Grating coupler and preparation method thereof

Abstract

The invention relates to a grating coupler and a preparation method thereof, and relates to the technical field of silicon-based optoelectronic chips, the grating coupler comprises a substrate and a waveguide layer located on one side of the substrate, the waveguide layer comprises a grating area, and a metasurface structure is arranged on the side, away from the substrate, of the waveguide layer. The metasurface structure can perform phase regulation and control on incident light so as to adjust the incident angles of the incident light with different wavelengths. The refractive index of the waveguide layer of the grating region is periodically changed, and incident light can be coupled into the waveguide layer through the Bragg scattering effect. The coupling angle of the grating region is related to the wavelength of the incident light, and the incident angles of the incident light with different wavelengths can be adjusted by arranging the metasurface structure, so that the incident light in the whole waveband range is closer to the proper coupling angle of Bragg diffraction, and the optical bandwidth of the grating coupler is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of silicon-based optoelectronic chips, in particular to a grating coupler and a preparation method thereof. BACKGROUND

[0002] With the development of cloud computing and artificial intelligence technology, the demand for data transmission speed of devices is getting higher and higher. Optical communication technology has the advantages of high speed, large capacity and low power consumption, and has become one of the solutions to this problem.

[0003] Silicon optical technology can independently complete the modulation, filtering, switching and detection of optical signals, and is a very important part of optical communication technology. However, the integration of on-chip light sources has always been a major difficulty in silicon optical technology, so current silicon optical chips need to introduce light through external light sources. The grating coupler is an extremely important device in silicon-based optoelectronic devices, with the advantages of simple manufacturing process, large alignment tolerance, and convenient wafer-level testing. However, its optical bandwidth is small, the wavelength-dependent loss is large, and the coupling efficiency will change greatly with the wavelength. SUMMARY

[0004] Therefore, it is necessary to provide a grating coupler and a preparation method thereof for improving the optical bandwidth of the grating coupler.

[0005] To achieve the above-mentioned purpose, on the one hand, the present application provides a grating coupler, comprising:

[0006] a substrate;

[0007] a waveguide layer located on one side of the substrate, the waveguide layer comprising a grating region;

[0008] a first cladding layer located on the side of the waveguide layer away from the substrate, covering the waveguide layer and the exposed substrate;

[0009] a metasurface structure located on the side of the waveguide layer away from the substrate, the metasurface structure having a plurality of spaced microstructure units.

[0010] In one embodiment, the plurality of microstructure units are arranged in an array on the substrate.

[0011] In the first direction, the distance between the adjacent two microstructure units is the same, and the first direction is parallel to the substrate.

[0012] In one embodiment, the plurality of microstructure units are arranged in a ring on the substrate.

[0013] In one embodiment, the shape of the microstructure unit includes a column or a prism.

[0014] In one of the embodiments, the material of the metasurface structure has the same refractive index as the material of the first cladding layer.

[0015] In one of the embodiments, the grating coupler further comprises:

[0016] A second cladding layer, which is located on the side of the metasurface structure away from the substrate.

[0017] In one of the embodiments, the material of the metasurface structure has a different refractive index from the material of the second cladding layer.

[0018] In one of the embodiments, the grating region comprises a plurality of grating units.

[0019] The thickness of the grating unit is smaller than the thickness of the waveguide layer.

[0020] Or, the thickness of the grating unit is the same as the thickness of the waveguide layer.

[0021] In one of the embodiments, the distance between two adjacent grating units is the same.

[0022] In another aspect, the present application also provides a method for preparing a grating coupler, comprising:

[0023] Providing a substrate;

[0024] Forming a waveguide layer on one side of the substrate, the waveguide layer comprising a grating region;

[0025] Forming a first cladding layer on the side of the waveguide layer away from the substrate, the first cladding layer covering the waveguide layer and the exposed substrate;

[0026] Forming a metasurface structure on the side of the waveguide layer away from the substrate, the metasurface structure having a plurality of spaced-apart microstructure units.

[0027] Compared with the prior art, the above technical solution has the following advantages:

[0028] The grating coupler comprises a substrate and a waveguide layer located on one side of the substrate, the waveguide layer comprises a grating area, and a metasurface structure is arranged on the side of the waveguide layer away from the substrate. The metasurface structure has a plurality of spaced microstructure units, the refractive index of the material of the microstructure unit is different from the refractive index of the material in the interval between the two adjacent microstructure units, and when the incident light enters the metasurface structure, the metasurface structure can phase control the incident light, thereby adjusting the incident angle of the incident light of different wavelengths. The refractive index of the waveguide layer of the grating area is periodically changed, which can couple the incident light into the waveguide layer through the Bragg scattering effect. The coupling angle of the grating area is related to the wavelength of the incident light, and the metasurface structure is arranged to adjust the incident angle of the incident light of different wavelengths, so that the incident light in the whole wavelength range is closer to the suitable coupling angle of the Bragg diffraction, thereby improving the optical bandwidth of the grating coupler. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0030] Figure 1 A cross-sectional structure schematic diagram of a grating coupler is provided for the embodiments of the present application;

[0031] Figure 2 A top view structure schematic diagram of a grating coupler is provided for the embodiments of the present application;

[0032] Figure 3 A cross-sectional structure schematic diagram of a metasurface structure is provided for the embodiments of the present application;

[0033] Figure 4 A cross-sectional structure schematic diagram of a grating coupler provided with a second cladding layer is provided for the embodiments of the present application;

[0034] Figure 5 A cross-sectional structure schematic diagram of a grating area is provided for the embodiments of the present application;

[0035] Figure 6 A flowchart of a preparation method of a grating coupler is provided for the embodiments of the present application;

[0036] Figure 7 A schematic diagram of the angle difference of light of different wavelengths after passing through the metasurface structure 04 is provided for the embodiments of the present application;

[0037] Figure 8A diagram showing the difference in coupling efficiency of the grating coupler with and without a metasurface is provided for the embodiments of the present application.

[0038] Label explanation: 01 - substrate; 011 - substrate; 012 - buried oxygen layer; 02 - waveguide layer; 021 - grating area; 022 - grating unit; 03 - first cladding layer; 04 - metasurface structure; 041 - microstructure unit; 042 - interval; 05 - second cladding layer. DETAILED DESCRIPTION

[0039] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the accompanying drawings. The embodiments of the present application are shown in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terminology used in the specification of the present application is only for the purpose of describing specific embodiments and is not intended to limit the present application.

[0041] It should be understood that when a layer is referred to as being "on", "adjacent", "connected to" or "coupled to" another layer, it can be directly on, adjacent, connected or coupled to the other layer, or intervening layers can be present. In contrast, when an element is referred to as being "directly on", "directly adjacent" or "directly connected to" another layer, there are no intervening layers present.

[0042] As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. It should also be understood that the term "comprising" or "including" or "having" or the like, as used herein, specifies the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.

[0043] Based on the content in the background art, the grating coupler currently used in wafer-level testing is mainly silicon-based grating coupler. In order to achieve a large bandwidth design, low refractive index materials are usually selected to manufacture the grating coupler. However, the low refractive index material will result in poor refractive index contrast, which will reduce the coupling efficiency of the grating coupler.

[0044] The traditional silicon-based grating coupler realizes grating coupling through Bragg diffraction, and the Bragg diffraction equation is as follows:

[0045]

[0046] wherein period is the period of the grating, λ is the wavelength of the light, n eff is the effective refractive index of the waveguide layer of the grating region, n1 is the effective refractive index of the cladding layer on the upside of the grating region, and θ is the incident angle of the light source. The grating period period, the effective refractive index n eff of the waveguide layer of the grating region, the effective refractive index n1 of the cladding layer on the upside of the grating region, and the incident angle θ of the light source do not change with the change of the wavelength λ, which causes that, in a certain spectral range of the wavelength, only one wavelength can well match the Bragg diffraction equation of the grating, and the coupling efficiency of the grating coupler is the highest at the wavelength; and for other wavelengths, the more serious the deviation from the Bragg equation, the lower the coupling efficiency.

[0047] Based on this, the present application provides a grating coupler and a preparation method thereof. The grating coupler comprises a substrate and a waveguide layer located on one side of the substrate, the waveguide layer comprising a grating region, and a metasurface structure is arranged on the side of the waveguide layer away from the substrate. The metasurface structure has a plurality of spaced microstructure units, the refractive index of the material of the microstructure unit is different from the refractive index of the material in the interval between the adjacent two microstructure units, and when the incident light enters the metasurface structure, the metasurface structure can perform phase control on the incident light, thereby adjusting the incident angle of the incident light of different wavelengths. The refractive index of the waveguide layer of the grating region is periodically changed, which can couple the incident light into the waveguide layer through the Bragg scattering effect. The coupling angle of the grating region is related to the wavelength of the incident light, and the metasurface structure can adjust the incident angle of the incident light of different wavelengths, so that the incident light in the entire wavelength range is closer to the suitable coupling angle of the Bragg diffraction, thereby improving the optical bandwidth of the grating coupler.

[0048] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0049] Reference Figure 1 , Figure 1 A cross-sectional structure schematic diagram of a grating coupler is provided for the embodiments of the present application; reference Figure 2 , Figure 2 A top view structure schematic diagram of a grating coupler is provided for the embodiments of the present application, which comprises:

[0050] A substrate 01;

[0051] A waveguide layer 02 is located on one side of the substrate 01, and the waveguide layer 02 comprises a grating region 021;

[0052] A first cladding layer 03 is located on the side of the waveguide layer 02 away from the substrate 01, covering the waveguide layer 02 and the exposed substrate 01;

[0053] The super surface structure 04 is located on the side of the waveguide layer 02 away from the substrate 01, and the super surface structure 04 comprises a plurality of spaced microstructure units 041.

[0054] Specifically, the substrate 01 comprises a substrate 011 and a buried oxygen layer 012, the substrate 011 can comprise a silicon substrate, and the buried oxygen layer 012 can comprise a silicon dioxide buried oxygen layer, without specific limitation.

[0055] The waveguide layer 02 is located on the side of the substrate 01, i.e. on the side of the buried oxygen layer 012 away from the substrate 011, and the material of the waveguide layer 02 can be silicon material. It should be noted that the waveguide layer 02 comprises a grating area 021 and a waveguide area, and the waveguide area is used for transmitting light field. The shape of the grating area 021 can be a sector, without specific limitation.

[0056] The side of the waveguide layer 02 away from the substrate 01 is also provided with a first cladding layer 03, and the material of the first cladding layer 03 can be silicon dioxide or transparent polymer. On the one hand, the first cladding layer 03 can protect the waveguide layer 02 from damage, so that the coupling efficiency remains stable in different environments. On the other hand, the refractive index of the first cladding layer 03 can also adjust the distribution of the incident light, thereby improving the coupling efficiency.

[0057] The super surface structure 04 is located on the side of the first cladding layer 03 away from the waveguide layer 02. It should be noted that the incident light will first pass through the super surface structure 04 and then enter the waveguide layer 02. After the incident light is adjusted in angle by the super surface structure 04, the coupling efficiency of the incident light in the waveguide layer 02 can be improved.

[0058] The super surface structure 04 has a plurality of microstructure units 041, and the plurality of microstructure units 041 are arranged at intervals, thereby forming periodically arranged microstructure units 041 and intervals 042 in the super surface structure 04. The material of the super surface structure 04 can be silicon nitride material or polycrystalline silicon material, etc.

[0059] In the present application, since the super surface structure 04 has a plurality of spaced microstructure units 041, the refractive index of the material of the microstructure unit 041 is different from the refractive index of the material in the interval between the two adjacent microstructure units 041. When the incident light enters the super surface structure 04, the super surface structure 04 can perform phase control on the incident light, thereby adjusting the incident angle of the incident light of different wavelengths. The refractive index of the waveguide layer of the grating area 021 is periodically changed, which can couple the incident light into the waveguide layer through the Bragg scattering effect. The coupling angle of the grating area 021 is related to the wavelength of the incident light. By arranging the super surface structure 04, the incident angle of the incident light of different wavelengths can be adjusted, so that the incident light in the entire waveband range is closer to the suitable coupling angle of the Bragg diffraction, thereby improving the optical bandwidth of the grating coupler.

[0060] Optionally, in some embodiments, the metasurface structure 04 can adjust the incident angle of incident light of different wavelengths, so that the incident light in the entire wavelength range meets the appropriate coupling angle of Bragg diffraction.

[0061] In another embodiment of the present application, as shown in Figure 2 The plurality of microstructure units 041 are arranged in an array on the substrate 01.

[0062] In the first direction X, the spacing between two adjacent microstructure units 041 is the same, and the first direction X is parallel to the substrate 01.

[0063] Specifically, the plurality of microstructure units 041 are arranged in an array on the substrate 01, for example, the plurality of microstructure units 041 are arranged and spaced apart on the substrate 01 in the first direction X, and the plurality of microstructure units 041 are arranged and spaced apart on the substrate 01 in the second direction Y, the first direction X and the second direction Y are perpendicular to each other and parallel to the substrate 01.

[0064] It should be noted that the spacing between two adjacent microstructure units 041 is the same. The same spacing means that the phase effect of each microstructure unit 041 and the spacing 042 on light has a periodic regularity. In the metasurface structure for beam deflection, the same spacing can make the phase accumulation of light in the propagation direction uniform and calculable, so that it is easier to achieve a preset phase gradient by designing the parameters of the microstructure unit 041, accurately control the refraction and / or reflection angle of the incident light, and further increase the coupling efficiency of the grating coupler.

[0065] In another embodiment of the present application, the plurality of microstructure units 041 are arranged in a ring on the substrate 01 (not shown).

[0066] Specifically, the plurality of microstructure units 041 are arranged in a ring on the substrate 01, that is, the plurality of microstructure units 041 are periodically arranged in a ring around the same center on the substrate 01. Due to the rotational symmetry of the ring arrangement, the spatial distribution of a specific light source can be matched by the structural symmetry, for example, the spatial distribution of a ring light source, thereby further improving the light coupling efficiency.

[0067] In another embodiment of the present application, the shape of the microstructure unit 041 includes a column or a prism.

[0068] Specifically, the shape of the microstructure unit 041 can be a column (as shown in Figure 1The microstructure unit 041 can be in a cylindrical or prismatic shape, etc., with the side surface perpendicular to the substrate 01, which is more convenient to prepare. At this time, the height, diameter or side length of the columnar structure can be used to control the phase of light, thereby affecting the angle of the incident light. In addition, the side surface of the columnar structure is perpendicular, and the scattering loss of the incident light in the microstructure unit 041 is low. Moreover, by optimizing the height-diameter ratio of the column, the phase modulation can be kept stable in a wide wavelength range.

[0069] Reference Figure 3 , Figure 3 A cross-sectional structure diagram of a metasurface structure is provided for an embodiment of the present application. The shape of the microstructure unit 041 can also be a prismatic shape. The inclined side surface of the prismatic shape can reduce the refractive index jump between air and the material of the microstructure unit 041, and reduce the reflection of light at the interface. Moreover, due to the inclination angle between the side wall and the substrate 01, the receiving angle range of light can be expanded, the utilization rate of incident light can be improved, and the coupling efficiency of light can be further enhanced.

[0070] In another embodiment of the present application, the refractive index of the material of the metasurface structure 04 is the same as the refractive index of the material of the first cladding layer 03.

[0071] Specifically, the refractive index of the material of the metasurface structure 04 is the same as the refractive index of the material of the first cladding layer 03. At this time, the space 042 between the microstructure units 041 of the metasurface structure 04 is filled with air, and the refractive index of the air is not the same as the refractive index of the material of the microstructure unit 041. The microstructure unit 041 controls the phase of the incident light, changes the incident angle of the incident light of different wavelengths, and makes the incident light in the entire wavelength range closer to the suitable coupling angle of Bragg diffraction, thereby improving the bandwidth of the grating coupler.

[0072] In another embodiment of the present application, the refractive index of the material of the metasurface structure 04 is the same as the refractive index of the material of the first cladding layer 03. Figure 4 , Figure 4 A cross-sectional structure diagram of a grating coupler provided with a second cladding layer is provided for an embodiment of the present application. The grating coupler further comprises:

[0073] The second cladding layer 05 is located on the side of the metasurface structure 04 away from the substrate 01.

[0074] Specifically, the side of the metasurface structure 04 away from the substrate 01 can also be provided with a second cladding layer 05. The material of the second cladding layer 05 can be silica material or transparent polymer, etc. The second cladding layer 05 fills the space 042 between the metasurface structures 04 and covers the metasurface structures 04, which can protect the metasurface structures 04 from damage.

[0075] In another embodiment of the present application, the refractive index of the material of the metasurface structure 04 is not the same as the refractive index of the material of the second cladding layer 05.

[0076] Specifically, in the embodiment, the refractive index of the material of the metasurface structure 04 is not the same as the refractive index of the material of the second cladding layer 05, and at this time, the second cladding layer 05 is in the interval 042 between the microstructure units 041 of the metasurface structure 04, and the refractive index of the second cladding layer 05 is not the same as the refractive index of the material of the microstructure unit 041. The microstructure unit 041 phase-modulates the incident light, changes the incident angle of the incident light of different wavelengths, makes the incident light in the entire wavelength range closer to the suitable coupling angle of the Bragg diffraction, and improves the bandwidth of the grating coupler.

[0077] In another embodiment of the present application, referring to Figure 4 , and referring to Figure 5 , Figure 5 is a schematic diagram of a cross-sectional structure of a grating region provided by an embodiment of the present application; the grating region 021 includes a plurality of grating units 022;

[0078] The thickness of the grating unit 022 is less than the thickness of the waveguide layer 02 (as shown in Figure 4 );

[0079] Or, the thickness of the grating unit 022 is the same as the thickness of the waveguide layer 02 (as shown in Figure 5 ).

[0080] Specifically, the grating region 021 includes a plurality of grating units 022, when the thickness of the grating unit 022 is less than the thickness of the waveguide layer 02, the grating region 021 only etches part of the waveguide layer 02 and does not expose the substrate 01, at this time, the refractive index of the grating region 021 changes gently, the modulation of the optical field is weak, the weak modulation characteristic reduces the resonance dependence on the wavelength, so that the working bandwidth is wider, and since the grating region 021 is continuous and uninterrupted, the transmission loss is also lower.

[0081] When the thickness of the grating unit 022 is the same as the thickness of the waveguide layer 02, the grating region 021 exposes part of the substrate 01, at this time, the refractive index of the grating region 021 changes greatly, and the modulation ability of the optical field is stronger. This strong modulation can more effectively diffract the optical energy in the waveguide layer 02 to the target direction, and the coupling efficiency is higher.

[0082] In another embodiment of the present application, the interval between two adjacent grating units 022 is the same.

[0083] Specifically, the same interval between two adjacent grating units 022 can ensure the grating period, and then produce regular diffraction, reflection and coupling, thereby producing a stable interference premise and increasing the effect of coupling.

[0084] It should be noted that in some embodiments, the interval between two adjacent grating units 022 can also be tapered, and is not specifically limited.

[0085] Based on the above grating coupler, referring to Figure 6 , Figure 6 A flowchart of a preparation method of a grating coupler provided by the embodiments of the present application is shown. The present application also provides a preparation method of a grating coupler, which comprises the following steps:

[0086] S10: providing a substrate 01;

[0087] S20: forming a waveguide layer 02 on one side of the substrate 01, wherein the waveguide layer 02 comprises a grating area 021;

[0088] S30: forming a first cladding layer 03 on the side of the waveguide layer 02 away from the substrate 01, wherein the first cladding layer 03 covers the waveguide layer 02 and the exposed substrate 01;

[0089] S40: forming a metasurface structure 04 on the side of the waveguide layer 02 away from the substrate 01, wherein the metasurface structure 04 comprises a plurality of spaced microstructure units 041.

[0090] Specifically, in step S10, the provided substrate 01 comprises a substrate 011 and a buried oxygen layer 012, wherein the substrate 011 can comprise a silicon substrate 011, and the buried oxygen layer 012 can comprise a silicon dioxide buried oxygen layer 012, and is not specifically limited.

[0091] In step S20, a waveguide material layer can be first formed on one side of the substrate 01, for example, a silicon layer. Then, a photolithography process is performed to form a waveguide area and a grating area 021.

[0092] In step S30, the first cladding layer 03 can be grown on the side of the waveguide layer 02 away from the substrate 01 by using a plasma-enhanced chemical vapor deposition (PECVD) method or a thermal oxidation method, wherein the first cladding layer 03 covers the waveguide layer 02 and the exposed substrate 01.

[0093] The material of the first cladding layer 03 can be silicon dioxide or a transparent polymer. On the one hand, the first cladding layer 03 can protect the waveguide layer 02 from damage, so that the coupling efficiency remains stable in different environments. On the other hand, the refractive index of the material of the first cladding layer 03 can also adjust the distribution of incident light, thereby improving the coupling efficiency.

[0094] It should be noted that when the first cladding layer 03 is formed, a cladding layer material with a thickness greater than 3 μm can be formed first, and then chemical mechanical polishing (CMP) is performed on the formed cladding layer material to facilitate the subsequent preparation of the metasurface structure 04.

[0095] In step S40, a layer of metasurface structure 04 material can be formed on the side of the waveguide layer 02 away from the substrate 01 by plasma enhanced chemical vapor deposition (PECVD) or low pressure chemical vapor deposition (LPCVD), and then a plurality of microstructure units 041 are formed by photolithography and etching process. The plurality of microstructure units 041 are arranged at intervals, and the material of the metasurface structure 04 can be silicon nitride material or polycrystalline silicon material, etc.

[0096] In this application, since the metasurface structure 04 has a plurality of microstructure units 041 arranged at intervals, the refractive index of the material of the microstructure unit 041 is different from the refractive index of the material between the adjacent two microstructure units 041, and when the incident light enters the metasurface structure 04, the metasurface structure 04 can adjust the phase of the incident light, thereby adjusting the incident angle of the incident light of different wavelengths. The refractive index of the waveguide layer of the grating area 021 is periodically changed, which can couple the incident light into the waveguide layer through Bragg scattering effect. The coupling angle of the grating area 021 is related to the wavelength of the incident light, and the setting of the metasurface structure 04 can adjust the incident angle of the incident light of different wavelengths, so that the incident light in the whole wavelength range is closer to the suitable coupling angle of Bragg diffraction, thereby improving the optical bandwidth of the grating coupler.

[0097] It should be noted that after the metasurface structure 04 is formed, a second cladding layer 05 can also be deposited by plasma enhanced chemical vapor deposition (PECVD), and the formed cladding layer material needs to be chemically mechanically polished (CMP) when the second cladding layer 05 is formed.

[0098] Based on the above grating coupling structure and its preparation method, the present application also provides a comparative example for reference. When the wavelength is in the spectral range of 1260 nm-1360 nm, the present application and the existing grating coupler are tested, the incident light with wavelength of 1260 nm-1360 nm has different incident angles, and the setting of the metasurface structure can reduce the degree of deviation of the incident light in the whole range from the Bragg equation of the grating area. Referring to FIG. Figure 7 The angle difference diagram of different wavelengths of light provided by the embodiment of the present application after passing through the metasurface structure 04; referring to FIG. Figure 8The coupling efficiency difference diagram of the grating coupler with and without the metasurface is provided for the embodiments of the present application. Figure 7 As can be seen from FIG. 12, the incident angles of the incident light of 1260 nm, 1310 nm and 1360 nm reaching the grating area 021 after passing through the metasurface structure 04 are all different, and the exit angles of the light of 1260 nm and 1360 nm are different by 1°. Then the exit angle of the light passing through the metasurface structure 04 is brought into the grating coupling efficiency model to simulate the coupling efficiency of the grating, and as can be seen from FIG. 13, in the case of the metasurface structure 04, the coupling efficiency of the central wavelength of the grating area 021 is basically unchanged, and for other wavelengths deviating from the central wavelength, the coupling efficiency is slightly improved, which improves the bandwidth of the grating coupler. Figure 8

[0099] It should be noted that the metasurface structure 04 can be further optimized to make the light of different wavelengths satisfy the Bragg equation of the grating, further improving the bandwidth of the grating coupler; and the design can also be used in the polarization multiplexing field of the grating coupler.

[0100] In the description of the present specification, the description referring to the terms "some embodiments", "another embodiment" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiments or examples are contained in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example.

[0101] The technical features of the above-described embodiments can be combined in any manner. To make the description brief, all possible combinations of the technical features of the above-described embodiments are not described, however, as long as the combinations of the technical features do not contradict each other, they should be considered as within the scope of the present specification.

[0102] The above-described embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the patent application scope. It should be noted that for ordinary skilled persons in the art, some modifications and improvements can be made without departing from the concept of the present application, and these are within the protection scope of the present application. Therefore, the patent protection scope of the present application should be subject to the appended claims.​

Claims

1. A grating coupler, characterized in that: include: substrate; a waveguide layer, located on one side of the substrate, the waveguide layer comprising a grating region; a first cladding layer, located on a side of the waveguide layer away from the substrate, covering the waveguide layer and the exposed substrate; The super surface structure is located on a side of the waveguide layer away from the substrate, and the super surface structure has a plurality of micro structure units arranged at intervals.

2. The grating coupler according to claim 1, wherein A plurality of the microstructure units are arranged in an array on the substrate; In a first direction, the distances between two adjacent microstructure units are the same, and the first direction is parallel to the substrate.

3. The grating coupler according to claim 1, wherein A plurality of the microstructure units are arranged in a ring shape on the substrate.

4. The grating coupler according to claim 1, wherein The shape of the microstructure unit includes a column shape or a pyramid shape.

5. The grating coupler according to claim 1, wherein The refractive index of the material of the metasurface structure is the same as the refractive index of the material of the first cladding layer.

6. The grating coupler according to claim 1, wherein The grating coupler further comprises: A second cladding layer is located on a side of the metasurface structure away from the substrate.

7. The grating coupler according to claim 6, characterized in that The refractive index of the material of the metasurface structure is different from the refractive index of the material of the second cladding layer.

8. The grating coupler according to claim 1, wherein The grating region includes a plurality of grating units; The thickness of the grating unit is smaller than the thickness of the waveguide layer; Alternatively, the thickness of the grating unit is the same as the thickness of the waveguide layer.

9. The grating coupler according to claim 8, characterized in that The distances between two adjacent grating units are the same.

10. A method for preparing a grating coupler, characterized in that: include: providing a substrate; forming a waveguide layer on one side of the substrate, wherein the waveguide layer includes a grating region; forming a first cladding layer on a side of the waveguide layer away from the substrate, wherein the first cladding layer covers the waveguide layer and the exposed substrate; A super surface structure is formed on a side of the waveguide layer away from the substrate, wherein the super surface structure has a plurality of micro structure units arranged at intervals.

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