Optical module, optical coupler and preparation method of optical coupler

Abstract

The invention provides an optical module, an optical coupler and a preparation method of the optical coupler. The optical module comprises an optical chip, an optical fiber array and an optical coupler. The optical coupler comprises a substrate, a refractive index difference layer and a transmission waveguide layer. The optical coupler comprises a coupling waveguide located in the transmission waveguide layer, the first end of the coupling waveguide faces the optical fiber array, and the second end of the coupling waveguide faces the interior of the optical chip. The width of the coupling waveguide tends to increase in the direction from the first end to the second end. The optical coupler comprises a first limiting waveguide and a second limiting waveguide. The first limiting waveguide comprises a first inclined plane, and the first inclined plane gradually inclines in the direction away from the central axis of the coupling waveguide so as to gradually increase the distance between the first inclined plane and the coupling waveguide and reduce the coupling loss between the first limiting waveguide and the coupling waveguide. The second limiting waveguide comprises a second inclined plane, and the second inclined plane gradually inclines in the direction away from the central axis of the coupling waveguide, so that the distance between the second inclined plane and the coupling waveguide is gradually increased, and coupling loss between the second limiting waveguide and the coupling waveguide is reduced.

Description

Optical module, optical coupler and method for manufacturing optical coupler

[0001] This application claims priority to the application filed on April 25, 2025 with the China Patent Office and application number 202510534221.5; the application filed on July 24, 2024 with the China Patent Office and application number 202410998365.1; the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0002] The present disclosure relates to the field of optical communication technology, in particular to an optical module, an optical coupler and a method for manufacturing the optical coupler. BACKGROUND

[0003] With the development of new business and application modes such as cloud computing, mobile Internet, video, etc., the progress of optical communication technology becomes increasingly important. In optical communication technology, the optical module, as one of the key devices in optical communication equipment, can realize optical-electrical signal conversion; in the development process of optical communication technology, the data transmission rate of the optical module is required to be continuously improved. SUMMARY

[0004] The present disclosure provides an optical module, comprising a fiber array, an optical chip and an optical coupler; the optical chip is used for modulation and demodulation of optical signals, the optical chip is optically connected with the fiber array, so that the optical signal generated by the modulation of the optical chip is transmitted along the fiber array; the optical coupler is arranged between the optical chip and the fiber array; the optical coupler comprises a substrate and a refractive index difference layer, the refractive index difference layer is located above the substrate;

[0005] The optical coupler further comprises:

[0006] A coupling waveguide, in the direction in which the fiber array points to the optical chip, the width of the coupling waveguide shows a trend of increasing;

[0007] A first limiting waveguide, located on one side of the first end of the coupling waveguide, the first end of the coupling waveguide faces the fiber array, in the direction in which the fiber array points to the optical chip, the width of the first limiting waveguide shows a trend of decreasing;

[0008] A second limiting waveguide, located on the other side of the first end of the coupling waveguide, in the direction in which the fiber array points to the optical chip, the width of the second limiting waveguide shows a trend of decreasing; or,

[0009] The optical coupler further comprises:

[0010] A coupling waveguide array, located at one end of the optical coupler facing the optical port of the optical chip, to optically couple with the fiber array;

[0011] A transmission waveguide, located above the refractive index difference layer;

[0012] A transition waveguide, located above the transmission waveguide;

[0013] a high refractive index region above the refractive index difference layer, the high refractive index region enclosing the transmission waveguide, the array of coupling waveguides and the transition waveguide, the high refractive index region comprising a region with a refractive index greater than the refractive index of the refractive index difference layer.

[0014] The present disclosure also provides an optical coupler comprising a substrate and a refractive index difference layer above the substrate;

[0015] The optical coupler further comprises:

[0016] the coupling waveguide having a width that increases in a direction from the first end to the second end of the coupling waveguide;

[0017] a first confinement waveguide on one side of the first end of the coupling waveguide, the first confinement waveguide having a width that decreases in the direction from the first end to the second end of the coupling waveguide;

[0018] a second confinement waveguide on another side of the first end of the coupling waveguide, the second confinement waveguide having a width that decreases in the direction from the first end to the second end of the coupling waveguide; or

[0019] The optical coupler further comprises:

[0020] the array of coupling waveguides is located at an edge of the optical coupler;

[0021] the transmission waveguide is located above the refractive index difference layer;

[0022] the transition waveguide is located above the transmission waveguide;

[0023] a high refractive index region above the refractive index difference layer, the high refractive index region enclosing the transmission waveguide, the array of coupling waveguides and the transition waveguide, the high refractive index region comprising a region with a refractive index greater than the refractive index of the refractive index difference layer.

[0024] The present disclosure also provides a method for manufacturing an optical coupler, applied to the optical coupler described above, comprising:

[0025] etching a top layer of silicon on a surface of an SOI wafer to form the transmission waveguide, the SOI wafer comprising a substrate, a refractive index difference layer and a top layer of silicon from bottom to top;

[0026] forming the transition waveguide above one end of the transmission waveguide;

[0027] forming the array of coupling waveguides at one end of the transition waveguide;

[0028] The high-refractive-index region with uniform refractive index and greater refractive index than the refractive-index-difference layer is grown epitaxially upward along the refractive-index-difference layer; or the refractive-index-difference layer is grown epitaxially upward along the refractive-index-difference layer to form each sub-layer with different refractive index, wherein the refractive index of one sub-layer is greater than the refractive index of the refractive-index-difference layer. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the present disclosure, the drawings used in some embodiments of the present disclosure will be briefly introduced as follows. Obviously, the drawings in the following description are only some drawings of the embodiments of the present disclosure, and other drawings can also be obtained by those skilled in the art according to these drawings. In addition, the drawings in the following description can be regarded as schematic diagrams, and are not limited to the actual size, actual process, actual time sequence, etc. of the product, method, signal, etc. involved in the embodiments of the present disclosure.

[0030] FIG. 1 is a partial architecture diagram of an optical communication system according to some embodiments;

[0031] FIG. 2 is a partial structure diagram of a host computer according to some embodiments;

[0032] FIG. 3 is a structure diagram of an optical module according to some embodiments;

[0033] FIG. 4 is an exploded view of an optical module according to some embodiments;

[0034] FIG. 5 is a schematic diagram of the internal structure of an optical module according to some embodiments;

[0035] FIG. 6 is a schematic diagram of the internal structure of an optical chip according to some embodiments;

[0036] FIG. 7 is a schematic diagram of the structure of an optical coupler according to some embodiments;

[0037] FIG. 8 is a diagram of the internal structure of an optical coupler according to some embodiments;

[0038] FIG. 9 is a diagram of the internal structure of an optical coupler according to some embodiments;

[0039] FIG. 10 is a perspective view of another optical coupler according to some embodiments;

[0040] FIG. 11 is a cross-sectional view of another optical coupler according to some embodiments;

[0041] FIG. 12 is a perspective view of another optical coupler according to some embodiments;

[0042] FIG. 13 is a cross-sectional view of another optical coupler according to some embodiments;

[0043] FIG. 14 is an assembly view between a transmission waveguide and a transition waveguide according to some embodiments;

[0044] FIG. 15 is an assembly view between a transition waveguide and a coupling waveguide array according to some embodiments. DETAILED DESCRIPTION

[0045] Some embodiments of the present disclosure will be described in detail below with reference to the drawings. However, the described embodiments are only some embodiments of the present disclosure, not all embodiments. Based on the embodiments provided in the present disclosure, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present disclosure.

[0046] Unless otherwise required by the context, throughout the specification and claims, the term "comprising" is to be interpreted as open, inclusive, meaning "including, but not limited to"; the terms "first", "second" are not to be interpreted as indicating or implying relative importance or indicating the upper limit of the number; the term "multiple" means two or more; the term "connected" should be interpreted broadly, for example, "connected" can be fixed connection, or detachable connection, or integral, can be directly connected, or indirectly connected through an intermediate medium; the use of the terms "adapted to" or "configured to" means open and inclusive language, which does not exclude devices adapted to or configured to perform additional tasks or steps; the terms "parallel", "vertical", "same", "consistent", "flush" and the like are not limited to absolute mathematical relationships, but also include acceptable error ranges generated in practice, and also include differences based on the same design concept but due to manufacturing reasons.

[0047] In optical communication technology, information transmission needs to be established between information processing devices. Information needs to be loaded onto light to achieve transmission by using the propagation of light. The light loaded with information is an optical signal. The optical signal can reduce the loss of optical power when transmitted in the information transmission device, so as to achieve high-speed, long-distance, low-cost information transmission. Information processing devices can identify and process electrical signals. Information processing devices usually include optical network units (ONUs), gateways, routers, switches, mobile phones, computers, servers, tablets, televisions, etc. Information transmission devices usually include optical fibers and optical waveguides.

[0048] The optical module can realize information transmission between the information processing device and the information transmission device. The optical module can realize mutual conversion between optical signal and electrical signal. For example, at least one of the optical signal input end and the optical signal output pin of the optical module is connected with an optical fiber, and at least one of the electrical signal input end and the electrical signal output pin of the optical module is connected with an optical network terminal. A first optical signal from the optical fiber is transmitted to the optical module. The optical module converts the first optical signal into a first electrical signal. The optical module transmits the first electrical signal to the optical network terminal. A second electrical signal from the optical network terminal is transmitted to the optical module. The optical module converts the second electrical signal into a second optical signal. The optical module transmits the second optical signal to the optical fiber. Since information transmission between multiple information processing devices can be realized through electrical signals, at least one of the multiple information processing devices needs to be directly connected with the optical module. All of the information processing devices do not need to be directly connected with the optical module. Here, the information processing device directly connected with the optical module is referred to as a host computer of the optical module. In addition, the optical signal input end of the optical module or the optical signal output pin of the optical module can be referred to as an optical port, and the electrical signal input end of the optical module or the electrical signal output pin of the optical module can be referred to as an electrical port.

[0049] FIG. 1 is a partial structure diagram of an optical communication system according to some embodiments. As shown in FIG. 1, the optical communication system mainly includes a remote information processing device 1000, a local information processing device 2000, a host computer 100, an optical module 200, an optical fiber 101, and a network cable 103.

[0050] One end of the optical fiber 101 extends towards the remote information processing device 1000, and the other end of the optical fiber 101 is connected with the optical module 200 through the optical port of the optical module 200. The optical signal can be totally reflected in the optical fiber 101, and the propagation of the optical signal in the totally reflected direction can almost maintain the original optical power. The optical signal is totally reflected multiple times in the optical fiber 101 to transmit the optical signal from the remote information processing device 1000 to the optical module 200, or to transmit the optical signal from the optical module 200 to the remote information processing device 1000, thereby realizing long-distance and low-power-loss information transmission.

[0051] The optical communication system can include one or more optical fibers 101, and the optical fiber 101 is detachably connected with the optical module 200 or fixedly connected. The host computer 100 is configured to provide a data signal to the optical module 200, or receive a data signal from the optical module 200, or monitor or control the working state of the optical module 200.

[0052] The host computer 100 includes a housing substantially in the shape of a rectangular cuboid, and an optical module interface 102 disposed on the housing. The optical module interface 102 is configured to access the optical module 200, so that the host computer 100 establishes a unidirectional or bidirectional electrical signal connection with the optical module 200.

[0053] The host computer 100 further comprises an external electrical interface which can access an electrical signal network. For example, the external electrical interface comprises a Universal Serial Bus (USB) interface or a network cable interface 104 configured to access a network cable 103 to establish a unidirectional or bidirectional electrical signal connection between the host computer 100 and the network cable 103. One end of the network cable 103 is connected to the local information processing device 2000, and the other end of the network cable 103 is connected to the host computer 100 to establish an electrical signal connection between the local information processing device 2000 and the host computer 100 through the network cable 103. For example, a third electrical signal emitted by the local information processing device 2000 is transmitted to the host computer 100 through the network cable 103, and the host computer 100 generates a second electrical signal according to the third electrical signal. The second electrical signal from the host computer 100 is transmitted to the optical module 200, and the optical module 200 converts the second electrical signal into a second optical signal and transmits the second optical signal to the optical fiber 101. The second optical signal is transmitted in the optical fiber 101 to the remote information processing device 1000. For example, the first optical signal from the remote information processing device 1000 is transmitted through the optical fiber 101, the first optical signal from the optical fiber 101 is transmitted to the optical module 200, the optical module 200 converts the first optical signal into a first electrical signal, the optical module 200 transmits the first electrical signal to the host computer 100, the host computer 100 generates a fourth electrical signal according to the first electrical signal, and the fourth electrical signal is transmitted to the local information processing device 2000. It should be noted that the optical module is a tool for converting optical signals and electrical signals, and the information does not change in the conversion process of the optical signals and the electrical signals, and the encoding and decoding mode of the information can change.

[0054] In addition to the optical network terminal, the host computer 100 further comprises an Optical Line Terminal (OLT), an Optical Network Terminal (ONT), or a data center server, etc.

[0055] FIG. 2 is a partial structural diagram of a host computer according to some embodiments. In order to clearly show the connection relationship between the optical module 200 and the host computer 100, FIG. 2 only shows the structure of the host computer 100 related to the optical module 200. As shown in FIG. 2, the host computer 100 further comprises a PCB circuit board 105 arranged in the shell, a cage 106 arranged on the surface of the PCB circuit board 105, a heat sink 107 arranged on the cage 106, and an electrical connector arranged inside the cage 106. The electrical connector is configured to access the electrical port of the optical module 200; the heat sink 107 has a protruding structure such as fins to increase the heat dissipation area.

[0056] The optical module 200 is inserted into the cage 106 of the host computer 100, and the optical module 200 is fixed by the cage 106. The heat generated by the optical module 200 is conducted to the cage 106, and then diffused through the heat sink 107. After the optical module 200 is inserted into the cage 106, the electrical port of the optical module 200 is connected to the electrical connector inside the cage 106, so that the optical module 200 and the host computer 100 establish a bidirectional electrical signal connection. In addition, the optical port of the optical module 200 is connected to the optical fiber 101, so that the optical module 200 and the optical fiber 101 establish a bidirectional optical signal connection.

[0057] FIG. 3 is a structural diagram of an optical module according to some embodiments, and FIG. 4 is an exploded view of an optical module according to some embodiments. As shown in FIGS. 3 and 4, the optical module 200 includes a shell, a circuit board 300 arranged in the shell, an optical chip 400, and a light source 500. The optical chip 400 and the light source 500 are electrically connected to the circuit board 300, respectively, and the light emitting end of the light source 500 is optically coupled to the optical chip 400. In some embodiments, the light emitting end of the light source 500 is coupled to the optical chip 400 through an optical fiber.

[0058] The shell includes an upper shell 201 and a lower shell 202. The upper shell 201 is covered on the lower shell 202 to form the above-mentioned shell with two openings 204 and 205. The outer contour of the shell generally presents a square body.

[0059] In some embodiments, the lower shell 202 includes a bottom plate 2021 and two lower side plates 2022 arranged perpendicularly to the bottom plate 2021 on both sides of the bottom plate 2021. The upper shell 201 includes a cover plate 2011, and the cover plate 2011 is covered on the two lower side plates 2022 of the lower shell 202 to form the above-mentioned shell.

[0060] In some embodiments, the lower shell 202 includes a bottom plate 2021 and two lower side plates 2022 arranged perpendicularly to the bottom plate 2021 on both sides of the bottom plate 2021. The upper shell 201 includes a cover plate 2011 and two upper side plates arranged perpendicularly to the cover plate 2011 on both sides of the cover plate 2011. The two upper side plates and the two lower side plates 2022 are combined to achieve that the upper shell 201 is covered on the lower shell 202.

[0061] The direction of the line connecting the two openings 204 and 205 can be consistent with the length direction of the optical module 200, or can be inconsistent with the length direction of the optical module 200. For example, the opening 204 is located at the end of the optical module 200 (the left end of FIG. 3), and the opening 205 is also located at the end of the optical module 200 (the right end of FIG. 3). Alternatively, the opening 204 is located at the end of the optical module 200, and the opening 205 is located at the side of the optical module 200. The opening 204 is an electrical port, and the gold fingers 301 of the circuit board 300 extend from the opening 204 and are inserted into the electrical connector of the host computer 100. The opening 205 is an optical port configured to access the external optical fiber 101, so that the optical fiber 101 is connected to the optical chip 400 in the optical module 200.

[0062] The assembly of the upper shell 201 and the lower shell 202 facilitates the installation of the circuit board 300, the optical modulation chip, and the light source into the shells. The upper shell 201 and the lower shell 202 can encapsulate and protect the above-mentioned devices. In addition, when assembling the circuit board 300, the optical chip 400, and the light source, the positioning components, the heat dissipation components, and the electromagnetic shielding components of these devices can be easily deployed, which facilitates the automated production.

[0063] In some embodiments, the upper shell 201 and the lower shell 202 are made of metal materials, which facilitates electromagnetic shielding and heat dissipation.

[0064] In some embodiments, the optical module 200 further includes an unlocking component 600 located outside the shell of the optical module 200. The unlocking component 600 is configured to achieve the fixed connection between the optical module 200 and the host computer, or to release the fixed connection between the optical module 200 and the host computer.

[0065] For example, the unlocking component 600 is located outside the two lower side plates 2022 of the lower shell 202 and includes a clamping component matched with the cage 106 of the host computer 100. When the optical module 200 is inserted into the cage 106, the clamping component of the unlocking component 600 fixes the optical module 200 in the cage 106. When the unlocking component 600 is pulled, the clamping component of the unlocking component 600 moves, thereby changing the connection relationship between the clamping component and the host computer, to release the fixed connection between the optical module 200 and the host computer, so that the optical module 200 can be pulled out of the cage 106.

[0066] The circuit board 300 includes circuit traces, electronic components, and chips, etc. The electronic components and chips are connected according to circuit design through the circuit traces to realize power supply, electrical signal transmission, and grounding, etc. The electronic components may, for example, include capacitors, resistors, transistors, and Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs). The chips may, for example, include Microcontroller Units (MCUs), laser drive chips, Transimpedance Amplifiers (TIAs), Limiting Amplifiers (LAs), Clock and Data Recovery (CDR) chips, power management chips, and Digital Signal Processing (DSP) chips.

[0067] The circuit board 300 is generally a rigid circuit board. Due to its relatively hard material, the rigid circuit board can also realize a bearing function, such as the rigid circuit board can stably bear the above-mentioned electronic components and chips. The rigid circuit board can also be inserted into the electrical connector in the cage 106 of the host computer 100.

[0068] The circuit board 300 also includes a gold finger 301 formed on the surface of the end thereof. The gold finger 301 is composed of a plurality of pins independent of each other. The circuit board 300 is inserted into the cage 106, and the gold finger 301 is in conduction with the electrical connector in the cage 106. The gold finger 301 can be provided only on the surface (e.g., the upper surface shown in FIG. 4) of one side of the circuit board 300, or can be provided on the surfaces of both upper and lower sides of the circuit board 300 to provide a larger number of pins to adapt to occasions requiring a large number of pins. The gold finger 301 is configured to establish electrical connection with the host computer to realize power supply, grounding, Inter-Integrated Circuit (I2C) signal transmission, data signal transmission, etc. Of course, flexible circuit boards are also used in some optical modules. The flexible circuit board is generally used in cooperation with the rigid circuit board to supplement the rigid circuit board.

[0069] FIG. 5 is a schematic diagram of the internal structure of an optical module according to some embodiments. As shown in FIG. 5, in some embodiments, the optical chip 400 is used for modulating and demodulating optical signals: the optical chip 400 modulates the received electrical signals into optical signals, and the optical chip 400 demodulates the received optical signals into electrical signals.

[0070] In some embodiments, the optical chip 400 can be a monolithically integrated optical chip. Monolithically integrated refers to directly epitaxially growing optical device materials on a single substrate to fabricate optical devices with desired functions.

[0071] In some embodiments, the optical chip 400 can be a monolithically integrated silicon optical chip. Silicon material is easy to etch, and thus functional devices can be integrated inside the silicon optical chip, with good integration. For example, a light splitter, a light combiner, a light mixer, a light detector, and the like can be integrated inside the silicon optical chip. As an indirect bandgap semiconductor material, silicon does not have linear electro-optic effect, but only weak second-order electro-optic effect, resulting in a low modulation rate of the silicon optical chip.

[0072] In some embodiments, the optical chip 400 can be a monolithically integrated thin-film lithium niobate chip. Thin-film lithium niobate has linear electro-optic effect, and an applied electric field causes linear change in the refractive index in the corresponding direction, so that the light wave transmitted in the medium has controllable intensity, phase, and the like. Therefore, thin-film lithium niobate is selected as the material of the optical modulator, so as to achieve a high modulation rate, and the like. Thin-film lithium niobate material is relatively hard and difficult to etch, so it is difficult to integrate multiple functional devices on its surface. Meanwhile, the thin-film lithium niobate chip has low optical loss.

[0073] In some embodiments, the optical chip 400 can be a hybrid integrated optical chip. Hybrid integration refers to fabricating optical devices on different substrates according to the advantages of the respective material systems and the characteristics of the fabrication processes, and then integrating them together. The advantage of hybrid integration is that the excellent performance of different material systems can be fully utilized.

[0074] In some embodiments, the optical chip 400 can be a III-V / Si hybrid integrated optical chip. In the III-V / Si hybrid integrated optical chip, the growth material system of the optical modulator is a III-V semiconductor material. The III-V is a direct bandgap semiconductor material, which has strong quantum well limited Stark effect. By controlling the change of the applied electric field, the change of the carrier is caused to realize the modulation of the optical signal. The growth material system of the light splitter, the light combiner, the light mixer, the light detector, and the like is a Si-based material. In some embodiments, the III-V / Si hybrid integrated optical chip can be an InP / Si hybrid integrated optical chip.

[0075] In some embodiments, the optical chip 400 can be a thin-film lithium niobate / Si hybrid integrated optical chip. Compared with the III-V / Si hybrid integrated optical chip, the optical modulator in the thin-film lithium niobate / Si hybrid integrated optical chip is a thin-film lithium niobate-based optical modulator.

[0076] In some embodiments, the optical chip 400 can be a monolithic integrated silicon optical chip. Since Si is an indirect bandgap semiconductor material, its light emitting efficiency is very low. Therefore, a light source 500 is provided on one side of the optical chip 400. The light source 500 emits light out of the side and couples into the optical chip 400. The light emitted by the light source 500 is not data-carrying light. After entering the optical chip 400, the light is phase-modulated by the optical chip 400 to load electrical signals into the light, thereby obtaining data-carrying light, i.e., generating an optical emission signal, so as to realize optical signal emission.

[0077] In some embodiments, the optical chip 400 can be an InP / Si hybrid integrated optical chip. Group III-V is a direct bandgap semiconductor material and has strong gain characteristics. Therefore, group III-V has good light emitting characteristics, such as InP lasers. In the InP / Si hybrid integrated optical chip, an InP laser is integrated as a light source.

[0078] FIG. 6 is a schematic diagram of an internal structure of an optical chip according to some embodiments. As shown in FIG. 6, in some embodiments, the optical chip 400 can be a monolithic integrated silicon optical chip.

[0079] In some embodiments, the light source 500 is provided outside the optical chip 400. The light source 500 generates non-signal-carrying light which is coupled into the optical chip 400. The non-signal-carrying light generated by the light source 500 is split into a first light beam and a second light beam by the optical splitter 410 integrated inside the optical chip 400.

[0080] In some embodiments, the first light beam is coupled into the optical demodulator 420 built-in the optical chip 400 as a local light, and an external optical signal is simultaneously coupled into the optical demodulator 420. The first light beam and the external optical signal to be demodulated are coherently demodulated in the optical demodulator to demodulate a corresponding electrical signal. The second light beam is transmitted into the polarization beam splitter 430 as a light source, and is split by the polarization beam splitter 430 into two beams of light with different polarization directions: TE polarized light and TM polarized light.

[0081] In some embodiments, the TE polarized light is split by the optical splitter 450 into two beams of light, which are coupled into the two optical modulators 460 located on the upper side in FIG. 6, respectively. In the two optical modulators 460, the optical modulator 460 on the upper side modulates the received light to generate an I modulated signal, and the optical modulator 460 on the lower side modulates the received light to generate a Q modulated signal. The I modulated signal and the Q modulated signal of the light beam generate a first sub-modulated light signal through the combiner 470.

[0082] In some embodiments, the TM polarized light is split by the optical splitter 440 into two beams of light, which are coupled into two lower optical modulators 460 in FIG. 6, respectively. Among the two optical modulators 460, the upper optical modulator 460 modulates the received light in I modulation to generate an I modulated signal, and the lower optical modulator 460 modulates the received light in Q modulation to generate a Q modulated signal. The I modulated signal and the Q modulated signal of the beam of light generate a second sub-modulated optical signal via the optical combiner 480.

[0083] In some embodiments, the first sub-modulated optical signal and the second sub-modulated optical signal are coupled into the optical combiner 490, respectively, to generate an optical modulated signal via the optical combiner to realize signal modulation.

[0084] In some embodiments, the optical chip 400 has an optical output port, a first optical input port, and a second optical input port. The optical output port of the optical chip 400 is optically connected to the optical combiner 490, the first optical input port is optically connected to the optical splitter 410, and the second optical input port is optically connected to the optical demodulator 420. The optical output port of the optical chip 400 is used to output the optical transmission signal generated by the optical chip 400. The first optical input port is used to input the light generated by the light source 500 and not carrying data into the optical chip 400, and the second optical input port is used to input the external optical signal to be demodulated into the optical chip 400.

[0085] In some embodiments, the optical chip 400 is externally provided with an optical fiber array 700. The optical fiber array 700 includes a first optical fiber ribbon 710, a second optical fiber ribbon 720, and a third optical fiber ribbon 730.

[0086] In some embodiments, the first optical fiber ribbon 710 is coupled to the optical output port of the optical chip 400. The optical transmission signal generated by the optical chip 400 is output from the optical chip 400 via the optical output port, coupled into the first optical fiber ribbon 710, and output to the outside of the optical module via the first optical fiber ribbon 710.

[0087] In some embodiments, the second optical fiber ribbon 720 is coupled to the first optical input port of the optical chip 400. The light generated by the light source 500 and not carrying data is transmitted to the first optical input port of the optical chip 400 via the second optical fiber ribbon 720, thereby being coupled into the optical chip 400 and coupled into the optical splitter 410 for subsequent modulation of the optical signal.

[0088] In some embodiments, the third optical fiber ribbon 730 is coupled to the second optical input port of the optical chip 400. The external optical signal to be demodulated is transmitted to the second optical input port of the optical chip 400 via the third optical fiber ribbon 730, thereby being coupled into the optical chip 400 and coupled into the optical demodulator 420 for demodulation of the optical signal.

[0089] In some embodiments, the light chip 400 modulates the generated optical transmission signals to be transmitted to the first optical fiber ribbon 710 through waveguides inside the light chip 400. The light source input to the light chip 400 through the second optical fiber ribbon 720 is transmitted to the optical splitter 410 through waveguides inside the light chip 400. The optical signal to be demodulated input to the light chip 400 through the third optical fiber ribbon 730 is transmitted to the optical demodulator 420 through waveguides inside the light chip.

[0090] In some embodiments, the waveguides inside the light chip 400 are Silicon-On-Insulator (SOI) waveguides. The SOI waveguide includes, from bottom to top, a substrate, a refractive index difference layer, and a top layer of silicon. The refractive index difference layer is, for example, a SiO2 layer.

[0091] In some embodiments, the refractive index difference between the top layer of silicon and the refractive index difference layer is large, which has a strong constraint on the light beam and a small effective area of the mode field. The refractive index contrast of the SOI waveguide is greater than the refractive index contrast of the optical fiber, so the effective area of the SOI waveguide mode field is smaller than the effective area of the optical fiber mode field. Therefore, there is a mode mismatch between the SOI waveguide and the optical fiber, and the coupling loss is large when the two are coupled, thereby reducing the coupling efficiency between the two. For example, the effective area of the silicon waveguide waveguide mode field is usually less than 1 μm2, while the effective area of the light field of a standard single-mode optical fiber is usually about 70 μm2.

[0092] In some embodiments, the optical module 200 includes an optical coupler 800. The optical coupler 800 is arranged between the light chip 400 and the optical fiber array 700. For example, the optical coupler 800 can be integrated into the light chip 400, or can be arranged outside the light chip 400. The optical coupler 800 is an end-face coupler. The optical coupler 800 serves as a bridge for the transmission of light field energy between the SOI waveguide and the optical fiber, and can improve the optical coupling efficiency between the two. For example, the output light port, the first input light port, and the second input light port of the light chip 400 are respectively provided with optical couplers 800.

[0093] In some embodiments, an optical coupler 800 is arranged between the optical combiner 490 and the first optical fiber ribbon 710 to improve the optical coupling efficiency between the SOI waveguide inside the light chip 400 and the first optical fiber ribbon 710. Another optical coupler 800 is arranged between the optical splitter 410 and the second optical fiber ribbon 720 to improve the optical coupling efficiency between the SOI waveguide inside the light chip 400 and the second optical fiber ribbon 720. Another optical coupler 800 is arranged between the optical demodulator 420 and the third optical fiber ribbon 730 to improve the optical coupling efficiency between the SOI waveguide inside the light chip 400 and the third optical fiber ribbon 730.

[0094] FIG. 7 is a structural schematic diagram of an optical coupler according to some embodiments. As shown in FIG. 7, in some embodiments, the optical coupler 800 is configured to improve the optical coupling efficiency between the SOI waveguide and the fiber ribbon, and thus improve the coupling efficiency between the optical chip 400 and the fiber array 700. The optical coupler 800 can include a substrate 801. Exemplarily, the substrate 801 can be a silicon-based substrate.

[0095] In some embodiments, the optical coupler 800 can include a refractive index difference layer 802. Exemplarily, the refractive index difference layer 802 can be a SiO2layer.

[0096] In some embodiments, the optical coupler 800 can include a transmission waveguide layer 803. The transmission waveguide layer 803 has a higher refractive index, forms a larger refractive index difference with the refractive index difference layer 802, enhances the light beam constraint, reduces the effective area of the mode field, effectively reduces the mode mismatch between the SOI waveguide and the fiber, and improves the coupling efficiency.

[0097] In some embodiments, the refractive index difference layer 802 is located between the substrate 801 and the transmission waveguide layer 803, and the refractive index relationship among them is: the refractive index of the transmission waveguide layer 803 is greater than the refractive index of the refractive index difference layer 802, and the refractive index of the refractive index difference layer 802 is greater than the refractive index of the substrate 801, forming a gradient refractive index structure. Through this gradient refractive index structure, the optical coupler 800 can more effectively guide the light beam.

[0098] In some embodiments, the transmission waveguide layer 803 has a higher refractive index, has a stronger limiting effect on the light field, and the light field is mainly limited within the transmission waveguide layer 803, reducing the leakage of optical energy and further optimizing the optical coupling efficiency.

[0099] In some embodiments, the optical coupler 800 can include a coupling waveguide 804. The coupling waveguide 804 is located in the transmission waveguide layer 803. The coupling waveguide 804 can be a silicon nitride waveguide. Silicon nitride has a transparent window and low temperature sensitivity in the optical communication waveband, and is highly compatible with COMS. The refractive index of silicon nitride is about 1.98, the refractive index of silicon waveguide is about 3.4, and the refractive index of SiO2is about 1.44. Therefore, the constraint ability of silicon nitride on the light field is between that of the silicon waveguide and the SiO2waveguide, and becomes one of the application materials in the end-face coupling design based on high-refractive-index and small-section-size waveguides.

[0100] In some embodiments, one end of the coupling waveguide 804 is coupled and connected with the fiber ribbon, and the other end is coupled and connected with the SOI waveguide, realizing the transition coupling between the fiber ribbon and the SOI waveguide.

[0101] In some embodiments, the coupling waveguide 804 can present a tapered structure to achieve a smooth transition between the fiber ribbons and the SOI waveguide, and to improve the optical coupling efficiency. For example, the width of the coupling waveguide 804 increases in the direction from the fiber array 700 to the fiber ribbons 400, i.e. in the direction from the first end to the second end of the coupling waveguide 804. As the width of the coupling waveguide 804 gradually increases, the confinement of the optical field gradually increases, the effective mode area gradually decreases, the mode matching with the SOI waveguide is improved, and the optical coupling efficiency between the first fiber ribbons 710 and the SOI waveguide is improved.

[0102] In some embodiments, the optical coupler 800 can include a first confinement waveguide 805 and a second confinement waveguide 806. The first confinement waveguide 805 and the second confinement waveguide 806 are respectively located on both sides of the coupling waveguide 804 to confine the optical field in a certain coupling area at the beginning of the coupling, so as to control the mode size of the optical field. The optical field on one side of the coupling waveguide 804 is confined at the first confinement waveguide 805, and the optical field on the other side is confined at the second confinement waveguide 806, forming a symmetrical optical field distribution. For example, the coupling waveguide 804 includes a first end facing the fiber array 700, and the first confinement waveguide 805 and the second confinement waveguide 806 are respectively located on both sides of the first end of the coupling waveguide 804.

[0103] In some embodiments, the coupling waveguide 804 includes a first end and a second end. The first end faces the fiber array 700, and the second end faces the inside of the optical chip 400. The optical field incident along the first end is gradually coupled into the coupling waveguide 804, and the first confinement waveguide 805 and the second confinement waveguide 806 on both sides of the coupling waveguide 804 can limit and adjust the mode size at the beginning of the optical field coupling. For example, by adjusting the spacing between the first confinement waveguide 805 and the second confinement waveguide 806 and the coupling waveguide 804 respectively, the mode size of the optical field can be controlled and optimized to improve the matching degree with the mode size of the optical field of the fiber array 700, and the optical coupling efficiency is improved. The spacing between the first confinement waveguide 805 and the second confinement waveguide 806 and the coupling waveguide 804 respectively determines the optical field coupling area, and further adjusts the mode size of the optical field.

[0104] In some embodiments, the first confinement waveguide 805 and the second confinement waveguide 806 can be located at the same height layer as the coupling waveguide 804 respectively. The first confinement waveguide 805 and the second confinement waveguide 806 can be symmetrically distributed on both sides of the coupling waveguide 804. Through this symmetrical distribution, the concentration of the optical field in the coupling area is further strengthened. For example, the first confinement waveguide 805, the second confinement waveguide 806 and the coupling waveguide 804 are provided as single-layer waveguides, and then the waveguide etching process is realized once.

[0105] In some embodiments, the coupling waveguide 804, the first confinement waveguide 805 and the second confinement waveguide 806 are located in the same height layer, which simplifies the waveguide structure manufacturing process and ensures the precise alignment between the waveguides, further improving the quality of optical signal transmission.

[0106] In some embodiments, the coupling waveguide 804, the first confinement waveguide 805 and the second confinement waveguide 806 have the same refractive index, which ensures the phase consistency of the optical signal when transmitted between the waveguides, reduces the phase distortion and improves the signal stability.

[0107] In some embodiments, the first confinement waveguide 805 and the second confinement waveguide 806 respectively use the same waveguide material as the coupling waveguide 804, so that their refractive index characteristics are consistent, further ensuring the stable transmission of the optical field in the coupling region. For example, the coupling waveguide 804, the first confinement waveguide 805 and the second confinement waveguide 806 all use silicon nitride material, which maintains the consistency of the refractive index, effectively reduces the distortion of the optical field and improves the coupling stability. In addition, the low loss characteristics of the silicon nitride material also help to reduce the overall optical transmission loss.

[0108] In some embodiments, in the direction in which the fiber array 700 points to the optical chip 400, i.e. in the direction in which the first end of the coupling waveguide 804 points to the second end, the width of the first confinement waveguide 805 and the second confinement waveguide 806 decreases, which reduces the diffusion and coupling of the optical field generated by the coupling waveguide 804 to the first confinement waveguide 805 and the second confinement waveguide 806, and further focuses the distribution of the optical field in the coupling waveguide 804.

[0109] In some embodiments, in the direction in which the fiber array 700 points to the optical chip 400, i.e. in the direction in which the first end of the coupling waveguide 804 points to the second end, the width of the first confinement waveguide 805 and the second confinement waveguide 806 can gradually decrease, so as to reduce the mutual coupling of the optical field fundamental mode between the coupling waveguide 804 and the first confinement waveguide 805, and reduce the mutual coupling of the optical field fundamental mode between the coupling waveguide 804 and the second confinement waveguide 806, thereby ensuring the stable transmission of the optical field in the coupling waveguide 804 and improving the optical coupling efficiency.

[0110] In some embodiments, when the second optical fiber ribbon 720 and the third optical fiber ribbon 730 transmit the light outputted by the light source 500 and the light signal to be demodulated from the outside to the optical chip respectively, the width of the coupling waveguide 804 gradually increases along the direction of the light field transmission, and the width of the first limiting waveguide 805 and the second limiting waveguide 806 gradually decreases, so that more light fields are coupled into the coupling waveguide 804 from the first limiting waveguide 805 and the second limiting waveguide 806. In the initial stage of the light field coupling, the first limiting waveguide 805 and the second limiting waveguide 806 can adjust the light field distribution and then adjust the light field mode spot size. The width of the coupling waveguide 804 gradually increases, so that the light field restriction gradually increases, and the light field mode spot size gradually decreases. With the increase of the width of the coupling waveguide 804, the light field is gradually focused, the mode spot size gradually decreases, and finally tends to adapt to the mode spot size of the SOI waveguide, which is more conducive to matching the light field mode spot of the SOI waveguide and improving the coupling efficiency.

[0111] In some embodiments, the light signal modulated by the optical chip 400 is outputted through the combiner 490 and transmitted along the coupling waveguide 804. Along the direction of the light field transmission, the width of the coupling waveguide 804 gradually decreases, and the width of the first limiting waveguide 805 and the second limiting waveguide 806 gradually increases, so that the light field restriction of the coupling waveguide 804 gradually decreases, and more light fields are coupled towards the first limiting waveguide 805 and the second limiting waveguide 806. In the initial stage of the light field coupling, the first limiting waveguide 805 and the second limiting waveguide 806 can adjust the light field distribution and then adjust the light field mode spot size. The width of the coupling waveguide 804 gradually decreases, so that the light field restriction gradually decreases, and the light field mode spot size gradually increases. With the decrease of the width of the coupling waveguide 804, the light field is gradually diverged, the mode spot size gradually increases, and finally tends to adapt to the mode spot size of the optical fiber array 700, which is more conducive to matching the light field mode spot of the optical fiber array 700 and improving the coupling efficiency.

[0112] FIG. 8 is an internal structure diagram of an optical coupler according to some embodiments. As shown in FIG. 8, in some embodiments, the first limiting waveguide 805 and the second limiting waveguide 806 are symmetrically distributed on both sides of the coupling waveguide 804.

[0113] In some embodiments, the light field generated by the coupling waveguide 804 is coupled to the first limiting waveguide 805 and the second limiting waveguide 806 respectively, which causes coupling loss, so the first limiting waveguide 805 and the second limiting waveguide 806 should be as far away from the coupling waveguide 804 as possible, and the size of the first limiting waveguide 805 and the second limiting waveguide 806 should be reduced.

[0114] In some embodiments, the first limiting waveguide 805 can include a first inclined surface 8052. In the direction in which the optical fiber array 700 points to the optical chip 400, the first inclined surface 8052 gradually inclines away from the central axis of the coupling waveguide 804.

[0115] In some embodiments, the first confinement waveguide 805 can include a first horizontal surface 8051. The first horizontal surface 8051 is parallel to the central axis of the coupling waveguide 804, and the first inclined surface 8052 is inclined at an angle. The first inclined surface 8052 is disposed close to the coupling waveguide 804. The first inclined surface 8052 gradually inclines towards the first horizontal surface 8051 away from the central axis of the coupling waveguide 804.

[0116] In some embodiments, the second confinement waveguide 806 can include a second inclined surface 8062. In the direction in which the fiber array 700 points to the optical chip 400, the second inclined surface 8062 gradually inclines away from the central axis of the coupling waveguide 804.

[0117] In some embodiments, the second confinement waveguide 806 can include a second horizontal surface 8061. The second horizontal surface 8061 is parallel to the central axis of the coupling waveguide 804, and the second inclined surface 8062 is inclined at an angle. The second inclined surface 8062 is disposed close to the coupling waveguide 804. The second inclined surface 8062 gradually inclines towards the second horizontal surface 8061 away from the central axis of the coupling waveguide 804.

[0118] In some embodiments, in the direction in which the fiber array 700 points to the optical chip 400, i.e. in the direction in which the first end of the coupling waveguide 804 points to the second end, the first inclined surface 8052 gradually inclines towards the first horizontal surface 8051 away from the coupling waveguide 804, so as to gradually increase the distance between the first confinement waveguide 805 and the coupling waveguide 804, and reduce the coupling loss between the first confinement waveguide 805 and the coupling waveguide 804. In the direction in which the fiber array 700 points to the optical chip 400, the second inclined surface 8062 gradually inclines towards the second horizontal surface 8061 away from the coupling waveguide 804, so as to gradually increase the distance between the second confinement waveguide 806 and the coupling waveguide 804, and reduce the coupling loss between the second confinement waveguide 806 and the coupling waveguide 804.

[0119] In some embodiments, in the direction in which the fiber array 700 points to the inside of the optical chip 400, i.e. in the direction in which the first end of the coupling waveguide 804 points to the second end, the first inclined surface 8052 gradually inclines away from the coupling waveguide 804 until the end of the first inclined surface 8052 coincides with the end of the first horizontal surface 8051. Exemplarily, the distance between the first horizontal surface 8051 and the first inclined surface 8052 at the first end of the first confinement waveguide 805 is greater than the distance between the first horizontal surface 8051 and the first inclined surface 8052 at the second end of the first confinement waveguide 805. The first end of the first confinement waveguide 805 points to the fiber array 700, and the second end points to the inside of the optical chip 400.

[0120] In some embodiments, the second inclined surface 8062 is gradually inclined away from the coupling waveguide 804 in the direction in which the fiber array 700 is directed towards the inside of the optical chip 400, i.e. in the direction in which the first end of the coupling waveguide 804 is directed towards the second end. Exemplarily, the spacing between the second horizontal surface 8061 and the second inclined surface 8062 is greater at the first end portion of the second confinement waveguide 806 than at the second end portion of the second confinement waveguide 806. Here, the first end portion of the second confinement waveguide 806 is directed towards the fiber array 700, and the second end portion of the second confinement waveguide 806 is directed towards the inside of the optical chip 400.

[0121] In some embodiments, the first inclined surface 8052 is arranged with one end portion coinciding with one end portion of the first horizontal surface 8051 to reduce the mutual coupling of the optical field fundamental mode between the coupling waveguide 804 and the first confinement waveguide 805. The second inclined surface 8062 is arranged with one end portion coinciding with one end portion of the second horizontal surface 8061 to reduce the mutual coupling of the optical field fundamental mode between the coupling waveguide 804 and the second confinement waveguide 806, to ensure stable transmission of the optical field in the coupling waveguide 804 and to improve the optical coupling efficiency.

[0122] In some embodiments, the first horizontal surface 8051 and the second horizontal surface 8061 are respectively parallel to the central axis of the coupling waveguide 804, and the first horizontal surface 8051 and the second horizontal surface 8061 are symmetrical with respect to the central axis of the coupling waveguide 804. The first inclined surface 8052 and the second inclined surface 8062 are symmetrical with respect to the central axis of the coupling waveguide 804, and thus the first confinement waveguide 805 and the second confinement waveguide 806 are symmetrical with respect to the central axis of the coupling waveguide 804. In this way, the waveguide interfaces are arranged symmetrically to form a symmetrical distribution of the optical field, and the polarization loss in the optical transmission process is reduced.

[0123] FIG. 9 is a diagram of the internal structure of an optical coupler according to some embodiments. As shown in FIG. 9, in some embodiments, the first confinement waveguide 805 and the second confinement waveguide 806 are symmetrically distributed on both sides of the coupling waveguide 804.

[0124] In some embodiments, the coupling waveguide 804 adopts a segmented design. The coupling waveguide 804 includes a plurality of waveguide segments of different lengths, and the different waveguide segments have specific refractive index distributions to reduce transmission loss and improve overall coupling efficiency.

[0125] In some embodiments, the coupling waveguide 804 includes a first waveguide segment 8041, a second waveguide segment 8042, a third waveguide segment 8043, and a fourth waveguide segment 8044, which are sequentially connected to form a gradually changing refractive index distribution.

[0126] FIG. 10 is a perspective view of an optical coupler according to some embodiments. As shown in FIG. 10, in some embodiments, the optical coupler 800 is configured to improve the optical coupling efficiency between the SOI waveguide and the optical fiber. The optical coupler 800 can include a substrate 810. Illustratively, the substrate 810 can be a silicon-based substrate.

[0127] In some embodiments, the optical coupler 800 can include a refractive index difference layer 820. Illustratively, the refractive index difference layer 820 is a SiO2layer. The refractive index difference layer 820 is located above the substrate 810. The thickness of the refractive index difference layer 820 is less than the thickness of the substrate 810.

[0128] In some embodiments, the optical coupler 800 can include a transmission waveguide 830. The transmission waveguide 830 is located on one side of the refractive index difference layer 820. The top layer of silicon of the SOI wafer is photoetched to obtain the transmission waveguide 830. Illustratively, the transmission waveguide 830 is a silicon waveguide.

[0129] In some embodiments, the refractive index difference layer 820 is located between the substrate 810 and the transmission waveguide 830. The refractive index of the refractive index difference layer 820 is less than the refractive index of the transmission waveguide 830, and the difference between the refractive indices is large, so the transmission waveguide 830 has a strong restriction on the optical field, and the optical field is mainly restricted in the transmission waveguide 830 for transmission, thereby reducing the transmission loss.

[0130] In some embodiments, the optical coupler 800 can include a coupling waveguide array 850 to improve the optical coupling efficiency between the optical chip 400 and the optical fiber ribbon. The coupling waveguide array 850 is located at the edge of the optical coupler 800. The coupling waveguide array 850 is located at the end of the optical coupler 800 facing the optical port of the optical chip 400 to optically couple with the optical fiber array. The coupling waveguide array 850 is located at the optical port of the optical coupler 800.

[0131] In some embodiments, the optical coupler 800 can include a transition waveguide 840. The transition waveguide 840 is located above the transmission waveguide 830. One end of the transition waveguide 840 faces the coupling waveguide array 850 to optically couple with the coupling waveguide array 850, and the other end faces the transmission waveguide 830 to optically couple with the transmission waveguide 830.

[0132] In some embodiments, the coupling waveguide array 850 and the transition waveguide 840 can be silicon nitride waveguides. Silicon nitride has a transparent window and low temperature sensitivity in the optical communication band, and is highly compatible with COMS. The refractive index of silicon nitride is about 1.98, the refractive index of silicon waveguide is about 3.4, and the refractive index of SiO2is about 1.44. Therefore, the constraint ability of silicon nitride on the optical field is between that of the silicon waveguide and the SiO2waveguide, and becomes one of the application materials in the design of the end-face coupler based on the high-refractive-index, small-section-size waveguide.

[0133] In some embodiments, the coupling waveguide array 850 and the transition waveguide 840 are both silicon nitride waveguides, and the coupling waveguide array 850 and the transition waveguide 840 have the same refractive index.

[0134] In some embodiments, the transition waveguide 840 has a refractive index smaller than the substrate 810, and the transition waveguide 840 has a refractive index smaller than the transmission waveguide 830.

[0135] In some embodiments, the coupling waveguide array 850 can be arranged in different combinations. The coupling waveguide array 850 is located at one end of the transition waveguide 840, which is closer to the fiber array 700.

[0136] In some embodiments, the coupling waveguide array 850 includes at least two coupling waveguides. The coupling waveguides are symmetrically distributed with respect to the central axis of the transition waveguide 840. FIG. 10 shows that the coupling waveguide array 850 includes two coupling waveguides: a coupling waveguide 851 and a coupling waveguide 852. The coupling waveguide 851 and the coupling waveguide 852 are located on the two sides of the transition waveguide 840, respectively.

[0137] Since the refractive index of the coupling waveguide 851 and the coupling waveguide 852 is greater than that of SiO2, and the coupling waveguide 851 and the coupling waveguide 852 are located on the two sides of the transition waveguide 840, respectively, it can better constrain the light field in the horizontal direction and limit the light field in the transition waveguide 840, thereby increasing the light coupling efficiency.

[0138] In some embodiments, the coupling waveguide 851 and the coupling waveguide 852 are thin strip waveguides. They can also be tapered waveguides.

[0139] In some embodiments, the transition waveguide 840 can include a first tapered region 841 and a second tapered region 842. The first tapered region 841 is formed at one end of the transition waveguide 840 closer to the coupling waveguide array 850, and the second tapered region 842 is formed at one end of the transition waveguide 840 closer to the transmission waveguide 830. The waveguide width of the first tapered region 841 and the second tapered region 842 presents an opposite tapered shape.

[0140] In some embodiments, the transition waveguide 840 can include a flat region 843. The flat region 843 is formed between the first tapered region 841 and the second tapered region 842, and is used to connect the first tapered region 841 and the second tapered region 842.

[0141] In some embodiments, the transmission waveguide 830 can include a third tapered region 831. The third tapered region 831 is formed at one end of the transmission waveguide 830 closer to the transition waveguide 830. The waveguide width of the third tapered region 831 and the second tapered region 842 also presents an opposite tapered shape.

[0142] In some embodiments, the waveguide width of the first taper region 841 gradually increases, the waveguide width of the second taper region 842 gradually decreases, and the waveguide width of the third taper region 831 gradually increases in the direction in which the array of coupling waveguides 850 is directed to the transmission waveguide 830.

[0143] In some embodiments, when the second optical fiber ribbon 720 and the third optical fiber ribbon 730 transmit the light output by the light source 500 and the light signal to be demodulated from the outside to the optical chip respectively, the waveguide width of the first taper region 841 gradually increases in the direction of the light field transmission, and more light fields are squeezed into the first taper region 841 of the transition waveguide 840 from the coupling waveguides 851 and 852. The light field continues to transmit along the first taper region 841 into the flat region 843 and maintains a large light field energy in the flat region 843, and then continues to transmit into the second taper region 842. The waveguide width of the second taper region 842 gradually decreases, and the waveguide width of the third taper region 831 gradually increases, so that more light fields are squeezed into the transmission waveguide 830 from the second taper region 842 of the transition waveguide 840 and enter the optical demodulator 420 or the optical demodulator 420 along the transmission waveguide 830 to modulate or demodulate the optical signal.

[0144] In some embodiments, the light emission signal generated by the optical chip 400 is output through the combiner 490 and transmitted along the transmission waveguide 830. In the direction of the light field transmission, the waveguide width of the third taper region 831 gradually decreases, and the waveguide width of the second taper region 842 gradually increases, so that more light fields are squeezed into the second taper region 842 of the transition waveguide 840 from the transmission waveguide 830. Then the light field transmits to the flat region 843 and maintains the light field energy in the flat region 843, and continues to transmit into the first taper region 841. In the direction of the light field transmission, the waveguide width of the first taper region 841 gradually decreases, so that the light field is squeezed into the array of coupling waveguides 850 and enters the first optical fiber ribbon 710 along the array of coupling waveguides 850 to transmit the light emission signal to the outside. Wherein, the waveguide width of the first taper region 841 gradually decreases, so that the restriction of the waveguide to the light gradually decreases, and a large cross-section light field is formed at the end of the first taper region 841 to adapt to the light field area of the first optical fiber ribbon 710, so that the first optical fiber ribbon 710 can be directly coupled, and the optical coupling efficiency between the two is increased.

[0145] In some embodiments, the hybrid waveguide system composed of the array of coupling waveguides 850 and the transition waveguide 840 and the optical fiber ribbon can achieve high-efficiency coupling.

[0146] In some embodiments, when the light source 500 outputs light without carrying data and the light signal to be demodulated from outside are transmitted to the optical chip 400 through the second optical fiber ribbon 720 and the third optical fiber ribbon 730 respectively, the optical field is gradually coupled into the transition waveguide 840 along the hybrid waveguide system composed of the coupling waveguide array 850 and the transition waveguide 840. With the transmission of the optical field, the optical field is gradually coupled into the transmission waveguide 830 and then transmitted inside the optical chip 400 through the transmission waveguide 830.

[0147] In some embodiments, the optical signal 400 modulated light emission signal is transmitted inside the optical chip 400 along the transmission waveguide 830, and with the transmission of the optical field, the optical field is gradually coupled into the transition waveguide 840, and then coupled into the hybrid waveguide system composed of the coupling waveguide array 850 and the transition waveguide 840, and finally coupled into the first optical fiber ribbon 710 to transmit the light emission signal outside the optical module along the first optical fiber ribbon 710.

[0148] In some embodiments, the transition waveguide 840 and the transmission waveguide 830 are longitudinally adjacent to improve the coupling efficiency therebetween. For example, the longitudinal gap between the transition waveguide 840 and the transmission waveguide 830 is small.

[0149] In some embodiments, the transmission waveguide 830 is separated from the substrate 810 by the refractive index difference layer 820. When the refractive index difference layer 820 is thin, the transmission waveguide 830 is close to the substrate 810. Since the transition waveguide 840 is close to the transmission waveguide 830, the transition waveguide 840 is also close to the substrate 810.

[0150] In some embodiments, the coupling waveguide array 850 and the transition waveguide 840 have the same refractive index, for example, both are silicon nitride waveguides. When the transition waveguide 840 is close to the substrate 810 and the refractive index of the transition waveguide 840 is less than that of the substrate 810, the optical field may leak towards the substrate 810 when the hybrid waveguide system composed of the coupling waveguide array 850 and the transition waveguide 840 is coupled with the transition waveguide 840.

[0151] In some embodiments, when the transmission waveguide 830 and the transition waveguide 840 are close to the substrate, the optical field leaks less towards the substrate 810 when the optical field is coupled between the transition waveguide 840 and the transmission waveguide 830 because the refractive index of the transition waveguide 840 is less than that of the transmission waveguide 830. It can be understood that when the refractive index difference layer 820 is further reduced in thickness, the optical field also leaks towards the substrate 810 when the optical field is coupled between the transition waveguide 840 and the transmission waveguide 830.

[0152] In some embodiments, the SOI silicon wafer is used to fabricate the SOI waveguide. Illustratively, the silicon on the top surface of the SOI silicon wafer is etched by lithography to form the transmission waveguide 830. Illustratively, the surface etching performance of the SOI silicon wafer with a size of 12 inches is better than that of the SOI silicon wafer with a size of 8 inches. The thickness of the refractive index difference layer of the SOI silicon wafer with a size of 12 inches is 2 μm, and the thickness of the refractive index difference layer of the SOI silicon wafer with a size of 8 inches is 3 μm. Therefore, when the SOI silicon wafer with a size of 12 inches is used, the thickness of the refractive index difference layer of 2 μm causes the light field to be more easily leaked toward the substrate 810 when the hybrid waveguide system is coupled with the transition waveguide 840.

[0153] In some embodiments, the optical coupler 800 can include a high refractive index region 860. The high refractive index region 860 is formed above the refractive index difference layer 820. The high refractive index region 860 wraps the transmission waveguide 830, the array of coupling waveguides 850, and the transition waveguide 840. Illustratively, the substrate 810, the refractive index difference layer 820, and the high refractive index region 860 are stacked from bottom to top, and the transmission waveguide 830, the array of coupling waveguides 850, and the transition waveguide 840 are formed in the high refractive index region 860.

[0154] In some embodiments, the high refractive index region 860 includes a region with a refractive index greater than that of the refractive index difference layer 820. The refractive index of the refractive index difference layer 820 can be a fixed value.

[0155] In some embodiments, based on the characteristic that the light field tends to be transmitted toward a region with a high refractive index, the high refractive index region 860 is located above the refractive index difference layer 820, and the high refractive index region 860 includes a region with a refractive index greater than that of the refractive index difference layer 820. Under the action of the refractive index difference between the high refractive index region 860 and the refractive index difference layer 820, the light field inside the optical chip is gradually transferred upward, the light field is lifted upward, the distance between the light field and the substrate 810 is increased, the leakage of the light field toward the substrate 810 is reduced, and the optical coupling efficiency is improved.

[0156] In some embodiments, the high refractive index region 860 shown in FIG. 10 is a region with a uniform refractive index, and the refractive index of the entire region of the high refractive index region 860 is greater than that of the refractive index difference layer 820. The transmission waveguide 830, the transition waveguide 840, and the array of coupling waveguides 850 are wrapped in the high refractive index region 860.

[0157] In some embodiments, the refractive index difference layer 820 is a SiO2 layer. The high refractive index region 860 is a SiO2 region. The refractive index of the SiO2 medium in the high refractive index region 860 is greater than the refractive index of the SiO2 medium in the refractive index difference layer 820. The SiO2 mediums with different refractive indices are stacked together, and the refractive index difference between the two can better constrain the light field in the longitudinal direction, so as to lift the light field away from the substrate 810, thereby reducing the light leakage loss to the substrate 810.

[0158] In some embodiments, the refractive index of the SiO2 medium can be changed by changing the deposition rate, gas ratio, gas flow, etc. in the SiO2 preparation process.

[0159] FIG. 11 is a cross-sectional structure diagram of an optical coupler according to some embodiments. As shown in FIG. 11, in some embodiments, the substrate 810, the refractive index difference layer 820, and the high refractive index region 860 are sequentially stacked. The transmission waveguide 830, the transition waveguide 840, and the array of coupling waveguides 850 are wrapped in the high refractive index region 860.

[0160] In some embodiments, the high refractive index region 860 is a region with uniform refractive index, the high refractive index region 860 has a single refractive index, and the refractive index of the high refractive index region 860 is greater than the refractive index of the refractive index difference layer 820, thereby better constraining the light field in the longitudinal direction, lifting the light field, and making the light field away from the substrate 810, thereby reducing the light leakage loss to the substrate 810.

[0161] In some embodiments, the total thickness of the high refractive index region 860 is limited by the effective area of the optical field of the optical fiber. The thickness of the high refractive index region 860 determines the maximum light field size of the optical coupler 800, so the thickness of the high refractive index region 860 has a predetermined thickness, which should adapt the effective area of the light field between the transmission waveguide 830 and the optical fiber array 700.

[0162] In some embodiments, the array of coupling waveguides 850 includes a coupling waveguide 851 and a coupling waveguide 853. The coupling waveguide 851 and the coupling waveguide 853 are longitudinally arranged on one side of the transition waveguide 840. The other side of the transition waveguide 840 is provided with a coupling waveguide which is symmetrically arranged with the coupling waveguide 851 and the coupling waveguide 853, respectively.

[0163] In some embodiments, the relative positional relationship between the coupling waveguide 851, the coupling waveguide 853, and the transition waveguide 840 is not limited. For example, the coupling waveguide 851 and the coupling waveguide 853 can be both above the transition waveguide 840. For example, the coupling waveguide 851 and the coupling waveguide 853 can be above and below the transition waveguide 840, respectively.

[0164] FIG. 12 is a perspective view of a light coupler according to some embodiments. As shown in FIG. 12, in some embodiments, the substrate 810, the refractive index difference layer 820, and the high refractive index region 860 are stacked in sequence. The transmission waveguide 830, the transition waveguide 840, and the array of coupling waveguides 850 are wrapped in the high refractive index region 860.

[0165] In some embodiments, the high refractive index region 860 includes a plurality of layers with different refractive indexes, and at least one of the layers has a refractive index greater than that of the refractive index difference layer 820.

[0166] In some embodiments, the high refractive index region 860 is formed by stacking a plurality of layers with different refractive indexes, and at least one of the layers has a refractive index greater than that of the refractive index difference layer 820.

[0167] In some embodiments, the high refractive index region 860 includes four layers with different refractive indexes, and the high refractive index region 860 includes a first refractive index layer 861, a second refractive index layer 862, a third refractive index layer 863, and a fourth refractive index layer 864.

[0168] The first refractive index layer 861, the second refractive index layer 862, the third refractive index layer 863, and the fourth refractive index layer 864 are stacked in sequence from bottom to top.

[0169] In some embodiments, the first refractive index layer 861, the second refractive index layer 862, the third refractive index layer 863, and the fourth refractive index layer 864 have different refractive indexes, respectively.

[0170] In some embodiments, the first refractive index layer 861, the second refractive index layer 862, the third refractive index layer 863, and the fourth refractive index layer 864 are SiO2 layers with different refractive indexes, i.e., each layer is a SiO2 medium. As described above, by changing the deposition rate, gas ratio, and gas flow during the SiO2 preparation process, the SiO2 can exhibit changes in refractive index.

[0171] In some embodiments, the medium of the first refractive index layer 861, the second refractive index layer 862, the third refractive index layer 863, and the fourth refractive index layer 864 can be SiO2 or non-SiO2, as long as the refractive index of the medium meets the requirement that at least one layer has a refractive index greater than that of the refractive index difference layer 820.

[0172] In some embodiments, at least one of the first refractive index layer 861, the second refractive index layer 862, the third refractive index layer 863, and the fourth refractive index layer 864 has a refractive index greater than that of the refractive index difference layer 820, so as to lift the light field upward and make the light field away from the substrate 810, thereby reducing the light field leakage to the substrate 810.

[0173] Exemplarily, the refractive index of the first refractive index layer 861 is greater than the refractive index of the refractive index difference layer 820. The refractive index of the second refractive index layer 862, the third refractive index layer 863, and the fourth refractive index layer 864 can be greater than or less than the refractive index of the refractive index difference layer 820.

[0174] Exemplarily, the refractive index of the third refractive index layer 863 is greater than the refractive index of the refractive index difference layer 820. The refractive index of the first refractive index layer 861, the second refractive index layer 862, and the fourth refractive index layer 864 can be greater than or less than the refractive index of the refractive index difference layer 820.

[0175] FIG. 13 is a cross-sectional structural diagram of an optical coupler according to some embodiments. As shown in FIG. 13, in some embodiments, the substrate 810, the refractive index difference layer 820, the first refractive index layer 861, the second refractive index layer 862, the third refractive index layer 863, and the fourth refractive index layer 864 are sequentially stacked from bottom to top.

[0176] In some embodiments, taking the refractive index of the third refractive index layer 863 being greater than the refractive index of the refractive index difference layer 820 as an example, the refractive index of the third refractive index layer 863 is greater than the refractive index of the refractive index difference layer 820, so as to lift the optical field upward and make the optical field away from the substrate 810, thereby reducing the optical field leakage to the substrate 810.

[0177] In some embodiments, the total thickness of the high refractive index region 860 is limited by the effective area of the optical field of the optical fiber. The high refractive index region 860 has a preset thickness to adapt the effective area of the optical field between the transmission waveguide 830 and the optical fiber array 700.

[0178] In some embodiments, taking the refractive index of the third refractive index layer 863 being greater than the refractive index of the refractive index difference layer 820 as an example, the thickness of the third refractive index layer 863 with the highest refractive index determines the maximum optical field size of the optical coupler 800. In order to be coupled with the optical fiber efficiently, the thickness of the third refractive index layer 863 should be as large as possible, so that in the trade-off design, the number of layers of different refractive indices should not be too much, so as to avoid the thickness of the third refractive index layer 863 being too small.

[0179] In some embodiments, taking the refractive index of the third refractive index layer 863 being greater than the refractive index of the refractive index difference layer 820 as an example, the thickness of the third refractive index layer 863 is greater than the thickness of the first refractive index layer 861, the second refractive index layer 862, and the fourth refractive index layer 864.

[0180] FIG. 14 is an assembly view between a transmission waveguide and a transition waveguide according to some embodiments. As shown in FIG. 14, in some embodiments, the transition waveguide 840 is formed with a first tapered region 841 towards one end of the coupling waveguide array 850, and the transition waveguide 840 is formed with a second tapered region 842 towards one end of the transmission waveguide 830. The first tapered region 841 and the second tapered region 842 are formed with a flat region 843 therebetween. The waveguide width of the first tapered region 841 and the second tapered region 842 presents an opposite tapered form.

[0181] In some embodiments, the transmission waveguide 830 is formed with a third tapered region 831 towards one end of the transition waveguide 830. The waveguide width of the third tapered region 831 and the second tapered region 842 also presents an opposite tapered form.

[0182] In some embodiments, the first tapered region 841 and the third tapered region 831 have opposite tapered trends along the light field transmission direction, which is conducive to the coupling of light between the transition waveguide 840 and the transmission waveguide 830 and improves the coupling efficiency.

[0183] FIG. 15 is an assembly view between a transition waveguide and a coupling waveguide array according to some embodiments. As shown in FIG. 15, in some embodiments, the coupling waveguide array 850 is located at one end of the first tapered region 841.

[0184] In some embodiments, the coupling waveguide array 850 includes a coupling waveguide 851, a coupling waveguide 852, and a coupling waveguide 854. The coupling waveguide 854 is located above the first tapered region 841, and the coupling waveguide 851 and the coupling waveguide 852 are respectively located on both sides of the first tapered region 841. The coupling waveguide 851 and the coupling waveguide 852 are symmetrically arranged relative to the central axis of the first tapered region 841.

[0185] In some embodiments, the coupling waveguide array 850 is wrapped in a high refractive index region 860. The maximum refractive index region in the high refractive index region 860 is still smaller than the refractive index of the coupling waveguide array 850, and therefore, when the coupling waveguide 851 and the coupling waveguide 852 are respectively located on both sides of the first tapered region 841, the light field can be better constrained in the horizontal direction.

[0186] Based on the light coupler provided in the above embodiments, the disclosure provides a preparation method of a light coupler for preparing the light coupler. The preparation method of the light coupler includes:

[0187] S110: etching the top layer of silicon on the surface of the SOI wafer to form a transmission waveguide, the SOI wafer including a substrate, a refractive index difference layer, and a top layer of silicon from bottom to top.

[0188] In some embodiments, the top layer of silicon of the SOI wafer is etched by photolithography to obtain the transmission waveguide 830.

[0189] S120: Forming a transition waveguide 840 above one end of the transmission waveguide.

[0190] In some embodiments, in order to improve the coupling efficiency between the transmission waveguide 830 and the transition waveguide 840, the gap between them in the longitudinal direction is small.

[0191] S130: Forming a coupling waveguide array at one end of the transition waveguide.

[0192] In some embodiments, the coupling waveguide array 850 is located at the edge of the optical coupler.

[0193] S140: Epitaxially growing a high refractive index region with uniform refractive index and greater refractive index than the refractive index difference layer 820 above the refractive index difference layer 820; or epitaxially growing a plurality of layers with different refractive indices above the refractive index difference layer 820, wherein the refractive index of one of the layers is greater than the refractive index of the refractive index difference layer 820.

[0194] In some embodiments, the transmission waveguide 830 is separated from the substrate 810 by the refractive index difference layer 820. When the refractive index difference layer 820 is thin, the transmission waveguide 830 is closer to the substrate 810. Since the transition waveguide 840 is closer to the transmission waveguide 830, the transition waveguide 840 is also closer to the substrate 810.

[0195] In some embodiments, the coupling waveguide array 850 and the transition waveguide 840 have the same refractive index, for example, both are silicon nitride waveguides. When the transition waveguide 840 is closer to the substrate 810, and the refractive index of the transition waveguide 840 is less than the refractive index of the substrate 810, the hybrid waveguide system composed of the coupling waveguide array 850 and the transition waveguide 840 may leak light towards the substrate 810 when coupling between the hybrid waveguide system and the transition waveguide 840.

[0196] In some embodiments, the high-refractive-index region 860 contains a region with a refractive index greater than that of the refractive-index difference layer 820, and thus the light field inside the optical chip gradually shifts upward under the effect of the refractive-index difference between the high-refractive-index region 860 and the refractive-index difference layer 820, the light field is lifted upward, the distance between the light field and the substrate 810 is increased, thus reducing the light field leakage toward the substrate 810, and improving the light coupling efficiency. The high-refractive-index region contains a region with a refractive index greater than that of the refractive-index difference layer. Exemplarily, when the high-refractive-index region is a region with a uniform refractive index, the refractive index of the high-refractive-index region is greater than that of the refractive-index difference layer; or when the high-refractive-index region includes multiple layers with different refractive indices, the refractive index of at least one layer is greater than that of the refractive-index difference layer. Based on the feature that the light field tends to transmit toward a region with a high refractive index, the high-refractive-index region is located above the refractive-index difference layer, and the high-refractive-index region contains a region with a refractive index greater than that of the refractive-index difference layer, and thus the light field inside the optical chip gradually shifts upward under the effect of the refractive-index difference between the high-refractive-index region and the refractive-index difference layer, the light field is lifted upward, the distance between the light field and the substrate is increased, thus reducing the light field leakage toward the substrate, and improving the light coupling efficiency.

[0197] The above merely illustrates the specific implementation of the present disclosure, but the protection scope of the present disclosure is not limited thereto, any modification or replacement within the technical range disclosed by the present disclosure should be covered within the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be subject to the protection scope of the claims.

Claims

1. An optical module comprising an optical fiber array, an optical chip and an optical coupler; the optical chip is used for modulation and demodulation of optical signals, the optical chip is optically connected with the optical fiber array, so that the optical chip modulated generated optical signals are transmitted along the optical fiber array; The optical coupler is arranged between the optical chip and the optical fiber array; The optical coupler comprises a substrate and a refractive index difference layer, the refractive index difference layer is located above the substrate; The optical coupler further comprises: A coupling waveguide, in the direction in which the optical fiber array points to the optical chip, the width of the coupling waveguide tends to increase; A first limiting waveguide, located on one side of the first end of the coupling waveguide, the first end of the coupling waveguide faces the optical fiber array, in the direction in which the optical fiber array points to the optical chip, the width of the first limiting waveguide tends to decrease; A second limiting waveguide, located on the other side of the first end of the coupling waveguide, in the direction in which the optical fiber array points to the optical chip, the width of the second limiting waveguide tends to decrease; or, The optical coupler further comprises: A coupling waveguide array, located at one end of the optical coupler facing the optical chip optical port, to optically couple with the optical fiber array; A transmission waveguide, located above the refractive index difference layer; A transition waveguide, located above the transmission waveguide; A high refractive index region, located above the refractive index difference layer, the high refractive index region wraps the transmission waveguide, the coupling waveguide array and the transition waveguide, the high refractive index region comprises a region with a refractive index greater than the refractive index of the refractive index difference layer.

2. The optical module of claim 1, further comprising a circuit board, the optical chip is electrically connected with the circuit board; The optical coupler further comprises a transmission waveguide layer located above the refractive index difference layer, and the coupling waveguide is located in the transmission waveguide layer; The first limiting waveguide comprises a first inclined surface, in the direction in which the optical fiber array points to the optical chip, the first inclined surface gradually inclines away from the central axis of the coupling waveguide; the second limiting waveguide comprises a second inclined surface, in the direction in which the optical fiber array points to the optical chip, the second inclined surface gradually inclines away from the central axis of the coupling waveguide.

3. The optical module according to claim 1, wherein The refractive index of the high refractive index region is greater than the refractive index of the refractive index difference layer; Alternatively, when the high refractive index region comprises a plurality of layers with different refractive indices, the refractive index of at least one layer is greater than the refractive index of the refractive index difference layer.

4. The optical module according to claim 2, wherein The first limiting waveguide comprises a first horizontal surface, and the first inclined surface gradually inclines towards the first horizontal surface away from the central axis of the coupling waveguide; The second limiting waveguide comprises a second horizontal surface, and the second inclined surface gradually inclines towards the first horizontal surface away from the central axis of the coupling waveguide; The first limiting waveguide and the second limiting waveguide are symmetrically arranged with respect to the coupling waveguide; The first horizontal surface and the second horizontal surface are respectively parallel to the central axis of the coupling waveguide; The first inclined surface and the second inclined surface are symmetrically arranged with respect to the central axis of the coupling waveguide.

5. The optical module according to claim 4, wherein One end of the first inclined surface coincides with one end of the first horizontal surface; one end of the second inclined surface coincides with one end of the second horizontal surface.

6. The optical module of claim 1, wherein, The optical coupler is located at the optical chip optical port, and the thickness of the refractive index difference layer is less than the thickness of the substrate; The transmission waveguide is used for transmitting the optical signal modulated by the optical chip and transmitting the optical signal to be demodulated to the optical chip; The transition waveguide is longitudinally arranged adjacent to the transmission waveguide, and the refractive index of the transition waveguide is less than the refractive index of the substrate; one end of the transition waveguide is directed towards the array of coupling waveguides to be optically coupled with the array of coupling waveguides; the other end is directed towards the transmission waveguide to be optically coupled with the transmission waveguide.

7. The optical module according to claim 6, wherein The transition waveguide is formed with a first tapered zone at one end directed towards the array of coupling waveguides, and a second tapered zone at the other end directed towards the transmission waveguide, and the waveguide width of the first tapered zone and the second tapered zone presents an opposite tapered form; The transmission waveguide is formed with a third tapered zone, and the waveguide width of the third tapered zone and the second tapered zone presents an opposite tapered form.

8. The optical module according to claim 6, wherein The refractive index of the transition waveguide is the same as that of the array of coupling waveguides; and the refractive index of the transition waveguide is less than that of the transmission waveguide.

9. The optical module of claim 6, wherein, The refractive index difference layer is a SiO2 layer, and the high refractive index region is a SiO2 region.

10. An optical coupler comprising a substrate and a refractive index difference layer above the substrate; The optical coupler further comprises: a coupling waveguide, in a direction from a first end to a second end of the coupling waveguide, the width of the coupling waveguide presents an increasing trend; a first limiting waveguide located on one side of the first end of the coupling waveguide, in a direction from the first end to the second end of the coupling waveguide, the width of the first limiting waveguide presents a decreasing trend; a second limiting waveguide located on the other side of the first end of the coupling waveguide, in a direction from the first end to the second end of the coupling waveguide, the width of the second limiting waveguide presents a decreasing trend; or The optical coupler further comprises: an array of coupling waveguides located at the edge of the optical coupler; a transmission waveguide above the refractive index difference layer; a transition waveguide above the transmission waveguide; a high refractive index region above the refractive index difference layer, the high refractive index region wrapping the transmission waveguide, the array of coupling waveguides and the transition waveguide, and the high refractive index region comprising a region with a refractive index greater than that of the refractive index difference layer.

11. The optical coupler of claim 10, further comprising a transmission waveguide layer above the refractive index difference layer; and the coupling waveguide is located in the transmission waveguide layer. The first limiting waveguide comprises a first horizontal plane and a first inclined plane, in a direction from the first end to the second end of the coupling waveguide, the first inclined plane gradually inclines towards the first horizontal plane in a direction away from the coupling waveguide; The second limiting waveguide comprises a second horizontal plane and a second inclined plane, in a direction from the first end to the second end of the coupling waveguide, the second inclined plane gradually inclines towards the second horizontal plane in a direction away from the coupling waveguide.

12. The optical coupler of claim 11, the first limiting waveguide and the second limiting waveguide are symmetrically arranged with respect to the coupling waveguide; The first horizontal plane and the second horizontal plane are respectively parallel to the central axis of the coupling waveguide; The first inclined surface and the second inclined surface are symmetrically arranged relative to the central axis of the coupling waveguide.

13. The optical coupler of claim 11, wherein one end of the first inclined surface is arranged coincident with one end of the first horizontal surface, and one end of the second inclined surface is arranged coincident with one end of the second horizontal surface.

14. The optical coupler of claim 11, wherein, The coupling waveguide, the first confinement waveguide and the second confinement waveguide are located at the same height level.

15. The optical coupler of claim 11, wherein, The coupling waveguide, the first confinement waveguide and the second confinement waveguide have the same refractive index.

16. The optical coupler of claim 10, wherein, The thickness of the refractive index difference layer is less than the thickness of the substrate. The refractive index of the transmission waveguide is greater than the refractive index of the refractive index difference layer. The transition waveguide is longitudinally arranged adjacent to the transmission waveguide, the refractive index of the transition waveguide is less than the refractive index of the substrate, one end of the transition waveguide is directed towards the array of coupling waveguides for optical coupling therewith, and the other end of the transition waveguide is directed towards the transmission waveguide for optical coupling therewith.

17. The optical coupler of claim 16, wherein the high refractive index region is a region of uniform refractive index, and the refractive index of the high refractive index region is greater than the refractive index of the refractive index difference layer. Alternatively, the high refractive index region comprises a plurality of layers of different refractive indices, and the refractive index of at least one of the layers is greater than the refractive index of the refractive index difference layer.

18. The optical coupler of claim 16, wherein, The refractive index of the array of coupling waveguides is the same as the refractive index of the transition waveguide, and the refractive index of the transition waveguide is less than the refractive index of the transmission waveguide.

19. A method for manufacturing an optical coupler, applied to the optical coupler of any one of claims 16-18, comprising: etching a top layer of silicon on a surface of an SOI wafer to form a transmission waveguide, the SOI wafer comprising, from bottom to top, a substrate, a refractive index difference layer and a top layer of silicon; forming a transition waveguide above one end of the transmission waveguide; forming an array of coupling waveguides at one end of the transition waveguide; epitaxially growing a high refractive index region of uniform refractive index and greater than the refractive index of the refractive index difference layer along the refractive index difference layer, or epitaxially growing a plurality of layers of different refractive indices along the refractive index difference layer, wherein the refractive index of at least one of the layers is greater than the refractive index of the refractive index difference layer.

20. The method of claim 19, wherein the optical coupling is prepared by, The array of coupling waveguides is located at an edge position of the optical coupler. One end of the transition waveguide is directed towards the array of coupling waveguides for optical coupling therewith, and the other end of the transition waveguide is directed towards the transmission waveguide for optical coupling therewith. A first tapering region is formed at one end of the transition waveguide directed towards the array of coupling waveguides, a second tapering region is formed at the other end of the transition waveguide directed towards the transmission waveguide, and the waveguide widths of the first tapering region and the second tapering region present opposite tapering patterns. A third tapering region is formed at the transmission waveguide, and the waveguide widths of the third tapering region and the second tapering region present opposite tapering patterns.

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