Heterogeneous integrated lithium niobate film based on coupling structure, preparation method and optical device

Abstract

The application relates to the technical field of optical devices, and discloses a hetero-integrated thin-film lithium niobate wafer coupling structure, a preparation method and an optical device. The application comprises a thin-film lithium niobate photonic chip, and the thin-film lithium niobate photonic chip is integrated with a III-V active waveguide layer through a hetero-integrated wafer bonding technology; the thin-film lithium niobate photonic chip is provided with a lithium niobate waveguide layer, and the output end of the lithium niobate waveguide layer is coupled with the input end of the III-V active waveguide layer in a vertical evanescent wave mode; and the III-V active waveguide layer is covered with an N-type metal electrode and a P-type metal electrode. The III-V active waveguide layer is integrated onto the lithium niobate photonic chip through the hetero-integrated wafer bonding technology, and the function of on-chip light detection of the thin-film lithium niobate platform is realized. The III-V active waveguide layer and the thin-film lithium niobate photonic chip are optically interconnected in a vertical evanescent wave coupling mode through an III-V / LN mode spot converter which is designed in an optimized mode, and high-efficiency coupling between the III-V active waveguide layer and the lithium niobate waveguide is realized.

Description

Technical Field

[0001] This invention relates to the field of optical device technology, and more specifically, to an on-chip coupling structure based on heterogeneous integrated thin film lithium niobate, its fabrication method, and an optical device. Background Technology

[0002] Lithium niobate (LNO) materials have long attracted researchers' attention due to their high electro-optic effect. Recently, the emergence of high-performance thin-film LNO modulators has brought the LNO platform (LNOI) into the researchers' view. Large-scale photonic integrated circuits (PICs) based on thin-film LNO (TFLN) are becoming a promising technology for realizing high-speed and high-capacity optical interconnects. Since LN materials lack the ability to effectively generate and detect light at telecommunication wavelengths, an electrically pumped light source and detector must be combined to realize practical LNO optical I / O chips.

[0003] Currently, the main methods for integrating active devices on thin-film lithium niobate include micro-transfer printing, end-to-end coupling, and wafer bonding. Micro-transfer printing requires high-precision flip-chip equipment; however, overlay errors in the equipment can lead to low coupling efficiency between devices, and the placement of individual devices is time-consuming and costly. End-to-end coupling is relatively simple, but it requires aligning two devices of different sizes or materials to sub-micron precision for effective coupling during device packaging, resulting in time-consuming and inefficient processes, making it less than ideal for mass production. Integrating III-V materials on lithium niobate photonic chips via wafer bonding is a highly effective technique. It allows for the integration of active devices (such as lasers and amplifiers) and detectors on the same chip using a single-chip to wafer bonding step. The III-V layer provides efficient light generation, amplification, and detection, while the high refractive index contrast (LNOI) allows for optical functions with a low footprint. However, current wafer bonding techniques for integrating III-V materials on lithium niobate photonic chips still suffer from low integration density and coupling efficiency. Summary of the Invention

[0004] To overcome the shortcomings of low integration and coupling efficiency in integrating III-V materials on lithium niobate photonic chips using wafer bonding technology in the prior art, this invention provides a heterogeneous integrated thin-film lithium niobate on-chip coupling structure, preparation method, and optical device.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0006] A heterogeneous integrated thin-film lithium niobate on-chip coupling structure includes a thin-film lithium niobate photonic chip, on which a III-V active waveguide layer is integrated via heterogeneous integrated wafer bonding technology; the thin-film lithium niobate photonic chip has a lithium niobate waveguide layer disposed on it, and the output end of the lithium niobate waveguide layer is perpendicularly evanescently coupled to the input end of the III-V active waveguide layer; the III-V active waveguide layer is covered with an N-type metal electrode and a P-type metal electrode.

[0007] In this technical solution, light input to the thin-film lithium niobate photonic chip is detected by applying a reverse voltage to the N-type and P-type metal electrodes, generating a photocurrent output. Specifically, a III-V active waveguide layer is integrated onto the lithium niobate photonic chip using heterogeneous wafer bonding technology, achieving on-chip photodetection of the thin-film lithium niobate. The output end of the lithium niobate waveguide layer is perpendicularly evanescently coupled to the input end of the III-V active waveguide layer, achieving high-efficiency coupling between the III-V active waveguide layer and the lithium niobate waveguide layer.

[0008] As a preferred embodiment, the III-V active waveguide layer comprises, from bottom to top, an N-type metal layer, a multiple quantum well layer, a P-type cladding layer, and a P-type metal layer.

[0009] As a preferred embodiment, the III-V active waveguide layer is a two-layer cascaded tapered waveguide structure.

[0010] As a preferred embodiment, the lithium niobate waveguide layer includes a grating coupler, a lithium niobate straight waveguide, and a lithium niobate tapered waveguide connected in sequence, wherein the grating coupler is coupled to an external single-mode optical fiber; the III-V active waveguide layer further includes a III-V group tapered waveguide, wherein the lithium niobate tapered waveguide and the III-V group tapered waveguide form a III-V / LN optical mode converter and maintain mode matching.

[0011] Specifically, the output end of the lithium niobate waveguide layer is vertically evanescently coupled to the input end of the III-V active waveguide layer through a III-V / LN mode converter, thereby achieving high-efficiency coupling between the III-V active waveguide layer and the lithium niobate waveguide layer.

[0012] As a preferred embodiment, a silicon oxide layer and a BCB curing layer are disposed between the III-V active waveguide layer and the thin-film lithium niobate photonic chip.

[0013] Furthermore, this invention also proposes a method for fabricating an on-chip coupling structure based on a heterogeneous integrated thin-film lithium niobate, used to prepare the on-chip coupling structure proposed in any of the above-mentioned technical solutions. This includes the following steps:

[0014] S1. Fabrication of grating couplers, lithium niobate straight waveguides, and lithium niobate tapered waveguides on thin-film lithium niobate photonic chips;

[0015] S2. A silicon oxide layer is deposited on the thin-film lithium niobate photonic chip obtained in step S1 using thin film deposition technology, and then the silicon oxide layer is polished flat to a thickness of no more than 50 nm using chemical mechanical polishing technology.

[0016] S3. After spin-coating a BCB curing layer with a thickness of less than 70 nm onto the thin-film lithium niobate photonic chip obtained in step S2, the III-V active waveguide layer is bonded to the thin-film lithium niobate photonic chip using heterogeneous integration wafer bonding technology; wherein, the output end of the thin-film lithium niobate photonic chip is perpendicularly evanescently coupled to the input end of the III-V active waveguide layer, and the lithium niobate tapered waveguide is matched with the III-V group tapered waveguide mode in the III-V active waveguide layer;

[0017] S4. An N-type metal electrode and a P-type metal electrode are disposed on the III-V active waveguide layer of the lithium niobate photonic chip obtained in step S3.

[0018] Furthermore, the present invention also proposes an optical device, specifically an optical detector, including a thin-film lithium niobate photonic chip, wherein the thin-film lithium niobate photonic chip integrates the heterogeneous integrated thin-film lithium niobate on-chip coupling structure proposed in any of the above technical solutions.

[0019] The thin-film lithium niobate photonic chip integrates a III-V group photodetector using heterogeneous wafer bonding technology. The thin-film lithium niobate photonic chip is equipped with a grating coupler, a lithium niobate straight waveguide, and a lithium niobate tapered waveguide, all fabricated from lithium niobate waveguides. The lithium niobate tapered waveguide and the III-V group tapered waveguide located at the bottom of the III-V group photodetector form a III-V / LN optical mode converter and maintain mode matching. The III-V group photodetector is covered with N-type and P-type metal electrodes for applying a reverse voltage to detect light input to the thin-film lithium niobate photonic chip and generate a photocurrent output.

[0020] As a preferred embodiment, the III-V group photodetector has a multi-quantum-well structure, comprising an N-type region, an intrinsic region, and a P-type region arranged sequentially from bottom to top; wherein, the N-type region includes an N-type metal layer, the intrinsic region includes a multi-quantum-well layer, and the P-type region includes a P-type cladding layer and a P-type metal layer.

[0021] As a preferred embodiment, a silicon oxide layer and a BCB curing layer are disposed between the III-V group photodetector and the lithium niobate photonic chip.

[0022] As a preferred embodiment, the lithium niobate photonic chip includes a silicon substrate, a silicon dioxide layer, a lithium niobate waveguide layer, and a silicon oxide layer arranged sequentially from bottom to top; the lithium niobate waveguide layer includes a grating coupler, a lithium niobate straight waveguide, and a lithium niobate tapered waveguide.

[0023] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention integrates a III-V active waveguide layer onto a lithium niobate photonic chip using heterogeneous wafer bonding technology, realizing on-chip optical detection functionality on a thin-film lithium niobate platform. The III-V active waveguide layer is optically interconnected with the lithium niobate photonic chip via a III-V / LN mode converter using vertical evanescent wave coupling, achieving high-efficiency coupling between the III-V active waveguide layer and the lithium niobate waveguide. The wafer bonding method, employing a small-size III-V active waveguide layer bonded to a large-size lithium niobate photonic chip, features high integration, cost savings, and ease of mass production, facilitating the realization of high-performance on-chip integrated photodetectors. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the heterogeneous integrated thin film lithium niobate on-chip coupling structure of Example 1.

[0025] Figure 2 This is a schematic diagram of the III-V active waveguide layer in Example 1.

[0026] Figure 3 This is a flowchart of the fabrication method of the heterogeneous integrated thin film lithium niobate on-chip coupling structure in Example 2.

[0027] Figure 4 This is a schematic diagram of the structure of the on-chip photodetector based on heterogeneous integrated thin-film lithium niobate in Example 3.

[0028] Figure 5 This is a cross-sectional view of the heterogeneous integrated thin-film lithium niobate on-chip photodetector in Example 3.

[0029] Figure 6 This is a schematic diagram of the on-chip wavelength response in Example 3.

[0030] Among them, 100-lithium niobate photonic chip, 110-lithium niobate waveguide layer, 111-grating coupler, 112-lithium niobate straight waveguide, 113-lithium niobate tapered waveguide, 120-silicon substrate, 130-silicon dioxide layer, 200-III-V active waveguide layer, 201-N-type metal layer, 202-multiple quantum well layer, 203-P-type cladding, 204-P-type metal layer, 205-III-V group tapered waveguide, 300-N-type metal electrode, 400-P-type metal electrode, 500-silicon oxide layer, 600-BCB curing layer. Detailed Implementation

[0031] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this patent.

[0032] To better illustrate this embodiment, some parts in the accompanying drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions;

[0033] It will be understood by those skilled in the art that certain well-known structures and their descriptions may be omitted in the accompanying drawings.

[0034] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0035] Example 1

[0036] This embodiment proposes an on-chip coupling structure based on heterogeneous integrated thin-film lithium niobate, such as... Figure 1 The diagram shown is a schematic diagram of the heterogeneous integrated thin-film lithium niobate on-chip coupling structure in this embodiment.

[0037] The heterogeneous integrated thin-film lithium niobate on-chip coupling structure proposed in this embodiment includes a thin-film lithium niobate photonic chip 100, on which a III-V active waveguide layer 200 is integrated by heterogeneous integrated wafer bonding technology.

[0038] In this embodiment, a lithium niobate waveguide layer 110 is disposed on the thin-film lithium niobate photonic chip 100, and the output end of the lithium niobate waveguide layer 110 is vertically evanescently coupled to the input end of the III-V active waveguide layer 200.

[0039] The III-V active waveguide layer 200 is covered with an N-type metal electrode 300 and a P-type metal electrode 400, which are used to apply a reverse voltage to the on-chip coupling structure to detect the light input to the thin-film lithium niobate photonic chip 100 and generate photocurrent output.

[0040] In this embodiment, a III-V active waveguide layer 200 is integrated onto a thin-film lithium niobate photonic chip 100 using heterogeneous wafer bonding technology, realizing on-chip photodetector functionality for lithium niobate. The III-V active waveguide layer 200 is optically interconnected with the thin-film lithium niobate photonic chip 100 via vertical evanescent wave coupling, achieving high-efficiency coupling between the III-V active waveguide layer 200 and the lithium niobate waveguide. Wafer bonding, employing a bonding method from a small-sized III-V active waveguide layer 200 to a large-sized thin-film lithium niobate photonic chip 100, features high integration, cost savings, and ease of mass production, facilitating the realization of high-performance on-chip integrated photodetectors.

[0041] In an optional embodiment, the III-V active waveguide layer 200 includes an N-type metal layer 201, a multiple quantum well layer 202, a P-type cladding layer 203, and a P-type metal layer 204 arranged sequentially from bottom to top.

[0042] like Figure 2 The diagram shown is a schematic diagram of the III-V active waveguide layer 200 in this embodiment.

[0043] The III-V active waveguide layer 200 is a two-layer cascaded conical waveguide structure. The multi-quantum well layer 202 of the III-V active waveguide layer 200 is used to detect incident light, generating electron-hole pairs. Under reverse bias, the electrons and holes move to the two poles respectively, generating photocurrent.

[0044] In an optional embodiment, the lithium niobate waveguide layer 110 includes a grating coupler 111, a lithium niobate straight waveguide 112, and a lithium niobate tapered waveguide 113 connected in sequence, wherein the grating coupler 111 is coupled to an external single-mode optical fiber; the III-V active waveguide layer 200 further includes a III-V group tapered waveguide 205, wherein the lithium niobate tapered waveguide 112 and the III-V group tapered waveguide 205 form a III-V / LN optical mode converter and maintain mode matching.

[0045] In this embodiment, the III-V / LN optical mode converter is composed of a lithium niobate tapered waveguide 113 and a III-V group tapered waveguide 205, wherein the III-V group tapered waveguide 205 is an N-type metal layer 201 waveguide, and the III-V group tapered waveguide 205 and the N-type metal layer 201 in the III-V active waveguide layer 200 are an integrated waveguide layer.

[0046] In a specific implementation, the incident light input from the external single-mode fiber is coupled by the grating coupler 110 to the lithium niobate straight waveguide 111 and the lithium niobate tapered waveguide 113. The lithium niobate tapered waveguide 113 couples the optical signal to the III-V group tapered waveguide 205, and then to the N-type metal layer 201 in the III-V active waveguide layer 200. Then, through the III-V active waveguide layer 200, the light is gradually coupled to the multi-quantum well layer 202. After receiving photons, the multi-quantum well layer 202 undergoes stimulated emission, generating electron-hole pairs. Under the action of reverse bias, the electrons and holes move to the two poles respectively, generating photocurrent, thereby realizing the detection of the incident light.

[0047] Furthermore, in an optional embodiment, the grating coupler 111 is a lithium niobate one-dimensional coupling grating, which enables high-efficiency coupling between the thin-film lithium niobate photonic chip 100 and an external single-mode optical fiber.

[0048] Furthermore, in an optional embodiment, a silicon oxide layer 500 and a BCB curing layer 600 are disposed between the III-V active waveguide layer 200 and the lithium niobate photonic chip 100.

[0049] In this embodiment, the III-V active waveguide layer 200 is integrated onto the lithium niobate photonic chip 100 using heterogeneous integration wafer bonding technology. The heterogeneous integration bonding method adopts adhesive bonding. Specifically, BCB (benzocyclobutene) is used as an intermediate layer, and the III-V active waveguide layer 200 is integrated with the thin-film lithium niobate photonic chip 100 by BCB curing. This method has the characteristics of high integration, cost saving, and facilitating mass production.

[0050] Example 2

[0051] This embodiment proposes a method for preparing a heterogeneous integrated thin film lithium niobate on-chip coupling structure, which is used to prepare the heterogeneous integrated thin film lithium niobate on-chip coupling structure proposed in Example 1.

[0052] like Figure 3 The diagram shown is a flowchart of the fabrication method of the heterogeneous integrated thin film lithium niobate on-chip coupling structure in this embodiment.

[0053] The fabrication method based on heterogeneous integrated thin-film lithium niobate on-chip coupling structure proposed in this embodiment includes the following steps:

[0054] S1. A grating coupler 111, a lithium niobate straight waveguide 112, and a lithium niobate tapered waveguide 113 are fabricated on a lithium niobate photonic chip 100.

[0055] S2. A silicon oxide layer 500 is deposited on the thin-film lithium niobate photonic chip 100 obtained in step S1 using thin film deposition technology, and then the silicon oxide layer 500 is polished flat to a thickness of no more than 50 nm using chemical mechanical polishing technology.

[0056] S3. After spin-coating a BCB curing layer 600 with a thickness of less than 70 nm onto the thin-film lithium niobate photonic chip 100 obtained in step S2, the III-V active waveguide layer 200 is bonded to the thin-film lithium niobate photonic chip 100 using heterogeneous integration wafer bonding technology. The output end of the thin-film lithium niobate photonic chip 100 is vertically evanescently coupled to the input end of the III-V active waveguide layer 200, and the lithium niobate tapered waveguide 113 is mode-matched with the III-V group tapered waveguide 205 in the III-V active waveguide layer 200.

[0057] S4. An N-type metal electrode 300 and a P-type metal electrode 400 are disposed on the III-V active waveguide layer 200 of the lithium niobate photonic chip 100 obtained in step S3.

[0058] In an optional embodiment, the thin-film lithium niobate photonic chip 100 includes a silicon substrate 120 and a silicon dioxide layer 130 arranged sequentially from bottom to top. In step S1, a grating coupler 111, a lithium niobate straight waveguide 112, and a lithium niobate tapered waveguide 113 are fabricated on the silicon dioxide layer 130 in the thin-film lithium niobate photonic chip 100 to obtain a lithium niobate waveguide layer 110.

[0059] In this embodiment, the III-V active waveguide layer 200 is integrated onto the thin-film lithium niobate photonic chip 100 using heterogeneous wafer bonding technology. The resulting thin-film lithium niobate photonic chip 100 has the function of on-chip photodetection of lithium niobate. Furthermore, in this embodiment, the III-V active waveguide layer 200 acts as a III-V / LN mode converter, vertically coupling with the lithium niobate waveguide layer 110 to achieve high-efficiency coupling between the III-V active waveguide layer 200 and the lithium niobate waveguide.

[0060] Example 3

[0061] This embodiment proposes an optical device, specifically, an on-chip photodetector based on heterogeneous integrated thin-film lithium niobate. For example... Figure 4 , 5 The diagram shown is a schematic representation of the heterogeneous integrated thin-film lithium niobate on-chip photodetector in this embodiment. Figure 4 The representation of N-type metal electrode 300, P-type metal electrode 400, and BCB curing layer 600 is omitted.

[0062] The optical device proposed in this embodiment includes a thin-film lithium niobate photonic chip 100, on which the thin-film lithium niobate photonic chip 100 integrates the heterogeneous integrated thin-film lithium niobate on-chip coupling structure proposed in Embodiment 1.

[0063] The thin-film lithium niobate photonic chip 100 integrates a III-V group photodetector through heterogeneous integration wafer bonding technology.

[0064] The thin-film lithium niobate photonic chip 100 is provided with a grating coupler 111, a lithium niobate straight waveguide 112 and a lithium niobate tapered waveguide 113. The lithium niobate tapered waveguide 113 and the III-V group tapered waveguide 205 provided at the bottom of the III-V group photodetector form a III-V / LN optical mode converter and maintain mode matching.

[0065] The III-V group photodetector is covered with an N-type metal electrode 300 and a P-type metal electrode 400, which are used to apply a reverse voltage to detect the light input to the thin-film lithium niobate photonic chip and generate photocurrent output.

[0066] In one specific implementation, the grating coupler 111 is connected to an external single-mode fiber. The incident light input from the external single-mode fiber is coupled by the grating coupler 111 and transmitted through the lithium niobate straight waveguide 112 to the lithium niobate tapered waveguide 113 of the optical mode converter. The lithium niobate tapered waveguide 113 couples the optical signal to the III-V group photodetector. Simultaneously, the III-V group photodetector detects the input light by applying a reverse voltage to the N-type metal electrode 300 and the P-type metal electrode 400. Under the action of the reverse bias voltage, electrons and holes move to the two electrodes respectively, generating photocurrent, thereby realizing the detection of light.

[0067] like Figure 6 The figure shows a schematic diagram of the on-chip wavelength response of the heterogeneous integrated thin-film lithium niobate on-chip photodetector in this embodiment. As can be seen from the figure, using the heterogeneous integrated thin-film lithium niobate on-chip photodetector proposed in this embodiment, the waveguide coupling effect for input wavelengths of 1550nm and 1560nm can reach 0.52A / W and 0.48A / W, respectively, when a reverse voltage of 5V is applied.

[0068] In this embodiment, a III-V group photodetector is integrated onto a thin-film lithium niobate photonic chip 100 using heterogeneous integration wafer bonding technology, realizing on-chip photodetection of lithium niobate. Specifically, the III-V group photodetector is vertically evanescently coupled to a lithium niobate tapered waveguide 113, achieving high-efficiency coupling between the III-V group photodetector and the lithium niobate waveguide. This approach features high integration, cost savings, and ease of mass production.

[0069] In an optional embodiment, the III-V group photodetector is a multi-quantum-well structure, including an N-type region, an intrinsic region, and a P-type region arranged sequentially from bottom to top; wherein, the N-type region includes an N-type metal layer 201, the intrinsic region includes a multi-quantum-well layer 202, and the P-type region includes a P-type cladding layer 203 and a P-type metal layer 204.

[0070] In the III-V group photodetector, the multi-quantum well layer 202 receives photons and undergoes stimulated emission, generating electron-hole pairs. Under the action of reverse bias, the electrons and holes move to the two poles respectively, generating photocurrent.

[0071] In an optional embodiment, a silicon oxide layer 500 and a BCB curing layer 600 are disposed between the thin-film lithium niobate photonic chips 100.

[0072] Further, in an optional embodiment, the thin-film lithium niobate photonic chip 100 includes a silicon substrate 120, a silicon dioxide layer 130, a lithium niobate waveguide layer 110, and a silicon oxide layer 140 arranged sequentially from bottom to top; the lithium niobate waveguide layer 110 includes a grating coupler 111, a lithium niobate straight waveguide 112, and a lithium niobate tapered waveguide 113 made of lithium niobate waveguides.

[0073] The same or similar labels correspond to the same or similar parts;

[0074] The terms used to describe positional relationships in the accompanying drawings are for illustrative purposes only and should not be construed as limiting this patent.

[0075] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A heterogeneously integrated thin film lithium niobate chip based on a coupling structure, characterized in that, The invention includes a thin-film lithium niobate photonic chip (100), on which a III-V active waveguide layer (200) is integrated by heterogeneous integration wafer bonding technology. The thin-film lithium niobate photonic chip (100) is provided with a lithium niobate waveguide layer (110), the output end of the lithium niobate waveguide layer (110) is perpendicularly evanescently coupled to the input end of the III-V active waveguide layer (200); the III-V active waveguide layer (200) is covered with an N-type metal electrode (300) and a P-type metal electrode (400). The III-V active waveguide layer (200) is a two-layer cascaded tapered waveguide structure, wherein the lower layer is a III-V family tapered waveguide (205), and the upper layer is a III-V family photodetector composed of an N-type metal layer (201), a multi-quantum well layer (202), a P-type cladding layer (203), and a P-type metal layer (204) stacked sequentially; and the lithium niobate waveguide layer (110) includes a grating coupler (111), a lithium niobate straight waveguide (112), and a lithium niobate tapered waveguide (113) connected in sequence. The grating coupler (111) is coupled to an external single-mode fiber; the lithium niobate tapered waveguide (113) is directly and vertically coupled to the III-V family tapered waveguide (205) to form a III-V / LN optical mode converter and maintain mode matching.

2. The thin film lithium niobate on insulator based heterogeneously integrated on-chip coupling structure of claim 1, wherein, A silicon oxide layer (500) and a BCB curing layer (600) are disposed between the III-V active waveguide layer (200) and the thin-film lithium niobate photonic chip (100).

3. A method for fabricating a coupling structure on a lithium niobate film based on heterogeneous integration, characterized in that, The method for preparing the heterogeneous integrated thin-film lithium niobate on-chip coupling structure as described in claim 1 or 2 includes the following steps: S1. A grating coupler (111), a lithium niobate straight waveguide (112), and a lithium niobate tapered waveguide (113) are fabricated on a thin-film lithium niobate photonic chip (100). S2. A silicon oxide layer (500) is deposited on the thin-film lithium niobate photonic chip (100) obtained in step S1 using thin film deposition technology, and then the silicon oxide layer (500) is polished flat to a thickness of no more than 50 nm using chemical mechanical polishing technology. S3. After spin-coating a BCB curing layer (600) with a thickness of less than 70 nm onto the thin-film lithium niobate photonic chip (100) obtained in step S2, the III-V active waveguide layer (200) is bonded to the thin-film lithium niobate photonic chip (100) using heterogeneous integrated wafer bonding technology; wherein, the output end of the thin-film lithium niobate photonic chip (100) is perpendicularly evanescently coupled to the input end of the III-V active waveguide layer (200), and the lithium niobate tapered waveguide (113) is directly perpendicularly evanescently coupled to the III-V group tapered waveguide (205) in the III-V active waveguide layer (200) and the mode is matched; S4. An N-type metal electrode (300) and a P-type metal electrode (400) are disposed on the III-V active waveguide layer (200) of the thin-film lithium niobate photonic chip (100) obtained in step S3.

4. An optical device, characterized by The invention includes a thin-film lithium niobate photonic chip (100), on which the thin-film lithium niobate photonic chip (100) integrates the heterogeneous integrated thin-film lithium niobate on-chip coupling structure as described in claim 1 or 2, wherein: A III-V group photodetector is integrated on the thin-film lithium niobate photonic chip (100) using heterogeneous integration wafer bonding technology; The thin-film lithium niobate photonic chip (100) is provided with a grating coupler (111), a lithium niobate straight waveguide (112), and a lithium niobate tapered waveguide (113) made of lithium niobate waveguide. The lithium niobate tapered waveguide (113) is directly and vertically coupled to the III-V group tapered waveguide (205) provided at the bottom of the III-V group photodetector to form a III-V / LN optical mode converter and maintain mode matching. The III-V group photodetector is covered with an N-type metal electrode (300) and a P-type metal electrode (400) for applying a reverse voltage to detect the light input to the thin-film lithium niobate photonic chip (100) and generate photocurrent output.

5. The optical device of claim 4, wherein, The III-V group photodetector has a multi-quantum-well structure, including an N-type region, an intrinsic region, and a P-type region arranged sequentially from bottom to top; wherein, the N-type region includes an N-type metal layer (201), the intrinsic region includes a multi-quantum-well layer (202), and the P-type region includes a P-type cladding layer (203) and a P-type metal layer (204).

6. The optical device of claim 4, wherein, A silicon oxide layer (500) and a BCB curing layer (600) are disposed between the III-V group photodetector and the thin-film lithium niobate photonic chip (100).

7. The optical device according to any of claims 4-6, characterized in that The thin-film lithium niobate photonic chip (100) includes a silicon substrate (120), a silicon dioxide layer (130), a lithium niobate waveguide layer (110) and a silicon oxide layer (140) arranged sequentially from bottom to top; the lithium niobate waveguide layer (110) includes a grating coupler (111), a lithium niobate straight waveguide (112) and a lithium niobate tapered waveguide (113).

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