Optical coupling module

Abstract

To provide an optical coupling module capable of improving performance metrics. [Solution] The optical coupling module 1 comprises a substrate 30, a first optical waveguide 10 arranged in a first direction D1 in the planar direction of the substrate 30, and an optical semiconductor element 20 having a plurality of layers and arranged on the first optical waveguide 10, the optical semiconductor element 20 having a first optical coupling portion 211 facing the tip of the first optical waveguide 10 in the stacking direction D3 of the optical coupling module 1 which is orthogonal to the first direction D1, wherein in the first direction D1, the first tip E1 of the first optical coupling portion 211 is narrower than the first base end B1, and the tip of the first optical waveguide 10 is configured as a second optical coupling portion 11 that can be optically coupled with the first optical coupling portion 211, wherein in the first direction D1, the second optical coupling portion 11 is narrow on the side of the first tip E1, is widest between the first tip E1 and the first base end B1, and is narrow on the side of the first base end B1.

Description

Technical Field

[0001] The present disclosure relates to an optical coupling module.

Background Art

[0002] In recent years, increasing the speed of optical communication devices has become a trend. It is predicted that existing surface-type PDs (Photodiodes) will not be able to cope with future speed increases. As one solution, waveguide PDs are expected. There has been a problem that fabrication of a waveguide PD in a photonic integrated circuit (PIC) composed of a III-V group semiconductor is costly. Accordingly, a technique of integrating a waveguide PD on a Si-PIC fabricated by silicon photonics through a heterogeneous bonding process has attracted attention.

[0003] Conventionally, a technique related to an optical coupling module in which an optical waveguide such as a Si waveguide and a waveguide-type optical semiconductor element are heterogeneously bonded is known. For example, Patent Document 1 discloses an optical waveguide apparatus that provides an optical waveguide circuit with high optical coupling efficiency between an optical waveguide having a small spot size and a waveguide-type optical functional component.

Prior Art Literature

Patent Documents

[0004]

Patent Document 1

Summary of Invention

Problem to be Solved by the Invention

[0005] In a heterogeneous bonding PD, the optical coupling efficiency between the Si waveguide and the waveguide PD, the optical absorption efficiency in an active layer, for example, an absorption layer, within the waveguide PD, and the like are important performance indicators. The conventional technique described in Patent Document 1 leaves room for further improvement regarding these performance indicators.

[0006] This disclosure aims to provide an optical coupling module capable of improving performance metrics. [Means for solving the problem]

[0007] The means to achieve the above objectives are as follows:

[0008] (1) An optical coupling module, circuit board and A first optical waveguide is arranged in a first direction in the planar direction on the substrate, An optical semiconductor element having multiple layers and arranged on the first optical waveguide, the optical semiconductor element having a first optical coupling portion facing the tip of the first optical waveguide in the stacking direction of the optical coupling module which is orthogonal to the first direction, Equipped with, The first optical coupling portion has a first tip that is narrower than the first base in the first direction. The tip of the first optical waveguide is configured as a second optical coupling portion that can be optically coupled to the first optical coupling portion. The second photocoupler is narrower at the first tip end in the first direction, widest between the first tip end and the first base end, and narrower at the first base end end. Optical coupling module.

[0009] (2) The optical coupling module described in (1) above, The first optical coupling portion has a first tapered structure directed toward the first tip side. Optical coupling module.

[0010] (3) The optical coupling module described in (2) above, The second photocoupler has a reverse taper structure and a second taper structure in sequence from the first tip side to the first base side. Optical coupling module.

[0011] (4) The optical coupling module described in (3) above, The first tip in the first tapered structure and the second base in the reverse tapered structure are positioned at the same location relative to each other in the first direction. Optical coupling module.

[0012] (5) The optical coupling module described in (3) or (4) above, The second tip of the second tapered structure is located inside the optical semiconductor element in the first direction, compared to the first base. Optical coupling module.

[0013] (6) An optical coupling module as described in any one of (3) to (5) above, The first taper angle from the first tip to the first base of the first tapered structure is greater than the second taper angle from the second base of the inverse tapered structure to the second tapered structure. Optical coupling module.

[0014] (7) An optical coupling module as described in any one of (1) to (6) above, The system further comprises one or more second optical waveguides, which are located at a position offset from the center of the active layer of the optical semiconductor element in a second direction perpendicular to the first direction in the planar direction, and are located inside the optical semiconductor element in the first direction compared to the second optical coupling portion, and are spaced apart from the first optical waveguide. Optical coupling module.

[0015] (8) The optical coupling module described in (7) above, The pair of second optical waveguides are arranged symmetrically with respect to a central axis along the first direction, which is located at the center in the second direction. Optical coupling module.

[0016] (9) The optical coupling module described in (8) above, The pair of second optical waveguides are arranged parallel to each other. Optical coupling module.

[0017] (10) The optical coupling module according to the above (8) or (9), comprising: The pair of the second optical waveguides are arranged at the same height as the first optical waveguide in the stacking direction orthogonal to the first direction and the second direction, A center of the first optical waveguide in the second direction overlaps with the central axis, The optical coupling module. ADVANTAGEOUS EFFECTS OF INVENTION

[0018] According to the present disclosure, an optical coupling module capable of improving performance indicators can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] [Figure 1] FIG. 1 is a first schematic diagram illustrating an example configuration of an optical coupling module according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a second schematic diagram illustrating an example configuration of an optical coupling module according to an embodiment of the present disclosure. [Figure 3] FIG. 2 is a schematic top view showing the first optical coupling portion alone of the optical semiconductor element in FIG. 1. [Figure 4] FIG. 2 is a schematic top view showing the first optical waveguide alone in FIG. 1. [Figure 5] FIG. 2 is a schematic top view showing the pair of second optical waveguides alone in FIG. 1. [Figure 6] FIG. 4 is a graph diagram illustrating a change in light intensity in an optical coupling module according to an example of the present disclosure. [Figure 7A] FIG. 5 is a first electric field distribution diagram of light for optical coupling modules according to an example and a comparative example. [Figure 7B] FIG. 6 is a second electric field distribution diagram of light for optical coupling modules according to an example and a comparative example. MODE FOR CARRYING OUT THE INVENTION

[0020] Hereinafter, one embodiment of the present disclosure will be mainly described with reference to the accompanying drawings.

[0021] Figure 1 is a first schematic diagram showing an example of the configuration of an optical coupling module 1 according to one embodiment of the present disclosure. Figure 1 schematically shows the appearance of each component of the optical coupling module 1 when viewed from above. Components that are overlapped with other components and not visible from above are shown as transparently with dashed lines as necessary. Figure 2 is a second schematic diagram showing an example of the configuration of an optical coupling module 1 according to one embodiment of the present disclosure. Figure 2 schematically shows the appearance of each component of the optical coupling module 1 when viewed from the front in cross-section of the optical coupling module 1.

[0022] Referring to Figures 1 and 2, an example of the configuration of an optical coupling module 1 according to one embodiment of this disclosure will be mainly described. The optical coupling module 1 has as major components a first optical waveguide 10 and an optical semiconductor element 20.

[0023] In the optical coupling module 1, the first optical waveguide 10 and the optical semiconductor element 20 are optically coupleable to each other. In this disclosure, "optically coupleable" means that light can be transferred from one optical transmission medium to the other between two optical transmission media located at different spatial positions.

[0024] For example, in the optical coupling module 1, the first optical waveguide 10 and the optical semiconductor element 20 are optically coupled to each other by evanescent light. Evanescent light refers to the wave generated near the interface of the photomedium when light undergoes total internal reflection at the boundary between a material with a high refractive index and a material with a low refractive index. Optical coupling by evanescent light makes it possible for light to propagate without the optical waveguides directly touching each other.

[0025] In the optical coupling module 1, for example, most of the incident light L propagating through the first optical waveguide 10 may transition from the first optical waveguide 10 to the optical semiconductor element 20 and propagate inside the optical semiconductor element 20. That is, light may propagate from the first optical waveguide 10 toward the optical semiconductor element 20. In this case, the optical semiconductor element 20 may function as a semiconductor photodetector that detects the incident light L propagating through the first optical waveguide 10.

[0026] Alternatively, in the optical coupling module 1, for example, most of the emitted light propagating through the optical semiconductor element 20 may transition from the optical semiconductor element 20 to the first optical waveguide 10 and propagate within the first optical waveguide 10. That is, light may propagate from the optical semiconductor element 20 toward the first optical waveguide 10. In this case, the optical semiconductor element 20 may function as a semiconductor light-emitting element that outputs light toward the first optical waveguide 10.

[0027] In the following, the configuration of the optical coupling module 1 will be described in detail based on the example in which light propagates from the first optical waveguide 10 to the optical semiconductor element 20, one of the two examples described above. The optical semiconductor element 20 of the optical coupling module 1 will be described as, for example, a semiconductor photodetector that detects incident light L propagating through the first optical waveguide 10. However, the same description applies even if the optical semiconductor element 20 functions as a semiconductor light-emitting element that outputs light toward the first optical waveguide 10.

[0028] As shown in Figure 2, the optical coupling module 1 has a substrate 30 as its bottom layer. The optical coupling module 1 has a BOX layer (Buried Oxide Layer) 40 laminated on the substrate 30. The first optical waveguide 10 of the optical coupling module 1 is laminated on the BOX layer 40. The optical semiconductor element 20 of the optical coupling module 1 is heterojunction with the first optical waveguide 10 via an interface layer 50 formed by directly joining a layer located on the first optical waveguide 10 side and a layer located on the optical semiconductor element 20 side. The optical semiconductor element 20 has a laminated structure. The optical coupling module 1 has at least one second optical waveguide 60. For example, the optical coupling module 1 has a pair of second optical waveguides 60.

[0029] In addition, the optical coupling module 1 has a cladding layer 70 that covers the entire first optical waveguide 10 and the optical semiconductor element 20 from above. As shown in Figure 2, the cladding layer 70 covers the entire optical semiconductor element 20 from above. Note that in Figure 1, the cladding layer 70 is omitted for the sake of simplicity. However, in reality, the cladding layer 70 covers not only the entire optical semiconductor element 20 but also the entire first optical waveguide 10 from above.

[0030] The optical coupling module 1 has a stacked structure as a whole, based on the above-mentioned multiple components.

[0031] As shown in Figure 1, the first optical waveguide 10 is positioned in a first direction D1 in the planar direction on the substrate 30. In this disclosure, "first direction D1" refers to, for example, the direction along the propagation direction of the incident light L. For example, the first direction D1 corresponds to the up and down direction in Figure 1. The first optical waveguide 10 is located on the incident side of the incident light L in the optical coupling module 1. The tip of the first optical waveguide 10 overlaps with the optical semiconductor element 20 in the stacking direction of the optical coupling module 1. The tip of the first optical waveguide 10 is configured as a second optical coupling portion 11 that can be optically coupled to the first optical coupling portion 211 of the optical semiconductor element 20, which will be described later. The stacking direction corresponds to the "third direction D3" described in the claims. The third direction D3 refers to, for example, the direction perpendicular to the substrate 30 in a cross section perpendicular to the first direction D1.

[0032] The first optical waveguide 10 receives incident light L that enters the optical coupling module 1 from another optical element such as an optical fiber, and propagates it internally along the first direction D1. The first optical waveguide 10 optically couples the incident light L that has propagated internally with the optical semiconductor element 20 at the second optical coupling section 11. As an example, the light propagates from the bottom to the top of Figure 1.

[0033] Examples of materials that constitute the first optical waveguide 10 include Si. As shown in Figure 2, the cross-sectional shape of the first optical waveguide 10 in a cross section perpendicular to the first direction D1 is, for example, rectangular. As shown in Figure 1, the first optical waveguide 10 has a continuous linear structure along the first direction D1, and has an arrowhead-like rhombic shape at the second optical coupling portion 11 at its tip.

[0034] As shown in Figure 2, the optical semiconductor device 20 has multiple layers and is arranged on the first optical waveguide 10. The optical semiconductor device 20 has a first layer 21 on which an interface layer 50 is arranged on the face facing the first optical waveguide 10. Examples of materials that make up the first layer 21 include InP. The optical semiconductor device 20 has a second layer 22 stacked on the first layer 21. Examples of materials that make up the second layer 22 include InGaAs. The optical semiconductor device 20 has a third layer 23 stacked on the second layer 22. Examples of materials that make up the third layer 23 include InP. The optical semiconductor device 20 has a fourth layer 24 stacked on the third layer 23. Examples of materials that make up the fourth layer 24 include InGaAsP.

[0035] The optical semiconductor device 20 has a fifth layer 25 stacked on the fourth layer 24. Examples of materials constituting the fifth layer 25 include InGaAs. The fifth layer 25 functions as an active layer in the optical semiconductor device 20. The fifth layer 25 acts as an absorption layer, absorbing incident light L that is optically coupled from the first optical waveguide 10 and propagates through the interior of the optical semiconductor device 20. The optical semiconductor device 20 has a sixth layer 26 stacked on the fifth layer 25. Examples of materials constituting the sixth layer 26 include InGaAsP. The optical semiconductor device 20 has a gold electrode 27 stacked on the sixth layer 26.

[0036] For example, the laminated structure from the second layer 22 to the gold electrode 27 has a width w1 in the second direction D2. In this disclosure, "second direction D2" refers to a direction orthogonal to the first direction D1 and the third direction D3, for example. For example, the first direction D1, the second direction D2, and the third direction D3 are orthogonal to each other. For example, the second direction D2 corresponds to the left-right direction in Figure 2. For example, the third direction D3 corresponds to the up-down direction in Figure 2. The first layer 21 has a width w2 in the second direction D2. As an example, the first layer 21 is configured to be wider in the second direction D2 than the laminated structure from the second layer 22 to the gold electrode 27, such that its width w2 is greater than its width w1.

[0037] The width w1 in the second direction D2 of the laminated structure from the second layer 22 to the gold electrode 27 may be in the range of 0.5 μm to 10 μm, preferably 1 μm to 6 μm, and more preferably 2 μm to 5 μm. The width w2 in the second direction D2 of the first layer 21 may be in the range of 5 μm to 1000 μm, preferably 6 μm to 500 μm, and more preferably 10 μm to 100 μm.

[0038] As shown in Figure 1, the optical semiconductor element 20 has a first optical coupling portion 211 that faces the tip of the first optical waveguide 10 in the third direction D3, which is the stacking direction of the optical coupling module 1 that is orthogonal to the first direction D1. The first optical coupling portion 211 faces the tip of the first optical waveguide 10 by protruding in the first direction D1 along the first optical waveguide 10. The first optical coupling portion 211 is located only in the first InP layer 21 in the stacked structure of the optical semiconductor element 20 shown in Figure 2, for example. The first optical coupling portion 211 is constructed, for example, by making a part of the end face of the first layer 21 in the first direction D1 protrude outward in the first direction D1.

[0039] As shown in Figure 1, in the first direction D1, the first optical coupling portion 211 has a first tip E1 that is narrower than the first base B1. For example, the first optical coupling portion 211 has a first tapered structure directed toward the first tip E1. The first optical coupling portion 211 gradually tapers from the end face of the first layer 21 in the first direction D1, located at the first base B1, toward the incident side of the incident light L. The width of the first optical coupling portion 211 in the second direction D2 decreases monotonically from the first base B1 toward the first tip E1.

[0040] The second optical coupling portion 11 of the first optical waveguide 10 is narrower in the first direction D1 at the first tip E1 side of the first optical coupling portion 211, widest between the first tip E1 and the first base end B1 of the first optical coupling portion 211, and narrower at the first base end B1 side of the first optical coupling portion 211. The second optical coupling portion 11 has a reverse taper structure and a second taper structure sequentially from the first tip E1 side of the first optical coupling portion 211 to the first base end B1 side of the first optical coupling portion 211.

[0041] The second optical coupler 11 is located on the first tip E1 side of the first optical coupler 211 and gradually widens from the end of the linear structure of the first optical waveguide 10 toward the first base end B1 side of the first optical coupler 211. The width of the second optical coupler 11 in the second direction D2 increases monotonically from the end of the linear structure of the first optical waveguide 10 toward the center of the first direction D1 of the second optical coupler 11. The second optical coupler 11 gradually tapers from the center of the first direction D1 toward the first base end B1 side of the first optical coupler 211. The width of the second optical coupler 11 in the second direction D2 decreases monotonically from the center of the first direction D1 toward the first base end B1 side of the second optical coupler 11.

[0042] The first tip E1 of the first tapered structure of the first optical coupling portion 211 and the second base end B2 of the inverse tapered structure of the second optical coupling portion 11 are positioned at the same location in the first direction D1. The second tip E2 of the second tapered structure of the second optical coupling portion 11 is located inside the optical semiconductor element 20 in the first direction D1, compared to the first base end B1 of the first optical coupling portion 211.

[0043] The central axis of the first optical coupling portion 211 along the first direction D1 coincides, for example, with the central axis of the second optical coupling portion 11 along the first direction D1. The first optical coupling portion 211 and the second optical coupling portion 11 are arranged such that their centers coincide along the second direction D2. Each of the first optical coupling portion 211 and the second optical coupling portion 11 is configured to be symmetric with respect to the central axis in the second direction D2.

[0044] The first taper angle of the first tapered structure of the first photocoupler 211, from the first tip E1 to the first base B1, is greater than the second taper angle of the inverse tapered structure of the second photocoupler 11, from the second base B2 to the second tapered structure. When viewed along the first direction from the first tip E1 to the first base B1, the first tapered structure of the first photocoupler 211 widens at a larger angle than the inverse tapered structure of the second photocoupler 11. Therefore, even if the width in the second direction D2 at the first tip E1 of the first photocoupler 211 is smaller than the width in the second direction D2 at the second base B2 of the first photocoupler 211, the first tapered structure of the first photocoupler 211 widens immediately in the second direction D2 compared to the inverse tapered structure of the second photocoupler 11, and overlaps with most of the inverse tapered structure of the second photocoupler 11 from above.

[0045] As shown in Figure 2, the substrate 30 is the base member located at the bottom layer in the optical coupling module 1. Examples of materials that make up the substrate 30 include Si. The BOX layer 40 is placed between the substrate 30 and the first optical waveguide 10. Examples of materials that make up the BOX layer 40 include SiO2. The interface layer 50 is formed by directly joining, for example, a layer placed on the first optical waveguide 10 side and a layer placed on the optical semiconductor element 20 side. Examples of materials that make up the interface layer 50 include SiO2.

[0046] As shown in Figure 1, the second optical waveguide 60 is positioned on the substrate 30 in a first direction D1. The second optical waveguide 60 is positioned offset from the center of the fifth layer 25, which is the active layer of the optical semiconductor element 20, in a second direction D2 that is perpendicular to the first direction D1 in the planar direction. The pair of second optical waveguides 60 are positioned symmetrically with respect to the central axis along the first direction D1, which is located at the center. The pair of second optical waveguides 60 are positioned symmetrically with respect to the first optical waveguide 10 along the second direction D2. The center of the second direction D2 located between the pair of second optical waveguides 60 coincides with the center of the second direction D2 of the first optical waveguide 10. The center of the second direction D2 of the first optical waveguide 10 coincides with the central axis along the first direction D1. The pair of second optical waveguides 60 are positioned parallel to each other.

[0047] The second optical waveguide 60 is positioned in the first direction D1, inside the second optical coupling portion 11 of the first optical waveguide 10, and spaced apart from the first optical waveguide 10. One end of the second optical waveguide 60 in the first direction D1 is located between the second tip E2 of the second optical coupling portion 11 of the first optical waveguide 10 and the first base end B1 of the first optical coupling portion 211 of the optical semiconductor element 20. The other end of the second optical waveguide 60 in the first direction D1 is located near the inner end of the gold electrode 27 in the first direction D1.

[0048] Examples of materials that make up the second optical waveguide 60 include Si. As shown in Figure 2, the cross-sectional shape of the second optical waveguide 60 in a cross section perpendicular to the first direction D1 is, for example, rectangular. The pair of second optical waveguides 60 are arranged at the same height as the first optical waveguide 10 in a third direction D3 perpendicular to the first direction D1 and the second direction D2. As shown in Figure 1, the second optical waveguide 60 has a continuous linear structure along the first direction D1.

[0049] The cladding layer 70 covers the first optical waveguide 10 and the optical semiconductor element 20 on the substrate 30. In the optical coupling module 1, the first optical waveguide 10 and the optical semiconductor element 20 are arranged on the substrate 30. The cladding layer 70 is arranged to cover the periphery of the first optical waveguide 10 and the optical semiconductor element 20. Examples of materials that make up the cladding layer 70 include SiO2.

[0050] Figure 3 is a schematic diagram showing the first optical coupling portion 211 of the optical semiconductor device 20 in Figure 1 in a top view. The configuration of the first optical coupling portion 211 of the optical semiconductor device 20 will be explained in more detail with reference to Figure 3.

[0051] The first base end B1 of the first optical coupler 211 has a width w31 in the second direction D2. The first tip E1 of the first optical coupler 211 has a width w32 in the second direction D2. The width w32 is smaller than the width w31. The first optical coupler 211 has a width w33 as the width along the first direction D1 from the first tip E1 to the first base end B1. In addition, the first optical coupler 211 has a first taper angle θ1 from the first tip E1 to the first base end B1 of the first tapered structure.

[0052] The width w31 of the first base end B1 in the second direction D2 may be in the range of 0.5 μm to 10 μm, preferably 1 μm to 6 μm, more preferably 2 μm to 5 μm. The width w32 of the first tip E1 in the second direction D2 may be in the range of 0.01 μm to 1 μm, preferably 0.05 μm to 0.5 μm, more preferably 0.1 μm to 0.25 μm. The width w33 of the first photocoupler 211 in the first direction D1 may be in the range of 1 μm to 100 μm, preferably 2 μm to 50 μm, more preferably 5 μm to 20 μm. The first taper angle θ1 of the first photocoupler 211 may be in the range of 0.1° to 77°, preferably 0.5° to 54°, more preferably 2° to 25°.

[0053] Figure 4 is a schematic diagram showing the first optical waveguide 10 from Figure 1 in a top view. The configuration of the first optical waveguide 10 will be explained in more detail with reference to Figure 4.

[0054] The second base end B2 of the second optical coupling section 11 of the first optical waveguide 10 has a width w41 in the second direction D2. The widest central portion of the second optical coupling section 11, located between the second base end B2 and the second tip end E2, i.e., the boundary portion between the inverse tapered structure and the second tapered structure, has a width w42 in the second direction D2. The second tip end E2 of the second optical coupling section 11 has a width w43 in the second direction D2. The width w43 is smaller than both the width w41 and the width w42. The width w42 is the largest in the second optical coupling section 11.

[0055] The second optical coupling portion 11 of the first optical waveguide 10 has a width w44 along the first direction D1 from the second tip E2 to the second base end B2. In addition, the second optical coupling portion 11 has a second taper angle θ2 from the second base end B2 of the inverse taper structure toward the second taper structure.

[0056] The width w41 of the second base end B2 in the second direction D2 may be in the range of 0.1 μm to 2 μm, preferably 0.3 μm to 1 μm, and more preferably 0.4 μm to 0.6 μm. The width w42 of the boundary portion between the reverse taper structure and the second taper structure in the second direction D2 may be in the range of 0.5 μm to 10 μm, preferably 0.7 μm to 5 μm, and more preferably 1 μm to 3 μm. The width w43 of the second tip E2 in the second direction D2 may be in the range of 0.01 μm to 1 μm, preferably 0.05 μm to 0.5 μm, and more preferably 0.1 μm to 0.25 μm. The width w44 of the second photocoupler 11 in the first direction D1 may be in the range of 1 μm to 100 μm, preferably 2 μm to 50 μm, and more preferably 5 μm to 20 μm. The second taper angle θ2 of the second optical coupling portion 11 may be within the range of 0.2° to 83°, preferably 0.8° to 68°, and more preferably 2° to 41°.

[0057] Figure 5 is a schematic diagram showing a top view of the pair of second optical waveguides 60 shown in Figure 1. The configuration of the pair of second optical waveguides 60 will be explained in more detail with reference to Figure 5.

[0058] One of the pair of second optical waveguides 60 has a width w51 in the second direction D2. One of the pair of second optical waveguides 60 has a width w52 in the first direction D1. The other of the pair of second optical waveguides 60 has a width w53 in the second direction D2. The other of the pair of second optical waveguides 60 has a width w54 in the first direction D1. The pair of second optical waveguides 60 have a spacing d as the distance between their centers in the second direction D2.

[0059] For example, widths w51 and w53 may be the same as each other. Widths w52 and w54 may be the same as each other. Each of the pair of second optical waveguides 60 is configured in a rectangular shape with a long side along the first direction D1, and the width in the first direction D1 is sufficiently larger than the width in the second direction D2.

[0060] The width w51 in the second direction D2 of one of the pair of second optical waveguides 60 may be in the range of 0.01 μm to 1 μm, preferably 0.25 μm to 0.75 μm, and more preferably 0.3 μm to 0.5 μm. The width w52 in the first direction D1 of one of the pair of second optical waveguides 60 may be in the range of 1 μm to 100 μm, preferably 5 μm to 50 μm, and more preferably 10 μm to 30 μm.

[0061] The width w53 in the second direction D2 of the other of the pair of second optical waveguides 60 may be in the range of 0.01 μm to 1 μm, preferably 0.25 μm to 0.75 μm, and more preferably 0.3 μm to 0.5 μm. The width w54 in the first direction D1 of the other of the pair of second optical waveguides 60 may be in the range of 1 μm to 100 μm, preferably 5 μm to 50 μm, and more preferably 10 μm to 30 μm.

[0062] The spacing d between the pair of second optical waveguides 60 in the second direction D2 may be in the range of 0.1 μm to 10 μm, preferably 0.5 μm to 5 μm, and more preferably 1 μm to 3 μm.

[0063] The function of the optical coupling module 1 having the above configuration will now be explained. In explaining the function of the optical coupling module 1, it is possible to consider the optical coupling module 1 as being divided into two regions, as shown in Figure 1. The first region R1 includes, for example, a region in which the second optical coupling portion 11 of the first optical waveguide 10 and the first optical coupling portion 211 of the optical semiconductor element 20 are optically coupled to each other, and incident light L is transferred from the second optical coupling portion 11 to the first optical coupling portion 211. The second region R2 includes, for example, a region in which incident light L propagating along the first direction D1 while repeatedly reflecting in the third direction D3 inside the optical semiconductor element 20 is absorbed by the fifth layer 25, which is the active layer of the optical semiconductor element 20.

[0064] For example, the second optical coupling section 11 of the first optical waveguide 10 has an inverse taper structure on the incident side of the incident light L, thereby continuously changing the average refractive index in a cross section perpendicular to the first direction D1 along the first direction D1. For example, the average refractive index of the second optical coupling section 11 of the first optical waveguide 10 gradually increases in the inverse taper structure as it moves from the incident side of the incident light L toward the second taper structure. Therefore, the optical coupling module 1 avoids discontinuous structures in the second optical coupling section 11 of the first optical waveguide 10 and reduces reflection due to abrupt changes in refractive index.

[0065] For example, the second optical coupling section 11 of the first optical waveguide 10 has a second tapered structure that is continuous with the inverse tapered structure, thereby continuously changing the average refractive index in a cross section perpendicular to the first direction D1 along the first direction D1. For example, the average refractive index of the second optical coupling section 11 of the first optical waveguide 10 gradually decreases in the second tapered structure as it moves from the inverse tapered structure toward the second tip E2. Therefore, the optical coupling module 1 avoids discontinuous structures in the second optical coupling section 11 of the first optical waveguide 10 and reduces reflection due to abrupt changes in refractive index.

[0066] The second optical coupler 11, while monotonically increasing the area of ​​the cross-section perpendicular to the first direction D1 in the inverse tapered structure, transfers at least a portion of the incident light L to the optically coupled first optical coupler 211. The second optical coupler 11, while monotonically decreasing the area of ​​the cross-section perpendicular to the first direction D1 in the second tapered structure, transfers the remaining incident light L to the optically coupled first optical coupler 211 in an action that pushes it out. The second optical coupler 11 and the first optical coupler 211 are optically coupled to each other by evanescent light.

[0067] The above functions improve the optical coupling efficiency between the second optical coupling unit 11 and the first optical coupling unit 211. In other words, the optical coupling loss between the first optical waveguide 10 and the optical semiconductor element 20 is reduced in the optical coupling module 1. In this disclosure, "optical coupling efficiency" means, for example, the proportion of incident light L that enters the first optical coupling unit 11 of the first optical waveguide 10 that is transferred to the optical semiconductor element 20 without loss.

[0068] The incident light L that has been transferred to the optical semiconductor element 20 propagates along the first direction D1, while repeatedly reflecting in the third direction D3 between, for example, the gold electrode 27 located in the uppermost layer of the optical semiconductor element 20 and the interface layer 50 or air gap adjacent to the lowermost layer of the optical semiconductor element 20. At this time, the second optical waveguide 60 is optically coupled to the optical semiconductor element 20 by evanescent light. A portion of the incident light L propagating inside the optical semiconductor element 20 is transferred to the second optical waveguide 60, causing the second optical waveguide 60 to change the light intensity distribution of the incident light L propagating inside the optical semiconductor element 20. With its light intensity distribution changed by the second optical waveguide 60, the incident light L propagates inside the optical semiconductor element 20 along the first direction D1 and is absorbed by the fifth layer 25, which is the active layer of the optical semiconductor element 20.

[0069] As described above, the second optical waveguide 60 of the optical coupling module 1 is for changing the light intensity distribution of the incident light L that transitions from the first optical waveguide 10 and propagates inside the optical semiconductor element 20. Preferably, the electric field of the incident light L propagating inside the optical coupling module 1 is distributed mainly inside the optical semiconductor element 20. [Examples]

[0070] The optical coupling module 1 according to one embodiment of this disclosure will be described in more detail below with reference to examples, but this disclosure is not limited in any way to the following examples. The numerical values ​​described in the examples are merely examples and do not limit the scope of this disclosure. The scope of this disclosure should be determined based on the description in the claims. In the following, components similar to those in the embodiments will be denoted by the same reference numerals, and redundant explanations will be omitted.

[0071] As an example of the optical coupling module 1, an optical coupling module 1 having the same configuration as the optical coupling module 1 according to one embodiment described with reference to Figures 1 to 5 was created in simulation. The simulation included, for example, FDTD (Finite-Difference Time-Domain) simulation. In the simulation, the computational domain R0 shown in Figures 1 and 2 was used. The width of the computational domain R0 in the second direction D2 is a value of +1 to 2 μm centered on the width w1 in the second direction D2 of the stacked structure from the second layer 22 to the gold electrode 27 of the optical semiconductor element 20. In the simulation, light output from a mode light source in TE mode at a wavelength of 1.55 μm was used as the incident light L.

[0072] In the optical coupling module 1 according to the embodiment, the first optical waveguide 10 was made of Si. Each of the pair of second optical waveguides 60 was made of Si. The cladding layer 70 was made of SiO2. The refractive index of Si was 3.5, and the refractive index of SiO2 was 1.4.

[0073] In the simulation, the width w1 in the second direction D2 of the stacked structure from the second layer 22 to the gold electrode 27 of the optical semiconductor device 20, as shown in Figure 1, was 2.5 μm. The width w2 of the first layer 21 in the second direction D2 was 6 μm. The distance of the first region R1 in the first direction D1 was 10 μm. The distance of the second region R2 in the first direction D1 was 25 μm.

[0074] In the simulation, the thickness of the substrate 30 in the third direction D3, as shown in Figure 2, was 1 μm. The thickness of the BOX layer 40 in the third direction D3 was 3 μm. The thickness of the first optical waveguide 10 and the second optical waveguide 60 in the third direction D3 was 220 nm. The thickness of the interface layer 50 in the third direction D3 was 10 nm.

[0075] In the simulation, the thickness of the first layer 21 of the optical semiconductor device 20 shown in Figure 2 in the third direction D3 was 300 nm. The thickness of the second layer 22 in the third direction D3 was 10 nm. The thickness of the third layer 23 in the third direction D3 was 300 nm. The thickness of the fourth layer 24 in the third direction D3 was 20 nm. The thickness of the fifth layer 25 in the third direction D3 was 120 nm. The thickness of the sixth layer 26 in the third direction D3 was 200 nm. The thickness of the gold electrode 27 in the third direction D3 was 1000 nm.

[0076] In the simulation, the width w31 of the first base end B1 of the first photocoupler 211 in the second direction D2, as shown in Figure 3, was 2.5 μm. The width w32 of the first tip E1 of the first photocoupler 211 in the second direction D2 was 0.1 μm. The width w33 of the first photocoupler 211 in the first direction D1 was 10 μm. The first taper angle θ1 of the first photocoupler 211 was 26°.

[0077] In the simulation, the width w41 of the second base end B2 of the second photocoupler 11 in the second direction D2, as shown in Figure 4, was 0.48 μm. The width w42 of the boundary portion between the inverted tapered structure and the second tapered structure of the second photocoupler 11 in the second direction D2 was 1 μm. The width w43 of the second tip E2 of the second photocoupler 11 in the second direction D2 was 0.1 μm. The width w44 of the second photocoupler 11 in the first direction D1 was 10.7 μm. Of this, the width in the first direction D1 from the second base end B2 of the second photocoupler 11 to the boundary portion between the inverted tapered structure and the second tapered structure was 5 μm. The second taper angle θ2 of the second photocoupler 11 was 3°.

[0078] In the simulation, the width w51 in the second direction D2 of one of the pair of second optical waveguides 60 shown in Figure 5 was 0.4 μm. The width w52 in the first direction D1 of one of the pair of second optical waveguides 60 was 24 μm. The width w53 in the second direction D2 of the other of the pair of second optical waveguides 60 was 0.4 μm. The width w54 in the first direction D1 of the other of the pair of second optical waveguides 60 was 24 μm. The spacing d in the second direction D2 of the pair of second optical waveguides 60 was 1.5 μm.

[0079] Figure 6 is a graph showing the change in light intensity in the optical coupling module 1 according to an embodiment of the present disclosure. In the simulation, the light intensity was monitored at 0.3 μm intervals along the first direction D1 through which the incident light L propagates. In Figure 6, circles indicate the total light intensity of the incident light L propagating inside the optical coupling module 1. Cross marks indicate the light intensity of the incident light L propagating inside the optical semiconductor element 20 of the optical coupling module 1. Triangle marks indicate the light intensity of the incident light L propagating inside the first optical waveguide 10 of the optical coupling module 1.

[0080] As can be seen from the values ​​on the horizontal axis of the graph in Figure 6, the sum of the distance in the first direction D1 of the first region R1 and the distance in the first direction D1 of the second region R2 was 35 μm. As shown in Figure 6, in the first region R1, which includes the position in the first direction D1 from 0 μm to 10 μm, it can be seen that the incident light L is transferred from the first optical waveguide 10 to the optical semiconductor element 20 based on optical coupling by evanescent light. In the first region R1, the light intensity of the incident light L propagating inside the first optical waveguide 10 gradually decreases, while the light intensity of the incident light L propagating inside the optical semiconductor element 20 gradually increases.

[0081] On the other hand, in the second region R2, which includes the position of the first direction D1 from 10 μm to 35 μm, it can be seen that the incident light L is absorbed by the fifth layer 25, which is the active layer of the optical semiconductor device 20. In the second region R2, the light intensity of the incident light L propagating inside the optical semiconductor device 20 gradually decreases, and the overall light intensity of the incident light L also gradually decreases.

[0082] Figure 7A shows the first electric field distribution diagrams for optical coupling modules according to the examples and comparative examples. The lower part of Figure 7A shows the electric field distribution diagram for optical coupling module 1 according to the example. The lower left part of Figure 7A shows the electric field distribution diagram when the optical semiconductor element 20 is viewed in a front view of a cross section perpendicular to the first direction D1 at position P1 in the second region R2 of Figure 1. The lower center part of Figure 7A shows the electric field distribution diagram when the optical semiconductor element 20 is viewed in a front view of a cross section perpendicular to the first direction D1 at position P2 in the second region R2 of Figure 1. The lower right part of Figure 7A shows the electric field distribution diagram when the optical semiconductor element 20 is viewed in a front view of a cross section perpendicular to the first direction D1 at position P3 in the second region R2 of Figure 1.

[0083] The upper part of Figure 7A shows the electric field distribution diagram of light for the optical coupling module according to the comparative example. The optical coupling module according to the comparative example differs from the optical coupling module 1 according to the embodiment in that it does not have a pair of second optical waveguides 60. The optical coupling module 1 according to the comparative example has the same structure as the optical coupling module 1 according to the embodiment, except for the absence of the second optical waveguides 60.

[0084] The upper left diagram in Figure 7A corresponds to the electric field distribution diagram in the lower left diagram of Figure 7A. The upper center diagram in Figure 7A corresponds to the electric field distribution diagram in the lower center diagram of Figure 7A. The upper right diagram in Figure 7A corresponds to the electric field distribution diagram in the lower right diagram of Figure 7A. In each diagram of Figure 7A, the vertical axis represents the relative position (μm) in the third direction D3. The horizontal axis represents the relative position (μm) in the second direction D2. As an example, the center of the optical semiconductor element 20 in the second direction D2 is taken as the origin of the horizontal axis.

[0085] Figure 7B shows the second electric field distribution diagrams for optical coupling modules according to the examples and comparative examples. The lower part of Figure 7B shows the electric field distribution diagram for optical coupling module 1 according to the example. The lower left part of Figure 7B shows the electric field distribution diagram when the optical semiconductor element 20 is viewed in a front view of a cross section perpendicular to the first direction D1 at position P4 in the second region R2 of Figure 1. The lower center part of Figure 7B shows the electric field distribution diagram when the optical semiconductor element 20 is viewed in a front view of a cross section perpendicular to the first direction D1 at position P5 in the second region R2 of Figure 1. The lower right part of Figure 7B shows the electric field distribution diagram when the optical semiconductor element 20 is viewed in a front view of a cross section perpendicular to the first direction D1 at position P6 in the second region R2 of Figure 1.

[0086] The upper part of Figure 7B shows the electric field distribution diagram for an optical coupling module related to a comparative example. The upper left diagram in Figure 7B corresponds to the electric field distribution diagram in the lower left part of Figure 7B. The upper center diagram in Figure 7B corresponds to the electric field distribution diagram in the lower center of Figure 7B. The upper right diagram in Figure 7B corresponds to the electric field distribution diagram in the lower right part of Figure 7B. In each diagram of Figure 7B, the vertical axis represents the relative position (μm) in the third direction D3. The horizontal axis represents the relative position (μm) in the second direction D2. As an example, the center of the optical semiconductor element 20 in the second direction D2 is taken as the origin of the horizontal axis.

[0087] Comparing the upper and lower panels in Figures 7A and 7B, it can be seen that the light intensity distribution inside the optical semiconductor element 20 changes compared to the comparative example due to the arrangement of the pair of second optical waveguides 60 as the incident light L propagates through the optical semiconductor element 20 along the first direction D1. The optical coupling module 1 according to the embodiment increases the number of local peaks in the light intensity distribution inside the optical semiconductor element 20 due to this change in light intensity distribution, thereby increasing the degree of overlap of the light intensity distribution with respect to the fifth layer 25, which is the active layer of the optical semiconductor element 20. Therefore, in the optical coupling module 1 according to the embodiment, the absorption rate of the incident light L in the fifth layer 25, which is the active layer of the optical semiconductor element 20, is improved. In fact, the absorption rate of the active layer in the comparative example was 0.789, while the absorption rate of the active layer in the embodiment was 0.808.

[0088] (effect) According to the optical coupling module 1 of the above embodiment, performance indicators can be improved. For example, the optical coupling module 1 can improve the optical coupling efficiency between the first optical waveguide 10 and the optical semiconductor element 20. For example, the optical coupling module 1 has a first optical coupling portion 211 and a second optical coupling portion 11 that can be optically coupled to each other. The second optical coupling portion 11 is narrower on the first tip E1 side in the first direction D1, widest between the first tip E1 and the first base B1, and narrower on the first base B1 side. With the above configuration, the optical coupling module 1 can achieve higher optical coupling efficiency in the optical coupling between the first optical waveguide 10 and the optical semiconductor element 20.

[0089] The first optical coupling portion 211 has a first tapered structure directed toward the first tip E1. This allows the optical coupling module 1 to facilitate the smooth transfer of light between the first optical coupling portion 211 and the second optical coupling portion 11 from the first tip E1 toward the first base B1. Therefore, the optical coupling module 1 can achieve higher optical coupling efficiency in the optical coupling between the first optical waveguide 10 and the optical semiconductor element 20.

[0090] The second optical coupling section 11 has a reverse taper structure and a second taper structure sequentially from the first tip E1 side to the first base end B1 side. This allows the optical coupling module 1 to facilitate the smooth transfer of light between the first optical coupling section 211 and the second optical coupling section 11 from the first tip E1 to the first base end B1. Therefore, the optical coupling module 1 can achieve higher optical coupling efficiency in the optical coupling between the first optical waveguide 10 and the optical semiconductor element 20.

[0091] The first tip E1 of the first tapered structure of the first optical coupling portion 211 and the second base end B2 of the inverse tapered structure of the second optical coupling portion 11 are positioned at the same location in the first direction D1. This allows the optical coupling module 1 to have a large overlap between the first optical coupling portion 211 and the second optical coupling portion 11. Therefore, the optical coupling module 1 can achieve a higher optical coupling efficiency in the optical coupling between the first optical waveguide 10 and the optical semiconductor element 20.

[0092] The second tip E2 of the second tapered structure of the second optical coupling portion 11 is located inside the optical semiconductor element 20 in the first direction D1, compared to the first base end B1. This allows the optical coupling module 1 to increase the overlap between the first optical coupling portion 211 and the second optical coupling portion 11. Therefore, the optical coupling module 1 can achieve higher optical coupling efficiency in the optical coupling between the first optical waveguide 10 and the optical semiconductor element 20.

[0093] The first taper angle θ1 of the first tapered structure of the first optical coupling portion 211, from the first tip E1 to the first base tip B1, is greater than the second taper angle θ2 of the inverse tapered structure of the second optical coupling portion 11, from the second base tip B2 to the second tapered structure. This allows the optical coupling module 1 to have a larger overlap of the first optical coupling portion 211 with respect to the second optical coupling portion 11. Therefore, the optical coupling module 1 can achieve a higher optical coupling efficiency in optical coupling from the first optical waveguide 10 to the optical semiconductor element 20.

[0094] The optical coupling module 1 further has at least one second optical waveguide 60 located at a position offset from the center of the active layer of the optical semiconductor element 20 in the second direction D2, and at a position inside the optical semiconductor element 20 relative to the second optical coupling portion 11 in the first direction D1. This makes it possible for the optical coupling module 1 to change the light intensity distribution inside the optical semiconductor element 20 compared to the comparative example while the incident light L propagates through the inside of the optical semiconductor element 20 along the first direction D1.

[0095] The optical coupling module 1 can increase the number of local peaks in the light intensity distribution within the optical semiconductor device 20 by changing the light intensity distribution in this way, thereby increasing the degree of overlap of the light intensity distribution with respect to the fifth layer 25, which is the active layer of the optical semiconductor device 20. Therefore, the optical coupling module 1 can improve the absorption rate of incident light L in the fifth layer 25, which is the active layer of the optical semiconductor device 20.

[0096] The pair of second optical waveguides 60 are arranged symmetrically with respect to a central axis along the first direction D1, which is located at the center of the active layer of the optical semiconductor element 20 in the second direction D2. This allows the optical coupling module 1 to arrange local peaks in the change of light intensity distribution within the optical semiconductor element 20 symmetrically with respect to the central axis. Therefore, the optical coupling module 1 can increase the degree of overlap of the light intensity distribution with respect to the fifth layer 25, which is the active layer of the optical semiconductor element 20. As a result, the optical coupling module 1 can improve the absorption rate of incident light L in the fifth layer 25, which is the active layer of the optical semiconductor element 20.

[0097] The pair of second optical waveguides 60 are arranged parallel to each other. This makes it possible for the optical coupling module 1 to arrange the pair of second optical waveguides 60 along the first direction D1 over the entire optical semiconductor element 20. Therefore, the optical coupling module 1 can also realize a change in the light intensity distribution inside the optical semiconductor element 20 over the entire optical semiconductor element 20 along the first direction D1. As a result, the optical coupling module 1 can improve the absorption rate of incident light L in the fifth layer 25, which is the active layer of the optical semiconductor element 20.

[0098] The pair of second optical waveguides 60 are positioned at the same height as the first optical waveguide 10 in the stacking direction, i.e., the third direction D3. This facilitates the arrangement of the pair of second optical waveguides 60 and the first optical waveguide 10 on the substrate 30 in the optical coupling module 1. The optical coupling module 1 is easily manufactured. In addition, the center of the first optical waveguide 10 in the second direction D2 coincides with the aforementioned central axis. Therefore, the optical coupling module 1 can improve the overall symmetry of the first optical waveguide 10 and the optical semiconductor element 20 in the second direction D2, thereby improving performance metrics.

[0099] (modified version) It will be apparent to those skilled in the art that this disclosure can be implemented in other predetermined forms besides the embodiments described above without deviating from its spirit or essential features. Therefore, the prior description is illustrative and not limiting. The scope of the disclosure is defined not by the prior description but by the added claims. Any modifications within their equivalent scope are included therein.

[0100] For example, the shape, pattern, size, arrangement, orientation, type, and number of each component described above are not limited to those shown in the above description and drawings. The shape, pattern, size, arrangement, orientation, type, and number of each component may be configured arbitrarily as long as it can realize its function. Each component of the illustrated optical coupling module 1 is a functional concept. The specific form of each component is not limited to those shown. For example, if the performance indicators can be improved, the following modifications of the optical coupling module 1 are also possible.

[0101] In the above embodiment, the first optical coupling portion 211 was described as having a first tapered structure directed toward the first tip E1, but it is not limited thereto. The first optical coupling portion 211 may have any other shape between the first tip E1 and the first base B1, as long as the first tip E1 is narrower than the first base B1 in the first direction D1. For example, the first optical coupling portion 211 may have a curved shape instead of a straight line between the first tip E1 and the first base B1, and the width in the second direction D2 between the first tip E1 and the first base B1 does not have to change monotonically.

[0102] In the above embodiment, the second optical coupling portion 11 was described as having a reverse taper structure and a second taper structure sequentially from the first tip E1 side to the first base end B1 side, but it is not limited to this. In the first direction D1, the second optical coupling portion 11 may have any other shape between the first tip E1 and the first base end B1, as long as it is narrow at the first tip E1 side, widest between the first tip E1 and the first base end B1, and narrow at the first base end B1 side.

[0103] For example, the second optical coupling portion 11 may have a curved shape rather than a straight line between the second base end B2 and the central part in the first direction D1, and the width in the second direction D2 between the second base end B2 and the central part does not have to be monotonically varied. The second optical coupling portion 11 may have a curved shape rather than a straight line between the central part in the first direction D1 and the second tip E2, and the width in the second direction D2 between the central part and the second tip E2 does not have to be monotonically varied.

[0104] In the above embodiment, it was explained that the first tip E1 in the first tapered structure of the first photocoupler 211 and the second base end B2 in the reverse tapered structure of the second photocoupler 11 are located at the same position in the first direction D1, but the embodiment is not limited to this. The first tip E1 in the first tapered structure of the first photocoupler 211 and the second base end B2 in the reverse tapered structure of the second photocoupler 11 may be located at different positions in the first direction D1.

[0105] In the above embodiment, it was explained that the second tip E2 of the second tapered structure of the second optical coupling portion 11 is located inside the optical semiconductor element 20 in the first direction D1, but it is not limited to this. The second tip E2 of the second tapered structure of the second optical coupling portion 11 may be located outside the optical semiconductor element 20 in the first direction D1, or it may be located at the same position as the first base end B1.

[0106] In the above embodiment, as shown in Figure 1, the optical semiconductor element 20 mainly overlaps with the first optical waveguide 10 only at the first optical coupling portion 211. That is, the laminated structure located inside the first optical coupling portion 211 in the optical semiconductor element 20 is located on the opposite side of the first direction D1 with respect to the first optical waveguide 10. However, the arrangement of the optical semiconductor element 20 with respect to the first optical waveguide 10 is not limited to this. The laminated structure located inside the first optical coupling portion 211 in the optical semiconductor element 20 may be located on the same side of the first direction D1 with respect to the first optical waveguide 10. For example, in Figure 1, the laminated structure may be located below the second optical coupling portion 11.

[0107] In the above embodiment, the first taper angle θ1 of the first tapered structure of the first photocoupler 211, from the first tip E1 to the first base end B1, is described as being greater than the second taper angle θ2 of the inverse taper structure of the second photocoupler 11, from the second base end B2 to the second tapered structure. However, the embodiment is not limited to this. The first taper angle θ1 may be less than or equal to the second taper angle θ2.

[0108] In the above embodiment, the optical coupling module 1 was described as having at least one second optical waveguide 60, but it is not limited to this. The optical coupling module 1 does not have to have a second optical waveguide 60.

[0109] In the above embodiment, the pair of second optical waveguides 60 were described as being positioned offset from the center of the active layer of the optical semiconductor element 20 in the second direction D2, but this is not limited to that. The second optical waveguides 60 may be positioned at the same location as the center of the active layer of the optical semiconductor element 20 in the second direction D2. The pair of second optical waveguides 60 were described as being positioned spaced apart from the first optical waveguide 10, but this is not limited to that. The pair of second optical waveguides 60 may be positioned in contact with the first optical waveguide 10.

[0110] In the above embodiment, the pair of second optical waveguides 60 were described as being arranged symmetrically with respect to a central axis along the first direction D1, which is located at the center of the active layer of the optical semiconductor element 20 in the second direction D2, but this is not limited to this. The pair of second optical waveguides 60 do not have to be arranged symmetrically with respect to the said central axis.

[0111] In the above embodiment, the pair of second optical waveguides 60 were described as being arranged parallel to each other, but this is not limited to this configuration. The pair of second optical waveguides 60 may be arranged non-parallel to each other.

[0112] In the above embodiment, the pair of second optical waveguides 60 were described as being arranged at the same height as the first optical waveguide 10 in the third direction D3, but this is not limited to this. The pair of second optical waveguides 60 may be arranged at different heights from the first optical waveguide 10 in the third direction D3.

[0113] In the above embodiment, it was explained that the center of the second direction D2 of the first optical waveguide 10 coincides with the central axis, but this is not limited to this. The center of the second direction D2 of the first optical waveguide 10 does not have to coincide with the central axis. It was explained that the central axis of the first optical coupling section 211 along the first direction D1 coincides with the central axis of the second optical coupling section 11 along the first direction D1, but this is not limited to this. The central axis of the first optical coupling section 211 along the first direction D1 does not have to coincide with the central axis of the second optical coupling section 11 along the first direction D1. For example, the first optical coupling section 211 and the second optical coupling section 11 may be arranged so that their centers are offset from each other along the second direction D2.

[0114] In the above embodiment, the material of the first optical waveguide 10 was described as, for example, Si, but it is not limited to this. The material of the first optical waveguide 10 may be other materials other than Si. For example, the material of the first optical waveguide 10 may be InGaAs, InGaAsP, InAlAs, GaAs, Ge, SiN, or a compound semiconductor of InP and group III-V.

[0115] In the above embodiment, the material of the second optical waveguide 60 was described as, for example, Si, but it is not limited to this. The material of the second optical waveguide 60 may be other materials other than Si. For example, the material of the second optical waveguide 60 may be InGaAs, InGaAsP, InAlAs, GaAs, Ge, SiN, or a compound semiconductor of InP and group III-V.

[0116] In the above embodiment, the material of the cladding layer 70 was described as, for example, SiO2, but it is not limited to this. The material of the cladding layer 70 may be other materials other than SiO2. For example, the material of the cladding layer 70 may be an insulating material such as epoxy resin. The cladding layer 70 may be composed of multiple layers, for example, by depositing a film of SiN to a thickness of several hundred nm and then depositing a film of SiO2.

[0117] In the above embodiment, the cross-sectional shape of the first optical waveguide 10 in a cross-section perpendicular to the first direction D1 was described as rectangular, but it is not limited to this. The cross-sectional shape of the first optical waveguide 10 in a cross-section perpendicular to the first direction D1 may be other shapes such as polygons and circles. For example, the first optical waveguide 10 may be rib-shaped.

[0118] In the above embodiment, the cross-sectional shape of the second optical waveguide 60 in a section perpendicular to the first direction D1 was described as rectangular, but it is not limited to this. The cross-sectional shape of the second optical waveguide 60 in a section perpendicular to the first direction D1 may be other shapes such as polygons and circles. For example, the second optical waveguide 60 may be rib-shaped.

[0119] In the above embodiment, the first optical coupling portion 211 was described as being located only in the first InP layer 21 of the stacked structure of the optical semiconductor device 20 shown in Figure 2, but it is not limited to this. The first optical coupling portion 211 may also be located in at least one of the second to fourth layers 24 in addition to the first InP layer 21 of the stacked structure of the optical semiconductor device 20 shown in Figure 2. [Explanation of Symbols]

[0120] 1. Optical coupling module 10 First optical waveguide 11 Second optical coupling section 20 Optoelectronic semiconductor devices 21 1st layer 211 1st optical coupling section 22 2nd layer 23 3rd layer 24 4th layer 25 5th layer (active layer) 26 Layer 6 27 Gold electrodes 30 circuit boards 40 BOX layer 50 Interface layer 60 Second optical waveguide 70 Clad layer B1 1st proximal end B2 2nd proximal end D1 1st direction D2 2nd direction D3 Third direction d interval E1 First tip E2 Second Front L Incident light P1 position P2 position P3 position P4 position P5 position P6 position R0 calculation area R1 1st area R2 2nd area w1 width w2 width w31 width w32 width w33 width w41 width w42 width w43 width w44 width w51 width w52 width w53 width w54 width θ1 First taper angle θ2 Second taper angle

Claims

1. It is an optical coupling module, circuit board and A first optical waveguide is arranged in a first direction in the planar direction on the substrate, An optical semiconductor element having multiple layers and arranged on the first optical waveguide, the optical semiconductor element having a first optical coupling portion facing the tip of the first optical waveguide in the stacking direction of the optical coupling module which is perpendicular to the first direction, Equipped with, The first optical coupling portion has a first tip that is narrower than the first base in the first direction. The tip of the first optical waveguide is configured as a second optical coupling portion that can be optically coupled to the first optical coupling portion. The second photocoupler is narrower at the first tip end in the first direction, widest between the first tip end and the first base end, and narrower at the first base end end. Optical coupling module.

2. The optical coupling module according to claim 1, The first optical coupling portion has a first tapered structure directed toward the first tip side. Optical coupling module.

3. The optical coupling module according to claim 2, The second photocoupler has a reverse taper structure and a second taper structure in sequence from the first tip side to the first base end side. Optical coupling module.

4. The optical coupling module according to claim 3, The first tip in the first tapered structure and the second base in the reverse tapered structure are positioned at the same location relative to each other in the first direction. Optical coupling module.

5. The optical coupling module according to claim 3 or 4, The second tip of the second tapered structure is located inside the optical semiconductor element in the first direction, compared to the first base. Optical coupling module.

6. The optical coupling module according to claim 3 or 4, The first taper angle from the first tip to the first base of the first tapered structure is greater than the second taper angle from the second base of the inverse tapered structure to the second tapered structure. Optical coupling module.

7. An optical coupling module according to any one of claims 1 to 4, The system further comprises one or more second optical waveguides, which are located at a position offset from the center of the active layer of the optical semiconductor element in a second direction perpendicular to the first direction in the planar direction, and are located inside the optical semiconductor element in the first direction compared to the second optical coupling portion, and are spaced apart from the first optical waveguide. Optical coupling module.

8. The optical coupling module according to claim 7, The pair of second optical waveguides are arranged symmetrically with respect to a central axis along the first direction, which is located at the center in the second direction. Optical coupling module.

9. The optical coupling module according to claim 8, The pair of the second optical waveguides are arranged parallel to each other. Optical coupling module.

10. The optical coupling module according to claim 8, The pair of second optical waveguides are arranged at the same height as the first optical waveguide in the stacking direction perpendicular to the first and second directions. The center of the first optical waveguide in the second direction coincides with the central axis, Optical coupling module.

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