to the perpendicular direction of the surface of the stepped portion 113. The first inclined surface 13A is a surface that abuts against a second inclined surface 3A1 of the second chip 3, which will be described later. The first output section 15A and the second output section 15B are arranged on the first inclined surface 13A of the step section 13 and are parts that output the signal light from the optical modulator 12 to the second optical waveguide 23 of the second chip 3.

[0028] The first optical waveguide 11 has an input waveguide 11A, a folded waveguide 11B, a first output waveguide 11C1, and a second output waveguide 11C2. The input waveguide 11A is a linear TF-LN optical waveguide that extends from the input section 14 in the longitudinal direction of the first chip 2 and connects to the folded waveguide 11B. The first inclined surface 13A is a wall surface to which the input end of the input waveguide 11A reaches. The folded waveguide 11B is a folded TF-LN waveguide that connects the input waveguide 11A and the input stage of the optical modulator 12. The first output waveguide 11C1 is a TF-LN waveguide that connects the output stage of the optical modulator 12 and the first output section 15A. The second output waveguide 11C2 is a TF-LN waveguide that connects the output stage of the optical modulator 12 and the second output section 15B. The first inclined surface 13A is a wall surface to which the output ends of the first output waveguide 11C1 and the second output waveguide 11C2 reach.

[0029] The second chip 3 has a first input section 21A, a second input section 21B, a third input section 21C, a first output section 22A, a second output section 22B, a second optical waveguide 23, and an optical circuit 24. The optical circuit 24 has a PR (Polarization Rotator) 24A formed of a Si material and a PBC (Polarization Beam Combiner) 24B formed of a Si material. The second chip 3 has a tip step section 3A formed by etching and digging down near the bottom of the chip end face to be mounted on the step section 13 of the first chip 2. Furthermore, the second chip 3 has a second inclined surface 3A1 that is inclined by etching and digging down the bottom of the tip step section 3A and abuts against the first inclined surface 13A of the step section 13. The second inclined surface 3A1 is a surface that is inclined with respect to the vertical direction of the chip surface. The second inclined surface 3A1 of the second chip 3 has the same inclination direction as the first inclined surface 13A of the first chip 2.

[0030] The first input section 21A is disposed on the surface connected to the optical fiber array 4 and is a section that inputs light from the input-side optical fiber 4A in the optical fiber array 4. The first output section 22A is disposed on the second inclined surface 3A1 that abuts against the first inclined surface 13A of the first chip 2 and is a section that outputs light from the first input section 21A to the first chip 2. The second input section 21B is disposed on the second inclined surface 3A1 that abuts against the first inclined surface 13A of the first chip 2 and is a section that inputs light from the optical modulator 12 in the first chip 2 to the PR 24A. The third input section 21C is disposed on the second inclined surface 3A1 that abuts against the first inclined surface 13A of the first chip 2 and is a section that inputs light from the optical modulator 12 in the first chip 2 to the PBC 24B. The second output section 22B is disposed on the surface connected to the optical fiber array 4, and outputs the signal light from the PBC 24B to the optical fiber 4B on the output side within the optical fiber array 4.

[0031] The second optical waveguide 23 has an input waveguide 23A, a first input waveguide 23B1, a second input waveguide 23B2, and an output waveguide 23C. The input waveguide 23A is a Si waveguide that connects the first input unit 21A and the first output unit 22A. The second inclined surface 3A1 is a wall surface to which the output end of the input waveguide 23A reaches. The first input waveguide 23B1 is a Si waveguide that connects the second input unit 21B and the PR 24A. The second input waveguide 23B2 is a Si waveguide that connects the third input unit 21C and the PBC 24B. The second inclined surface 3A1 is a wall surface to which the input ends of the first input waveguide 23B1 and the second input waveguide 23B2 reach. The output waveguide 23C is a Si waveguide that connects the second output section 22B and the PBC 24B.

[0032] PR24A is a polarization rotation unit that rotates the TE polarized signal light from the first input waveguide 23B1 by 90 degrees to convert it into TM polarized signal light and outputs the TM polarized signal light to PBC 24B. PBC 24B is a polarization multiplexing unit that polarization multiplexes the TE polarized signal light from the second input waveguide 23B2 and the TM polarized signal light after polarization rotation from PR24A and outputs the polarization multiplexed signal light to output waveguide 23C.

[0033] A stepped portion 13 with a terrace structure is provided in a portion near the chip end surface 2A1 of the first chip 2, for example, to mount the second chip 3 face down. The stepped portion 13 is formed, for example, by etching and digging down the surface of the first chip 2. As described above, the first output portion 22A, the first input portion 21A, and the second input portion 21B are arranged on the first inclined surface 13A, which is the wall surface of the stepped portion 13.

[0034] When the second chip 3 is mounted face-down in the stepped portion 13 of the first chip 2, the second inclined surface 3A1 and the first inclined surface 13A are brought into contact with each other. This reduces the gap between the first inclined surface 13A of the first chip 2 and the second inclined surface 3A1 of the second chip 3. Then, with the second inclined surface 3A1 and the first inclined surface 13A in contact with each other, adhesive A is used to optically couple the first optical waveguide 11 of the first chip 2 and the second optical waveguide 23 of the second chip 3 by butt coupling. As a result, the input section 14 in the first chip 2 and the first output section 22A in the second chip 3 are optically connected. Furthermore, the first output section 15A in the first chip 2 and the second input section 21B of the second chip 3 are optically connected, and the second output section 15B in the first chip 2 and the third input section 21C of the second chip 3 are optically connected.

[0035] 2, when the second chip 3 is mounted face-down in the stepped portion 13 of the first chip 2, a gap is generated between the tip stepped portion 3A and the chip end face of the first chip 2, but adhesive A is applied to the gap between the tip stepped portion 3A and the chip end face of the first chip 2. As a result, the second chip 3 can be mounted in the stepped portion 13 of the first chip 2 using adhesive A between the tip stepped portion 3A and the chip end face of the first chip 2.

[0036] Furthermore, the second chip 3 is connected to the optical fiber array 4 with adhesive A, thereby optically connecting the first input section 21A to the input side optical fiber 4A, and optically connecting the second output section 22B to the output side optical fiber 4B.

[0037] In the optical integrated device 1 of Example 1, the first optical waveguide 11 on the first inclined surface 13A and the second optical waveguide 23 on the second inclined surface 3A1 are optically coupled by butt coupling using adhesive A while the second inclined surface 3A1 and the first inclined surface 13A are abutted against each other. In other words, the gap between the second optical waveguide 23 on the second inclined surface 3A1 and the first optical waveguide 11 on the first inclined surface 13A is reduced. As a result, the optical coupling efficiency between the second optical waveguide 23 and the first optical waveguide 11 can be improved.

[0038] In the optical integrated device 1, the second chip 3 having the optical circuit 24 is mounted on the step portion 13 in the first chip 2 having the electro-optic effect, and the first optical waveguide 11 of the first chip 2 is optically coupled to the second optical waveguide 23 of the second chip 3 by butt coupling. As a result, it is no longer necessary to mount the components PR24A and PBC24B individually, which reduces the number of components and significantly reduces the workload required for mounting the first chip 2 having the electro-optic effect.

[0039] Generally, an LN modulator chip is larger than a SiPh chip, and when a step portion is formed on the SiPh chip and an LN modulator is mounted thereon, the size of the SiPh chip must also be increased to match the size of the LN modulator. In contrast, in the optical integrated device 1 of the first embodiment, the size of the second chip 3, which is a SiPh chip, does not need to be adjusted to the size of the first chip 2, which is an LN modulator chip, so waste of the second chip 3 can be eliminated.

[0040] Since the second chip 3 is mounted face down on the step portion 13 in the first chip 2, the depth of the step portion 13 formed on the first chip 2 can be made shallow. Therefore, the burden of etching when forming the step portion 13 can be reduced.

[0041] The optical modulator 12 of the first chip 2 is an optical modulator made of TF-LN crystal, and therefore, by obtaining a large electro-optic effect, the drive voltage of the modulator can be reduced.

[0042] Since the second chip 3 is a SiPh chip, it is possible to reduce the size of the optical circuit 24 including the PR 24A and the PBC 24B.

[0043] For convenience of explanation, the case where the second chip 3 is mounted face-down on the stepped portion 13 of the first chip 2 is illustrated, but face-up mounting is also possible and can be modified as appropriate. In the second chip 3, the second optical waveguide 23 is formed near the chip surface, so by deepening the depth of the stepped portion 13, the second chip 3 can also be mounted face-up on the stepped portion 13 of the first chip 2.

[0044] Although TF-LN is used as an example of the material for the electro-optic effect, it is not limited to this and may be, for example, TF-Barium Titanate, and may be changed as appropriate. Other examples of the material for the electro-optic effect include TF-BTO (BaTiO3), TF-PLZT (PbLaZrTiO3), and TF-PZT (PbZrTiO3).

[0045] In the optical integrated device 1 of Example 1, the first optical waveguide 11 in the first chip 2 and the second optical waveguide 23 in the second chip 3 are optically coupled by butt coupling. However, if the distance X between the input waveguide 11A and the first output waveguide 11C1 of the first optical waveguide 11 in the first chip 2 becomes large, the misalignment of the optical axis increases if the arrangement angle of the second chip 3 is misaligned when the second chip 3 is mounted relative to the first chip 2. As a result, the coupling loss between the first optical waveguide 11 and the second optical waveguide 23 increases. Therefore, an embodiment that addresses this situation will be described below as Example 2. [Example]

[0046] FIG. 3 is a plan view diagram illustrating an example of an optical integrated device 1A according to a second embodiment, and FIG. 4 is a cross-sectional view diagram illustrating an example of the optical integrated device 1A. The same components as those in the optical integrated device 1 according to the first embodiment are designated by the same reference numerals, and redundant descriptions of the components and operations will be omitted. The butt coupling point of the first chip 2 is a point where the distance X between the input waveguide 11A1 and the first output waveguide 11C1 and the distance X between the input waveguide 23A and the first input waveguide 23B1 at the butt coupling point are narrowed. The butt coupling point is a location where the first chip 2 and the second chip 3 are optically coupled by butt coupling. The distance X between the input waveguide 11A1 and the first output waveguide 11C1 and the distance X between the input waveguide 23A and the first input waveguide 23B1 are narrower than the distance X1 between the input optical fiber 4A and the output optical fiber 4B.

[0047] When the second chip 3 is mounted face-down in the stepped portion 13 of the first chip 2, the first optical waveguide 11 of the first chip 2 and the second optical waveguide 23 of the second chip 3 are optically coupled by butt coupling using adhesive A. That is, the input waveguide 11A1 of the input unit 14 in the first chip 2 is optically connected to the input waveguide 23A of the first output unit 22A in the second chip 3. The first output waveguide 11C1 of the first output unit 15A in the first chip 2 is optically connected to the first input waveguide 23B1 of the second input unit 21B of the second chip 3. Furthermore, the second output waveguide 11C2 of the second output unit 15B in the first chip 2 is optically connected to the second input waveguide 23B2 of the third input unit 21C of the second chip 3.

[0048] Since the distance X between the input waveguide 11A1 and the first output waveguide 11C1 of the first chip 2 is narrowed, the radius of curvature of the folded waveguide 11B1 is smaller than that of the folded waveguide 11B shown in FIG.

[0049] The input waveguide 23A1 in the second chip 3 is curved so that the distance between the input waveguide 23A1 and the output waveguide 23C in the second chip 3 matches the distance X1 between the optical fiber 4A on the input side and the optical fiber 4B on the output side of the optical fiber array 4.

[0050] In the optical integrated device 1A of Example 2, the distance X between the input waveguide 11A1 and the first output waveguide 11C1 at the butt-coupling point of the first chip 2 is made narrower than the distance X1 between the input optical fiber 4A and the output optical fiber 4B of the optical fiber array 4. As a result, the tolerance due to deviation in the arrangement angle of the second chip 3 when the second chip 3 is mounted is relaxed, and deterioration of the coupling loss between the first optical waveguide 11 and the second optical waveguide 23 can be suppressed.

[0051] In the optical integrated device 1A of Example 2, the distance X between the input waveguide 11A1 and the first output waveguide 11C1 of the first chip 2 is narrowed, which reduces the radius of curvature of the folded waveguide 11B1. As a result, there is a risk of radiation loss occurring in the folded waveguide 11B1. Therefore, an embodiment that addresses this situation will be described below as Example 3. [Example]

[0052] Fig. 5 is a schematic plan view showing an example of an optical integrated device 1B of Example 3, and Fig. 6 is a schematic cross-sectional view showing an example of the optical integrated device 1B. Note that the same components as those in the optical integrated device 1A of Example 2 are given the same reference numerals, and redundant descriptions of the components and operations will be omitted. The diameter of the folded waveguide 11B2 in the first chip 2 is wider than the distance between the input waveguide 11A2 and the first output waveguide 11C1 at the butt-coupling point in the first chip 2.

[0053] In the optical integrated device 1B of the third embodiment, the diameter X2 of the folded waveguide 11B2 in the first chip 2 is set larger than the distance X between the input waveguide 11A2 and the first output waveguide 11C1 at the butt-coupling point in the first chip 2. As a result, the radius of curvature of the folded waveguide 11B2 is increased, and radiation loss in the folded waveguide 11B2 can be suppressed.

[0054] In the optical integrated device 1B of Example 3, the first inclined surface 13A is formed along the entire inner wall surface of the step portion 13, but this is not limited to this, and an embodiment thereof will be described below as Example 4. [Example]

[0055] Fig. 7 is a plan view showing an example of an optical integrated device 1C of Example 4, Fig. 8A is a schematic cross-sectional view taken along line AA shown in Fig. 7, and Fig. 8B is a schematic cross-sectional view taken along line BB shown in Fig. 7. Note that the same components as those in the optical integrated device 1A of Example 2 are denoted by the same reference numerals, and redundant explanations of the components and operations will be omitted.

[0056] The optical integrated device 1C has a protruding portion 13B that protrudes from the wall surface of the stepped portion 13 at the locations of the input waveguide 11A1 of the input portion 14, the first output waveguide 11C1 of the first output portion 15A, and the second output waveguide 11C2 of the second output portion 15B. As shown in FIG. 8A , the protruding portion 13B has a first inclined surface 13A1 that abuts the second inclined surface 3A1. Furthermore, as shown in FIG. 8B , the wall surface of the stepped portion 13 excluding the protruding portion 13B has a third inclined surface 13A2 that does not abut the second inclined surface 3A1.

[0057] Input section 14, first output section 15A, and second output section 15B are arranged on first inclined surface 13A1, which abuts second inclined surface 3A1. First inclined surface 13A1 is a wall surface to which the input end of input waveguide 11A reaches. First inclined surface 13A1 is a wall surface to which the output ends of first output waveguide 11C1 and second output waveguide 11C2 reach.

[0058] When the second chip 3 is mounted face-down in the stepped portion 13 of the first chip 2, the second inclined surface 3A1 and the first inclined surface 13A1 are brought into contact with each other, as shown in FIG. 8A . As a result, the gap between the first inclined surface 13A1 of the first chip 2 and the second inclined surface 3A1 of the second chip 3 is reduced. Then, with the second inclined surface 3A1 and the first inclined surface 13A1 in contact with each other, adhesive A is used to optically couple the first optical waveguide 11 of the first chip 2 and the second optical waveguide 23 of the second chip 3 by butt coupling. As a result, the input section 14 of the first chip 2 and the first output section 22A of the second chip 3 are optically connected. Furthermore, the first output section 15A in the first chip 2 and the second input section 21B of the second chip 3 are optically connected, and the second output section 15B in the first chip 2 and the third input section 21C of the second chip 3 are optically connected.

[0059] 8A, a gap is generated between the tip step portion 3A and the protruding portion 13B of the first chip 2, but adhesive A is applied to the gap between the tip step portion 3A and the protruding portion 13B. As a result, the second chip 3 can be mounted in the step portion 13 of the first chip 2 using adhesive A between the tip step portion 3A and the protruding portion 13B.

[0060] When mounting the second chip 3 face-down in the stepped portion 13 of the first chip 2, a gap is generated between the second inclined surface 3A1 and the third inclined surface 13A2 as shown in Fig. 8B, but adhesive A is applied to the gap between the second inclined surface 3A1 and the third inclined surface 13A2. As a result, the second chip 3 can be mounted in the stepped portion 13 of the first chip 2 using adhesive A between the second inclined surface 3A1 and the third inclined surface 13A2.

[0061] In the optical integrated device 1C of Example 4, the first optical waveguide 11 on the first inclined surface 13A1 and the second optical waveguide 23 on the second inclined surface 3A1 are optically coupled by butt coupling using adhesive A while the second inclined surface 3A1 and the first inclined surface 13A1 of the protruding portion 13B are abutted against each other. In other words, the gap between the second optical waveguide 23 on the second inclined surface 3A1 and the first optical waveguide 11 on the first inclined surface 13A1 is reduced. As a result, the optical coupling efficiency between the second optical waveguide 23 and the first optical waveguide 11 can be improved.

[0062] In the optical integrated device 1B of Example 3, the second inclined surface 3A1 is formed along the entire surface facing the wall surface of the lower step portion 13 of the tip step portion 3A of the second chip 3. However, the present invention is not limited to this, and an embodiment thereof will be described below as Example 5. [Example]

[0063] Fig. 9 is a plan view showing an example of an optical integrated device 1D of Example 5, Fig. 10A is a schematic cross-sectional view taken along line AA shown in Fig. 9, and Fig. 10B is a schematic cross-sectional view taken along line BB shown in Fig. 9. Note that the same components as those in the optical integrated device 1C of Example 4 are denoted by the same reference numerals, and redundant descriptions of the components and operations will be omitted.

[0064] The optical integrated device 1D has a protruding portion 3B protruding from the inner wall surface at the location of the input waveguide 23A of the first output section 22A, the first input waveguide 23B1 of the second input section 21B, and the second input waveguide 23B2 of the third input section 21C on the inner wall surface of the lower tip step section 3A. As shown in FIG. 10A, the protruding portion 3B on the inner wall surface of the tip step section 3A has a second inclined surface 3B1 that abuts the first inclined surface 13A1 of the protruding portion 13B in the step section 13. Furthermore, as shown in FIG. 10B, the inner wall surface of the tip step section 3A excluding the protruding portion 3B has a fourth inclined surface 3B2 that does not abut the third inclined surface 13A2 in the step section 13.

[0065] The first output portion 22A, the second input portion 21B, and the third input portion 21C are arranged on a second inclined surface 3B1 that abuts on the first inclined surface 13A1 of the protrusion 13B in the step portion 13. The second inclined surface 3B1 is a wall surface to which the output end of the input waveguide 23A reaches. The second inclined surface 3B1 is a wall surface to which the input ends of the first input waveguide 23B1 and the second input waveguide 23B2 reach.

[0066] When the second chip 3 is mounted face-down within the stepped portion 13 of the first chip 2, as shown in FIG. 10A , the second inclined surface 3B1 is brought into contact with the first inclined surface 13A1 of the protruding portion 13B. As a result, the gap between the first inclined surface 13A1 of the first chip 2 and the second inclined surface 3B1 of the second chip 3 is reduced. Then, with the second inclined surface 3B1 and the first inclined surface 13A1 in contact with each other, adhesive A is used to optically couple the first optical waveguide 11 of the first chip 2 and the second optical waveguide 23 of the second chip 3 by butt coupling. As a result, the input section 14 of the first chip 2 and the first output section 22A of the second chip 3 are optically connected. Furthermore, the first output section 15A in the first chip 2 and the second input section 21B of the second chip 3 are optically connected, and the second output section 15B in the first chip 2 and the third input section 21C of the second chip 3 are optically connected.

[0067] 10A, a gap is generated between the tip step portion 3A and the chip end face of the first chip 2, but adhesive A is applied to the gap between the tip step portion 3A and the chip end face. As a result, the second chip 3 can be mounted in the step portion 13 of the first chip 2 using adhesive A between the tip step portion 3A and the chip end face.

[0068] 10B, a gap is generated between the fourth inclined surface 3B2 and the third inclined surface 13A2, but adhesive A is applied to the gap between the fourth inclined surface 3B2 and the third inclined surface 13A2. As a result, the second chip 3 can be mounted in the step portion 13 of the first chip 2 using adhesive A between the fourth inclined surface 3B2 and the third inclined surface 13A2.

[0069] In the optical integrated device 1D of Example 5, the second inclined surface 3B1 of the protrusion 3B and the first inclined surface 13A1 of the protrusion 13B are abutted against each other, and adhesive A is used to optically couple the first optical waveguide 11 on the first inclined surface 13A1 to the second optical waveguide 23 on the second inclined surface 3B1 by butt coupling. In other words, the gap between the second optical waveguide 23 on the second inclined surface 3B1 and the first optical waveguide 11 on the first inclined surface 13A1 is reduced. As a result, the optical coupling efficiency between the second optical waveguide 23 and the first optical waveguide 11 can be improved.

[0070] In the optical integrated device 1D of Example 5, the first optical waveguide 11 on the first inclined surface 13A1 and the second optical waveguide 23 on the second inclined surface 3B1 are optically coupled by butt coupling when the second inclined surface 3B1 of the protruding portion 3B and the first inclined surface 13A1 of the protruding portion 13B are in contact with each other. However, the first optical waveguide 11 on the first inclined surface 13A and the second optical waveguide 23 on the second inclined surface 3B1 may be optically coupled by butt coupling when the second inclined surface 3B1 of the protruding portion 3B of the second chip 3 is in contact with the first inclined surface 13A on the wall surface of the stepped portion 13 of the first chip 2, and this can be modified as appropriate.

[0071] Note that waveguides such as the first optical waveguide 11 and the second optical waveguide 23 may be, for example, rib waveguides, ridge waveguides, rectangular waveguides, or high mesa waveguides. Rib waveguides are preferable because they allow light to seep into the slab portion, making them less susceptible to the effects of rough core sidewalls and enabling low-loss propagation. Rectangular waveguides are preferable because they have strong optical confinement, resulting in low loss even when the bending radius R is small. Furthermore, low-loss bent waveguides may also be used as the waveguides, and can be modified as appropriate.

[0072] The second optical waveguide 23 may be a PLC, an InP waveguide, or a GaAs waveguide, both of which have a core and clad of SiO2. It may also be a Si waveguide, with a core of Si, a lower clad of SiO2, and an upper clad of SiO2, air, SiN, or the like. When the waveguide is a Si waveguide, the relative refractive index difference is large, so light is confined strongly, and therefore a low-loss bending waveguide can be realized even with a small bending radius R, which is preferable because it allows for the miniaturization of optical devices.

[0073] Next, an optical transceiver 50 employing the optical integrated device 1 of this embodiment will be described. FIG. 11 is an explanatory diagram showing an example of the optical transceiver 50 of this embodiment. The optical transceiver 50 shown in FIG. 11 includes an optical transmitter / receiver 51 and a DSP (Digital Signal Processor) 52. The optical transmitter / receiver 51 includes an optical modulator element 54, a driver circuit 55, an optical receiver element 56, and a TIA (Transimpedance Amplifier) ​​57. The DSP 52 controls the entire optical transmitter / receiver 51. The DSP 52 is an electrical component that performs digital signal processing, such as IQ modulation of a transmission signal and demodulation of a reception signal.

[0074] The DSP 52 executes processes such as encoding of transmission data, generates an electrical signal including the transmission data, and outputs the generated electrical signal to a driver circuit 55. The driver circuit 55 drives an optical modulator element 54 in response to the electrical signal from the DSP 52. The optical modulator element 54 incorporates an optical integrated device 1 including an optical modulator that optically modulates signal light.

[0075] The optical receiver element 56 converts the optical signal into an electrical signal. The TIA 57 amplifies the electrical signal after the electrical conversion and outputs the amplified electrical signal to the DSP 52. The DSP 52 performs processing such as decoding of the electrical signal received from the TIA 57 to obtain received data.

[0076] For ease of explanation, the optical transceiver 50 is exemplified as incorporating an optical modulator element 54 and an optical receiver element 56, but the optical transceiver 50 may also be an optical transmitter incorporating only the optical modulator element 54, and can be modified as appropriate.

[0077] 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.

[0078] 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) or MCU (Micro Controller Unit)). 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]

[0079] 1. Optical integrated devices 2. First Chip 3. Second Chip 11 First optical waveguide 11A1 Input waveguide 11B folded waveguide 11C1 first output waveguide 11C2 second output waveguide 12 Optical Modulator 13 Step 23 Second optical waveguide 23A Input waveguide 23C Output waveguide 24 Optical circuit 24A PR 24B PBC 50 Optical Transceiver 54 Optical modulator element 56 Optical receiver element

Claims

1. a first chip having a step portion; a second chip mounted on the step portion and optically connected to the first chip, the first chip having an optical waveguide including a material having a larger electro-optic effect than a material of the second chip, a first inclined surface formed on a wall surface of the step portion on a side where the optical waveguide and the second chip are optically connected; a second inclined surface formed on an end surface of the second chip on a side that is to be mounted in the step portion, the second inclined surface facing the first inclined surface and in contact with the first inclined surface; An optical integrated device comprising:

2. The first chip includes: a first optical waveguide that is the optical waveguide that reaches the first inclined surface; The second chip includes: a second optical waveguide that reaches the second inclined surface; 2. The optical integrated device according to claim 1, wherein the first inclined surface and the second inclined surface are brought into contact with each other to optically couple the first optical waveguide and the second optical waveguide by butt coupling.

3. The first chip includes:

2. The optical integrated device according to claim 1, wherein the step portion has a protruding portion protruding from a wall surface optically connected to the second chip, and the first inclined surface is formed on the protruding portion.

4. The second chip includes:

2. The optical integrated device according to claim 1, wherein the second chip has a protruding portion protruding from a wall surface of the end face that is optically connected to the first chip, and the second inclined surface is formed on the protruding portion.

5. The second chip includes:

2. The optical integrated device according to claim 1, wherein the optical integrated device is mounted face down on the step portion formed on the first chip.

6. The first chip includes: Thin film LN (LiNbO 3 2. The optical integrated device according to claim 1, further comprising an optical modulator including a crystalline material and optically connecting to said optical waveguide.

7. The second chip includes: The optical circuit includes a silicon material. The optical circuit comprises: a polarization rotation unit that rotates the polarization of the signal light from the optical modulator; a polarization multiplexing unit that polarization-multiplexes the signal light from the optical modulator and the signal light after polarization rotation by the polarization rotation unit; 7. The optical integrated device according to claim 6, further comprising:

8. The first optical waveguide in the first chip includes: a first input waveguide optically coupled to the second chip; a folded waveguide that connects the first input waveguide and an optical modulator by folding back; 3. The optical integrated device according to claim 2, further comprising: a first output waveguide connected to said optical modulator and connected to said second chip.

9. 9. The optical integrated device according to claim 8, wherein the folded waveguide has a diameter longer than a distance between the first input waveguide and the first output waveguide at a junction where the first chip and the second chip are butt-coupled.

10. The second optical waveguide in the second chip includes: a second input waveguide connecting the input optical fiber and the first input waveguide; a second output waveguide connecting an output optical fiber and the first output waveguide; 9. The optical integrated device according to claim 8, wherein the distance between the first input waveguide and the first output waveguide at a junction where the first chip and the second chip are butt-coupled is narrower than the distance between the second input waveguide and the second output waveguide at a junction surface between the input optical fiber and the output optical fiber.

11. An optical transmitter having an optical modulator element that modulates light using an electrical signal and transmits transmission light, The optical modulator element comprises: a first chip having a step portion; a second chip mounted on the step portion and optically connected to the first chip, the first chip having an optical waveguide including a material having a larger electro-optic effect than a material of the second chip, a first inclined surface formed on a wall surface of the step portion on a side where the optical waveguide and the second chip are optically connected; a second inclined surface formed on an end surface of the second chip on a side that is to be mounted in the step portion, the second inclined surface facing the first inclined surface and in contact with the first inclined surface; An optical transmitter comprising:

12. An optical transceiver having an optical modulator element that optically modulates light using a transmission signal and transmits the transmission light, and an optical receiver element that receives a reception signal from the reception light using light, The optical modulator element comprises: a first chip having a step portion; a second chip mounted on the step portion and optically connected to the first chip, the first chip having an optical waveguide including a material having a larger electro-optic effect than a material of the second chip, a first inclined surface formed on a wall surface of the step portion on a side where the optical waveguide and the second chip are optically connected; a second inclined surface formed on an end surface of the second chip on a side that is to be mounted in the step portion, the second inclined surface facing the first inclined surface and in contact with the first inclined surface; An optical transceiver comprising:

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