Semiconductor Optical Devices

Abstract

This semiconductor optical device comprises: a first cladding layer (102) formed above a Si substrate (101); a core (103) formed on the first cladding layer (102); and a second cladding layer (104) formed over the first cladding layer (102) by covering the core (103). A lower cladding layer (106) comprising SiO2 or the like is formed on (the surface of) the Si substrate (101), and the first cladding layer (102) is formed on the lower cladding layer (106). The first cladding layer (102) is constituted from a material having thermal conductivity higher than that of a direct transition-type semiconductor. A refractive index of the first cladding layer (102) is set higher than that of the second cladding layer (104) and lower than that of the core (103). In an optical coupling region of an optical waveguide formed by the core (103), a cross-section shape of the core (103) is in a state in which a substrate radiation mode is manifested.

Description

[Technical field]

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

[0002] Si photonics is a technology that integrates electronic and optical devices on a large-diameter Si substrate using CMOS technology. Because Si is an indirect transition semiconductor, its light emission efficiency is extremely low, making it difficult to use Si as a light-emitting device. For this reason, III-V compound semiconductors such as GaAs and InP, which are direct transition semiconductors with high light emission efficiency, are used as optical devices.

[0003] For example, according to Non-Patent Document 1, as a Si photonics optical device, it is possible to fabricate a laser structure on a SiO2 / Si substrate by bonding an InP substrate to a SiO2 / Si substrate. Substrate bonding techniques include hydrophilic bonding and surface activated bonding. A layer of insulating material such as SiO2 is used at the bonding interface in these bonding methods.

[0004] In a membrane laser structure on a SiO2 / Si substrate, the refractive index of the Si substrate is higher than that of the upper cladding medium, and is comparable to that of the active layer medium. Therefore, in order to obtain high optical confinement in the active layer, it is necessary to design the SiO2 thickness to be on the order of several μm, so that the guided mode is not distributed in the Si substrate. For example, in a membrane laser structure on a SiO2 / Si substrate, the active layer is sandwiched between layers of low refractive index medium, so a high optical confinement coefficient is obtained. As a result, a directly modulated laser with high efficiency and low power consumption has been realized (Non-Patent Document 1).

[0005] However, in the above laser structure, the thermal conductivity of SiO2 is low, so the heat dissipation effect in the active layer is small, which causes a large temperature rise due to current injection, and the optical output and modulation speed become saturated with a relatively small bias current.

[0006] To solve this problem, it has been proposed to fabricate a laser on a heat-dissipating substrate that has a lower refractive index and higher thermal conductivity than the core. For example, a laser structure has been fabricated using a SiC substrate, which has a higher thermal conductivity and a smaller refractive index than Si or InP, and the heat dissipation characteristics of the laser active layer are improved. As a result, a directly modulated laser with a 60 GHz bandwidth has been realized, since it is possible to inject more current than in conventional structures (Non-Patent Document 3). [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] T. Fujii, T. Sato, K. Takeda, K. Hasebe, T. Kakitsuka, and S. Matsuo, "Epitaxial growth of InP to bury directly bonded thin active layer on SiO2 / Si substrate for fabricating distributed feedback lasers on silicon", IET Optoelectronics, vol. 9, no. 4, pp. 151-157, 2015. [Non-Patent Document 2] W. Kobayashi, T. Ito, T. Yamanaka, T. Fujisawa, Y. Shibata, T. Kurosaki, M. Kohtoku, T. Tadokoro, and H. Sanjoh, "50-Gb / s direct modulation of a 1.3-μm InGaAlAs-based DFB laser with a ridge waveguide structure", IEEE Journal of Selected Topics in Quantum Electronics, vol. 19, no. 4, pp. 1500908-1500908, 2013. [Non-Patent Document 3] S. Yamaoka, N. -P. Diamantopoulos, H. Nishi, R. Nakao, T. Fujii, K. Takeda, T. Hiraki, T. Tsurugaya, S. Kanazawa, H. Tanobe, T. Kakitsuka, T. Tsuchizawa, F. Koyama, and S. Matsuo, "Directly modulated membrane lasers with 108GHz bandwidth on a high-thermal-conductivity silicon carbide "substrate", Nature Photonics, vol. 15, pp. 28-35, 2021. Summary of the Invention [Problem to be solved by the invention]

[0008] Incidentally, while lasers formed on heat-dissipating substrates are expected to have extremely excellent operating characteristics as standalone optical elements, with the current structure it is difficult to optically couple the optical output from the laser on the heat-dissipating substrate to the Si optical waveguide embedded in the SiO2 of the SiO2 / Si substrate, making its application to Si photonics a challenge.

[0009] As mentioned above, by forming a laser on a highly heat-dissipating layer, the amount of current that can be injected into the semiconductor laser section increases due to the high heat dissipation in the active layer, so high optical output, high-speed modulation, and high-temperature operation can be expected. However, simply placing a laser on a heat-dissipating layer is not sufficient for application to Si photonics. For example, it is necessary to optically couple the optical output from the laser on the highly heat-dissipating layer to a Si optical waveguide with high efficiency, separating it from the layer with high heat dissipation, which is several μm to several tens of μm thick. However, there is a problem in that such optical coupling is not easy.

[0010] The present invention has been made to solve the above problems, and aims to make it easier to obtain optical coupling between an optical element and a Si optical waveguide, which are arranged across a highly heat-dissipating layer. [Means for solving the problem]

[0011] The semiconductor optical device of the present invention comprises a first cladding layer formed on a Si substrate and made of a material having a higher thermal conductivity than a direct transition semiconductor, a core made of a direct transition semiconductor formed on the first cladding layer, and a second cladding layer formed on the first cladding layer to cover the core, wherein the refractive index of the first cladding layer is higher than that of the second cladding layer and lower than that of the core, and in the optical coupling region of the optical waveguide formed by the core, the cross-sectional shape of the core is in a state in which a substrate radiation mode is expressed. Effect of the Invention

[0012] As described above, according to the present invention, optical coupling between an optical element and a Si optical waveguide, which are arranged across a layer with high heat dissipation properties, can be more easily achieved. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a cross-sectional view showing a configuration of a semiconductor optical device according to an embodiment of the present invention. [Figure 2A] FIG. 2A is a cross-sectional view showing the configuration of a semiconductor laser used to examine the heat dissipation characteristics of a semiconductor optical device according to an embodiment. [Figure 2B] FIG. 2B is a characteristic diagram showing the results of an investigation into the heat dissipation characteristics of the semiconductor optical device according to the embodiment. [Figure 3A] FIG. 3A is a distribution diagram showing the calculation results of the profile of the substrate radiation mode in the optical waveguide formed by the core 103 when the rib structure 105 is not provided (detch=0 μm). [Figure 3B]FIG. 3B is a distribution diagram showing the calculation results of the profile of the substrate radiation mode in the optical waveguide formed by the core 103 when the thickness of the rib structure 105 is set to 0.1 μm (detch=0.1 μm). [Figure 3C] FIG. 3C is a distribution diagram showing the calculation results of the profile of the substrate radiation mode in the optical waveguide formed by the core 103 when the thickness of the rib structure 105 is set to 0.2 μm (detch=0.2 μm). [Figure 4A] FIG. 4A is a distribution diagram showing the calculation results of the profile of the substrate radiation mode in an optical waveguide using core 103 with a core width of 0.5 μm. [Figure 4B] FIG. 4B is a distribution diagram showing the calculation results of the profile of the substrate radiation mode in the optical waveguide using the core 103 with a core width of 0.4 μm. [Figure 4C] FIG. 4C is a distribution diagram showing the calculation results of the profile of the substrate radiation mode in the optical waveguide using the core 103 with a core width of 0.3 μm. [Figure 5A] FIG. 5A is a distribution diagram showing the calculation results of the profile of the substrate radiation mode in an optical waveguide using core 103 with a core width of 0.5 μm. [Figure 5B] FIG. 5B is a distribution diagram showing the calculation results of the profile of the substrate radiation mode in the optical waveguide using the core 103 with a core width of 0.4 μm. [Figure 5C] FIG. 5C is a distribution diagram showing the calculation results of the profile of the substrate radiation mode in the optical waveguide using the core 103 with a core width of 0.3 μm. [Figure 6] FIG. 6 is a cross-sectional view showing a configuration of another semiconductor optical device according to an embodiment of the present invention. [Figure 7A] FIG. 7A is a distribution diagram showing the calculation results of the mode profile when the core width of core 103 is 0.7 μm and the core width of lower core 107 is 0.3 μm. [Figure 7B] FIG. 7B is a distribution diagram showing the calculation results of the mode profile when the core width of core 103 is 0.5 μm and the core width of lower core 107 is 0.3 μm. [Figure 7C] FIG. 7C is a distribution diagram showing the calculation results of the mode profile when the core width of core 103 is set to 0.3 μm and the core width of lower core 107 is set to 0.3 μm. [Figure 7D] FIG. 7D is a distribution diagram showing the calculation results of the mode profile when the core width of core 103 is 0.3 μm and the core width of lower core 107 is 0.35 μm. [Figure 7E] FIG. 7E is a distribution diagram showing the calculation results of the mode profile when the core width of core 103 is 0.3 μm and the core width of lower core 107 is 0.4 μm. [Figure 8] FIG. 8 is a distribution diagram showing a calculation of mode transition from the optical waveguide based on the core 103 to the optical waveguide based on the lower core 107 when no rib structure is provided. [Figure 9] FIG. 9 is a cross-sectional view showing a configuration of another semiconductor optical device according to an embodiment of the present invention. [Figure 10] FIG. 10 is a cross-sectional view showing the configuration of another semiconductor optical device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] A semiconductor optical device according to an embodiment of the present invention will be described below with reference to Fig. 1. This semiconductor optical device comprises a first cladding layer 102 formed on a Si substrate 101, a core 103 formed on the first cladding layer 102, and a second cladding layer 104 formed on the first cladding layer 102 to cover the core 103. In this example, a lower cladding layer 106 made of SiO2 or the like is formed on the top (surface) of the Si substrate 101, and the first cladding layer 102 is formed on the lower cladding layer 106.

[0015] The first cladding layer 102 is made of a material having a higher thermal conductivity than a direct transition semiconductor. The core 103 is made of a direct transition semiconductor. The core 103 can be made of a III-V group compound semiconductor such as InP or InGaAsP. The core 103 is formed in connection with an active layer of a semiconductor laser not shown in FIG. 1. Laser light oscillated by the semiconductor laser is guided through the optical waveguide formed by the core 103.

[0016] In this semiconductor optical device, the refractive index of the first cladding layer 102 is higher than that of the second cladding layer 104 and lower than that of the core 103. The first cladding layer 102 can be made of, for example, SiC, AlN, GaN, diamond, etc. The second cladding layer 104 can be made of, for example, SiO2 or SiO x It can be composed of the following:

[0017] In the optical coupling region of the optical waveguide by the core 103, the cross-sectional shape of the core 103 is in a state in which the substrate radiation mode is expressed. FIG. 1 shows a cross section of the optical coupling region of this semiconductor optical device. For example, the width of the core 103 in the planar direction of the Si substrate 101 is made smaller as it approaches the optical coupling region. By making the width of the core 103 (core width) smaller, do By this, it is possible to realize a substrate radiation mode. As an example, the core width of the core 103 in the optical coupling region can be set to 0.3 μm, and the thickness can be set to 0.32 μm. The thickness of the core 103, 0.32 μm, is approximately the upper limit value at which the light with a wavelength of 1.31 μm propagating in the active layer becomes a single mode in the thickness direction of the active layer.

[0018] By using the substrate radiation mode, the laser light guided through the optical waveguide made of the core 103 can be coupled to the optical waveguide made of the lower core formed under the first cladding layer 102 (not shown in Fig. 1). The optical waveguide made of the lower core arranged under the first cladding layer 102 is arranged so as to overlap with the core 103 in the optical coupling region. For example, the lower core may be made of Si and embedded in the lower cladding layer 106. The optical waveguide made of the lower core is arranged in a range in the optical coupling region where it can be optically coupled to the optical waveguide made of the core 103.

[0019] In this example, the first cladding layer 102 in the optical coupling region has a rib structure 105 that is thickened in a convex shape on the surface, and the core 103 is formed on the rib structure 105. For example, the first cladding layer 102 is etched using a resist pattern formed by a known lithography technique as a mask, thereby forming the rib structure 105. The etching depth d etch is the thickness of the rib structure 105.

[0020] The provision of the rib structure 105 improves the optical confinement in the lateral direction of the substrate radiation mode, and the above-mentioned coupling of light by the substrate radiation mode can be performed more efficiently. Furthermore, in the optical coupling region, by forming a first grating coupler in the core 103 and forming a second grating coupler in the lower core disposed below the above-mentioned first cladding layer 102, the above-mentioned optical coupling can be realized more efficiently. The first grating coupler formed in the core 103 allows the laser light guided through the optical waveguide of the core 103 to be emitted to the side of the Si substrate 101. The light thus emitted is coupled to the second grating coupler formed in the lower core.

[0021] For example, a core 103 and a semiconductor laser connected to the core 103 are fabricated on a substrate to be the first cladding layer 102, and a rib structure 105 is formed, and then SiO2 is deposited to cover these to form the second cladding layer 104. Next, the substrate is thinned from the back side to form the first cladding layer 102, and then bonded to a Si substrate 101 on which a lower cladding layer 106 is formed. In this way, a semiconductor optical device according to the embodiment can be fabricated. For example, an optical waveguide using a lower core or the like can be formed in the lower cladding layer 106 before bonding.

[0022] Next, the results of an investigation into the heat dissipation characteristics of the above-mentioned configuration will be described. In this investigation, a semiconductor laser whose cross section is shown in FIG. 2A was used. In this semiconductor laser, a lower cladding layer 306 made of SiO2 is formed on a Si substrate 301, and a SiC layer with a thickness of d SiC A first cladding layer 302 is formed.

[0023] Also, on the first cladding layer 302, there is provided a so-called membrane laser structure made up of an active layer 303, and a p-InP layer 307 and an n-InP layer 308 arranged on either side of the active layer 303. The active layer 303 has a multiple quantum well structure made of, for example, InGaAlAs or InGaAsP. In addition, in the region sandwiched between the p-InP layer 307 and the n-InP layer 308, the upper surface of the active layer 303 is covered with a semiconductor layer 309 made of non-doped InP.

[0024] A second cladding layer 304 made of SiO2 is formed on the active layer 303, the p-InP layer 307, and the n-InP layer 308. A p-electrode 311 is ohmic-connected to the p-InP layer 307, and an n-electrode 312 is ohmic-connected to the n-InP layer 308.

[0025] The active layer 303 is a core-shaped layer having a core width of 0.7 μm and a thickness of 0.33 μm. FIG. 2B shows the thermal resistance d of a semiconductor laser with an active layer length of 50 μm in the waveguiding direction. SiCThe heat source was placed only on the p-InP layer 307 and had a power of 100 mW. SiC It is clear that the thermal resistance value decreases as the thickness of the first cladding layer made of SiC increases. This indicates that the amount of current injected into the semiconductor laser can be increased as the thickness of the first cladding layer made of SiC increases, and the modulation bandwidth can be increased by increasing the relaxation oscillation frequency.

[0026] Next, a mode profile centered on the optical waveguide formed by the core 103 will be described.

[0027] First, the effect of the rib structure 105 will be described with reference to Figures 3A, 3B, and 3C. Figure 3A shows a case where the rib structure 105 is not provided (d etch FIG. 3B shows the calculation results of the profile of the substrate radiation mode in the optical waveguide with the core 103 when the thickness of the rib structure 105 is 0.1 μm (d etch FIG. 3C shows the calculation results of the profile of the substrate radiation mode in the optical waveguide formed by the core 103 when the thickness of the rib structure 105 is set to 0.2 μm (d etch 1 shows the calculation results of the profile of the substrate radiation mode in the optical waveguide with the core 103 when the axial length is set to 0.2 μm.

[0028] The lower cladding layer 106 is made of SiO2, the first cladding layer 102 is made of SiC, the core 103 is made of InP, and the second cladding layer 104 is made of SiO x The core 103 had a core width of 0.3 μm and a thickness of 0.25 μm. The first cladding layer 102 had a thickness of 2 μm, and the lower cladding layer 106 had a thickness of 1 μm. A location 2 μm away in the planar direction from the formation position of the core 103 was etched to form a rib structure 105.

[0029] As shown in Figures 3A, 3B, and 3C, the guided mode is a substrate radiation mode. In addition, when the rib structure 105 is formed, the lateral light confinement of the first cladding layer 102 by SiC is strengthened. Therefore, the use of the rib structure 105 allows light to be more effectively coupled to the optical waveguide by the lower core.

[0030] Next, the relationship between the core width of the core 103 and the substrate radiation mode will be described with reference to Figures 4A, 4B, and 4C. Figure 4A shows the calculation results of the profile of the substrate radiation mode in an optical waveguide using the core 103 with a core width of 0.5 μm. Figure 4B shows the calculation results of the profile of the substrate radiation mode in an optical waveguide using the core 103 with a core width of 0.4 μm. Figure 4c shows the calculation results of the profile of the substrate radiation mode in an optical waveguide using the core 103 with a core width of 0.3 μm.

[0031] The lower cladding layer 106 is made of SiO2, the first cladding layer 102 is made of SiC, the core 103 is made of InP, and the second cladding layer 104 is made of SiO2. x The core 103 had a thickness of 0.25 μm. The first cladding layer 102 had a thickness of 2 μm, and the lower cladding layer 106 had a thickness of 1 μm. A location 2 μm away in the planar direction from the formation position of the core 103 was etched to form a rib structure 105, and the thickness of the rib structure 105 was 2 μm.

[0032] As shown in Fig. 4A, when the core width is 0.5 μm, the mode is distributed in the optical waveguide formed by the core 103. In contrast, as shown in Fig. 4B and Fig. 4C, when the core width is 0.4 μm and 0.3 μm, the substrate radiation mode is obtained. Therefore, by setting the core width to about 0.5 μm in the region other than the optical coupling region and gradually decreasing this width toward the optical coupling region, it is possible to gradually radiate to the substrate during the mode propagation of the optical waveguide formed by the core 103.

[0033] Next, the relationship between the core width of the core 103 and the substrate radiation mode when the first cladding layer 102 is made thicker will be described with reference to Figures 5A, 5B, and 5C. In this example, the thickness of the first cladding layer 102 made of SiC is set to 5 μm.

[0034] Fig. 5A shows the calculation results of the substrate radiation mode profile in an optical waveguide with a core 103 having a core width of 0.5 μm. Fig. 5B shows the calculation results of the substrate radiation mode profile in an optical waveguide with a core 103 having a core width of 0.4 μm. Fig. 5c shows the calculation results of the substrate radiation mode profile in an optical waveguide with a core 103 having a core width of 0.3 μm.

[0035] Thus, even if the first cladding layer 102 is made thicker, as shown in the results of Figures 4A, 4B, and 4C, substrate radiation occurs as the core width of the core 103 becomes narrower. This calculation result also shows that the use of the rib structure 105 confines the mode in the lateral direction in the first cladding layer 102. Note that by reducing the thickness as well as the width of the core 103, the substrate radiation mode occurs more efficiently.

[0036] Next, optical coupling to the optical waveguide by the lower core will be described. The following description will be given taking the semiconductor optical device shown in FIG. 6 as an example. This semiconductor optical device includes a lower cladding layer 106 formed on a Si substrate 101, a first cladding layer 102 formed on the lower cladding layer 106, a core 103 formed on the first cladding layer 102, and a second cladding layer 104 formed on the first cladding layer 102 to cover the core 103. In addition, a rib structure 105 is formed in the first cladding layer 102. These configurations are the same as those of the semiconductor optical device described with reference to FIG. 1.

[0037] In this example, a lower core 107 is provided on the Si substrate 101 below the first cladding layer 102 and embedded in the lower cladding layer 106. The lower core 107 is made of, for example, Si. Note that Fig. 6 shows a cross section of the optical coupling region of the semiconductor optical device.

[0038] 7A, 7B, 7C, 7D, and 7E show the mode profile calculation results for this semiconductor optical device, calculated by changing the core width of the core 103 and the core width of the lower core 107. The core 103 is made of InP, the lower core 107 is made of Si, the first cladding layer 102 is made of SiC, and the second cladding layer 104 is made of SiO x and the lower cladding layer 106 is made of SiO2.

[0039] FIG. 7A shows the calculation result of the mode profile when the core width of the core 103 is 0.7 μm and the core width of the lower core 107 is 0.3 μm. FIG. 7B shows the calculation result of the mode profile when the core width of the core 103 is 0.5 μm and the core width of the lower core 107 is 0.3 μm. FIG. 7C shows the calculation result of the mode profile when the core width of the core 103 is 0.3 μm and the core width of the lower core 107 is 0.3 μm. FIG. 7D shows the calculation result of the mode profile when the core width of the core 103 is 0.3 μm and the core width of the lower core 107 is 0.35 μm. FIG. 7E shows the calculation result of the mode profile when the core width of the core 103 is 0.3 μm and the core width of the lower core 107 is 0.4 μm.

[0040] As shown in Figures 7A, 7B, 7C, 7D, and 7E, by making the core width of core 103 and the core width of lower core 107 smaller, the mode transition is efficient from the optical waveguide formed by core 103 to the optical waveguide formed by lower core 107.

[0041] Fig. 8 shows mode transition from the optical waveguide of core 103 to the optical waveguide of lower core 107 when no rib structure is provided. In this calculation, the core width of core 103 is set to 0.5 µm, and the core width of lower core 107 is set to 0.3 µm. Compared to the case where the rib structure is used, the mode in first cladding layer 102 spreads in the lateral direction. For this reason, the efficiency of mode transition from the optical waveguide of core 103 to the optical waveguide of lower core 107 is reduced.

[0042] Next, a configuration in which a semiconductor laser is integrated will be described with reference to FIG. 9. FIG. 9 shows a schematic cross section parallel to the waveguide level. A semiconductor laser 112 made of an active layer 111 having a multiple quantum well structure is formed on a first cladding layer 102, and a core 103 is formed optically connected to the semiconductor laser 112. The semiconductor laser 112 is, for example, a distributed feedback (DFB) laser. The semiconductor laser 112 and the core 103 are covered by a second cladding layer 104. The core 103 has a gradually narrower core width from the coupling point with the semiconductor laser 112 to the optical coupling region 121.

[0043] Furthermore, in the lower cladding layer 106, a lower core 107 is formed in an optical coupling region 121 so as to vertically overlap the core 103. The lower core 107 extends from the optical coupling region 121 in a direction away from the semiconductor laser 112. In the extending region of the lower core 107, for example, the first cladding layer 102 and the second cladding layer 104 are not formed.

[0044] In the optical waveguide of the core 103 in the optical coupling region 121, where the core width is small, for example, 0.3 μm, the waveguide mode becomes a substrate radiation mode, and can be coupled to the optical waveguide of the lower core 107. Also, in the optical coupling region 121, the core width of the lower core 107 is made smaller than other regions, for example, 0.3 μm. Therefore, the waveguide mode transitions from the optical waveguide of the core 103 to the optical waveguide of the lower core 107.

[0045] Also, an optical feedback section 113 is formed at a predetermined location in the extension region away from the optical coupling region 121 in the waveguiding direction of the lower core 107. The optical feedback section 113 can be, for example, a DBR using a diffraction grating or a gap. Also, the optical feedback section 113 can be formed by Fresnel reflection in the optical waveguide of the lower core 107.

[0046] The semiconductor laser 112 interacts with a Fabry-Perot type resonance mode formed in the optical feedback section 113, and a photon-photon resonance phenomenon (photon-photon resonance: PPR) occurs under the condition that the phase matching condition is satisfied. This PPR enables the semiconductor laser 112 to have a broadband.

[0047] In addition, it is possible to control the phase by providing a heater 114 on the lower cladding layer 106 at a location where the optical feedback section 113 is formed and adjusting the temperature in the optical feedback section 113. For example, the lower cladding layer 106 made of SiO2 has low thermal conductivity, making it possible to efficiently adjust the temperature of the optical feedback section 113.

[0048] 10, in the optical coupling region 121, by forming a first grating coupler 115 in the core 103 and a second grating coupler 116 in the lower core 107, the above-mentioned optical coupling can be realized more efficiently. The first grating coupler 115 formed in the core 103 allows the laser light guided through the optical waveguide of the core 103 to be emitted toward the Si substrate 101. This emitted light is coupled to the second grating coupler 116 formed in the lower core 107. The coupled laser light is guided in the direction in which the lower core 107 extends.

[0049] As described above, according to the semiconductor optical device of the embodiment, it is possible to couple light from the semiconductor laser 112 formed on the first cladding layer 102 having high heat dissipation properties to the Si optical waveguide formed by the lower core 107 via the optical waveguide formed by the core 103, and thus a laser operating at a wide bandwidth and high temperature can be applied to Si photonics.

[0050] As described above, in the present invention, a first cladding layer made of a material having a higher thermal conductivity than a direct transition semiconductor is formed on a Si substrate, a core made of a direct transition semiconductor is formed on the first cladding layer, the refractive index of the first cladding layer is made lower than that of the core, and the cross-sectional shape of the core is set to a state in which the substrate radiation mode is expressed in the optical coupling region of the optical waveguide by the core. As a result, according to the present invention, optical coupling between an optical element arranged across a layer having high heat dissipation properties and a Si optical waveguide can be more easily obtained.

[0051] It should be noted that the present invention is not limited to the above-described embodiments, and it is apparent 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. [Explanation of symbols]

[0052] 101...Si substrate, 102...first cladding layer, 103...core, 104...second cladding layer, 105...rib structure, 106...lower cladding layer.

Claims

1. a first cladding layer formed on a Si substrate and made of a material having a higher thermal conductivity than a direct transition semiconductor; a core made of a direct band gap semiconductor formed on the first cladding layer; a second clad layer formed on the first clad layer and covering the core; Equipped with The refractive index of the first cladding layer is higher than that of the second cladding layer and lower than that of the core; In an optical coupling region of the optical waveguide by the core, a cross-sectional shape of the core is set in a state in which a substrate radiation mode is expressed, the first cladding layer in the optical coupling region has a rib structure that is thickened in a convex shape on a surface thereof; The semiconductor optical device according to claim 1, wherein the core is formed on the rib structure.

2. 2. The optical device according to claim 1, 2. A semiconductor optical device comprising: a core having a width in a plane direction of the Si substrate, the width of the core being gradually reduced as it approaches the optical coupling region.

3. 3. The optical device according to claim 1, a lower core formed on the Si substrate under the first cladding layer; The optical waveguide formed of the core is arranged in the optical coupling region so as to be optically coupled to the optical waveguide formed of the lower core. A semiconductor optical device comprising:

4. 4. The optical device according to claim 3, a first grating coupler formed in the core in the optical coupling region; a second grating coupler formed in the lower core in the optical coupling region; The semiconductor optical device further comprises:

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