Semiconductor optical element

Abstract

The present invention provides a semiconductor optical element that can achieve good characteristics and can be miniaturized. The semiconductor optical element includes: an SOI substrate having a silicon waveguide; and a gain region that is bonded to the SOI substrate, formed of a group III-V compound semiconductor, and has optical gain. The waveguide includes a bent portion and a plurality of straight portions. The plurality of straight portions are connected to each other via the bent portion and extend linearly, and the gain region is located on each of the plurality of straight portions.

Description

Technical Field

[0001] The present invention relates to a semiconductor optical element. Background Art

[0002] There is a known technique of bonding a gain region formed of a III-V compound semiconductor to an SOI (Silicon On Insulator) substrate (so-called silicon photon) on which a waveguide is formed (for example, Non-Patent Document 1). A waveguide, a resonator, etc. formed of silicon (Si) are provided on the SOI substrate. The III-V compound semiconductor is a direct transition type and has a high optical gain. Light emitted from the gain region propagates through the waveguide of the SOI substrate.

[0003] Non-Patent Document 1: M.A. Tran et al. “Ultra-low Noise Widely-Tunable Semiconductor Lasers Fully Integrated on Silicon”, Compound Semiconductor Week 2019, TuA3-1 Summary of the Invention

[0004] In order to narrow the line width, improve the monochromaticity of the laser, and achieve high output, a longer gain region is effective. However, since the gain region becomes longer, the semiconductor optical element also becomes larger. Here, an object is to provide a semiconductor optical element that can obtain good characteristics and can be miniaturized.

[0005] The semiconductor optical element of the present invention includes: an SOI substrate having a silicon waveguide; and a gain region bonded to the SOI substrate, formed of a III-V compound semiconductor, and having an optical gain, wherein the waveguide includes a bent portion and a plurality of straight portions, the plurality of straight portions are connected to each other via the bent portion and extend linearly, and the gain region is located on each of the plurality of straight portions.

[0006] Advantages of the Invention

[0007] According to the above invention, good characteristics can be obtained and miniaturization can be achieved. Description of the Drawings

[0008] Figure 1A It is a top view illustrating the semiconductor optical element of Embodiment 1. Figure 1B It is a top view with an enlarged gain region.

[0009] Figures 2A to 2D It is a cross-sectional view illustrating the semiconductor optical element.

[0010] Figure 3It is a top view of a semiconductor optical element showing a comparative example.

[0011] Figure 4A It is a top view of a semiconductor optical element showing Embodiment 2. Figure 4B It is a cross-sectional view of a semiconductor optical element.

[0012] Reference Numeral Explanation

[0013] 10, 12 Substrate

[0014] 11 Waveguide

[0015] 11a Bending Portion

[0016] 11b Straight Portion

[0017] 13 Groove

[0018] 14 SiO2 Layer

[0019] 16 Si Layer

[0020] 17, 30, 32 Electrode

[0021] 19 Ring Resonator

[0022] 20 Gain Region

[0023] 21, 23 Wedge Portion

[0024] 22 n-Type Semiconductor Layer

[0025] 24 Core Layer

[0026] 26 p-Type Semiconductor Layer

[0027] 30a, 32a Pad

[0028] 30b, 32b Connection Portion

[0029] 28, 34 Insulating Film

[0030] 100, 200 Semiconductor Optical Element Detailed Embodiment

[0031] [Description of Embodiments of the Present Invention]

[0032] First, the content of the embodiments of the present invention will be listed and explained.

[0033] One aspect of the present invention is (1) a semiconductor optical element including: an SOI substrate having a silicon waveguide; and a gain region bonded to the SOI substrate, formed of a III-V compound semiconductor, and having optical gain. The waveguide includes a bent portion and a plurality of straight portions. The plurality of straight portions are connected to each other via the bent portion and extend linearly. The gain region is located on each of the plurality of straight portions. By bending the waveguide, the semiconductor optical element can be miniaturized. In addition, good characteristics such as a narrow spectral line width and high output can be obtained through a plurality of gain regions.

[0034] (2) Alternatively, the bending angle of the waveguide may be 90° or more. The semiconductor optical element can be miniaturized.

[0035] (3) Alternatively, the semiconductor optical element may include a first insulating film provided on both sides of the bent portion. The refractive index difference between the bent portion and the first insulating film is large, and the light confinement is strong. Therefore, light loss in the bent portion can be suppressed.

[0036] (4) Alternatively, the semiconductor optical element may include a second insulating film covering the side surface of the gain region, and the width of the gain region is larger than the width of the waveguide. Compared with the waveguide, the light confinement in the gain region in the lateral direction is weak. The gain region is provided on the straight portion and does not bend, so light loss can be suppressed.

[0037] (5) Alternatively, the radius of curvature of the bent portion may be 10 μm or more. Thereby, the semiconductor optical element can be miniaturized.

[0038] (6) Alternatively, the waveguide may include three or more of the straight portions, and the gain region is located on each of the three or more straight portions. Thereby, good characteristics can be obtained and miniaturization can be achieved.

[0039] (7) Alternatively, the semiconductor optical element may include a first electrode and a second electrode provided on the SOI substrate. The gain region has an n-type semiconductor layer, a core layer, and a p-type semiconductor layer laminated in this order from the SOI substrate side. The n-type semiconductor layer, the core layer, and the p-type semiconductor layer are each formed of a III-V compound semiconductor. The first electrode is connected to the n-type semiconductor layer, and the second electrode is connected to the p-type semiconductor layer. Carriers can be injected into the core layer using the first electrode and the second electrode.

[0040] (8) Alternatively, each of the plurality of gain regions may include the core layer and the p-type semiconductor layer, the plurality of gain regions may share the n-type semiconductor layer, and the n-type semiconductor layer electrically connects the plurality of gain regions. The first electrode is disposed on the n-type semiconductor layer and has a first connection portion connected to the n-type semiconductor layer and a first pad portion. The first connection portion is located between the plurality of gain regions. The first pad portion is connected to the first connection portion and has a width larger than that of the first connection portion. The second electrode has a second connection portion and a second pad portion. The second connection portion is connected to the p-type semiconductor layer. The second connection portion is disposed on the p-type semiconductor layer of each of the plurality of gain regions. The second pad portion is connected to the second connection portion and has a width larger than that of the second connection portion. Carriers can be injected into the core layer using the first electrode and the second electrode. In addition, the resistance can be reduced by the first connection portion and the second connection portion.

[0041] (9) Alternatively, the gain region may have a wedge portion located on the waveguide. The efficiency of optical coupling between the gain region and the waveguide can be improved.

[0042] (10) Alternatively, the SOI substrate may have a resonator formed of silicon, and the resonator is optically coupled to the waveguide. The wavelength of light can be selected by the resonator.

[0043] [Details of Embodiments of the Present Invention]

[0044] Hereinafter, specific examples of the semiconductor optical element according to the embodiment of the present invention will be described with reference to the drawings. In addition, the present invention is not limited to these examples, but is shown by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0045] Example 1

[0046] Figure 1A is a top view illustrating the semiconductor optical element 100 of Example 1. Figure 1B is a magnified top view of the vicinity of the gain region. Figures 2A to 2D is a cross-sectional view illustrating the semiconductor optical element 100.

[0047] As Figure 1A and Figure 1B shown, the semiconductor optical element 100 is a hybrid wavelength-variable laser element having a substrate 10 and gain regions 20 and using silicon photonics. Three gain regions 20, two ring resonators 19, and electrodes 17, 30, and 32 are provided on the surface of the substrate 10. The surface of the semiconductor optical element 100 is covered with an insulating film (not shown).

[0048] As Figure 2AAs shown, the gain region 20 is located on the waveguide 11 and has an n-type semiconductor layer 22, a core layer 24, and a p-type semiconductor layer 26 stacked in sequence. As Figures 2A to 2D shown, the substrate 10 is a SOI substrate including a substrate 12, a silicon oxide (SiO2) layer 14, and a silicon (Si) layer 16 stacked in sequence. The thickness of the SiO2 layer 14 is, for example, 2 μm. The thickness of the Si layer 16 is, for example, 220 nm. In the Si layer 16 of the substrate 10, there are provided Figure 1A shown waveguide 11 and ring resonator 19. Coating for preventing light reflection is applied to the end face of the substrate 10. The length L1 of the semiconductor optical element 100 in the X-axis direction is, for example, 1700 μm, and the length L2 in the Y-axis direction is, for example, 600 μm.

[0049] As Figure 1A and Figure 1B shown, the waveguide 11 has a bent portion 11a and a straight portion 11b. The bent portion 11a is, for example, in a semi-circular arc shape. The bent portion 11a may also be a shape combining a clothoid and a raised cosine curve. From each end of the bent portion 11a, there is a straight portion 11b extending in the X-axis direction. The three straight portions 11b are arranged in the Y-axis direction, separated from each other, and connected to each other via the bent portion 11a. That is, in the region of the substrate 10 sandwiched by the two ring resonators 19, the waveguide 11 bent at 180° at the bent portion 11a is arranged.

[0050] The +Y side straight portion 11b among the three straight portions 11b branches into two near the -X side end of the substrate 10. These two waveguides 11 are optically coupled to the ring resonator 19 and reach the -X side end of the substrate 10. The -Y side straight portion 11b among the three straight portions 11b branches into two near the +X side end of the substrate 10. These two waveguides 11 are optically coupled to the ring resonator 19 and reach the +X side end of the substrate 10. Both ends of the central straight portion 11b among the three straight portions 11b are connected to the bent portion 11a.

[0051] A gain region 20 is joined to each of the three straight portions 11b, and no gain region 20 is joined to the bent portion 11a. One gain region 20 overlaps with and is optically coupled to one straight portion 11b. The gain region 20 has a linear shape extending in the X-axis direction in the same manner as the straight portion 11b. The length L3 of the gain region 20 in the X-axis direction is, for example, 800 μm.

[0052] The electrode 30 is an n-type ohmic electrode and has a pad 30a and three connection portions 30b. The electrode 32 is a p-type ohmic electrode and has a pad 32a and three connection portions 32b. The pad 30a is located on the -Y side of the three gain regions 20. The connection portion 30b is electrically connected to the pad 30a, adjacent to and separated from the gain region 20, and extends in the X-axis direction. The pad 32a is located on the +Y side of the three gain regions 20. The connection portion 32b is electrically connected to the pad 32a, is located on the gain region 20, and extends in the X-axis direction.

[0053] The electrode 30 is formed of a metal such as an alloy (AuGeNi) of gold, germanium, and Ni. The electrode 32 is, for example, a laminate (Ti / Pt / Au) of titanium, platinum, and gold. The thicknesses of the electrodes 30 and 32 are, for example, 1 μm. The widths of the pads 30a and 32a in the Y-axis direction are each, for example, 100 μm or more. The width of the connection portion 30b is, for example, 15 μm. A plating layer of Au or the like may be provided on the electrodes 30 and 32. The electrode 17 is provided on the ring resonator 19 and is formed of a metal such as Ti.

[0054] As Figure 1B shown, the gain region 20 and the n-type semiconductor layer 22 each have tapered portions 21 and 23. The tapered portions 21 and 23 are tapered at the front end along the X-axis direction and are located on the waveguide 11. The tapered portion 21 is provided at the end of the n-type semiconductor layer 22 in the X-axis direction. The tapered portion 23 is located above the tapered portion 21 and is provided at the ends of the core layer 24 and the p-type semiconductor layer 26 of the gain region 20 in the X-axis direction. The lengths of the tapered portions 21 and 23 are each, for example, 150 μm, and the width of the front end is 0.4 μm. Tapered portions 21 and 23 are also provided on the -X side end side of the gain region 20.

[0055] Figure 2A is a cross-sectional view along Figure 1A the line A-A. Figure 2B is a cross-sectional view along Figure 1A the line B-B. Figure 2C is a cross-sectional view along Figure 1A the line C-C. Figure 2D is a cross-sectional view along Figure 1A the line D-D.

[0056] As Figure 2A shown, a waveguide 11 and a groove 13 are provided in the Si layer 16 of the substrate 10. The groove 13 is located on both sides of one waveguide 11 in the Y-axis direction. The width W2 of the waveguide 11 and the width of the groove 13 are each, for example, 1 μm. The SiO2 layer 14 may be exposed in the groove 13, or the bottom surface of the groove 13 may be formed in the Si layer 16. In the portion of the waveguide 11 that overlaps with the gain region 20, the side surface of the waveguide 11 is exposed in the air.

[0057] An insulating film 34 is provided on the surface of the substrate 10. As Figures 2B to 2D shown, the portion of the waveguide 11 that does not overlap with the gain region 20 is covered by the insulating film 34, and both sides are buried by the insulating film 34. As Figure 2B and Figure 2C shown, an insulating film 34 is interposed between the pads 30a, 32a and the waveguide 11, and the pads and the waveguide 11 do not contact. As Figure 2D shown, the side surface and the upper surface of the bent portion 11a of the waveguide 11 are covered by the insulating film 34. The bent portion 11a may or may not overlap with the pad.

[0058] As Figure 2A shown, the gain region 20 is located on the waveguide 11 and has an n-type semiconductor layer 22, a core layer 24, and a p-type semiconductor layer 26 stacked in sequence. The width W1 in the Y-axis direction of the core layer 24 and the p-type semiconductor layer 26 of one gain region 20 is, for example, 2 μm. The n-type semiconductor layer 22 is provided on three waveguides 11 and is shared by three gain regions 20. The three gain regions 20 are electrically connected through the n-type semiconductor layer 22. The side surfaces of the core layer 24 and the p-type semiconductor layer 26 are covered by the insulating film 28. The distance D1 between the insulating films 28 is, for example, 20 μm.

[0059] The n-type semiconductor layer 22 is formed of, for example, n-type indium phosphide (n-InP) with a thickness of 0.3 μm. The core layer 24 includes, for example, a plurality of well layers and barrier layers formed of undoped gallium indium arsenide phosphide (i-GaInAsP) and has a multi-quantum well structure (MQW: Multi-Quantum Well). The thickness of the core layer 24 is, for example, 0.3 μm. The p-type semiconductor layer 26 is formed of, for example, p-InP with a thickness of 2 μm. Alternatively, the p-type semiconductor layer 26 may further include a layer of p-type gallium indium arsenide (p-GaInAs) on the upper part of the p-InP. The insulating films 28, 34 are formed of an insulator such as SiO2, for example. The thickness of the insulating film 28 is, for example, 0.5 μm, and the thickness of the insulating film 34 is, for example, 1.5 μm.

[0060] As Figure 2A shown, the pad 30a and the connecting portion 30b are provided on the surface of the n-type semiconductor layer 22 and are electrically connected to the n-type semiconductor layer 22. As Figure 2B and Figure 2C shown, the pads 30a, 32a are located on the surface of the insulating film 34 and are separated from the waveguide 11. As Figure 2A shown, the connecting portion 32b is provided on the surface of the p-type semiconductor layer 26 and is electrically connected to the p-type semiconductor layer 26.

[0061] Each gain region 20 has a pin structure along the Z-axis direction. By applying voltages to the electrodes 30 and 32, carriers are injected into the core layer 24 of the three gain regions 20 to emit light. The light propagates in the waveguide 11 and is incident on the ring resonator 19. The ring resonator 19 reflects a part of the light back to the gain region 20 side and allows a part to pass through. Light can be emitted from any one of the four waveguides 11 that reach the end of the substrate 10. The radii of the two ring resonators 19 are different from each other, and the reflection spectra are also different. The wavelength at which the reflection peaks of the two ring resonators 19 coincide becomes the oscillation wavelength. The electrode 17 functions as a heater that generates heat by the input of electricity. By changing the temperature of the ring resonator 19 through the electrode 17, the refractive index of the ring resonator 19 is changed, and the oscillation wavelength can be changed, for example, within a range of 40 nm. The oscillation wavelength is, for example, 1550 nm ± 20 nm.

[0062] A method for manufacturing the semiconductor optical element 100 will be described. The waveguide 11 and the ring resonator 19 are formed on the surface of the wafer-shaped substrate 10. An optical circuit such as a modulator may also be provided on the substrate 10. On the wafer of the compound semiconductor, a p-type semiconductor layer 26, a core layer 24, and an n-type semiconductor layer 22 are sequentially epitaxially grown by, for example, organometallic vapor phase epitaxy (OMVPE: Organometallic Vapor Phase Epitaxy). The wafer is cut and a plurality of chips are formed. For example, by irradiating plasma on the surfaces of the chip and the substrate 10, activation is performed and the chip is bonded to the substrate 10. The chip is etched to form Figure 1A and Figure 2A the gain region 20 as shown. The wafer is cut to obtain a plurality of semiconductor optical elements 100.

[0063] Figure 3 is a top view of the semiconductor optical element 100C of the comparative example. The waveguide 11 of the semiconductor optical element 100C does not have a bent portion, extends in the X-axis direction, and is optically coupled to the ring resonator 19. The semiconductor optical element 100C has one gain region 40.

[0064] In order to narrow the line width and obtain a higher optical output, the gain region 40 is made longer. For example, in order to obtain a line width and an optical output of the same degree as those of the three gain regions 20 of the first embodiment through one gain region 40, the length L6 of the gain region 40 is longer than the length L3 of the first embodiment, for example, 2400 μm. In order to accommodate the longer gain region 40, the length L4 of the substrate 10 in the X-axis direction is greater than the length L1 of the first embodiment, for example, 3300 μm. The length L5 of the substrate 10 in the Y-axis direction is, for example, the same as L2, which is 600 μm. In such a comparative example, the semiconductor optical element 100C is enlarged. As a result, the number of semiconductor optical elements obtained from one wafer becomes smaller, and the cost increases.

[0065] On the other hand, according to Embodiment 1, the waveguide 11 includes a bent portion 11a and a straight portion 11b. Each of the three straight portions 11b is joined to the gain region 20. Through the three gain regions 20, a narrower linewidth and a higher optical output comparable to those of a single longer gain region 40 can be obtained. The waveguide 11 is bent, so that the semiconductor optical element 100 can be miniaturized.

[0066] As Figure 1A and Figure 1B shown, the waveguide 11 turns back at 180° at the bent portion 11a to form a Z shape. As a result, three straight portions 11b can be arranged in parallel on the substrate 10. The three gain regions 20 are arranged in parallel in the same manner as the straight portions 11b. As a result, the semiconductor optical element 100 can be effectively miniaturized. Specifically, the length L3 of one gain region 20 is about 1 / 3 of the length L6 of the gain region 40. The length L1 of the semiconductor optical element 100 in the X-axis direction can be made about half of the length L4 of the comparative example. Therefore, the size of the semiconductor optical element 100 can be reduced to about 50% of that of the comparative example. The number of semiconductor optical elements 100 obtained from one wafer can be increased to 1.4 times, etc., and the cost can be reduced.

[0067] The waveguide 11 is formed of Si. As Figure 2A shown, both sides of the portion of the waveguide 11 that overlaps with the gain region 20 are exposed to air. As Figures 2B to 2D shown, the other portions of the waveguide 11 are exposed in the insulating film 34. The refractive index of Si is about 3.5, the refractive index of air is 1, and the refractive index of the SiO2 insulating film 34 is about 1.5. The refractive index difference between the waveguide 11 and the outside is large, and the optical confinement of the waveguide 11 is strong. Therefore, the optical loss in the waveguide 11 including the bent portion 11a is small.

[0068] The insulating film 34 on both sides of the bent portion 11a can be formed of an insulator such as SiN x (x represents the composition), polymer, etc. In order to enhance the optical confinement, an insulating film with a large refractive index difference from Si is preferably used. Both sides of the bent portion 11a can also be exposed to air. Both sides of the portion of the waveguide 11 that overlaps with the gain region 20 can also be buried in the insulating film 34.

[0069] The radius of curvature of the bent portion 11a is, for example, 50 μm, and the distance between the straight portions 11b can be reduced. Therefore, the semiconductor optical element 100 can be effectively miniaturized. The radius of curvature can also be 50 μm or less, 30 μm or less, 20 μm or less, and 10 μm or more. By reducing the radius of curvature, miniaturization can be achieved. In addition, the optical confinement of the waveguide 11 is strong, so that optical loss can be suppressed even when the radius of curvature is small.

[0070] On the other hand, the gain region 20 is formed of a group III-V compound semiconductor. The refractive index of the group III-V compound semiconductor is lower than that of Si, and the refractive index difference between the gain region 20 and the side insulating film 28 is smaller than the refractive index difference between Si and the insulating film. The lateral optical confinement is weak. Therefore, if the gain region 20 is bent with a small radius of curvature, the optical loss increases. In the first embodiment, the gain region 20 is linear, and the waveguide 11 is bent. Thereby, the optical loss is suppressed.

[0071] If the core layer 24 and the p-type semiconductor layer 26 of the gain region 20 are formed into a narrow high mesa structure and the sides are exposed to air with a small refractive index, the increase in loss caused by bending with a small radius of curvature can be suppressed. However, the core layer 24 of the high mesa structure processed to the same degree as the waveguide 11 is likely to deteriorate over time during continuous long-term carrier injection. The gain region 20 exposed to air is also likely to deteriorate over time from the sides of the MQW. The width of the gain region 20 in the first embodiment is larger than that of the waveguide 11, and the sides are covered with the insulating film 28, so it is not likely to deteriorate over time. On the other hand, the lateral optical confinement is weak, and the loss caused by bending becomes large. In order to suppress the increase in optical loss, the radius of curvature becomes 200 μm or more, making it difficult to miniaturize. In the first embodiment, by bending the waveguide 11 with strong optical confinement and making the plurality of gain regions 20 linear, it is possible to achieve both suppression of optical loss and miniaturization.

[0072] The gain region 20 has a pin structure including an n-type semiconductor layer 22, a core layer 24, and a p-type semiconductor layer 26. Carriers can be injected into the core layer 24 by applying a voltage to the electrodes 30 and 32 to cause it to emit light.

[0073] The three gain regions 20 share the n-type semiconductor layer 22. The pads 30a of the electrode 30 and the connection portions 32b are provided at the pads 30a and the connection portions 30b connected to the n-type semiconductor layer 22. The electrode 32 has a pad 32a and a connection portion 32b. The connection portion 32b is located on each gain region 20 and is connected to the p-type semiconductor layer 26. Carriers can be injected into each of the plurality of gain regions 20 separately by applying a voltage between one of the pads 30a and 32a to cause it to emit light. Compared with the case where a pair of pads 30a and 32a are provided in the gain region 20 respectively, the semiconductor optical element 100 can be miniaturized.

[0074] A metal connection portion 30b is provided between the gain regions 20, and wide pads 30a and 32a are provided on the substrate 10. Thereby, the heat dissipation performance is improved and the resistance is also reduced. In addition, as Figure 2AAs shown, the pad 30a of the electrode 30 is connected to the n-type semiconductor layer 22. Therefore, even without providing the connecting portion 30b that extends adjacent to the gain region 20, light emission of the gain region 20 can be achieved.

[0075] If light migrates to the metal electrodes 30 and 32, significant light loss occurs. It is preferred that the electrodes 30 and 32 do not contact the waveguide 11. As Figure 2B and Figure 2C shown, the waveguide 11 is covered with the insulating film 34 to prevent contact with the electrodes.

[0076] The gain region 20 and the n-type semiconductor layer 22 each have wedge portions 21 and 23 with a width as narrow as 0.4 μm at the front end. Therefore, the light coupling efficiency between the gain region 20 and the waveguide 11 is increased to 90% or more. The gain region 20 and the n-type semiconductor layer 22 may not have the wedge portions 21 and 23, or either one may have a wedge portion. If the wedge portions are omitted, the light coupling efficiency decreases, but the processing of the narrow front end can be omitted, making the manufacturing easier.

[0077] The number of the straight portions 11b and the gain regions 20 can be three, two, or four or more, respectively. By increasing their number, the semiconductor optical element 100 can be made more compact. However, even when the coupling efficiency is 90%, light is lost in the coupling portion between the gain region 20 and the waveguide 11. Therefore, as the number of the straight portions 11b and the gain regions 20 increases, the coupling portions also increase, and the light loss also increases. The number of the straight portions 11b and the gain regions 20 is determined in a manner that balances miniaturization and suppression of light loss. The waveguide 11 is optically coupled to the ring resonator 19. Therefore, a wavelength can be selected in the miniaturized semiconductor optical element 100. Instead of the ring resonator 19, a diffraction grating type distributed reflector formed of the silicon waveguide 11 may be provided for wavelength selection. Additionally, instead of causing the two waveguides 11 to reach the +X side end of the substrate 10, the two waveguides 11 may be connected to a curved waveguide such as a loop mirror waveguide that returns light.

[0078] Embodiment 2

[0079] Figure 4A is a top view illustrating the semiconductor optical element 200 of Embodiment 2. Figure 4B is a cross-sectional view illustrating the semiconductor optical element 200 and shows the cross-section along Figure 4A line E - E. Description of the same structure as in Embodiment 1 is omitted.

[0080] As Figure 4AAs shown, the waveguide 11 has two bent portions 11a and three straight portions 11b. The bent portion 11a corresponds to 1 / 4 of a circular arc and is connected to the straight portion 11b at both ends. The bending angle of the waveguide 11 is 90°. Two of the three straight portions 11b extend in the X-axis direction. One end of these two straight portions 11b is optically coupled to the ring resonator 19 near the -X side end of the substrate 10, and the other end is connected to the bent portion 11a. One of the three straight portions 11b extends in the Y-axis direction. Both ends of this one straight portion 11b are connected to the bent portion 11a. Linear-shaped gain regions 20 are joined to the three straight portions 11b respectively. No gain region 20 is joined to the bent portion 11a.

[0081] As Figure 4A shown, electrodes 30 and 32 are provided at positions surrounded by the three straight portions 11b on the substrate 10. As Figure 4B shown, the electrode 32 is located on the +X side compared to the electrode 30 and is provided from the insulating film 34 to the gain region 20. According to Embodiment 2, by bending the waveguide 11 at 90°, similarly to Embodiment 1, the size of the semiconductor optical element 200 can be reduced to about 50% of that of the comparative example.

[0082] The waveguide 11 of Embodiment 1 has a shape that bends at 180° and reciprocates in the X-axis direction. The waveguide 11 of Embodiment 2 has a U-shaped that bends at 90° and extends in the X-axis and Y-axis directions. The waveguide 11 may have a shape other than these. In order to miniaturize the semiconductor optical element, it is preferable that the bending angle of the waveguide 11 is 90° or more.

[0083] As described above, the embodiments of the present invention have been described in detail, but the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims.

Claims

1. A semiconductor optical element, wherein, Comprising: An SOI substrate having a waveguide made of silicon; and A gain region bonded to the SOI substrate, formed of a III-V compound semiconductor, and having optical gain, The waveguide includes a bent portion and a plurality of straight portions, and the plurality of straight portions are connected to each other via the bent portion and extend linearly, The gain region is located on each of the plurality of straight portions, The semiconductor optical element includes a first electrode and a second electrode provided on the SOI substrate, The gain region has an n-type semiconductor layer, a core layer, and a p-type semiconductor layer laminated in sequence from the SOI substrate side, The n-type semiconductor layer, the core layer, and the p-type semiconductor layer are each formed of a III-V compound semiconductor, The first electrode is connected to the n-type semiconductor layer, and the second electrode is connected to the p-type semiconductor layer, Each of the plurality of gain regions has the core layer and the p-type semiconductor layer, The plurality of gain regions share the n-type semiconductor layer, and the n-type semiconductor layer electrically connects the plurality of gain regions, The first electrode is provided on the n-type semiconductor layer and has a plurality of first connection portions and one first pad portion connected to the n-type semiconductor layer, The first connection portions are located between the plurality of gain regions, The first pad portion is connected to the first connection portion and has a width larger than that of the first connection portion, The second electrode has a plurality of second connection portions and one second pad portion, and the second connection portions are connected to the p-type semiconductor layer, The second connection portions are provided on the p-type semiconductor layer of each of the plurality of gain regions, The second pad portion is connected to the second connection portion and has a width larger than that of the second connection portion, Carriers can be injected into each of the plurality of gain regions by applying a voltage between one of the first pad portion and the second pad portion.

2. The semiconductor optical element according to claim 1, wherein The bending angle of the waveguide is 90° or more.

3. The semiconductor optical element according to claim 1 or 2, wherein The semiconductor optical element includes a first insulating film provided on both sides of the bent portion.

4. The semiconductor optical element according to claim 1 or 2, wherein The semiconductor optical element includes a second insulating film covering the side surface of the gain region, The width of the gain region is greater than the width of the waveguide.

5. The semiconductor optical element according to claim 1 or 2, wherein The radius of curvature of the bent portion is 10 μm or more.

6. The semiconductor optical element according to claim 1 or 2, wherein The waveguide includes three or more of the straight portions, The gain region is located on each of the three or more straight portions.

7. The semiconductor optical element according to claim 1 or 2, wherein The gain region has a wedge portion located on the waveguide.

8. The semiconductor optical element according to claim 1 or 2, wherein The SOI substrate has a resonator made of silicon, and the resonator is optically coupled to the waveguide.

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