Semiconductor optical device

Abstract

A semiconductor optical device is provided with a third optical waveguide formed from a third core (114). The third core (114) has a larger diameter than a first core (102) and a second core (112). The third optical waveguide is formed in a connection region (130) comprising a first region (131) in which a first tapered portion (102a) is disposed, a second region (132) between the leading end of the first core (102) and the leading end of the second core (112), and a third region (133) in which a second tapered portion (112a) is disposed.

Description

semiconductor optical devices

[0001] The present invention relates to semiconductor optical devices.

[0002] The integration of compound semiconductor optical devices and silicon photonics optical circuits is progressing toward higher speeds, larger capacities, and smaller optical transceivers for optical communications. Adiabatic optical mode transition is achieved between silicon photonics and optical waveguides made of compound semiconductors such as InP that constitute lasers and optical modulators using a tapered optical waveguide structure as shown in Figure 1, enabling low-loss optical coupling.

[0003] Heterogeneous integration technology has attracted attention as a way to integrate such compound semiconductor optical devices with silicon photonics to realize small, high-performance optical integrated circuits. Among heterogeneous integration technologies, transfer printing (also known as micro transfer printing) has attracted attention as a technology that can integrate completed compound semiconductor optical devices and silicon photonics optical circuits with high positional accuracy, high throughput, and low cost.

[0004] In the transfer printing method, as shown in Non-Patent Document 1, visible light and a high-resolution camera are used to align the compound semiconductor optical device to be transferred with the destination substrate on which the optical circuit is formed. In this type of integration by transfer, high alignment accuracy is important for achieving low-loss optical coupling between the compound semiconductor optical device and the silicon photonics optical circuit. For example, the alignment accuracy required for silicon photonics optical circuits is said to be on the order of sub-micrometers (Non-Patent Document 2).

[0005] J. McPhillimy et al., "Automated Nanoscale Absolute Accuracy Alignment System for Transfer Printing", ACS Applied Nano Materials, vol. 3, no. 10, pp. 10326-10332, 2020. N. YE et al., "High-alignment-accuracy transfer printing of passive silicon waveguide structures", Optics Express, vol. 26, no. 2, pp. 2023-2032, 2018.

[0006] In general, there is a trade-off between alignment accuracy and transfer throughput, making it difficult to achieve low-loss device integration with high throughput. To mitigate this trade-off, Non-Patent Document 2 explores increasing the tolerance for misalignment by optimizing the tapered structure of silicon optical waveguides and compound semiconductor optical waveguides. However, the tolerance based on 1 dB loss remains at ±1.0 μm or less, resulting in reduced yield and throughput due to misalignment.

[0007] The present invention has been made to solve the above problems, and aims to suppress a decrease in optical coupling efficiency due to misalignment in optical coupling between a semiconductor optical device and a substrate on which an optical circuit is formed.

[0008] The semiconductor optical device according to the present invention comprises a substrate and an optical device transferred onto the substrate, the substrate being embedded in the substrate and comprising a first optical waveguide having a first core made of Si and having a first tapered portion whose diameter decreases toward the tip in the arrangement direction of the optical device, and the optical device comprising an optical element made of a compound semiconductor, a protective layer formed to cover the optical element, and a second core made of a compound semiconductor and having a second tapered portion connected to the optical element and whose diameter decreases toward the tip in the arrangement direction of the first optical waveguide. The optical device is transferred to the substrate with the tip of the first core and the tip of the second core spaced apart and facing each other, and the first optical waveguide and the second optical waveguide are connected via a third optical waveguide with a third core having a diameter larger than the first and second cores, which is formed in a connection region consisting of a first region where the first tapered portion is arranged, a second region between the tip of the first core and the tip of the second core, and a third region where the second tapered portion is arranged.

[0009] As described above, according to the present invention, a third optical waveguide is formed using a third core having a diameter larger than the first and second cores in the first region where the first tapered portion is arranged and in the region including the area between the tip of the first core and the tip of the second core, thereby making it possible to suppress a decrease in optical coupling efficiency due to misalignment in the optical coupling between the semiconductor optical device and the substrate on which the optical circuit is formed.

[0010] FIG. 1 is a plan view showing the configuration of a semiconductor optical device according to a first embodiment of the present invention. FIG. 2A is a cross-sectional view (a) and a mode distribution diagram (b) showing a partial configuration of a semiconductor optical device according to a first embodiment of the present invention. FIG. 2B is a cross-sectional view (a) and a mode distribution diagram (b) showing a partial configuration of a semiconductor optical device according to a first embodiment of the present invention. FIG. 2C is a cross-sectional view (a) and a mode distribution diagram (b) showing a partial configuration of a semiconductor optical device according to a first embodiment of the present invention. FIG. 2D is a cross-sectional view (a) and a mode distribution diagram (b) showing a partial configuration of a semiconductor optical device according to a first embodiment of the present invention. FIG. 2E is a cross-sectional view (a) and a mode distribution diagram (b) showing a partial configuration of a semiconductor optical device according to a first embodiment of the present invention. FIG. 3 is a mode distribution diagram of a semiconductor optical device according to a first embodiment of the present invention. FIG. 4A is a plan view (a) and a mode distribution diagram (b) showing the configuration of a conventional semiconductor optical device. FIG. 4B is a cross-sectional view (a) and a mode distribution diagram (b) showing a partial configuration of a conventional semiconductor optical device. FIG. 4C is a cross-sectional view (a) and a mode distribution diagram (b) showing a partial configuration of a conventional semiconductor optical device. FIG. 4D is a cross-sectional view (a) and a mode distribution diagram (b) showing a partial configuration of a conventional semiconductor optical device. FIG. 5 is a characteristic diagram showing the results of calculating the optical coupling loss from the second optical waveguide to the first optical waveguide for the conventional semiconductor optical device (a) and the semiconductor optical device according to the first embodiment (b). FIG. 6 is a plan view showing the configuration of a semiconductor optical device according to a second embodiment of the present invention. FIG. 7 is a plan view showing the configuration of a semiconductor optical device according to a third embodiment of the present invention. FIG. 8A is a cross-sectional view (a) showing a partial configuration of a semiconductor optical device according to the third embodiment of the present invention. FIG. 8B is a cross-sectional view and a mode distribution diagram (b) showing a partial configuration of a semiconductor optical device according to the third embodiment of the present invention. FIG. 8C is a cross-sectional view (a) and a mode distribution diagram (b) showing a partial configuration of a semiconductor optical device according to the third embodiment of the present invention. FIG. 8D is a cross-sectional view (a) showing a partial configuration of a semiconductor optical device according to the third embodiment of the present invention. FIG. 8E is a cross-sectional view (a) and a mode distribution diagram (b) showing a partial configuration of a semiconductor optical device according to the third embodiment of the present invention.

[0011] Hereinafter, a semiconductor optical device according to an embodiment of the present invention will be described.

[0012] First Embodiment First, a semiconductor optical device according to a first embodiment of the present invention will be described with reference to Fig. 1. This semiconductor optical device includes a substrate 101 that constitutes silicon photonics, and an optical device 110 that is transferred onto the substrate 101. The optical device 110 is transferred onto the substrate 101 by micro transfer printing.

[0013] The substrate 101 includes a first optical waveguide formed by a first core 102 embedded in the substrate 101. The first optical waveguide has the substrate 101 as a cladding. The substrate 101 is made of SiO2, and the first core 102 is made of Si. The first core 102 also has a first tapered portion 102a whose diameter decreases toward the tip in a first direction facing the side where the optical device 110 is disposed.

[0014] The optical device 110 includes an optical element 111 made of a compound semiconductor such as InP, GaAs, or InGaAs, a protective layer 113 formed to cover the optical element 111, and a second optical waveguide formed by a second core 112 connected to the optical element 111. The second optical waveguide is clad with the protective layer 113. The optical element 111 may be, for example, a waveguide-type semiconductor laser or an optical modulator. For example, the second core 112 may be formed continuously with an active layer (not shown) of the waveguide-type semiconductor laser or optical modulator.

[0015] The second core 112 has a second tapered section 112a whose diameter decreases toward the tip in the direction of arrangement of the first optical waveguide (first core 102). The second core 112 including the second tapered section 112a is made of a compound semiconductor such as InP. The protective layer 113 is made of a material with a lower refractive index than the substrate 101 and the second core 112. The protective layer 113 can be made of an oxide or nitride with a low refractive index, such as SiON, SiO, or SiN.

[0016] In addition, in this semiconductor optical device, the optical device 110 is transferred to the substrate 101 in a state in which the tip of the first core 102 (first tapered portion 102a) and the tip of the second core 112 (second tapered portion 112a) are spaced apart and face each other.

[0017] Furthermore, this semiconductor optical device includes a third optical waveguide formed by a third core 114. The third core 114 has a larger diameter than the first core 102 and the second core 112. The third optical waveguide is formed in a connection region 130 that includes a first region 131 in which the first tapered portion 102a is arranged, a second region 132 between the tip of the first core 102 and the tip of the second core 112, and a third region 133 in which the second tapered portion 112a is arranged.

[0018] In the first embodiment, the third core 114 is formed from the protective layer 113 in the connection region 130. The third core 114 is formed between a first groove 113a and a second groove 113b formed in the protective layer 113. The first groove 113a and the second groove 113b sandwich the first optical waveguide and the second optical waveguide and are arranged parallel to the waveguiding directions of the first optical waveguide and the second optical waveguide.

[0019] The first optical waveguide and the second optical waveguide are optically connected via the third optical waveguide configured as described above.

[0020] The results of mode calculations of the light distribution in the first optical waveguide, the second optical waveguide, and the third optical waveguide of the semiconductor optical device according to the first embodiment will be described with reference to Figures 2A to 2E. In Figures 2A to 2E, (a) shows a cross section in the waveguiding direction, and (b) shows the results of calculations of the mode distribution. Figure 2A shows the state of the third region 133, Figure 2B shows the state at the tip of the second tapered portion 112a at the boundary between the third region 133 and the second region 132, Figure 2C shows the state of the second region 132, Figure 2D shows the state at the tip of the first tapered portion 102a at the boundary between the second region 132 and the first region 131, and Figure 2E shows the state of the first region 131.

[0021] 2A and 2B, as the core width of the second tapered portion 112a of the second core 112 becomes narrower, the optical mode widens and leaks out into the third core 114. As shown in Fig. 2C, in the second region 132 consisting only of the third core 114, the optical mode confined in the third core 114 has a mode field diameter of approximately 3.0 µm.

[0022] 2D and 2E , in the first region 131, as the core width of the first tapered portion 102 a increases, the optical mode gradually transitions from the third core 114 to the first core 102 (first tapered portion 102 a). In this way, according to the semiconductor optical device of the first embodiment, adiabatic low-loss optical coupling is achieved from the second optical waveguide to the first optical waveguide ( FIG. 3 ).

[0023] A conventional semiconductor optical device will now be described with reference to Figures 4A to 4D. The conventional semiconductor optical device comprises a substrate 301 that constitutes silicon photonics, and an optical device 310 that is transferred onto the substrate 301. The optical device 310 is transferred onto the substrate 301 by transfer printing.

[0024] The substrate 301 includes a first optical waveguide formed by a first core 302 embedded in the substrate 301. The first optical waveguide has the substrate 301 as a cladding. The first core 302 is made of Si. The first core 302 also has a first tapered portion 302a whose diameter decreases toward the tip in a first direction facing the side where the optical device 310 is disposed.

[0025] The optical device 310 includes an optical element 311 made of a compound semiconductor such as InP, GaAs, or InGaAs, a protective layer 313 formed to cover the optical element 311, and a second optical waveguide formed by a second core 312 connected to the optical element 311. The second optical waveguide has the protective layer 313 as a cladding.

[0026] The second core 312 has a second tapered portion 312a whose diameter decreases toward the tip in the direction of arrangement of the first optical waveguide (first core 302). The second core 312 having the second tapered portion 312a is made of a compound semiconductor such as InP.

[0027] Furthermore, in the conventional semiconductor optical device, the optical device 310 is transferred onto the substrate 301 in a state in which the first tapered portion 302 a and the second tapered portion 312 a overlap when viewed from the normal direction of the plane of the substrate 301. In the conventional semiconductor optical device, in the region in which the first tapered portion 302 a and the second tapered portion 312 a overlap, adiabatic transition of the optical mode is made from the second optical waveguide defined by the second core 312 to the first optical waveguide defined by the first core 302, thereby enabling low-loss optical coupling.

[0028] 4A to 4D show the results of mode calculations of the light distribution in the first optical waveguide and the second optical waveguide of a conventional semiconductor optical device. In FIG. 4A, (a) is a plan view, and (b) shows the results of calculations of the mode distribution in a cross section parallel to the waveguiding direction when the misalignment is 0 μm and the taper length is 300 μm. In FIGS. 4B to 4D, (a) shows a cross section in the waveguiding direction, and (b) shows the results of calculations of the mode distribution. FIG. 4B shows the state of the region where only the second optical waveguide exists, FIG. 4C shows the state of the region where the first tapered portion 302a and the second tapered portion 312a overlap, and FIG. 4D shows the state of only the first optical waveguide.

[0029] According to the semiconductor optical device of the embodiment, as shown in Figures 2C and 2D, the optical mode field diameter in the third core 114 is sufficiently wide compared to the case shown in Figure 4B of the conventional semiconductor optical device, and therefore high tolerance is obtained for misalignment between the first optical waveguide (first core 102) and the second optical waveguide (second core 112).

[0030] Here, the optical device 110 includes an optical element 111 and a second core 112 including a second tapered portion 112a, which are fabricated using well-known element fabrication techniques such as photolithography, electron beam lithography, and etching. After fabricating the optical device 110 in this manner, a protective layer 113 is formed by depositing a low-refractive-index material such as SiON, SiO, or SiN using a plasma CVD method or the like. A first groove 113a and a second groove 113b are formed in the protective layer 113 using a photolithography and etching technique or the like to form a third core 114 with a predetermined core width. Therefore, the second optical waveguide (second core 112) and the third optical waveguide (third core 114) can be aligned with lithography precision, and coupling loss due to misalignment is negligible.

[0031] In contrast, misalignment occurs during transfer between the second optical waveguide of the optical device 110 and the first optical waveguide formed on the substrate 101. However, according to the first embodiment, tolerance to misalignment in the direction perpendicular to the light propagation direction (waveguiding direction) is increased, making it possible to achieve low-loss optical coupling.

[0032] 5 shows the results of calculating the optical coupling loss from the second optical waveguide to the first optical waveguide for a conventional semiconductor optical device (a) and a semiconductor optical device according to the first embodiment (b). The horizontal axis in Fig. 5 represents the displacement of the optical device in a direction perpendicular to the light propagation direction. The displacement is set to 0 μm when the centers (optical axes) of the first optical waveguide and the second optical waveguide are aligned.

[0033] In this calculation, the refractive index of the SiON constituting the protective layer was set to n=1.51, the refractive index of the Si constituting the core of the first waveguide was set to n=3.449, and the refractive index of the InP constituting the core of the second optical waveguide was set to n=3.2.

[0034] The core width of the second optical waveguide was 0.5 μm, and the tip width of the tapered portion was 0.08 μm. The core width of the first optical waveguide was 0.44 μm, and the tip width of the tapered portion was 0.08 μm. The thickness of the protective layer was 0.8 μm. The core width of the third optical waveguide, which was formed by two grooves formed in the protective layer, was 3.0 μm. The core thickness of the second optical waveguide was 250 nm, and the core thickness of the first optical waveguide was 220 nm. The wavelength used in the calculation was the 1.55 μm band. Note that by optimizing the dimensions of each optical waveguide and core, a similar structure can be fabricated in the 1.31 μm band.

[0035] As shown in FIG. 5, the amount of misalignment at which an optical coupling loss of 1 dB occurs is 0.9 μm in the conventional structure as shown in (b), whereas according to the embodiment, it can be expanded to 1.6 μm as shown in (a).

[0036] Furthermore, it is clear that even if there is a positional deviation (during transfer) in the light propagation direction, as long as it is within the range of the waveguide length of the third optical waveguide defined by the third core 114, it will not affect the optical coupling efficiency.

[0037] As described above, the semiconductor optical device according to the first embodiment can reduce loss caused by misalignment between optical waveguides in the transfer printing method.

[0038] Second Embodiment Next, a semiconductor optical device according to a second embodiment of the present invention will be described with reference to Fig. 6. This semiconductor optical device includes a substrate 101 that constitutes silicon photonics, and an optical device 110 that is transferred onto the substrate 101. The optical device 110 is transferred onto the substrate 101 by micro transfer printing.

[0039] The substrate 101 includes a first optical waveguide formed by a first core 102 embedded in the substrate 101. The first optical waveguide has the substrate 101 as a cladding. The first core 102 is made of Si. The first core 102 also has a first tapered portion 102a whose diameter decreases toward the tip in a first direction facing the side where the optical device 110 is disposed.

[0040] The optical device 110 includes an optical element 111 made of a compound semiconductor such as InP, GaAs, or InGaAs, a protective layer 113' formed to cover the optical element 111, and a second optical waveguide formed by a second core 112 connected to the optical element 111. The second optical waveguide has the protective layer 113' as a cladding. The optical element 111 may be, for example, a waveguide-type semiconductor laser or an optical modulator. For example, the second core 112 may be formed continuously with an active layer (not shown) of the waveguide-type semiconductor laser or optical modulator.

[0041] The second core 112 has a second tapered section 112a whose diameter decreases toward the tip in the direction of arrangement of the first optical waveguide (first core 102). The second core 112 including the second tapered section 112a is made of a compound semiconductor such as InP. The protective layer 113' is made of a material with a lower refractive index than the substrate 101 and the second core 112. The protective layer 113' can be made of an oxide or nitride with a low refractive index, such as SiON, SiO2, or SiN.

[0042] In addition, in this semiconductor optical device, the optical device 110 is transferred to the substrate 101 in a state in which the tip of the first core 102 (first tapered portion 102a) and the tip of the second core 112 (second tapered portion 112a) are spaced apart and face each other.

[0043] Furthermore, this semiconductor optical device includes a third optical waveguide formed by a third core 114. The third core 114 has a larger diameter than the first core 102 and the second core 112. The third optical waveguide is formed in a connection region 130 that includes a first region 131 in which the first tapered portion 102a is arranged, a second region 132 between the tip of the first core 102 and the tip of the second core 112, and a third region 133 in which the second tapered portion 112a is arranged.

[0044] In the second embodiment, the protective layer 113′ is formed in the third region 133. In the second embodiment, a low refractive index layer 115 is provided that is continuous with the protective layer 113′ and is formed in the second region 132 and the first region 132. The low refractive index layer 115 has a refractive index lower than that of the substrate 101 and the second core 112, and is made of a different material from that of the protective layer 113′.

[0045] For example, the low refractive index layer 115 may be formed on the optical device 110 together with the protective layer 113'. Alternatively, the low refractive index layer 115 may be formed after the optical device 110 is transferred to the substrate 101. For example, the protective layer 113' may be made of SiON, and the low refractive index layer 115 may be made of SiO x It can be composed of:

[0046] In the second embodiment, the third core 114 is composed of the protective layer 113′ in the third region 133 and the low refractive index layer 115 in the second region 132 and the first region 131. Therefore, the third core 114 in the first region 131 and the second region 132 has a lower refractive index than the substrate 101 and the second core 112 and is composed of a material different from the protective layer 113′.

[0047] The third core 114 is formed between a first groove 115a and a second groove 115b formed in the protective layer 113′ and the low refractive index layer 115. The first groove 115a and the second groove 115b sandwich the first optical waveguide and the second optical waveguide and are arranged parallel to the waveguiding directions of the first optical waveguide and the second optical waveguide.

[0048] The first optical waveguide and the second optical waveguide are optically connected via the third optical waveguide configured as described above. In the second embodiment, similarly to the state shown in Figures 2C and 2D in the first embodiment, the optical mode field diameter in the third core 114 is sufficiently wide, and therefore high tolerance can be obtained for misalignment between the first optical waveguide (first core 102) and the second optical waveguide (second core 112).

[0049] Third Embodiment Next, a semiconductor optical device according to a third embodiment of the present invention will be described with reference to Fig. 7 and Figs. 8A to 8E. This semiconductor optical device includes a substrate 101 that constitutes silicon photonics, and an optical device 110 that is transferred onto the substrate 101. The optical device 110 is transferred onto the substrate 101 by micro transfer printing.

[0050] The substrate 101 includes a first optical waveguide formed by a first core 102 embedded in the substrate 101. The first optical waveguide has the substrate 101 as a cladding. The first core 102 is made of Si. The first core 102 also has a first tapered portion 102a whose diameter decreases toward the tip in a first direction facing the side where the optical device 110 is disposed.

[0051] The optical device 110 includes an optical element 111 made of a compound semiconductor such as InP, GaAs, or InGaAs, a protective layer 113' formed to cover the optical element 111, and a second optical waveguide formed by a second core 112 connected to the optical element 111. The second optical waveguide has the protective layer 113' as a cladding. The optical element 111 may be, for example, a waveguide-type semiconductor laser or an optical modulator. For example, the second core 112 may be formed continuously with an active layer (not shown) of the waveguide-type semiconductor laser or optical modulator.

[0052] The second core 112 has a second tapered section 112a whose diameter decreases toward the tip in the direction of arrangement of the first optical waveguide (first core 102). The second core 112 including the second tapered section 112a is made of a compound semiconductor such as InP. The protective layer 113' is made of a material with a lower refractive index than the substrate 101 and the second core 112. The protective layer 113' can be made of an oxide or nitride with a low refractive index, such as SiON, SiO2, or SiN.

[0053] In addition, in this semiconductor optical device, the optical device 110 is transferred to the substrate 101 in a state in which the tip of the first core 102 (first tapered portion 102a) and the tip of the second core 112 (second tapered portion 112a) are spaced apart and face each other.

[0054] Furthermore, this semiconductor optical device includes a third optical waveguide formed by a third core 114. The third core 114 has a larger diameter than the first core 102 and the second core 112. The third optical waveguide is formed in a connection region 130 that includes a first region 131 in which the first tapered portion 102a is arranged, a second region 132 between the tip of the first core 102 and the tip of the second core 112, and a third region 133 in which the second tapered portion 112a is arranged.

[0055] In the third embodiment, the protective layer 113' is formed in the third region 133. In the third embodiment, an intermediate layer 115' is provided. The intermediate layer 115' has a lower refractive index than the substrate 101 and the second core 112 and is made of a material different from the protective layer 113'. In the third embodiment, the optical device 110 is transferred onto the substrate 101 via the intermediate layer 115'. The intermediate layer 115' is formed in the connection region 130 consisting of the first region 131, the second region 132, and the third region 133. In the third region 133, the intermediate layer 115' is disposed on the substrate 101, and the protective layer 113' is disposed on the intermediate layer 115'.

[0056] For example, the intermediate layer 115' may be formed on the optical device 110 together with the protective layer 113'. Alternatively, the intermediate layer 115' may be formed after the optical device 110 is transferred to the substrate 101. For example, the protective layer 113' may be made of SiON, and the intermediate layer 115' may be made of SiO x It can be composed of:

[0057] In the third embodiment, the third core 114 is made of an intermediate layer 115'. The third core 114 is made of the intermediate layer 115' in the connection region 130. Therefore, the third core 114 has a lower refractive index than the substrate 101 and the second core 112, and is made of a material different from the protective layer 113'.

[0058] The third core 114 is formed between a first groove 115'a and a second groove 115'b formed in the intermediate layer 115'. The two grooves, the first groove 115'a and the second groove 115'b, sandwich the first optical waveguide and the second optical waveguide in a plan view seen from the normal direction to the plane of the substrate 101 and are arranged parallel to the waveguiding directions of the first optical waveguide and the second optical waveguide.

[0059] The first optical waveguide and the second optical waveguide are optically connected via the third optical waveguide configured as described above.

[0060] The results of mode calculations of the light distribution in the first optical waveguide, the second optical waveguide, and the third optical waveguide of the semiconductor optical device according to the third embodiment will be described with reference to Figures 8B, 8C, and 8E. In this calculation, the core width of the third core 114, which is determined by the distance between the first groove 115'a and the second groove 115'b, is set to 3 µm, and the thickness of the third core 114 (intermediate layer 115') is set to 1 µm. The third core 114 (intermediate layer 115') is made of SiO x It consisted of.

[0061] 8B, 8C, and 8E, (a) shows a cross section in the waveguiding direction, and (b) shows the calculation results of the mode distribution. Fig. 8A shows the state of the third region 133, Fig. 8B shows the state at the tip of the second tapered portion 112a at the boundary between the third region 133 and the second region 132, Fig. 8C shows the state of the second region 132, Fig. 8D shows the state at the tip of the first tapered portion 102a at the boundary between the second region 132 and the first region 131, and Fig. 8E shows the state of the first region 131.

[0062] As shown in (b) of Fig. 8B, as the core width of the second tapered portion 112a of the second core 112 becomes narrower, the optical mode widens and leaks into the third core 114. As shown in Fig. 8C, in the second region 132 consisting only of the third core 114, the optical mode confined in the third core 114 has a mode field diameter of approximately 3.0 µm.

[0063] 8E , in the first region 131, as the core width of the first tapered portion 102a increases, the optical mode gradually transitions from the third core 114 to the first core 102 (first tapered portion 102a). By providing an intermediate layer 115′ and expanding the optical mode to the third optical waveguide formed by the third core 114 in the intermediate layer 115′, it is possible to achieve high tolerance for misalignment during transfer printing.

[0064] As described above, according to the embodiment of the present invention, since the third optical waveguide is formed by the third core having a diameter larger than the first and second cores in the first region where the first tapered portion is arranged and in the region including the region between the tip of the first core and the tip of the second core, it is possible to suppress a decrease in optical coupling efficiency due to misalignment in optical coupling between the semiconductor optical device and the substrate on which the optical circuit is formed. According to the embodiment of the present invention, in optical coupling between the semiconductor optical device and silicon photonics, a decrease in optical coupling efficiency due to misalignment is suppressed (the misalignment tolerance is improved to ±1.5 μm), and as a result, it is possible to realize improvements in yield and throughput in the transfer printing method.

[0065] It should be noted that the present invention is not limited to the embodiments described above, and it is clear that many modifications and combinations can be made by a person having ordinary knowledge in the art within the technical concept of the present invention.

[0066] 101...substrate, 102...first core, 102a...first tapered portion, 110...optical device, 111...optical element, 112...second core, 112a...second tapered portion, 113...protective layer, 113a...first groove, 113b...second groove, 114...third core, 130...connection region, 131...first region, 132...second region, 133...third region.

Claims

1. A substrate and an optical device transferred onto the substrate, wherein the substrate is formed by being embedded in the substrate and is provided with a first optical waveguide having a first core made of Si and having a first tapered portion whose diameter decreases toward the tip in the arrangement direction of the optical device, and the optical device is provided with an optical element made of a compound semiconductor, a protective layer formed to cover the optical element, and a second optical waveguide connected to the optical element and having a second core made of a compound semiconductor and having a second tapered portion whose diameter decreases toward the tip in the arrangement direction of the first optical waveguide, wherein the first optical waveguide has the substrate as a clad, and the second optical waveguide has the protective layer as a clad, and the optical device is transferred onto the substrate with the tip of the first core and the tip of the second core facing each other at a distance, a semiconductor optical device in which the first optical waveguide and the second optical waveguide are connected via a third optical waveguide made of a third core having a diameter larger than that of the first core and the second core, the third optical waveguide being formed in a connection region consisting of a first region in which the first tapered portion is arranged, a second region between the tip of the first core and the tip of the second core, and a third region in which the second tapered portion is arranged.

2. A semiconductor optical device according to claim 1, wherein the protective layer is made of a material having a lower refractive index than the substrate and the second core, and the third core is made of the protective layer in the connection region.

3. A semiconductor optical device according to claim 1, wherein the protective layer is made of a material having a lower refractive index than the substrate and the second core, the third core in the third region is made of the protective layer in the connection region, and the third core in the first region and the second region is made of a material different from the protective layer and having a lower refractive index than the substrate and the second core.

4. A semiconductor optical device according to claim 2 or 3, comprising two grooves formed in the protective layer in the connection region, arranged parallel to the waveguiding directions of the first optical waveguide and the second optical waveguide, with the first optical waveguide and the second optical waveguide sandwiched therebetween, and the third core formed between the two grooves.

5. A semiconductor optical device according to claim 1, further comprising an intermediate layer formed on the substrate and made of a material having a lower refractive index than the substrate and the second core, the optical device being transferred onto the substrate via the intermediate layer, and the third core being made of the intermediate layer in the connection region.

6. A semiconductor optical device according to claim 5, comprising two grooves formed in the protective layer in the connection region, arranged parallel to the waveguiding directions of the first optical waveguide and the second optical waveguide, with the first optical waveguide and the second optical waveguide sandwiched therebetween, and the third core formed between the two grooves.

7. A semiconductor optical device according to claim 5 or 6, wherein the substrate is made of SiO2, the protective layer is made of SiON, and the intermediate layer is made of SiOx.

8. A semiconductor optical device according to any one of claims 1 to 5, wherein the substrate is made of SiO2, and the protective layer is made of SiON.

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