Photoelectric detector and light absorption enhancement method
By setting a reflective structure in the waveguide coupling structure of the photodetector, the secondary absorption of transmitted light is achieved, the problem of low light absorption of the waveguide coupling structure is solved, and the responsiveness of the photodetector is improved.
Patent Information
- Application Number
- CN202510532509.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-25
- Publication Date
- 2025-07-25
AI Technical Summary
The waveguide-coupled structure of existing photodetectors has lower light absorption, and new structures are needed to achieve higher light absorption.
A reflective structure is provided in the waveguide coupling structure, and the secondary light absorption is achieved by reflecting transmitted light, thereby improving the responsiveness of the photodetector.
By adding a reflective structure to reflect the transmitted light of the waveguide, the secondary light absorption of the photodetector is realized and the responsiveness of the photodetector is improved.
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Figure CN120379394A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of integrated photonics, and in particular to a photodetector and a method for enhancing light absorption. Background Art
[0002] A photoelectric detector (PD) can convert an optical signal into an electrical signal and is widely used in various optical interconnection systems.
[0003] Existing photodetectors can be divided into non-waveguide and waveguide coupling structures according to different optical coupling methods. In the non-waveguide structure, light is usually coupled from free space to the absorption region through an optical fiber. The light can be directly injected into the absorption surface (vertical incidence) or through the edge of the absorption layer (side incidence). Compared with the vertical coupling structure, edge coupling usually has a better balance of bandwidth and responsivity because the carrier drift direction is perpendicular to the light injection direction. In the waveguide structure, the incident light is confined within a sub-micron waveguide and transmitted, and then evanescently or directly coupled to the absorption region. Due to the reduced coupling loss, waveguide PDs exhibit much higher internal responsivity than non-waveguide PDs. However, the light absorption of the current waveguide coupling structure is still low, and new structures need to be developed to achieve higher light absorption.
[0004] The above content is only used to assist in understanding the technical solution of the present invention and does not represent an admission that the above content is prior art. Summary of the Invention
[0005] The main objective of the present invention is to provide a photodetector and a method for enhancing light absorption, aiming to solve the technical problem of low light absorption in the waveguide coupling structure of the existing photodetector.
[0006] To achieve the above objective, the present invention proposes a photodetector, which includes: a reflection structure and a waveguide coupling structure;
[0007] The waveguide coupling structure includes: a waveguide, an absorption layer, and a metal layer;
[0008] The reflection structure is disposed at one end of the absorption layer side in the waveguide coupling structure, and the bottom of the reflection structure is flush with the bottom of the waveguide coupling structure;
[0009] The reflection structure is configured to reflect the transmitted light transmitted by the waveguide through the waveguide coupling structure to form reflected light;
[0010] The waveguide coupling structure is configured to perform secondary absorption on the transmitted light of the waveguide and the reflected light of the reflection structure.
[0011] Optionally, the waveguide coupling structure is an evanescent coupling structure. The absorption layer is disposed on the end of the waveguide, the bottom of the absorption layer is flush with the top of the waveguide, and the metal layer is disposed on the absorption layer.
[0012] The reflection structure is disposed on the side of the waveguide close to the absorption layer. The bottom of the reflection structure is flush with the bottom of the waveguide, and the reflection structure coincides with the central axis of the waveguide.
[0013] Optionally, the reflection structure includes: a single-layer grating block, the single-layer grating block coincides with the central axis of the waveguide, and the width of the single-layer grating block is the same as the width of the waveguide.
[0014] Optionally, the reflection structure includes: a double-layer grating block, the double-layer grating blocks are aligned or staggered with each other, and the central axis of the double-layer grating block coincides with the central axis of the waveguide.
[0015] Optionally, the waveguide coupling structure is a direct coupling structure. The absorption layer is disposed at the end of the waveguide, the bottom of the absorption layer is flush with the bottom of the waveguide, and the metal layer is disposed on the absorption layer.
[0016] The reflection structure is disposed on the three side edges of the absorption layer not adjacent to the waveguide. The bottom of the reflection structure is flush with the bottom of the absorption layer, and the reflection structure coincides with the central axis of the absorption layer.
[0017] Optionally, the reflection structure includes: a single-layer grating block, and three single-layer grating blocks are correspondingly disposed on the three side edges of the absorption layer not adjacent to the waveguide.
[0018] Optionally, the reflection structure includes: a double-layer grating block, the double-layer grating blocks are aligned or staggered with each other, and three double-layer grating blocks are correspondingly disposed on the three side edges of the absorption layer not adjacent to the waveguide.
[0019] Optionally, the photodetector uses a silicon-on-insulator platform.
[0020] Optionally, the material of the absorption layer of the waveguide coupling structure is germanium.
[0021] In addition, to achieve the above object, the present invention further provides a method for enhancing light absorption. The method for enhancing light absorption is used for the photodetector as described above. The steps of the method for enhancing light absorption include:
[0022] Disposing a reflection structure at the end of one side of the absorption layer in the waveguide coupling structure;
[0023] Reflecting the transmitted light transmitted through the waveguide coupling structure by the waveguide to form reflected light;
[0024] Perform secondary absorption on the transmitted light of the waveguide and the reflected light of the reflection structure.
[0025] The present invention provides a photodetector and a method for enhancing light absorption. The photodetector includes a reflection structure and a waveguide coupling structure; the waveguide coupling structure includes: a waveguide, an absorption layer, and a metal layer; the reflection structure is disposed at an end of the waveguide coupling structure on one side of the absorption layer, and the bottom of the reflection structure is flush with the bottom of the waveguide coupling structure; the reflection structure is configured to reflect the transmitted light of the waveguide through the waveguide coupling structure to form reflected light; the waveguide coupling structure is configured to perform secondary absorption on the transmitted light of the waveguide and the reflected light of the reflection structure. By adding a reflection structure to reflect the transmitted light of the waveguide to achieve secondary light absorption, the responsivity of the photodetector is improved. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.
[0027] Figure 1 Schematic structural diagram of the first embodiment of the photodetector of the present invention;
[0028] Figure 2 Top view structural diagram of the second embodiment of the photodetector of the present invention;
[0029] Figure 3 Cross-sectional structural diagram of the second embodiment of the photodetector of the present invention;
[0030] Figure 4 Top view structural diagram of the double-layer grating structure in the second embodiment of the photodetector of the present invention;
[0031] Figure 5 Cross-sectional structural diagram of the double-layer grating structure in the second embodiment of the photodetector of the present invention;
[0032] Figure 6 Top view structural diagram of the third embodiment of the photodetector of the present invention;
[0033] Figure 7 Cross-sectional structural diagram of the third embodiment of the photodetector of the present invention;
[0034] Figure 8 Top view structural diagram of the double-layer grating structure in the third embodiment of the photodetector of the present invention;
[0035] Figure 9 This is a schematic cross-sectional view of the double-layer grating structure of the third embodiment of the photodetector of the present invention;
[0036] Figure 10 This is a schematic flow chart of the first embodiment of the light absorption enhancement method of the present invention.
[0037] Explanation of reference numerals: 10, reflection structure; 20, waveguide coupling structure; 101, single-layer grating block; 102, double-layer grating block; 201, waveguide; 202, absorption layer; 203, metal layer.
[0038] The realization, functional features and advantages of the object of the present invention will be further described with reference to the embodiments and the accompanying drawings. Detailed Embodiments
[0039] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.
[0040] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.
[0041] It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.
[0042] In addition, the descriptions involving "first", "second", etc. in the present invention are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments may be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.
[0043] The main solution of the embodiment of the present invention is that the photodetector includes a reflection structure and a waveguide coupling structure; the waveguide coupling structure includes a waveguide, an absorption layer, and a metal layer; the reflection structure is arranged at the end of the waveguide coupling structure on one side of the absorption layer, and the bottom of the reflection structure is flush with the bottom of the waveguide coupling structure; the reflection structure is used to reflect the transmitted light transmitted by the waveguide through the waveguide coupling structure to form reflected light; the waveguide coupling structure is used to perform secondary absorption on the transmitted light of the waveguide and the reflected light of the reflection structure.
[0044] Currently, photodetectors can be classified into non-waveguide and waveguide coupling structures according to different optical coupling methods. In the non-waveguide structure, light is usually coupled from free space to the absorption region through an optical fiber. Light can be directly injected into the absorption surface (vertical incidence) or through the edge of the absorption layer (side incidence). Compared with the vertical coupling structure, edge coupling usually has a better balance of bandwidth and responsivity because the carrier drift direction is perpendicular to the light injection direction. In the waveguide structure, the incident light is confined within a sub-micron waveguide and transmitted, and then evanescently or directly coupled to the absorption region. Due to the reduced coupling loss, waveguide PDs exhibit much higher internal responsivity than non-waveguide PDs. Almost all types of high-speed PDs demonstrated in silicon photonics are based on waveguide coupling structures. However, the light absorption of the waveguide coupling structure is still low, and new structures need to be developed to achieve higher light absorption.
[0045] This solution proposes a photodetector to achieve secondary light absorption of the waveguide coupling structure by adding a reflection structure to reflect the transmitted light of the waveguide, so as to improve the responsivity of the photodetector.
[0046] Refer to Figure 1 , Figure 1 is a schematic structural diagram of the first embodiment of the photodetector of the present invention. As Figure 1 shown, in this embodiment, the photodetector includes a reflection structure 10 and a waveguide coupling structure 20; the waveguide coupling structure includes a waveguide 201, an absorption layer 202, and a metal layer 203; the reflection structure is arranged at the end of the waveguide coupling structure on one side of the absorption layer, and the bottom of the reflection structure is flush with the bottom of the waveguide coupling structure.
[0047] Among them, the reflection structure can be used to reflect the transmitted light transmitted by the waveguide through the waveguide coupling structure to form reflected light; the waveguide coupling structure can be used to perform secondary absorption on the transmitted light of the waveguide and the reflected light of the reflection structure.
[0048] It should be noted that the waveguide coupling structure can include evanescent coupling and direct coupling. In the waveguide structure, the incident light is confined and transmitted within a sub-micron waveguide, and then evanescently or directly coupled to the absorption region. Evanescent coupling utilizes the overlap of the evanescent field of the waveguide between adjacent waveguides to achieve energy transfer through mode matching. Direct coupling directly transmits the optical signal through physical connection.
[0049] It should be understood that the basis of the waveguide coupling structure can adopt a Silicon-on-Insulator Platform (SOI). The silicon germanium (SiGe) detector is a typical choice for the SOI platform. It is highly compatible with silicon-based semiconductor processes and is suitable for large-scale integrated optoelectronic devices (such as modulators, detectors). The waveguide coupling structure can also adopt a Silicon Nitride Platform (SiN), which is suitable for long-distance optical signal transmission and low-noise environments. Or it can adopt a Thin-Film Lithium Niobate Platform (TFLN), which is suitable for high-speed optical communication and microwave photonics applications. In the following embodiments, the waveguide coupling structure of the SOI platform will be described. The absorption layer in the waveguide coupling structure can use germanium (Ge), or other materials, for example: group III-V materials formed by group 13 metals and group 15 anions.
[0050] Furthermore, the reflection structure can be an optical device with the ability to reflect light beams, such as a grating. Multiple parallel scratches can be etched on the surface coated with a metal layer, and the smooth metal surface between adjacent scratches is used to reflect light.
[0051] In this embodiment, the photodetector includes: a reflection structure and a waveguide coupling structure; the waveguide coupling structure includes: a waveguide, an absorption layer, and a metal layer; the reflection structure is arranged at the end of the absorption layer side in the waveguide coupling structure, and the bottom of the reflection structure is flush with the bottom of the waveguide coupling structure; the reflection structure is used to reflect the transmitted light transmitted by the waveguide through the waveguide coupling structure to form reflected light; the waveguide coupling structure is used to perform secondary absorption on the transmitted light of the waveguide and the reflected light of the reflection structure. By increasing the reflection of the transmitted light of the waveguide by the reflection structure, secondary light absorption of the waveguide coupling structure is realized to improve the responsivity of the photodetector.
[0052] Based on the first embodiment of the present application, in the second embodiment of the present application, the same or similar content as the above-mentioned embodiment one can be referred to the above introduction and will not be repeated hereinafter. On this basis, please refer to Figure 2 and Figure 3 , Figure 2 is a schematic top view structure diagram of the second embodiment of the photodetector of the present invention. Figure 3Schematic cross-sectional structure diagram of the second embodiment of the photodetector of the present invention. Figure 3 The cross-section along Figure 2 the dashed line in
[0053] Taking the SOI platform as an example, the waveguide coupling structure is an evanescent coupling structure. The absorption layer 202 is disposed on the end of the waveguide 201. The bottom of the absorption layer 202 is flush with the top of the waveguide 201. The metal layer 203 is disposed on the absorption layer 202. The reflection structure 10 is disposed on the side of the waveguide 201 close to the absorption layer 202. The bottom of the reflection structure 10 is flush with the bottom of the waveguide 201. The reflection structure 10 coincides with the central axis of the waveguide 201.
[0054] It should be noted that the reflection structure includes: a single-layer grating block 101. The single-layer grating block 101 coincides with the central axis of the waveguide. The width of the single-layer grating block 101 is the same as the width of the waveguide.
[0055] In another possible implementation, the reflection structure includes: a double-layer grating block 102. Refer to Figure 4 and Figure 5 , Figure 4 Schematic top-view structure diagram of the double-layer grating structure in the second embodiment of the photodetector of the present invention. Figure 5 Schematic cross-sectional structure diagram of the double-layer grating structure of the second embodiment of the photodetector of the present invention. Figure 5 The cross-section along Figure 4 the dashed line in
[0056] It should be noted that the double-layer grating blocks are aligned or staggered. The central axis of the double-layer grating blocks coincides with the central axis of the waveguide. The reflection effect of using the double-layer grating blocks is better than that of the single-layer grating block.
[0057] In this embodiment, the waveguide coupling structure is an evanescent coupling structure. The absorption layer is disposed on the end of the waveguide. The bottom of the absorption layer is flush with the top of the waveguide. The metal layer is disposed on the absorption layer. The reflection structure is disposed on the side of the waveguide close to the absorption layer. The bottom of the reflection structure is flush with the bottom of the waveguide. The reflection structure coincides with the central axis of the waveguide. Whether the reflection structure uses a single-layer grating block or a double-layer grating block, the transmitted light of the waveguide is reflected to achieve secondary optical absorption of the waveguide coupling structure, so as to improve the responsivity of the photodetector.
[0058] Based on the first embodiment and the second embodiment of the present application, please refer to Figure 6 and Figure 7 , Figure 6 Schematic top-view structure diagram of the third embodiment of the photodetector of the present invention.Figure 7 This is a schematic cross-sectional structure diagram of the third embodiment of the photodetector of the present invention. Figure 7 The cross-section of Figure 6 is shown in cross-section along the dashed line in
[0059] Taking the SOI platform as an example, the waveguide coupling structure is a direct coupling structure. The absorption layer 202 is disposed at the end of the waveguide 201. The bottom of the absorption layer 202 is flush with the bottom of the waveguide 201. The metal layer 203 is disposed on the absorption layer 202. The reflection structure 10 is disposed on three side edges of the absorption layer 202 that are not adjacent to the waveguide 201. The bottom of the reflection structure 10 is flush with the bottom of the absorption layer 202. The reflection structure 10 coincides with the central axis of the absorption layer 202.
[0060] It should be noted that the reflection structure 10 includes: a single-layer grating block 101. The three single-layer grating blocks 101 are correspondingly disposed on three side edges of the absorption layer 202 that are not adjacent to the waveguide 201.
[0061] In another possible implementation, the reflection structure includes: a double-layer grating block 102. Refer to Figure 8 and Figure 9 Figure 8 This is a schematic top view structure diagram of the double-layer grating structure in the third embodiment of the photodetector of the present invention. Figure 9 This is a schematic cross-sectional structure diagram of the double-layer grating structure of the third embodiment of the photodetector of the present invention. Figure 9 The cross-section of Figure 8 is shown in cross-section along the dashed line in
[0062] It should be noted that the double-layer grating blocks are aligned or staggered with each other. The three double-layer grating blocks are correspondingly disposed on three side edges of the absorption layer that are not adjacent to the waveguide.
[0063] In this embodiment, the waveguide coupling structure is a direct coupling structure. The absorption layer is disposed at the end of the waveguide. The bottom of the absorption layer is flush with the bottom of the waveguide. The metal layer is disposed on the absorption layer. The reflection structure is disposed on three side edges of the absorption layer that are not adjacent to the waveguide. The bottom of the reflection structure is flush with the bottom of the absorption layer. The reflection structure coincides with the central axis of the absorption layer. The reflection structure adopts a single-layer grating block or a double-layer grating block to reflect the waveguide transmitted light to achieve secondary optical absorption of the waveguide coupling structure, so as to improve the responsivity of the photodetector.
[0064] In addition, in order to achieve the above-mentioned purpose, an embodiment of the present invention also proposes a light absorption enhancement method. Since this light absorption enhancement method is used to construct the above-mentioned photodetector, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be described one by one here.
[0065] The execution subject of this embodiment can be a computing service device with data processing, network communication and program running functions, such as a tablet computer, a personal computer, a mobile phone, etc., or an electronic device that can realize the above functions.
[0066] Reference Figure 10 , Figure 10 FIG. 1 is a flow chart of the first embodiment of the light absorption enhancement method of the present invention. Figure 10 As shown, in this embodiment, the same or similar contents as those in the above embodiment can be referred to the above introduction, and will not be described in detail later. The steps of the light absorption enhancement method include:
[0067] Step S10: a reflective structure is provided at the end of the waveguide coupling structure on one side of the absorption layer.
[0068] It should be noted that the waveguide coupling structure includes a waveguide, an absorption layer and a metal layer. The incident light is confined in a submicron waveguide and transmitted, which may include evanescent coupling and direct coupling. Evanescent coupling utilizes the overlap of the evanescent field of the waveguide between adjacent waveguides to achieve energy transfer through mode matching. Direct coupling directly transmits optical signals through physical connections. The reflective structure can be an optical device with the ability to reflect light beams, such as a grating, which can be made by engraving multiple parallel grooves on the surface coated with a metal layer and using the smooth metal surface between two adjacent grooves to reflect light.
[0069] It should be understood that the waveguide coupling structure may adopt other platforms such as SOI platform, SiN platform or TFLN, etc. The photodetector PD may adopt Ge PD or PD of III-V group materials.
[0070] Step S20: reflecting the transmission light transmitted by the waveguide through the waveguide coupling structure to form reflected light.
[0071] Step S30: performing secondary absorption on the transmission light of the waveguide and the reflected light of the reflection structure.
[0072] It should be noted that for evanescent coupling, a single or double grating structure is added to the waveguide end of the waveguide coupling structure; for direct coupling, a single or double grating structure is added to the other three sides of the absorption region of the waveguide coupling structure that are not adjacent to the waveguide.
[0073] In this embodiment, a reflection structure is provided at the end of the absorption layer side in the waveguide coupling structure. The transmitted light transmitted through the waveguide through the waveguide coupling structure is reflected to form reflected light. The transmitted light of the waveguide and the reflected light of the reflection structure are secondarily absorbed. By increasing the reflection of the transmitted light of the waveguide by the reflection structure, secondary light absorption is achieved to improve the responsivity of the photodetector.
[0074] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be included in the patent protection scope of the present invention by the same token.
[0075] Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts belong to the protection scope of the present invention.
[0076] It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the relative position relationship and movement conditions between components in a specific posture (as shown in the drawings). If the specific posture changes, the directional indications will also change accordingly.
[0077] In addition, the descriptions involving "first", "second", etc. in the present invention are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions appears to be contradictory or unable to be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.
Claims
1. A photodetector, characterized in that, The photodetector includes a reflection structure and a waveguide coupling structure; The waveguide coupling structure includes: a waveguide, an absorption layer, and a metal layer; The reflection structure is disposed at an end of the absorption layer side in the waveguide coupling structure, and a bottom of the reflection structure is flush with a bottom of the waveguide coupling structure; The reflection structure is configured to reflect transmitted light transmitted by the waveguide through the waveguide coupling structure to form reflected light; The waveguide coupling structure is configured to perform secondary absorption on the transmitted light of the waveguide and the reflected light of the reflection structure.
2. The photodetector according to claim 1, wherein The waveguide coupling structure is an evanescent coupling structure, the absorption layer is disposed on an end of the waveguide, a bottom of the absorption layer is flush with a top of the waveguide, and the metal layer is disposed on the absorption layer; The reflection structure is disposed on a side of the waveguide close to the absorption layer, a bottom of the reflection structure is flush with a bottom of the waveguide, and the reflection structure coincides with a central axis of the waveguide.
3. The photodetector according to claim 2, wherein, The reflection structure includes: a single-layer grating block, the single-layer grating block coincides with the central axis of the waveguide, and a width of the single-layer grating block is the same as a width of the waveguide.
4. The photodetector according to claim 2, wherein The reflection structure includes: a double-layer grating block, the double-layer grating blocks are aligned or staggered with each other, and a central axis of the double-layer grating block coincides with the central axis of the waveguide.
5. The photodetector according to claim 1, characterized in that, The waveguide coupling structure is a direct coupling structure, the absorption layer is disposed at an end of the waveguide, a bottom of the absorption layer is flush with a bottom of the waveguide, and the metal layer is disposed on the absorption layer; The reflection structure is disposed on three sides of the absorption layer not adjacent to the waveguide, a bottom of the reflection structure is flush with a bottom of the absorption layer, and the reflection structure coincides with a central axis of the absorption layer.
6. The photodetector according to claim 5, characterized in that, The reflection structure includes: a single-layer grating block, and the three single-layer grating blocks are correspondingly disposed on the three sides of the absorption layer not adjacent to the waveguide.
7. The photodetector according to claim 5, wherein, The reflection structure includes: a double-layer grating block, the double-layer grating blocks are aligned or staggered with each other, and the three double-layer grating blocks are correspondingly disposed on the three sides of the absorption layer not adjacent to the waveguide.
8. The photodetector according to claim 1, wherein, The photodetector uses a silicon-on-insulator platform.
9. The photodetector according to claim 8, characterized in that, The material of the absorption layer of the waveguide coupling structure is germanium.
10. A method for enhancing light absorption, characterized in that, The light absorption enhancement method is applied to the photodetector according to any one of claims 1 to 9, and the steps of the light absorption enhancement method include: Disposing a reflection structure at an end of the absorption layer side in the waveguide coupling structure; Reflecting the transmitted light transmitted by the waveguide through the waveguide coupling structure to form reflected light; Performing secondary absorption on the transmitted light of the waveguide and the reflected light of the reflection structure.