Design method of metasurface and metasurface

Abstract

The invention provides a metasurface design method and a metasurface, and the design method comprises the steps: selecting different incident angles, and carrying out the simulation test of the metasurface formed by the arrangement of superstructure units with different periodic values, thereby obtaining the efficiency of the metasurface formed by the arrangement of the superstructure units with different periodic values at the same incident angle; selecting the optimal metasurface efficiency of different incident angles to obtain period values corresponding to the different incident angles; superstructure units with corresponding periodic values are arranged in the metasurface areas corresponding to different incident angles; by selecting the optimal metasurface efficiency of different incident angles, period values corresponding to the different incident angles are determined, after the superstructure units of the corresponding period values are arranged in the metasurface area, a better modulation effect on large-angle incident light can be achieved, the metasurface modulation method is suitable for a large numerical aperture (NA) system and a wide-angle imaging scene, and the application range of the metasurface modulation method is widened. The efficiency of a large NA system or the wide-angle imaging quality can be improved.

Description

Technical Field

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

[0002] Existing metasurfaces usually use a constant metastructure unit period value, and the phase control mechanism of the metasurface is generally based on normal incidence or small-angle incidence, with less consideration of optical performance under large-angle oblique incidence. In fields such as wide-angle imaging, it is necessary to consider large-angle incident light. At this time, the metasurface will have problems with reduced imaging quality, such as phase mutation, which makes the metasurface unsuitable for scenarios with large-angle incidence. Summary of the invention

[0003] The object of the present invention is to provide a design method for a metasurface suitable for wide-angle imaging scenes.

[0004] 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:

[0005] Select different incident angles and perform simulation tests on the metasurfaces composed of the superstructure units with different period values, so as to obtain the efficiency of the metasurfaces composed of the superstructure units with different period values ​​at the same incident angle;

[0006] Select the optimal metasurface efficiency at different incident angles to obtain the period values ​​corresponding to different incident angles;

[0007] In the metasurface area corresponding to different incident angles, superstructure units with corresponding periodicity values ​​are arranged.

[0008] As a further improvement of one embodiment of the present invention, the optimal metasurface efficiency for multiple incident angles is selected, multiple period values ​​corresponding to the incident angles are obtained, and a corresponding relationship is established between the incident angles and the period values, thereby obtaining the period values ​​corresponding to other incident angles that have not been selected.

[0009] As a further improvement of one embodiment of the present invention, a first incident angle and a second incident angle with increasing angles are selected to obtain corresponding first and second period values, and a first linear function is established between the incident angles and the period values ​​to obtain period values ​​corresponding to other angles between the first incident angle and the second incident angle, and / or to obtain period values ​​corresponding to other angles between the first incident angle and the second incident angle.

[0010] As a further improvement of one embodiment of the present invention, a first incident angle, a third incident angle, a fourth incident angle and a second incident angle with increasing angles are selected to obtain corresponding first period values, third period values, fourth period values ​​and second period values, a second linear function is established between the incident angles and the period values ​​to obtain period values ​​corresponding to other incident angles between the first incident angle and the third incident angle, a third linear function is established between the incident angles and the period values ​​to obtain period values ​​corresponding to other incident angles between the third incident angle and the fourth incident angle, a fourth linear function is established between the incident angles and the period values ​​to obtain period values ​​corresponding to other incident angles between the fourth incident angle and the second incident angle.

[0011] As a further improvement of one embodiment of the present invention, the slope of the first linear function k1=(P1-P2) / (θ1-θ2), θ1 is the first incident angle, θ2 is the second incident angle, P1 is the first period value, and P2 is the second period value.

[0012] As a further improvement of an embodiment of the present invention, the differences between adjacent incident angles among the first incident angle, the third incident angle, the fourth incident angle and the second incident angle are equal.

[0013] As a further improvement of one embodiment of the present invention, a first incident angle, a fifth incident angle, a second incident angle and a sixth incident angle with increasing angles are selected to obtain corresponding first period values, fifth period values, second period values ​​and sixth period values, and a fifth linear function is established between the incident angles and the period values ​​to obtain period values ​​corresponding to other incident angles between the fifth incident angle and the second incident angle, and the period values ​​corresponding to other incident angles between the first incident angle and the fifth incident angle and / or the period values ​​corresponding to other incident angles between the second incident angle and the sixth incident angle remain unchanged.

[0014] As a further improvement of an embodiment of the present invention, the period value specifically refers to: a radial period and / or a circumferential period of the superstructure unit.

[0015] As a further improvement of an embodiment of the present invention, a nanostructure is provided at the center and / or vertex of each superstructure unit, and the nanostructure is configured as a polarization-dependent structure or a polarization-independent structure.

[0016] As a further improvement of one embodiment of the present invention, the metasurface also includes a substrate connecting the nanostructure, a filler connecting the nanostructure and the substrate, and an anti-reflection film arranged on the substrate and / or the filler, the anti-reflection film includes a first material layer and a second material layer, and the first material layer or the second material layer is connected to the metasurface.

[0017] As a further improvement of an embodiment of the present invention, selecting different incident angles specifically refers to: selecting different incident angles of the first polarized light and the second polarized light, wherein the first polarized light and the second polarized light are orthogonal to each other;

[0018] Obtaining periodic values ​​corresponding to different incident angles specifically refers to: obtaining periodic values ​​corresponding to different incident angles of the first polarized light and periodic values ​​corresponding to different incident angles of the second polarized light, and averaging or selecting the periodic values ​​obtained in different directions at the same incident angle to obtain the periodic value.

[0019] In order to achieve the purpose of the above invention, the present invention also provides a super surface, which is designed by the above design method.

[0020] Compared with the prior art, in the embodiments of the present invention, the period values ​​corresponding to different incident angles are determined by selecting the optimal metasurface efficiency for different incident angles. After the metastructure units with corresponding period values ​​are arranged in the metasurface area, it can have a better modulation effect on incident light at a large angle. It is suitable for large numerical aperture (NA) systems and wide-angle imaging scenarios, and can improve the efficiency of large NA systems or the quality of wide-angle imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic diagram of a light path in an application scenario of the metasurface of the present invention and a top view of the metasurface;

[0022] Figure 2 is a schematic diagram of a light path in another application scenario of the metasurface of the present invention and a top view of the metasurface;

[0023] Figure 3 is a schematic diagram of a light path in another application scenario of the metasurface of the present invention and a top view of the metasurface;

[0024] Figure 4 is a top view of a super surface in a preferred embodiment of the present invention;

[0025] Figure 5 is a top view of a super surface in another preferred embodiment of the present invention;

[0026] Figure 6 yes Figure 4 and Figure 5 The efficiency of the metasurface at different incident angles;

[0027] Figure 7 yes Figure 1 Schematic diagram of the optical path at the super surface;

[0028] Figure 8 yes Figure 7An embodiment of the cross-sectional view at A;

[0029] Fig. 9 yes Figure 7 Another embodiment of the cross-sectional view at A;

[0030] Fig.10 is a schematic flow chart of a method for designing a metasurface in a preferred embodiment of the present invention;

[0031] Fig.11 is a graph showing the relationship between the period value, nanostructure radius and transmittance at different incident angles obtained after performing Bloch boundary scanning on the superstructure unit, and a graph showing the relationship between the period value, nanostructure radius and phase of the superstructure unit;

[0032] Fig.12 yes Fig.10 The simulation test diagram of step S20;

[0033] Fig.13 yes Fig.10 A preferred implementation of the corresponding relationship between the incident angle and the period value in step S30;

[0034] Fig.14 is based on Fig.13 The relative relationship between the outer diameter size and the period value of the determined metasurface area;

[0035] Fig.15 yes Fig.10 Another preferred embodiment of the corresponding relationship between the incident angle and the period value in step S30;

[0036] Fig.16 is based on Fig.15 The relative relationship between the outer diameter size and the period value of the determined metasurface area;

[0037] Fig.17 yes Fig.10 Another preferred implementation of the corresponding relationship between the incident angle and the period value in step S30;

[0038] Fig.18 is based on Fig.17 The relative relationship between the outer diameter size and the period value of the determined metasurface area;

[0039] Fig.19 It is through Fig.10 Metasurface efficiency at different incident angles after the design method;

[0040] Fig. 20 This is the measured image of the white screen focal plane of the fixed period metasurface module;

[0041] Fig.21 This is a measured image of the focal plane of a white screen after the variable-period metasurface module of the present invention. DETAILED DESCRIPTION

[0042] 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.

[0043] 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.

[0044] Furthermore, it should be understood that although the terms first, second, etc. may be used herein to describe various elements or structures, these described objects should not be limited by the above terms. The above terms are only used to distinguish these described objects from each other. For example, a first area may be referred to as a second area, and similarly, a second area may also be referred to as a first area, which does not deviate from the scope of protection of the application.

[0045] 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.

[0046] refer to Figures 1 to 9 As shown, the metasurface 10 provided in the preferred embodiment of the present invention refers to an artificial layered material with a thickness less than the wavelength, which can be regarded as the two-dimensional counterpart of the metamaterial. The metasurface 10 can control the polarization, phase, amplitude, frequency, propagation mode and other characteristics of the electromagnetic wave through the surface sub-wavelength superstructure unit 12, and realize the characteristics of beam shaping, beam deflection, super lens, super holography, optical rotation, anti-reflection and anti-reflection.

[0047] Specifically, Figure 1 The metasurface 10 in is applied to a collimating lens, Figure 2 The metasurface 10 in the embodiment is applied to focusing lens, Figure 3 The metasurface in the paper is applied to deflection focusing lens.

[0048] Specifically, a metasurface 10 includes a plurality of array-arranged metastructure units 12. In this embodiment, the metastructure unit 12 is a structure unit obtained by dividing the metasurface 10.

[0049] Further, the metasurface 10 has a first area 101 and a second area 102 where the superstructure units 12 are arranged. In this embodiment, the metasurface 10 includes at least two areas. After the metasurface 10 is divided into different areas, the superstructure units 12 can be arranged in each area. The number of superstructure units 12 is obtained according to the arrangement function, and the structural parameters of the superstructure units 12 can be obtained according to the corresponding phase distribution formula. The superstructure units 12 in the same area can be of the same period or different periods.

[0050] For the convenience of description, the following embodiments are all based on Figure 1 For example, the metasurface 10 is applied to the scene of the collimating lens. According to the reversibility of the optical path, the metasurface 10 is also applicable to other scenes. When the same laser is used to irradiate the metasurface 10, the incident angles of the light irradiated at different locations on the metasurface 10 are different. In the same incident plane, the metasurface 10 is divided into regions according to the different incident angles. In addition, each region does not overlap with each other and can be adjacent or spaced.

[0051] Furthermore, the center of the first region 101 coincides with the center of the second region 102. In this embodiment, the superstructure units 12 on the supersurface 10 are preferably distributed in a ring shape, and the ring shape can be as follows: Figure 1 and Figure 2 The closed structure in Figure 3 Therefore, the center of each region is at the center of the ring, that is, Figure 1-3 Moreover, the center point C and the focus of the metasurface 10 are arranged along the Z-axis direction, for example Figure 1 The laser in the image is irradiated directly at the center point C, the laser and the metasurface 10 are arranged coaxially, and the laser is located in the focal plane of the metasurface 10. Figure 2 and Figure 3 The light passing through the center point C is incident on the CMOS / CCD.

[0052] Mate Reference Figure 4 and Figure 5 As shown, further, the radial period 121 of the superstructure unit 12 in the second area 102 is correspondingly smaller than the radial period 121 of the superstructure unit 12 in the first area 101, and / or the circumferential period 122 of the superstructure unit 12 in the second area 102 is correspondingly smaller than the circumferential period 122 of the superstructure unit 12 in the first area 101.

[0053] In this embodiment, the radial period 121 and the circumferential period 122 of the superstructure unit 12 in the second region 102 are both smaller than the radial period 121 and the circumferential period 122 of the superstructure unit 12 in the first region 101. Alternatively, the radial period 121 of the superstructure unit 12 in the second region 102 is smaller than the radial period 121 of the superstructure unit 12 in the first region 101, and the circumferential period 122 of the superstructure unit 12 in the second region 102 is equal to the circumferential period 122 of the superstructure unit 12 in the first region 101. Alternatively, the circumferential period 122 of the superstructure unit 12 in the second region 102 is smaller than the circumferential period 122 of the superstructure unit 12 in the first region 101, and the radial period 121 of the superstructure unit 12 in the second region 102 is equal to the radial period 121 of the superstructure unit 12 in the first region 101.

[0054] Specifically, different superstructure unit 12 periods are used in the first region 101 and the second region 102. The different superstructure unit 12 periods may be different radial periods 121 and / or circumferential periods 122, that is, the different superstructure unit 12 periods may be different radial periods 121, circumferential periods 122, or radial periods 121 and circumferential periods 122. The radial period 121 refers to the period of time along the radius direction of the imaginary circle (such as Figure 4 and Figure 5 Similarly, the circumferential period 122 refers to the period of the imaginary circle formed in the plane where the X-axis and the Y-axis are located with the center C as the center (as shown in the direction of L1 in FIG. 1 ). Figure 4 and Figure 5 The periodicity value along the direction shown by L2 in the figure, or the periodicity value along the central angle direction of the imaginary circle.

[0055] Mate Reference Figure 7 As shown, preferably, the first region 101 is closer to the center C than the second region 102. Figure 1 For example, the incident angles of the light irradiated by the laser on the first area 101 and the second area 102 are different, that is, the incident angle at the second area 1021 is greater than the incident angle at the first area 101. At this time, relative to the first area 101, the light irradiated on the second area 102 is incident at a large angle, and the period of the superstructure unit 12 in the second area 102 is set to be smaller than the superstructure unit 12 in the first area 101, so that the superstructure unit 12 in the second area 102 has a better modulation effect on the incident light at a large angle, which is suitable for large numerical aperture (NA) systems and wide-angle imaging scenes, and can improve the efficiency of large NA systems or wide-angle imaging quality.

[0056] Preferably, the first region 101 is located at the center point C, and the second region 102 is located at the edge of the metasurface 10 away from the center point C. At this time, taking the metasurface 10 applied to a collimating lens as an example, the incident light irradiated by the laser on the first region 101 is normal incidence or small angle incidence (for example, the incident angle is 0° to 5°), and the incident light irradiated by the laser on the second region 102 is large angle incidence (for example, the incident angle is 45° to 50°).

[0057] Specifically, a nanostructure 123 is provided at the center and / or vertex position of each superstructure unit 12. In the present embodiment, the superstructure unit 12 is obtained by dividing the supersurface 10 to obtain a structural unit centered on each nanostructure 123. The supersurface 10 also includes a substrate 11 to which the nanostructures 123 are connected, and a plurality of nanostructures 123 are arranged on the substrate 11, wherein the nanostructures 123 in each period constitute a superstructure unit 12. The superstructure unit 12 is a densely packed figure, such as a regular quadrilateral, a regular hexagon, a fan, etc., each period contains a nanostructure 123, and the vertex and / or center of the superstructure unit 12 can be provided with a nanostructure 123. In the case where the superstructure unit 12 is a regular hexagon, at least one nanostructure 123 is provided at each vertex and center position of the regular hexagon. Similarly, the same is true in the case of a fan or a square.

[0058] Further, the nanostructure 123 is configured as a polarization-dependent structure or a polarization-independent structure. In this embodiment, the nanostructure 123 can select a polarization-dependent structure or a polarization-independent structure according to different usage scenarios. Polarization-independent structures, such as cylindrical, square cylindrical, cross cylindrical, square cylindrical with round holes, etc. Polarization-dependent structures, such as elliptical cylindrical, rectangular cylindrical, hexagonal prism, etc.

[0059] The substrate 11 can be made of a light-transmitting or light-impermeable material. When the substrate 11 transmits light, a transmissive metasurface, i.e., a transmissive metalens, is formed. Figure 1-3 When the substrate 11 is opaque or reflects light, it is a reflective supersurface, i.e., a reflective superlens. The material of the substrate 11 includes but is not limited to quartz glass, crystalline and amorphous silicon, aluminum oxide, silicon nitride, and calcium fluoride. The material of the nanostructure 123 includes but is not limited to titanium oxide, tantalum oxide, hafnium oxide, silicon nitride, photoresist, quartz glass, aluminum oxide, crystalline and amorphous silicon, gallium nitride, crystalline germanium, selenium sulfide, selenium sulfide, and chalcogenide glass.

[0060] Preferably, after the multiple nanostructures 123 are arranged on the substrate 11, they are circular when viewed from a top view, that is, they are circular in the plane where the X-axis and the Y-axis are located. At this time, the first area 101 and the second area 102 are both closed circles, and the center of the first area 101 and the center of the second area 102 both coincide with the center C. The first area 101 is located at the center of the circle, and the second area 102 is located at the outer circle.

[0061] Of course, if Figure 3 , it is also possible that the first area 101 is not located at the center of the circle, and the second area 102 is not located at the outer circle.

[0062] Moreover, in this manner, the multiple nanostructures 123 on the substrate 11 are centrally symmetric in the plane where the X-axis and the Y-axis are located, so that the metasurface 10 can modulate the light beam in multiple directions, thereby being applicable to more scenarios.

[0063] like Figure 4 The present invention provides a top view and a partially enlarged schematic diagram of a preferred embodiment of a metasurface 10. Compared with a metasurface with a constant period, this embodiment only changes the radial period 121.

[0064] Specifically, the radial period 121 of each superstructure unit 12 decreases from the first region 101 to the second region 102, and the circumferential period 122 of each superstructure unit 12 is equal. In this embodiment, the direction from the first region 101 to the second region 102 refers to: from the center of the circle (i.e., center C) to the outer circle. In the direction from the center of the circle (i.e., center C) to the outer circle, the radial period 121 of all superstructure units 12 on the supersurface 10 is decreasing, and the circumferential period 122 of all superstructure units 12 remains unchanged. It can be seen that the entire supersurface 10 adopts a variable period solution. Therefore, compared to the supersurface with a constant period, the nanostructure 123 of the supersurface 10 in this embodiment is denser along the radial direction of the first region 101 (i.e., the L1 direction in the figure), which satisfies the better modulation effect of the incident light at a large angle, while the structure is relatively simple and the manufacturing difficulty is low.

[0065] In addition, in this embodiment, at the edge of the metasurface 10 , the centers of four adjacent nanostructures 123 form a rectangle, and as the distance from the center C increases, the aspect ratio of the rectangle increases.

[0066] In an embodiment not shown, it is also possible that, in the direction from the center of the circle (i.e., center C) to the outer circle, the circumferential period 122 of all superstructure units 12 on the metasurface 10 shows a decreasing trend, and the radial period 121 of all superstructure units 12 remains unchanged, which can also meet the requirement of having a better modulation effect on incident light at a large angle.

[0067] like Figure 5The present invention provides a top view and a partially enlarged schematic diagram of a metasurface 10 in another preferred embodiment. Compared with the above embodiment, the radial period 121 and the circumferential period 122 are changed in this embodiment at the same time.

[0068] Specifically, the radial period 121 and the circumferential period 122 of each superstructure unit 12 decrease from the first region 101 to the second region 102. In this embodiment, the direction from the first region 101 to the second region 102 refers to: from the center of the circle (i.e., center C) to the outer circle. In the direction from the center of the circle (i.e., center C) to the outer circle, the radial period 121 and the circumferential period 122 of all superstructure units 12 on the supersurface 10 are in a decreasing trend. It can be seen that the entire supersurface 10 adopts a variable period scheme. Therefore, compared to the supersurface in the above-mentioned embodiment, the nanostructure 123 of the supersurface 10 in this embodiment is denser in the radial and circumferential directions of the first region 101, and has a better modulation effect on incident light at a large angle.

[0069] In addition, in this embodiment, at the edge of the metasurface 10 , the centers of four adjacent nanostructures 123 form a square.

[0070] In the above two embodiments, variable period is adopted in all regions of the entire metasurface 10. After combining the improvements of the above two embodiments, the efficiency of the metasurface 10 at different incident angles is finally obtained as follows: Figure 6 In the figure, the horizontal axis corresponds to the incident angle, the vertical axis corresponds to the metasurface efficiency, and the dotted line (Mode A in the figure) is Figure 5 The hypersurface of the variable period scheme of the implementation method, the broken line drawn by the dotted line (Mode B in the figure) is Figure 4 The solid line is the metasurface of the variable period scheme of the embodiment, and the broken line drawn by the solid line is the metasurface of the fixed period scheme (the period is 425nm). It can be seen from the figure that in the two embodiments of the metasurface with variable period provided by the present invention, the efficiency at any incident angle is greater than that of the metasurface with fixed period, and Figure 5 The corresponding implementation method has higher efficiency.

[0071] Further, continue to cooperate with reference Figure 7 As shown, the metasurface 10 also has a third region 103 where the metastructure units 12 are arranged. The centers of the first region 101, the third region 103 and the second region 102 coincide with each other, and the outer diameters increase in sequence. In this embodiment, the third region 103 is between the first region 101 and the second region 102, and the centers of the three regions coincide with the center C, but do not coincide with each other. Figure 1Preferably, the third region 103 is arranged adjacent to the first region 101 and the second region 102. Therefore, the first region 101, the third region 103 and the second region 102 are arranged in sequence on the metasurface 10 from the center (ie, center C) to the outer circle.

[0072] Of course, if Figure 2 , the third area 103 may also be arranged to be spaced apart from the first area 101 and the second area 102.

[0073] Or, if Figure 3 Alternatively, the first region 101, the third region 103 and the second region 102 may all be in an open ring shape.

[0074] Specifically, the radial period 121 and / or the circumferential period 122 of the superstructure units 12 in the third region 103 decreases from the first region 101 to the second region 102 .

[0075] In this embodiment, when the third region 103 is arranged adjacent to the first region 101 and the second region 102, the period (including the radial period 121 and / or the circumferential period 122) of the superstructure unit 12 in the third region 103 decreases from the center of the circle (i.e., the center C) to the outer circle direction. Therefore, all the superstructure units 12 in the area between the first region 101 and the second region 102 adopt a variable period scheme, while the area outside the first region 101 and the second region 102 can adopt a constant period or a variable period scheme, which has a better modulation effect on the incident light at different angles between the first region 101 and the second region 102.

[0076] When the third region 103 is spaced from the first region 101 and the second region 102, for example, one or more regions are spaced between the first region 101 and the second region 102. In the direction from the center of the circle (i.e., the center C) to the outer circle, the radial period 121 and / or the circumferential period 122 of the superstructure unit 12 in the third region 103 is decreasing. That is, in the direction from the center of the circle (i.e., the center C) to the outer circle, the radial period 121 and / or the circumferential period 122 of the superstructure unit 12 in at least one region among the multiple regions between the first region 101 and the second region 102 is decreasing, while the period of the superstructure unit 12 in other regions of the multiple regions is kept constant.

[0077] The above two methods enable at least a part of the metasurface 10 to adopt a variable period solution, while the remaining areas can adopt a constant period solution.

[0078] Of course, in an embodiment not shown, the period (including the radial period 121 and / or the circumferential period 122 ) of the superstructure unit 12 in the third region 103 may also be a constant period.

[0079] Further, the radial period 121 and the circumferential period 122 of the superstructure unit 12 in the first region 101 and / or the second region 102 remain unchanged. In this embodiment, the superstructure unit 12 in the first region 101 adopts a constant period, and the superstructure unit 12 in the second region 102 adopts a variable period. Alternatively, the superstructure unit 12 in the first region 101 adopts a variable period, and the superstructure unit 12 in the second region 102 adopts a constant period. Alternatively, the superstructure units in the first region 101 and the second region 102 both adopt a constant period.

[0080] Taking the application of the metasurface 10 to a collimating lens as an example, since the incident light irradiated by the laser on the first region 101 is normal incidence or small angle incidence, the superstructure unit 12 in this region adopts a variable period, which has little effect on the modulation effect. Similarly, the incident light irradiated by the laser on the second region 102 is large angle incidence, and the superstructure unit 12 in this region adopts a variable period, which has little effect on the modulation effect, and the edge of the second region 102 cannot accommodate more nanostructures 123. Therefore, using a constant period for the period (including the radial period 121 and the circumferential period 122) in the first region 101 and / or the second region 102 can reduce the manufacturing difficulty of the metasurface 10 and has little effect on the efficiency of the metasurface.

[0081] Further, the radial period 121 and / or the circumferential period 122 of the superstructure unit 12 in the third region 103 decreases in equal proportion from the first region 101 to the second region 102. In this embodiment, the period (including the radial period 121 and / or the circumferential period 122) of the superstructure unit 12 in the third region 103 is correspondingly smaller than the superstructure unit 12 in the first region 101, and correspondingly larger than the superstructure unit 12 in the second region 102. The period of the superstructure unit 12 in the third region 103 changes in equal proportion, so there is no need to obtain the period value corresponding to all incident angles in the third region 103, which facilitates the manufacture of the metasurface 10.

[0082] Specifically, by obtaining the incident angle and period value corresponding to the first region 101 and the second region 102 or their average value (for example, when there are multiple incident angles in the first region 101 or the second region 102), a first linear function is established between the incident angle and the period value, and the period and corresponding incident angle of the superstructure unit 12 in the third region 103 can be obtained by substituting into the first linear function, thereby simplifying the design and manufacturing process of the metasurface 10.

[0083] Of course, in some embodiments, other functions, such as quadratic functions, may also be established according to the incident angles and period values ​​corresponding to the first region 101 and the second region 102 .

[0084] Furthermore, the third region 103 comprises a first region 1031, a second region 1032 and a third region 1033, the outer diameters of which increase in sequence. Figure 1 , the third area 103 is further divided into a first area 1031, a second area 1032 and a third area 1033 whose centers coincide with each other. Taking the application of the metasurface 10 to a collimating lens as an example, the incident angles of the incident light on the three areas are different. For example, the incident angle on the first area 1031 is between 5° and 15°, the incident angle on the second area 1032 is between 15° and 30°, and the incident angle on the third area 1033 is between 30° and 45°.

[0085] Specifically, the radial period 121 and / or the circumferential period 122 of the superstructure unit 12 in the first zone 1031 decreases in equal proportion from the first zone 101 to the second zone 1032. In this embodiment, by obtaining the incident angle and the period value corresponding to the first zone 101 and the second zone 1032 or their average values ​​(for example, when there are multiple incident angles in the first zone 101 or the second zone 1032), a second linear function is established between the incident angle and the period value, and the period of the superstructure unit 12 in the first zone 1031 and the corresponding incident angle can be obtained by substituting into the second linear function, so that there is no need to obtain the period values ​​corresponding to all incident angles in the first zone 1031, which facilitates the manufacture of the metasurface 10.

[0086] Specifically, the radial period 121 and / or the circumferential period 122 of the superstructure unit 12 in the second zone 1032 decreases in equal proportion from the first zone 1031 to the third zone 1033. In this embodiment, by obtaining the incident angle and period value corresponding to the first zone 1031 and the third zone 1033 or their average values ​​(for example, when there are multiple incident angles in the first zone 1031 or the third zone 1033), a third linear function is established between the incident angle and the period value, and the period of the superstructure unit 12 in the second zone 1032 and the corresponding incident angle can be obtained by substituting into the third linear function, so that there is no need to obtain the period values ​​corresponding to all incident angles in the second zone 1032, which facilitates the manufacture of the metasurface 10.

[0087] Specifically, the radial period 121 and / or the circumferential period 122 of the superstructure unit 12 in the third zone 1033 decreases in proportion from the second zone 1032 to the second region 102. In this embodiment, by obtaining the incident angle and period value corresponding to the second zone 1032 and the second region 102 or their average values ​​(for example, when there are multiple incident angles in the second zone 1032 or the second region 102), a fourth linear function is established between the incident angle and the period value, and the period of the superstructure unit 12 in the third zone 1033 and the corresponding incident angle can be obtained by substituting the fourth linear function, so that there is no need to obtain the period values ​​corresponding to all incident angles in the third zone 1033, which facilitates the manufacture of the metasurface 10.

[0088] Therefore, the third region 103 is further divided into regions, and the linear functions corresponding to the respective regions are calculated, so as to more accurately arrange the superstructure units 12, so that the modulation effect produced by the period of the superstructure units 12 in the third region 103 is better, and the overall efficiency of the metasurface 10 is higher.

[0089] Of course, in other embodiments, the third area 103 may also be divided into other numbers of zones, such as two zones, four zones, five zones, etc.

[0090] Mate Reference Figure 8 and Fig. 9 As shown, further, the metasurface 10 also includes a substrate 11 connected to the nanostructure 123, a filler 14 connecting the nanostructure 123 and the substrate 11, and an anti-reflection film 13 provided on the substrate 11 and / or the filler 14. In this embodiment, it is preferred to provide an anti-reflection film 13 on both the substrate 11 and the filler 14. At this time, one layer of anti-reflection film 13 covers the surface of the filler 14 on the side away from the substrate 11, and another layer of anti-reflection film 13 covers the surface of the substrate 11 on the side away from the nanostructure 123. That is, as Figure 7 In the embodiment, both the light incident side and the light emitting side of the metasurface 10 are covered with an anti-reflection film 13. By providing the anti-reflection film 13, the reflectivity can be reduced, thereby increasing the transmittance of the metasurface and further improving the efficiency of the metasurface.

[0091] Specifically, the antireflection film 13 includes a first material layer 131 and a second material layer 132. In this embodiment, the first material layer 131 is preferably silicon nitride, and the second material layer 132 is preferably silicon oxide, so as to meet the high transmittance condition when the light beam is incident at a large angle.

[0092] Specifically, the first material layer 131 or the second material layer 132 is connected to the super surface 10. In this embodiment, different material layers are selected to connect the substrate 11 and the filler 14 according to the different materials. Figure 8 and Fig. 9When both the substrate 11 and the filler 14 are made of silicon oxide, the first material layer 131 (i.e., silicon nitride) is connected to the substrate 11 and the filler 14, and the second material layer 132 is connected to the outside of the first material layer 131. Similarly, when the substrate 11 and the filler 14 are made of other materials, the second material layer 132 can also be connected to the substrate 11 and the filler 14.

[0093] Preferably, Figure 8 The antireflection films 13 on both sides of the metasurface 10 each use a first material layer 131 and a second material layer 132. When the wavelength of the incident light is 940 nm, the thickness of the first material layer 131 is preferably 50 nm ± 5 nm, and the thickness of the second material layer 132 is preferably 215 nm ± 5 nm, so as to obtain the optimal metasurface efficiency.

[0094] Preferably, Fig. 9 , the anti-reflection films 13 on both sides of the metasurface 10 are made of two first material layers 131 and two second material layers 132. When the wavelength of the incident light is 940nm, on the light-emitting side of the metasurface 10, in the direction from the light-entering side to the light-emitting side, the thickness of the first material layer 131 is preferably 40nm±5nm, the thickness of the second material layer 132 is preferably 55nm±5nm, the thickness of the first material layer 131 is preferably 380nm±5nm, and the thickness of the second material layer 132 is preferably 165nm±5nm, so as to obtain the optimal metasurface efficiency.

[0095] According to another aspect of the present invention, a near-infrared imaging system is further provided. The near-infrared imaging system is provided with a metasurface 10 according to the present invention. The metasurface 10 is preferably a focusing lens.

[0096] Specifically, the near-infrared imaging system also includes a lens barrel, an optical detector module, and an optical narrow-band filter, etc. When in use, the light reflected or scattered by the imaging object is focused by the metasurface 10, and after the light of other bands is filtered out by the optical narrow-band filter, it is collected by the optical detector module and imaged to the photosensitive surface of the optical detector module, and the photosensitive surface absorbs the near-infrared light of the imaging object and converts it into an image electrical signal for output.

[0097] The specific implementation of the present invention also relates to a design method of a metasurface 10. The structure and function of the metasurface 10 are as described above and will not be repeated here.

[0098] Reference Fig.10 As shown, a flow chart of one embodiment of a design method of a metasurface 10 is shown. This flow chart is provided for exemplary purposes only and should not be interpreted as limiting the scope of any aspect of the present invention.

[0099] Specifically, the design method of the metasurface 10 includes the following steps:

[0100] In step S10 , different phase formulas are selected to determine the phase required by the metasurface 10 .

[0101] In this embodiment, in step S10, the metasurface 10 can be applied to different scenarios, such as Figure 1 Applied to collimating lenses, such as Figure 2 Applied to focusing lenses, such as Figure 3 It is applied to deflection focusing lenses and can also be applied to beam shaping, etc. When the metasurface 10 is applied to different scenarios, different phase formulas can be selected to calculate the phase required by the metasurface 10.

[0102] Similarly, for the convenience of description, the following implementation modes are all based on Figure 1 For example, the metasurface 10 is applied to the scene of the collimating lens. According to the reversibility of the optical path, the metasurface 10 is also applicable to other scenes. According to the wavelength of the incident light irradiated by the laser on the metasurface 10, the transmission radius of the metasurface 10, the focal length of the metasurface 10 and other parameters, the phase distribution of different areas of the metasurface 10 can be calculated. Moreover, in the following steps, these parameters are controlled to be unchanged to facilitate the calculation of other required parameter values.

[0103] Mate Reference Fig.11 and Fig.12 As shown, in step S20, different incident angles are selected, and a simulation test is performed on the metasurface 10 composed of the superstructure units 12 with different period values, so as to obtain the efficiency of the metasurface 10 composed of the superstructure units 12 with different period values ​​at the same incident angle.

[0104] In this embodiment, in step S20, the value range of the structural parameters of the superstructure unit 12 is obtained according to the wavelength of the incident light. For example, taking the wavelength of the incident light of 940nm as an example, the period value of the superstructure unit 12 is determined to be between 280 and 500nm, the height of the nanostructure 123 is determined to be between 400 and 800nm, etc. When performing the simulation test, in addition to changing the period value of the superstructure unit 12, other structural parameters of the superstructure unit 12 are controlled to remain unchanged, for example, the height of the nanostructure 123 is controlled to be 658nm.

[0105] Specific, with reference Fig.11As shown, in step S20, before the super surface 10 is simulated and tested, it is also necessary to simulate and test the super structure units 12 with different period values ​​to eliminate some nano structures 123 with low transmittance and meet the phase distribution of 0-2π. In this embodiment, after determining the structural parameters of the super structure unit 12, the super structure unit 12 is subjected to Bloch boundary scanning, and suitable parameters (super structure unit period value, structural parameters of nano structure 123) are selected to construct n (n≥2) order data sets, such as 2, 3, 4..., +∞ order (under the conditions, the more orders, the higher the efficiency of the super surface). Thus, a data set that satisfies the phase coverage of 0-2π and relatively high transmittance is obtained, and finally the data is imported into the simulation software for arrangement simulation, so as to obtain the super surface 10 composed of the super structure units 12 with different period values.

[0106] After performing Bloch boundary scanning on the superstructure unit 12, the relationship between the superstructure unit period value, the nanostructure radius and the transmittance at different incident angles is obtained (e.g. Fig.11 11a, 11c, 11e, 11g), and the relationship between the superstructure unit period value, the nanostructure radius and the phase (as shown in Fig.11 11b, 11d, 11f, 11h). Taking 0° incidence as an example, Fig.11 As shown in (11a), the horizontal axis corresponds to the radius of the nanostructure, and the vertical axis corresponds to the period value of the superstructure unit. The dark and light colors in the figure represent low and high efficiency. Assuming that the vertical axis is selected as a period value of 300nm, in order to adapt to the processing requirements and eliminate nanostructures that do not meet the efficiency requirements, the corresponding horizontal axis needs to eliminate nanostructures with radii of 110nm and between 150nm and 200nm. Then, from the data after the above processing, appropriate nanostructure parameters are selected to construct an n (n≥2) order data set so that it satisfies the phase arrangement of 0-2π. The same is true for other period values, thereby obtaining an n (n≥2) order data set corresponding to different period values. The obtained data set is then imported into the simulation software for arrangement and simulation, thereby obtaining a supersurface 10 composed of superstructure units 12 with different period values. Obviously, at 0° incidence, the period value of the superstructure unit is between 410-430nm, and the range of radius of the nanostructure with high efficiency and wide phase coverage that can be selected is larger, which is consistent with Fig.12 The relatively high supersurface efficiency obtained at the period of 410-430nm corresponds to each other, and the period for obtaining the optimal efficiency is 425nm.

[0107] like Fig.12, the horizontal axis represents the period value, the vertical axis represents the metasurface efficiency, that is, the lens efficiency, and the broken lines drawn with different lines represent different incident angles. Moreover, different period values ​​should be selected within the range of the period value, for example, between 310nm and 425nm. After selecting multiple incident angles for simulation testing, the metasurface efficiencies corresponding to multiple incident angles at different period values ​​were obtained. Fig.12 The multiple incident angles are selected for exemplary purposes only and are not exhaustive. Simulation tests may be performed on other incident angles or more incident angles.

[0108] In step S30, the optimal metasurface efficiency at different incident angles is selected to obtain the period values ​​corresponding to the different incident angles.

[0109] In this embodiment, in step S30, the optimal metasurface efficiency corresponding to each incident angle is selected, and then the period value corresponding to the incident angle is checked according to the optimal metasurface efficiency. The period value selected at this time can be used as the optimal period value corresponding to the incident angle. Taking the incident angle of 15° as an example, find the maximum value of the broken line composed of dotted lines on the ordinate (approximately at 0.87), and then check the horizontal coordinate value corresponding to the maximum ordinate value (approximately at 390), so that it can be determined that the optimal period value corresponding to the incident angle of 15° is 390nm. Other incident angles can also be obtained in this way.

[0110] In step S40, superstructure units with corresponding periodic values ​​are arranged in the supersurface regions corresponding to different incident angles, and nanostructures with corresponding structural parameters determined by specific scanning conditions are placed in the superstructure units.

[0111] In this embodiment, in step S40, the metasurface region specifically refers to: different incident regions, such as the first region, the second region, the third region or other unspecified regions mentioned above. That is, when the same laser is used to irradiate the metasurface 10, the incident angles of the light irradiated on different metasurface regions are different. Moreover, the metasurface region is preferably annular, and the annular shape is a circle with the center point C as the center. Therefore, the distances between different metasurface regions and the center point C are different, that is, different incident angles correspond to metasurface regions with different outer diameters.

[0112] Specifically, after selecting different incident angles, the tangent function can be used to obtain the hypersurface area corresponding to different incident angles according to the focal length and incident angle of the hypersurface 10, that is, the distance between the hypersurface area and the center point C is determined, thereby determining the hypersurface area with an outer diameter size corresponding to different incident angles.

[0113] Specifically, after obtaining the optimal period values ​​corresponding to different incident angles in step S30, the optimal period values ​​are arranged in the metasurface region corresponding to the incident angle, so that the superstructure unit 12 in the metasurface region can better modulate the incident light and obtain the optimal metasurface efficiency. Then, each different metasurface region of the metasurface 10 has the optimal metasurface efficiency.

[0114] Furthermore, in step S30, the optimal metasurface efficiency of multiple incident angles is selected, multiple period values ​​corresponding to the incident angles are obtained, and a corresponding relationship is established between the incident angles and the period values, thereby obtaining the period values ​​corresponding to other incident angles that have not been selected.

[0115] In this embodiment, in step S20, when selecting the incident angle, try to select more incident angles, and through simulation tests, obtain the optimal metasurface efficiency corresponding to more incident angles. Therefore, in step S30, obtain the optimal period values ​​corresponding to more incident angles, and use multiple corresponding incident angles and optimal period values ​​to establish a corresponding relationship, or a functional relationship, between the two. In this way, other incident angles that have not been simulated can be obtained by directly substituting them into the corresponding relationship, without exhausting all incident angles for simulation tests, thereby simplifying the design process. Among them, the optimal metasurface efficiency of selecting multiple incident angles can be two or more incident angles.

[0116] Mate Reference Fig.13 and Fig.14 As shown, the present invention provides a preferred implementation of the corresponding relationship between the incident angle and the optimal period value. This embodiment obtains the optimal period value corresponding to other incident angles by establishing a first linear function, thereby simplifying the design process of the metasurface.

[0117] Specifically, in step S30, a first incident angle and a second incident angle whose angles increase sequentially are selected to obtain corresponding first period value and second period value.

[0118] In this embodiment, in step S30, the first incident angle is configured as normal incidence or small angle incidence (for example, the incident angle is 0° to 5°), preferably 0°. The second incident angle is configured as large angle incidence (for example, the incident angle is 45° to 50°), preferably 45°. Fig.12 , it is possible to obtain the optimal period value corresponding to the first incident angle, that is, the first period value (approximately 425nm), and to obtain the optimal period value corresponding to the second incident angle, that is, the second period value (approximately 310nm).

[0119] Further, such as Fig.13, in step S30, a first linear function is established between the incident angle and the period value. In this embodiment, in step S30, based on the first period value being greater than the second period value, a change relationship between the incident angle and the optimal period value can be obtained, that is, as the incident angle increases, the optimal period value decreases accordingly. By establishing a linear function, that is, a linear function, between the incident angle and the obtained optimal period value, the above-mentioned change relationship can be satisfied, thereby obtaining the optimal period value corresponding to other incident angles, and then satisfying the optimal metasurface efficiency corresponding to different incident angles.

[0120] Of course, in other embodiments not shown, other functional relationships may be established between the incident angle and the optimal period value, such as a quadratic function or other nonlinear functions.

[0121] Specifically, in step S30, the slope k1 of the first linear function = (P1-P2) / (θ1-θ2), θ1 is the first incident angle, θ2 is the second incident angle, P1 is the first period value, and P2 is the second period value. In this embodiment, in step S30, the slope k1 of the first linear function can be obtained by calculating the ratio of the difference between the two optimal period values ​​and the difference between the two incident angles. The first linear function can be obtained by only obtaining the optimal period value corresponding to the two incident angles, thereby simplifying the difficulty of obtaining the corresponding relationship.

[0122] Mate Reference Fig.13 As shown, in step S30, the period values ​​corresponding to other angles between the first incident angle and the second incident angle are obtained by a first linear function, and / or the period values ​​corresponding to other angles between the first incident angle and the second incident angle are obtained.

[0123] In this embodiment, in step S30, when the first incident angle is 0° and the second incident angle is 45°, the incident angles between 0° and 45° can be calculated by the first linear function to obtain the corresponding optimal period value. After the conversion in step S40, the following is obtained: Fig.14 The linear function diagram between the optimal period value and the outer diameter size of the super surface area is shown in FIG. 1 . At this time, only the outer diameter size of the corresponding super surface area needs to be substituted to obtain the period value within the super surface area.

[0124] In step S30, the first incident angle can also be other angles between 0° and 5°, such as 3°. Similarly, the second incident angle can also be other angles between 45° and 50°, such as 48°. At this time, the first linear function can be used to obtain the optimal period value corresponding to the incident angle between 3° and 48°, and the first linear function can also be used to obtain the optimal period value corresponding to the incident angles between 0° and 3° and 48° and 60°.

[0125] Mate Reference Fig.15 and Fig.16 As shown, the present invention provides another preferred implementation of the corresponding relationship between the incident angle and the optimal period value. This embodiment establishes multiple linear functions to respectively obtain the optimal period values ​​corresponding to other incident angles in the corresponding angle interval, thereby improving the overall metasurface efficiency of the metasurface.

[0126] Specifically, in step S30, the first incident angle, the third incident angle, the fourth incident angle and the second incident angle, which increase in sequence, are selected to obtain the corresponding first period value, the third period value, the fourth period value and the second period value.

[0127] In this embodiment, in step S30, the third incident angle is set between 10° and 20°, for example, 15°, and the fourth incident angle is set between 25° and 35°, for example, 30°. Fig.12 , it is possible to obtain the optimal period value corresponding to the third incident angle, that is, the third period value (approximately 390nm), and to obtain the optimal period value corresponding to the fourth incident angle, that is, the fourth period value (approximately 350nm).

[0128] Furthermore, in step S30, a second linear function is established between the incident angle and the period value, so as to obtain the period values ​​corresponding to other incident angles between the first incident angle and the third incident angle.

[0129] In this embodiment, in step S30, Fig.15 When the first incident angle is 0° and the third incident angle is 15°, the incident angles between 0° and 15° can be calculated by the second linear function to obtain the corresponding optimal period value. After the conversion in step S40, the following is obtained: Fig.16 The linear function diagram between the optimal period value and the outer diameter of the hypersurface area is shown in FIG. At this time, only the corresponding outer diameter of the hypersurface area needs to be substituted to obtain the period value in the hypersurface area. The calculation method of the slope of the second linear function refers to the first linear function.

[0130] Furthermore, in step S30, a third linear function is established between the incident angle and the period value, so as to obtain the period values ​​corresponding to other incident angles between the third incident angle and the fourth incident angle.

[0131] In this embodiment, in step S30, Fig.15 When the third incident angle is 15° and the fourth incident angle is 30°, the incident angles between 15° and 30° can be calculated by the third linear function to obtain the corresponding optimal period value. After the conversion in step S40, the following is obtained: Fig.16The linear function diagram between the optimal period value and the outer diameter of the hypersurface area is shown in FIG. At this time, only the corresponding outer diameter of the hypersurface area needs to be substituted to obtain the period value in the hypersurface area. The calculation method of the slope of the third linear function refers to the first linear function.

[0132] Furthermore, in step S30, a fourth linear function is established between the incident angle and the period value, so as to obtain the period values ​​corresponding to other incident angles between the fourth incident angle and the second incident angle.

[0133] In this embodiment, in step S30, Fig.15 When the fourth incident angle is 30° and the second incident angle is 45°, the incident angles between 30° and 45° can be calculated by the fourth linear function to obtain the corresponding optimal period value. After the conversion in step S40, the following is obtained: Fig.16 The linear function diagram between the optimal period value and the outer diameter size of the hypersurface area is shown in FIG. At this time, only the corresponding outer diameter size of the hypersurface area needs to be substituted to obtain the period value in the hypersurface area. The calculation method of the slope of the fourth linear function refers to the first linear function.

[0134] In step S30, by further dividing the incident angle between the first incident angle and the second incident angle, multiple linear functions with different slopes are obtained, so that the correspondence between the incident angle and the optimal period value in each divided angle area (for example, 0°~15°, 15°~30°, 30°~45° area) is more accurate and closer to the optimal metasurface efficiency corresponding to each incident angle, thereby improving the overall metasurface efficiency of the metasurface 10.

[0135] Specifically, in step S30, the differences between adjacent incident angles of the first incident angle, the third incident angle, the fourth incident angle and the second incident angle are equal. In this embodiment, the first incident angle is preferably 0°, the third incident angle is preferably 15°, the fourth incident angle is preferably 30°, and the second incident angle is preferably 45°, and an arithmetic progression is formed between the four angles. The incident angles between the first incident angle and the second incident angle are equally divided, so that the error of the linear function obtained in each divided angle region (0°~15°, 15°~30°, 30°~45°) is minimized, which is closer to the optimal metasurface efficiency corresponding to each incident angle.

[0136] Of course, in some embodiments not shown, in step S30, the incident angle between the first incident angle and the second incident angle may be divided into more or fewer angle regions, or the incident angle between the first incident angle and the second incident angle may not be equally divided.

[0137] Mate Reference Fig.17 and Fig.18 As shown, the present invention provides another preferred implementation of the corresponding relationship between the incident angle and the optimal period value. This embodiment obtains the optimal period value corresponding to other incident angles by establishing a fifth linear function, while controlling the period value in a part of the angle region to remain unchanged, thereby simplifying the design process of the metasurface.

[0138] Specifically, in step S30, the first incident angle, the fifth incident angle, the second incident angle and the sixth incident angle are selected to increase in sequence to obtain the corresponding first period value, the fifth period value, the second period value and the sixth period value.

[0139] In this embodiment, in step S30, the fifth incident angle is configured between 1° and 15°, for example, 5°, and the sixth incident angle is configured between 46° and 65°, for example, 60°. Fig.12 , the optimal period value corresponding to the fifth incident angle can be obtained, that is, the fifth period value, and the optimal period value corresponding to the sixth incident angle can be obtained, that is, the sixth period value.

[0140] Further, such as Fig.17 In step S30, a fifth linear function is established between the incident angle and the period value, so as to obtain the period values ​​corresponding to other incident angles between the fifth incident angle and the second incident angle.

[0141] In this embodiment, in step S30, when the fifth incident angle is 5° and the second incident angle is 45°, the incident angles between 5° and 45° can be calculated by the fifth linear function to obtain the corresponding optimal period value. After the conversion in step S40, the following is obtained: Fig.18 The linear function diagram between the optimal period value and the outer diameter size of the super surface area is shown in FIG. 1 . At this time, only the outer diameter size of the corresponding super surface area needs to be substituted to obtain the period value within the super surface area.

[0142] Further, in step S30, the period values ​​corresponding to other incident angles between the first incident angle and the fifth incident angle and / or the period values ​​corresponding to other incident angles between the second incident angle and the sixth incident angle remain unchanged.

[0143] In this embodiment, in step S30, when the first incident angle is 0° and the sixth incident angle is 60°, the period value corresponding to the incident angle between 0° and 5° is a constant value, and / or the period value corresponding to the incident angle between 45° and 60° is a constant value, which can simplify the design process of the metasurface 10. This method includes: the period value corresponding to the incident angle between 0° and 5° is a constant value, and the period value corresponding to the incident angle between 45° and 60° is not a constant value, but a variable period superstructure unit 12 is used; or, the period value corresponding to the incident angle between 0° and 5° is not a constant value, but a variable period superstructure unit 12 is used, and the period value corresponding to the incident angle between 45° and 60° is a constant value; or, the period values ​​corresponding to the incident angles between 0° and 5° and between 45° and 60° are both constant values.

[0144] Considering that the laser irradiates the metasurface region between the first incident angle and the fifth incident angle with normal incidence or small-angle incidence (incident angle of 0° to 5°), the superstructure unit 12 in this region adopts variable period, which has little effect on the modulation effect. Also, the laser irradiates the metasurface region between the second incident angle and the sixth incident angle with large-angle incidence (incident angle of 45° to 60°), the superstructure unit 12 in this region adopts variable period, which has little effect on the modulation effect, and the edge of the metasurface 10 cannot accommodate more nanostructures 123. Therefore, the period value corresponding to the incident angle between 0° and 5° adopts a constant value, and / or the period value corresponding to the incident angle between 45° and 60° adopts a constant value, which can reduce the manufacturing difficulty of the metasurface 10 and has little effect on the efficiency of the metasurface.

[0145] Specifically, in step S20, the period value specifically refers to: the radial period and / or circumferential period of the superstructure unit. In this embodiment, in step S20, when the superstructure unit 12 with different period values ​​is simulated and tested, the different period values ​​may be different radial periods 121 and / or circumferential periods 122, while other periods of the superstructure unit 12 remain unchanged.

[0146] Specifically, when the superstructure unit 12 of the supersurface 10 is Figure 4 When arranging, different period values ​​are different radial periods 121. Similarly, when the superstructure unit 12 of the supersurface 10 is arranged according to Figure 5 When arranging, different period values ​​are the differences between the radial period 121 and the circumferential period 122 .

[0147] Of course, in some embodiments not shown, different period values ​​may also be different circumferential periods 122, or different periods in the X-axis and / or Y-axis directions.

[0148] Specifically, in step S20, selecting different incident angles specifically refers to: selecting different incident angles of the first polarized light and the second polarized light, wherein the first polarized light and the second polarized light are mutually orthogonal. In this embodiment, taking mutually orthogonal X-polarized light (i.e., the first polarized light) and Y-polarized light (i.e., the second polarized light) as an example, in the case of a large-angle field of view, i.e., oblique incidence, since the metasurface 10 can be equivalent to a birefringent crystal, polarized light in different directions has different propagation speeds in various anisotropic media, resulting in different group velocities of X-polarized light and Y-polarized light, thereby generating polarization separation. Therefore, in step S20, simulation tests are performed on different incident angles of X-polarized light and Y-polarized light, taking into account the influence of different polarizations, especially at large angles of incidence, thereby improving the overall efficiency of the metasurface.

[0149] Specifically, in step S30, obtaining the periodic values ​​corresponding to different incident angles specifically refers to: obtaining the periodic values ​​corresponding to different incident angles of the first polarized light and the periodic values ​​corresponding to different incident angles of the second polarized light, and averaging the periodic values ​​obtained in different polarization directions at the same incident angle.

[0150] In this embodiment, in step S30, the optimal period values ​​corresponding to different incident angles (especially large-angle incident) of the first polarized light and the optimal period values ​​corresponding to different incident angles (especially large-angle incident) of the second polarized light are obtained, and the two optimal period values ​​are averaged or weighed to obtain the optimal period values ​​for different incident angles. The optimal period value takes into account the influence of different polarizations, avoids polarization separation at large-angle incident locations, and further improves the lens efficiency.

[0151] Alternatively, in step S30, obtaining the periodic values ​​corresponding to different incident angles specifically refers to: obtaining the periodic values ​​corresponding to different incident angles of the first polarized light and the periodic values ​​corresponding to different incident angles of the second polarized light, and obtaining the periodic values ​​after selecting the periodic values ​​obtained in different polarization directions at the same incident angle.

[0152] In this embodiment, in step S30, the optimal period value corresponding to different incident angles (especially large-angle incident) of the first polarized light and the optimal period value corresponding to different incident angles (especially large-angle incident) of the second polarized light are obtained, and one of the two is selected as the optimal period value, so as to obtain the optimal period value for different incident angles. The optimal period value takes into account the influence of different polarizations, avoids polarization separation at large-angle incident, and further improves the lens efficiency.

[0153] After summarizing the improvements of the above embodiments, the efficiency of the metasurface 10 at different incident angles is finally obtained as follows: Fig.19In the figure, the horizontal axis corresponds to the incident angle, the vertical axis corresponds to the metasurface efficiency, the broken line drawn by the dotted line is the metasurface of the variable period scheme obtained by adopting the preferred metasurface design method, and the broken line drawn by the solid line is the metasurface of the fixed period scheme (the period is 425nm). It can be seen from the figure that the efficiency of the metasurface with a variable period provided by the present invention at any incident angle is greater than that of the metasurface with a fixed period.

[0154] Combination Fig. 20 and Fig.21 It can be seen that after the variable-period metasurface focusing of the present invention, the uniformity and efficiency of different fields of view are greatly improved, the sudden changes in light intensity are reduced, and the practicality is greatly increased.

[0155] 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.

[0156] 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: Select different incident angles and perform simulation tests on the metasurfaces composed of the superstructure units with different period values, so as to obtain the efficiency of the metasurfaces composed of the superstructure units with different period values ​​at the same incident angle; Select the optimal metasurface efficiency at different incident angles to obtain the period values ​​corresponding to different incident angles; In the metasurface area corresponding to different incident angles, superstructure units with corresponding periodicity values ​​are arranged.

2. The method for designing a supersurface according to claim 1, characterized in that: The optimal metasurface efficiency of multiple incident angles is selected, multiple period values ​​corresponding to the incident angles are obtained, and a corresponding relationship is established between the incident angles and the period values, so as to obtain the period values ​​corresponding to other incident angles that have not been selected.

3. The method for designing a supersurface according to claim 2, characterized in that: Select a first incident angle and a second incident angle with increasing angles to obtain corresponding first and second period values, establish a first linear function between the incident angles and the period values, and thus obtain period values ​​corresponding to other angles between the first incident angle and the second incident angle, and / or obtain period values ​​corresponding to other angles between the first incident angle and the second incident angle.

4. The method for designing a supersurface according to claim 2, wherein: Select the first incident angle, the third incident angle, the fourth incident angle and the second incident angle with increasing angles in sequence to obtain the corresponding first period value, the third period value, the fourth period value and the second period value, establish a second linear function between the incident angle and the period value, so as to obtain the period values ​​corresponding to other incident angles between the first incident angle and the third incident angle, establish a third linear function between the incident angle and the period value, so as to obtain the period values ​​corresponding to other incident angles between the third incident angle and the fourth incident angle, establish a fourth linear function between the incident angle and the period value, so as to obtain the period values ​​corresponding to other incident angles between the fourth incident angle and the second incident angle.

5. The method for designing a supersurface according to claim 3, characterized in that: The slope of the first linear function k1=(P1-P2) / (θ1-θ2), θ1 is the first incident angle, θ2 is the second incident angle, P1 is the first period value, and P2 is the second period value.

6. The method for designing a supersurface according to claim 4, characterized in that: The differences between adjacent incident angles among the first incident angle, the third incident angle, the fourth incident angle and the second incident angle are equal.

7. The method for designing a supersurface according to claim 2, characterized in that: Select the first incident angle, the fifth incident angle, the second incident angle and the sixth incident angle with increasing angles in sequence to obtain the corresponding first period value, the fifth period value, the second period value and the sixth period value, establish a fifth linear function between the incident angles and the period values, and thus obtain the period values ​​corresponding to other incident angles between the fifth incident angle and the second incident angle, and the period values ​​corresponding to other incident angles between the first incident angle and the fifth incident angle and / or the period values ​​corresponding to other incident angles between the second incident angle and the sixth incident angle remain unchanged.

8. The method for designing a supersurface according to claim 1, wherein: The period value specifically refers to: a radial period and / or a circumferential period of the superstructure unit.

9. The method for designing a supersurface according to claim 1, wherein: A nanostructure is disposed at the center and / or a vertex of each superstructure unit, and the nanostructure is configured as a polarization-dependent structure or a polarization-independent structure.

10. The method for designing a super surface according to claim 9, characterized in that: The metasurface also includes a substrate connecting the nanostructures, a filler connecting the nanostructures and the substrate, and an anti-reflection film arranged on the substrate and / or the filler, wherein the anti-reflection film includes a first material layer and a second material layer, and the first material layer or the second material layer is connected to the metasurface.

11. The method for designing a supersurface according to claim 1, wherein: Selecting different incident angles specifically refers to: selecting different incident angles of the first polarized light and the second polarized light, wherein the first polarized light and the second polarized light are orthogonal to each other; Obtaining periodic values ​​corresponding to different incident angles specifically refers to: obtaining periodic values ​​corresponding to different incident angles of the first polarized light and periodic values ​​corresponding to different incident angles of the second polarized light, and averaging or selecting the periodic values ​​obtained in different directions at the same incident angle to obtain the periodic value.

12. A metasurface, characterized in that: It includes a super surface designed by any design method described in claims 1-11 above.

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