Design method of metasurface and metasurface

Abstract

The invention provides a metasurface design method. The metasurface design method comprises the steps that metasurface efficiencies corresponding to different film layer parameters are calculated through simulation software; selecting ideal film layer parameters to form a multilayer film structure, wherein the metasurface efficiency corresponding to the ideal film layer parameters is not lower than a first threshold value; a nano structure is formed by adopting a multi-layer film structure, and nano structure arrangement is carried out; the multi-layer film structure is constructed through the screened ideal film layer parameters, the resonance effect can be reduced under the condition that the phase requirement range is large, the situation that the transmittance or reflectivity of a nano structure is suddenly reduced is avoided, and therefore high-efficiency metasurface design is achieved.

Description

Technical Field

[0001] The present invention relates to the field of optical technology, and in particular to a design method of a metasurface and a metasurface. Background Art

[0002] Metasurfaces control the polarization, phase, amplitude, frequency, propagation mode and other characteristics of electromagnetic waves through sub-wavelength nanostructures on the surface. In the prior art, when designing metasurfaces, in order to improve the efficiency of the metasurfaces, the characteristic dimensions of the nanostructures (such as the radius of cylindrical nanostructures) or the materials are usually optimized and adjusted.

[0003] However, in some application scenarios, such as the design of achromatic metasurfaces, it is necessary to cover as much phase range as possible based on one phase period, which means that a higher nanostructure is needed. At this time, improving the metasurface efficiency only by adjusting the characteristic size or material of the nanostructure is likely to produce a resonance effect, resulting in a sharp drop in the metasurface efficiency. Summary of the invention

[0004] The object of the present invention is to provide a design method of a metasurface and a metasurface for reducing resonance effect.

[0005] To achieve one of the above-mentioned purposes of the invention, an embodiment of the present invention provides a method for designing a metasurface, comprising:

[0006] Use simulation software to calculate the metasurface efficiency corresponding to different film layer parameters;

[0007] Selecting ideal film layer parameters to form a multilayer film structure, wherein the metasurface efficiency corresponding to the ideal film layer parameters is not less than a first threshold;

[0008] A multi-layer film structure is used to form a nanostructure and arrange the nanostructure.

[0009] As a further improvement of an embodiment of the present invention, the film layer parameters include a theoretical film layer thickness, and the theoretical film layer thickness is determined based on the working band of the metasurface.

[0010] As a further improvement of an embodiment of the present invention, the film layer parameters include a first film layer material and a second film layer material, and the refractive index of the first film layer material is greater than the refractive index of the second film layer material.

[0011] As a further improvement of an embodiment of the present invention, the film layer parameters include the number of film layers, and the corresponding number of film layers is selected based on the working band of the metasurface.

[0012] As a further improvement of an embodiment of the present invention, different nanostructure characteristic sizes are scanned, the scanned results are screened, a nanostructure characteristic size-phase library is constructed, and then the nanostructures are arranged.

[0013] As a further improvement of an embodiment of the present invention, screening the scanned results specifically includes:

[0014] There are at least two phase coverages in the 2π range within the characteristic size range of the nanostructure.

[0015] As a further improvement of an embodiment of the present invention, screening the scanned results specifically includes:

[0016] The supersurface efficiency within the characteristic size range of the nanostructure is no less than the second threshold.

[0017] As a further improvement of an embodiment of the present invention, different nanostructure heights are scanned, the database obtained by the scan is screened, the nanostructure height is determined, and then the nanostructure characteristic size-phase library is constructed.

[0018] As a further improvement of an embodiment of the present invention, different superstructure unit periods are scanned, the database obtained by the scan is screened, the superstructure unit period is determined, and then the nanostructure characteristic size-phase library is constructed.

[0019] As a further improvement of an embodiment of the present invention, different anti-reflection film parameters are scanned, the database obtained by the scan is screened, the anti-reflection film parameters are determined, and then the nanostructure characteristic size-phase library is constructed.

[0020] As a further improvement of an embodiment of the present invention, screening the database obtained by scanning specifically includes:

[0021] The efficiency of the screened metasurfaces is not lower than the third threshold.

[0022] As a further improvement of an embodiment of the present invention, an optimization program is used to optimize the theoretical phase distribution corresponding to different wavelengths, to obtain the ideal phase distribution corresponding to each wavelength, and then the nanostructure is arranged.

[0023] In order to achieve one of the purposes of the above invention, the present invention also provides a super surface, which is designed by any of the above design methods.

[0024] Compared with the prior art, in the embodiments of the present invention, a multilayer film structure is constructed by screening out ideal film layer parameters, and the multilayer film structure is used to form a nanostructure, which can reduce the resonance effect when the phase requirement range is large, avoid the sudden drop in the transmittance or reflectivity of the nanostructure, and thus avoid the sudden drop in the efficiency of the metasurface. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic cross-sectional view of a metasurface in one embodiment of the present invention;

[0026] Figure 2 yes Figure 1 Schematic diagram of the plane of the super surface along the Z axis;

[0027] Figure 3 is a schematic cross-sectional view of a superstructure unit in another preferred embodiment of the present invention;

[0028] Figure 4 is a schematic flow chart of a method for designing a metasurface in a preferred embodiment of the present invention;

[0029] Figure 5 Is adopted Figure 1 Nanostructure characteristic size-phase library constructed by medium nanostructures;

[0030] Figure 6 Is adopted Figure 3 Nanostructure characteristic size-phase library constructed by medium nanostructures;

[0031] Figure 7 It is the light field distribution on the XZ plane after the metasurface modulates the working band light in one embodiment. DETAILED DESCRIPTION

[0032] The present invention will be described in detail below in conjunction with the specific embodiments shown in the accompanying drawings. However, these embodiments do not limit the present invention, and any structural, methodological, or functional changes made by a person skilled in the art based on these embodiments are all within the scope of protection of the present invention.

[0033] It should be understood that the terms such as “having”, “including” and “comprising” used herein do not exclude the existence or addition of one or more other elements or combinations thereof.

[0034] In various drawings of the present invention, for the convenience of illustration, some sizes of structures or parts are exaggerated relative to other structures or parts, and thus, only the basic structure of the subject matter of the present invention is illustrated.

[0035] refer to Figure 1 and Figure 2As shown, one embodiment of the present invention provides a metasurface, which refers to an artificial layered material with a thickness less than the wavelength, and can be regarded as the two-dimensional counterpart of the metamaterial. The metasurface can control the polarization, phase, amplitude, frequency, propagation mode and other characteristics of the electromagnetic wave through the sub-wavelength nanostructure 20 on the surface, and realize the characteristics of beam shaping, beam deflection, super lens, super holography, optical rotation, anti-reflection and anti-reflection.

[0036] Specifically, the metasurface includes a plurality of array-arranged superstructure units 30, and a nanostructure 20 is provided at the center and / or vertex of each superstructure unit 30. The superstructure unit 30 is obtained by dividing the metasurface into structural units centered on each nanostructure 20, and the nanostructures 20 in each period constitute a superstructure unit. The period of the superstructure unit 30 can be the length of the superstructure unit 30 along the X-axis or Y-axis direction.

[0037] The superstructure unit 30 is a densely packed shape, for example, a regular quadrilateral (such as Figure 2 ), regular hexagon, fan-shaped, etc., each period contains a nanostructure 20, and the vertex and / or center of the superstructure unit 30 can be provided with a nanostructure 20. For example, when the superstructure unit 30 is a regular hexagon, at least one nanostructure 20 is provided at each vertex and center of the regular hexagon. Similarly, the same is true for the fan-shaped and square cases.

[0038] Exemplarily, the nanostructure 20 is configured as a polarization-dependent structure or a polarization-independent structure. The nanostructure 20 can select a polarization-dependent structure or a polarization-independent structure according to different usage scenarios. Polarization-independent structures include, for example, cylindrical, square cylindrical, cross cylindrical, square cylindrical with round holes, etc. Polarization-dependent structures include, for example, elliptical cylindrical, rectangular cylindrical, hexagonal prism, etc.

[0039] Exemplarily, the nanostructure 20 is made of only one material, that is, made of a single material.

[0040] The metasurface further includes a substrate 10 connected to the nanostructures 20, and a plurality of nanostructures 20 are arranged on the substrate 10. The substrate 10 can be made of a light-transmitting or light-impermeable material. When the substrate 10 transmits light, a transmissive metasurface is formed. When the substrate 10 is light-impermeable or reflects light, it is a reflective metasurface.

[0041] In some embodiments, the metasurface further includes a protective layer 40 covering the nanostructure 20 , and the protective layer 40 may also be air (ie, the protective layer 40 is not provided).

[0042] In some embodiments, the metasurface further includes an anti-reflection film 50 disposed on the light incident side and / or light emitting side of the metasurface, and the anti-reflection film 50 is disposed on the substrate 10 and / or the protective layer 40. In this embodiment, the anti-reflection film 50 is preferably disposed on both the substrate 10 and the protective layer 40. At this time, one layer of anti-reflection film 50 covers the surface of the protective layer 40 on the side away from the substrate 10, and another layer of anti-reflection film 50 covers the surface of the substrate 10 on the side away from the nanostructure 20. That is, the light incident side and the light emitting side of the metasurface are covered with an anti-reflection film 50. By providing the anti-reflection film 50, the reflectivity (for example, the transmittance of the enhanced transmissive metasurface) and / or the transmittance (for example, the reflectivity of the enhanced reflective metasurface) of the interface between the air and the metasurface structure is reduced, thereby improving the efficiency of the metasurface (for example, the transmittance or reflectivity).

[0043] In some embodiments, the anti-reflection film 50 includes at least two material layers, for example, a first material layer 501 and a second material layer 502 .

[0044] Exemplarily, the working band of the metasurface can be any one or more of a combination of a visible light band, a near infrared band, a mid-infrared band, and a far infrared band. For ease of description, the following description is based on the working band being the near infrared band.

[0045] Exemplarily, the metasurface is configured as a transmissive metalens with a central wavelength of 970 nm, a bandwidth of 60 nm, a metalens diameter D=50 um, and a numerical aperture NA=0.3. The material of the substrate 10 is glass (e.g., high borosilicate glass, BF33), and the length of the substrate 10 along the Z axis is 775 um. The material of the nanostructure 20 is amorphous silicon (a-Si pill ar), the length of the nanostructure 20 along the Z axis is 1300 nm, and its refractive index at the central wavelength is 3.486. The material of the protective layer 40 is silicon dioxide (SiO2), the length of the protective layer 40 along the Z axis is 1730 nm, and its refractive index at the central wavelength is 1.452. The material of the first material layer 501 is silicon nitride (Si N), and its refractive index at the central wavelength is 2.0031. The material of the second material layer 502 is silicon dioxide (SiO2), and its refractive index at the central wavelength is 1.452.

[0046] refer to Figure 3 As shown, another preferred embodiment of the present invention provides a metasurface, in which the nanostructure 20 is composed of a multilayer film structure, which reduces the resonance effect and improves the metasurface efficiency. In this embodiment, the same reference numerals represent the same components with similar functions and are not further described.

[0047] In some embodiments, the multilayer film structure (ie, nanostructure 20) includes a first film layer 201 and a second film layer 202. The first film layer 201 and the second film layer 202 are disposed adjacent to each other and are stacked in sequence to form a multilayer film structure.

[0048] In other embodiments, the number of film layers of the multilayer film structure may be greater than two, as long as the first film layer 201 and the second film layer 202 are arranged adjacent to each other. The more film layers there are, the higher the efficiency of the metasurface.

[0049] In some embodiments, the refractive index of the material of the first film layer 201 is different from the refractive index of the material of the second film layer 202, for example, the refractive index of the material of the first film layer 201 is greater than the refractive index of the material of the second film layer 202. The resonance effect can be reduced by using the interaction between high and low refractive index materials (for example, matching the refractive indices of different film layers).

[0050] For example, the material of the substrate 10 is glass (eg, high borosilicate glass BF33), and the length of the substrate 10 along the Z axis is 775 um. The length of the nanostructure 20 (ie, the multilayer film structure) along the Z axis is 4.4 um.

[0051] The material of the first material layer 501 is a dielectric film material (H4), and the refractive index of the dielectric film material at the central wavelength is 2.2.

[0052] The material of the second material layer 502 is silicon dioxide (SiO2), and its refractive index at the center wavelength is 1.452. The material of the first film layer 201 is amorphous silicon (a-Si pill ar), and its refractive index at the center wavelength is 3.486. The material of the second film layer 202 is silicon nitride (SiN), and its refractive index at the center wavelength is 2.0031.

[0053] In other embodiments, the materials of the first film layer 201 and the second film layer 202 may also be phase change materials or any material with adjustable refractive index, as long as the refractive indexes of the two film layer materials are different.

[0054] Moreover, taking the transmissive metasurface as an example, the multi-layer film structure can utilize the interference principle of light. By controlling the film layer parameters (such as film layer thickness, film layer material, etc.), the reflected light can interfere with each other to achieve a destructive effect, thereby reducing reflection.

[0055] The specific implementation of the present invention also relates to a design method of a super surface. The structure and function of the super surface are as described above and will not be repeated here.

[0056] Specific, with reference Figure 4 As shown, a method for designing a metasurface comprises the following steps:

[0057] The metasurface efficiency corresponding to different film layer parameters is calculated using simulation software. In this embodiment, different film layer parameters (such as film layer thickness, material, and number of layers) are selected, and simulation software (such as Lumer cal FDTD) is used to calculate the metasurface efficiency of different film layer parameters, thereby obtaining a film layer parameter-metasurface efficiency library. When the metasurface is transmissive, the metasurface efficiency is the transmittance; when the metasurface is reflective, the metasurface efficiency is the reflectance.

[0058] An ideal film layer parameter is selected to form a multilayer film structure, and the hypersurface efficiency corresponding to the ideal film layer parameter is not less than a first threshold. In this embodiment, the film layer parameter-hypersurface efficiency library calculated by the simulation software is selected, that is, the film layer parameter whose hypersurface efficiency is not less than the first threshold is selected to obtain the ideal film layer parameter.

[0059] The number of ideal film layer parameters can be one, for example, there is only one film layer parameter when the super surface efficiency is maximum. The number of ideal film layer parameters can be multiple, for example, there are multiple film layer parameters when the super surface efficiency is maximum, or as long as the super surface efficiency is not lower than the first threshold, it can be used as an ideal film layer parameter. The first threshold can be any one between 60% and 98%, for example, 90%.

[0060] The nanostructure 20 is formed by using a multilayer film structure. Figure 3 The nanostructure 20 is composed of a multilayer film structure, that is, it includes a first film layer 201 and a second film layer 202 that are adjacently arranged. The first film layer 201 and the second film layer 202 are stacked in sequence to form the nanostructure 20, for example, they are arranged on the substrate 10 by sequential plating.

[0061] Taking the transmissive metasurface as an example, the multilayer film structure (i.e., the nanostructure 20) can utilize the interference principle of light and, by controlling the film layer parameters (such as film layer thickness, film layer material), can make the reflected light interfere with each other to achieve a destructive effect, thereby reducing reflection and improving the efficiency of the metasurface.

[0062] In addition, the nanostructure 20 adopts a single material solution (eg Figure 1 In the embodiment shown in the figure, adjusting the characteristic size of the nanocolumn structure 20 (for example, the radius of the cylindrical nanostructure) to reduce the resonance can only alleviate the phenomenon of a sudden drop in transmittance, while the nanostructure using a multi-layer film structure can utilize the interaction between different layers to reduce the resonance effect, avoid the appearance of an obvious resonance peak in the efficiency curve, make the efficiency curve smoother (i.e., the fluctuation of the efficiency curve is smaller), and avoid the phenomenon of a sudden drop in supersurface efficiency.

[0063] Arrange the nanostructures 20. In this embodiment, after determining the characteristic size of the nanostructures 20, the nanostructures 20 are arranged on the substrate 10 according to the phase distribution, thereby completing the design of the metasurface.

[0064] By constructing a multilayer film structure using the selected ideal film layer parameters and using the multilayer film structure to form the nanostructure 20, the efficiency of the metasurface can be improved, the resonance effect can be reduced, and a sudden drop in the efficiency of the metasurface can be avoided.

[0065] In some embodiments, the film layer parameters include theoretical film layer thickness. In this embodiment, the theoretical film layer thickness includes theoretical film layer thicknesses of the first film layer 201 and the second film layer 202 .

[0066] In some embodiments, the theoretical film thickness is determined based on the working band of the metasurface. In this embodiment, the theoretical film thickness d i It can be calculated by formula (1), by selecting different theoretical film thicknesses, and using simulation software to calculate, thereby selecting the ideal film parameters (i.e., the ideal film thickness).

[0067] For example, the theoretical film thickness is

[0068] In formula (1), λ is the operating band, n i is the refractive index of the (i)th film layer.

[0069] It should be noted that after calculation using the simulation software, the ideal film layer parameters (i.e., the ideal film layer thickness) obtained is not necessarily one-quarter of the optical thickness in formula (1), that is, the final film layer thickness may be greater than, equal to, or less than one-quarter of the optical thickness in formula (1), depending on the optimization results of the simulation software.

[0070] It can be seen that when calculating the theoretical film thickness, the working band (such as the near-infrared band) is taken into account, that is, the influence of multiple working wavelengths is included, so that the ideal film parameters obtained are determined based on the working band and can be adapted to the working band. Therefore, the nanostructure 20 composed of the multi-layer film structure can maintain a higher super surface efficiency while providing more phase coverage, so that high transmittance can be maintained when more phase response amplitude is required.

[0071] In some embodiments, the film layer parameters include the first film layer material and the second film layer material. In this embodiment, the multilayer film structure (i.e., the nanostructure 20) includes at least two film layer materials, i.e., the first film layer 201 and the second film layer 202. The two film layer materials are stacked in sequence to form a multilayer film structure, and the two film layer materials are arranged adjacent to each other. At this time, the film layer parameters include the material of the first film layer 201 (of) and the material of the second film layer 202 (of).

[0072] In some embodiments, the refractive index of the first film layer material is greater than the refractive index of the second film layer material. In this embodiment, the refractive index of the first film layer 201 (of) the material of the second film layer 202 (of) is different, and the interaction between the film layers of high and low refractive index materials can reduce the resonance effect. In addition, by using the principle of interference of light, the reflected light can interfere with each other to achieve a destructive effect, thereby reducing reflection and improving the efficiency of the metasurface (such as transmittance).

[0073] In addition, based on the working band of the metasurface, the corresponding film layer material is selected, that is, when selecting the film layer material, it is selected according to the working band, which is in line with the use scenario of the metasurface. For example, in the near-infrared band, the material of the first film layer 201 is amorphous silicon (a-Si pill ar), and its refractive index at the center wavelength is 3.486; the material of the second film layer 202 is silicon nitride (Si N), and its refractive index at the center wavelength is 2.0031.

[0074] Of course, the materials of the first film layer 201 and the second film layer 202 can also be phase change materials or any material with adjustable refractive index, as long as the refractive index of the material of the first film layer 201 is greater than the refractive index of the material of the second film layer 202.

[0075] In some embodiments, the film layer parameters include the number of film layers. In this embodiment, the number of film layers is the total number of film layers of the first film layer 201 and the second film layer 202 .

[0076] In some embodiments, the corresponding number of film layers is selected based on the working band of the metasurface. In this embodiment, the number of film layers of the multilayer film structure (i.e., the nanostructure 20) is not less than two layers. The more film layers there are, the higher the efficiency of the metasurface. Based on the working band of the metasurface, the corresponding number of film layers is selected, that is, when selecting the number of film layers, it is selected according to the working band, which is in line with the use scenario of the metasurface.

[0077] In addition, the number of film layers is determined based on reflectivity (or transmittance), so that the number of film layers is more in line with design requirements and the efficiency of the metasurface is improved.

[0078] In other embodiments, different characteristic sizes of the nanostructures 20 are scanned, the scanned results are screened, a characteristic size-phase library of the nanostructures 20 is constructed, and then the nanostructures 20 are arranged.

[0079] In this embodiment, before arranging the nanostructures 20, it is necessary to determine the phase required for each nanostructure 20, so that the phase variation range of the metasurface covers 0-2π or even more. After constructing the nanostructure 20 characteristic size-phase library, the required phase can be obtained by simply selecting different nanostructure 20 characteristic sizes (such as radius), which simplifies the design and facilitates manufacturing.

[0080] For example, for the convenience of design and manufacturing, the nanostructure 20 is cylindrical, and the characteristic dimension of the nanostructure 20 is the radius of the cylinder. For the convenience of description, the nanostructure 20 is described below as cylindrical.

[0081] Of course, the nanostructure 20 may also be in other shapes, such as a rectangle, etc. In this case, the characteristic size of the nanostructure 20 will also change accordingly, such as the length along the X-axis or the Y-axis.

[0082] In addition, for the convenience of design, when scanning different characteristic sizes of the nanostructure 20 , the period of the superstructure unit 30 , the height of the nanostructure 20 , and the shape of the nanostructure 20 can be controlled to remain unchanged.

[0083] Compared to the “nanostructure 20 using a single material (e.g. Figure 1 As for the scheme of the "embodiment shown in the figure", when a multi-layer film structure is used to form the nanostructure 20, it is easier to manufacture (for example, by coating) a higher nanostructure 20, thereby increasing the height of the nanostructure 20 and facilitating increasing the phase of the nanostructure 20. Moreover, the multi-layer film structure composed of high and low refractive index materials reduces the overall equivalent refractive index of the superstructure unit 30, so when the same phase coverage is satisfied, the multi-layer film structure requires a larger nanostructure 20 height to achieve.

[0084] For example, the nanostructure 20 is made of a single material (e.g. Figure 1 The characteristic size-phase library of the nanostructure 20 corresponding to the solution of the embodiment shown in FIG. Figure 5 As shown, the characteristic size-phase library of the nanostructure 20 corresponding to the solution of the nanostructure 20 adopting the multilayer film structure is as follows Figure 6 shown.

[0085] In some embodiments, screening the scanned results specifically includes:

[0086] The nanostructure 20 has at least two phase coverages in the 2π range within the characteristic size range.

[0087] In this embodiment, after the phase is screened for the scanned result, the characteristic size-phase library of the nanostructure 20 satisfies the phase coverage of at least two 2π ranges (ie, two ranges of 0-2π).

[0088] The phase curve after screening is as follows Figure 6 As shown by the solid line in , the characteristic size-phase library of the nanostructure 20 contains two phase coverages in the range of 2π, that is, it has two phase coverages of 0-2π, which is convenient for the achromatic (for example, the focal lengths of incident light of different wavelengths are equal) design of the metasurface.

[0089] Exemplarily, each wavelength in the working band corresponds to two 2π range phase coverages (i.e., two 0-2π ranges). When phase matching is performed on different wavelengths, that is, all wavelengths must satisfy at least one phase coverage (i.e., a 0-2π range), the nanostructure 20 characteristic size-phase library can provide more nanostructure 20 characteristic sizes for selection, thereby improving the selectivity of the nanostructure 20 characteristic size within the range allowed by processing, thereby facilitating the achromatic design of the metasurface.

[0090] In other embodiments, the nanostructure 20 may have at least one phase coverage of 2π within the characteristic size range.

[0091] In some embodiments, screening the scanned results specifically includes:

[0092] The super surface efficiency within the characteristic size range of the nanostructure 20 is not lower than the second threshold.

[0093] In this embodiment, after the efficiency value is screened for the scanned results, the efficiency curve after screening is as follows: Figure 6 As shown by the dotted line in Figure 5 The efficiency curve in Figure 5 The dotted line in the figure shows a sudden drop in transmittance). Figure 6 The efficiency curve in the experiment is significantly smoother, that is, the fluctuation range is smaller, which avoids the situation where the efficiency of the metasurface drops suddenly. As a result, the influence of the resonance effect is eliminated, and the stability of the metasurface efficiency is ensured when the metasurface is designed to be achromatic.

[0094] Exemplarily, the second threshold may be 80%-90%. Figure 6 The super surface efficiency within the characteristic size range of the nanostructure 20 is not less than 90%.

[0095] In some embodiments, different nanostructure 20 heights are scanned, and a database obtained by the scan is screened to determine the nanostructure height 20, and then a nanostructure 20 characteristic size-phase library is constructed.

[0096] In this embodiment, the database obtained by scanning is screened, the height of the nanostructure 20 is determined, and the height of the nanostructure 20 is kept unchanged, and then the characteristic size-phase library of the nanostructure 20 is constructed, thereby reducing the amount of calculation in the construction process.

[0097] Furthermore, considering the limitation of the actual processing technology, the height of the nanostructure 20 is controlled to remain unchanged, so as to ensure that the manufacturing of the super surface can be realized and also facilitate the manufacturing of the super surface.

[0098] Similarly, the shape of the nanostructure (eg cylindrical) is kept unchanged, and the characteristic size-phase library of the nanostructure 20 is constructed.

[0099] In some embodiments, different superstructure units 30 periods are scanned, and the database obtained by the scan is screened to determine the superstructure unit 30 period, and then a nanostructure characteristic size-phase library is constructed.

[0100] In this embodiment, the database obtained by scanning is screened, the period of the superstructure unit 30 is determined, and the period of the superstructure unit 30 is kept unchanged, and then the characteristic size-phase library of the nanostructure 20 is constructed, thereby reducing the amount of calculation in the construction process.

[0101] Exemplarily, each region of the metasurface adopts the same period of the superstructure unit 30. Of course, at least some regions of the metasurface may also adopt different periods of the superstructure unit 30, for example, regions with different incident angles correspond to different periods of the superstructure unit 30.

[0102] In some embodiments, different anti-reflection film parameters are scanned, and the database obtained by the scan is screened to determine the anti-reflection film parameters, and then a characteristic size-phase library of the nanostructure 20 is constructed.

[0103] In this embodiment, the database obtained by scanning is screened, the anti-reflection film parameters are determined, and the anti-reflection film parameters are kept unchanged, and then the characteristic size-phase library of the nanostructure 20 is constructed, thereby reducing the amount of calculation in the construction process.

[0104] The antireflection film parameters include the material, number of layers, layer thickness, etc. of the first material layer 501 and the second material layer 502 .

[0105] In some embodiments, screening the database obtained by scanning specifically includes:

[0106] The efficiency of the screened metasurfaces is not lower than the third threshold.

[0107] In this embodiment, when the database obtained by scanning is screened for hypersurface efficiency, the screening result may be one, for example, there is only one screening result when the hypersurface efficiency is the maximum. The screening results may also be multiple, for example, there are multiple screening results when the hypersurface efficiency is the maximum, or any result whose hypersurface efficiency is not less than the third threshold value may be used as the screening result.

[0108] Exemplarily, the third threshold may be no higher than the second threshold, for example 60%-90%, so that when the database is screened, it is ensured that the required nanostructure 20 height, superstructure unit 30 period, and antireflection film parameters can be screened out.

[0109] In addition, when the database obtained by scanning is screened for phase, it is necessary to satisfy at least one phase coverage range (ie, a phase coverage of a 2π range) to ensure that the screened results can meet the phase requirements.

[0110] In some embodiments, an optimization program is used to optimize the theoretical phase distribution corresponding to different wavelengths to obtain an ideal phase distribution corresponding to each wavelength, and then the nanostructures 20 are arranged.

[0111] In this embodiment, an optimization program (such as a particle swarm optimization program) is used to optimize the theoretical phase distribution corresponding to all wavelengths in the working band, so that corresponding phase responses for different wavelengths are achieved (for example, light of different wavelengths has the same focal length), that is, the ideal phase distribution can achieve the effect of achromatism.

[0112] like Figure 7 ,After optimization, the focal lengths corresponding to incident light of various wavelengths (e.g., 940nm, 970nm, and 100nm) are the same, and are all located at the dotted lines in the figure.

[0113] The theoretical phase distribution can be obtained through a phase formula (such as a focusing phase formula). After obtaining the ideal phase distribution, the characteristic size of the nanostructure 20 (such as the radius) is selected from the characteristic size-phase library of the nanostructure 20, and the nanostructure 20 is arranged according to the corresponding ideal phase distribution, thereby completing the design of the metasurface.

[0114] Exemplarily, the focusing phase formula may be:

[0115] Wherein, in formula (2), λ is the operating wavelength, R is the radial coordinate, and f is the focal length.

[0116] It should be understood that although this specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each implementation mode may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

[0117] The series of detailed descriptions listed above are only specific descriptions of feasible implementation methods of the present invention. They are not intended to limit the scope of protection of the present invention. Any equivalent implementation methods or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for designing a metasurface, characterized in that: include: Use simulation software to calculate the metasurface efficiency corresponding to different film layer parameters; Selecting ideal film layer parameters to form a multilayer film structure, wherein the metasurface efficiency corresponding to the ideal film layer parameters is not less than a first threshold; A multi-layer film structure is used to form a nanostructure and arrange the nanostructure.

2. The method for designing a supersurface according to claim 1, characterized in that: The film layer parameters include theoretical film layer thickness, and the theoretical film layer thickness is determined based on the working band of the metasurface.

3. The method for designing a supersurface according to claim 1, characterized in that: The film layer parameters include a first film layer material and a second film layer material, and the refractive index of the first film layer material is greater than the refractive index of the second film layer material.

4. The method for designing a supersurface according to claim 1, characterized in that: The film layer parameters include the number of film layers, and the corresponding number of film layers is selected based on the working band of the metasurface.

5. The method for designing a supersurface according to claim 1, characterized in that: The different characteristic dimensions of nanostructures are scanned, the scanning results are screened, a nanostructure characteristic dimension-phase library is constructed, and then the nanostructure is arranged.

6. The method for designing a supersurface according to claim 5, characterized in that: Filter the scanned results, including: There are at least two phase coverages in the 2π range within the characteristic size range of the nanostructure.

7. The method for designing a supersurface according to claim 5, characterized in that: Filter the scanned results, including: The supersurface efficiency within the characteristic size range of the nanostructure is no less than the second threshold.

8. The method for designing a supersurface according to claim 5, characterized in that: The different nanostructure heights are scanned, and the database obtained by the scanning is screened to determine the nanostructure height, and then a nanostructure characteristic size-phase library is constructed.

9. The method for designing a supersurface according to claim 5, characterized in that: The different superstructure unit periods are scanned, and the database obtained by the scanning is screened to determine the superstructure unit period, and then a nanostructure characteristic size-phase library is constructed.

10. The method for designing a super surface according to claim 5, characterized in that: Scanning is performed for different anti-reflection film parameters, and the database obtained by the scanning is screened to determine the anti-reflection film parameters, and then a nanostructure characteristic size-phase library is constructed.

11. The method for designing a supersurface according to any one of claims 8 to 10, characterized in that: The database obtained by scanning is screened, including: The efficiency of the screened metasurfaces is not lower than the third threshold.

12. The method for designing a supersurface according to claim 1, wherein: The optimization program is used to optimize the theoretical phase distribution corresponding to different wavelengths, obtain the ideal phase distribution corresponding to each wavelength, and then arrange the nanostructure.

13. A metasurface, characterized in that: The metasurface is designed by any of the design methods described in claims 1-12 above.

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