Metasurface structure and design method thereof

Abstract

The invention provides a metasurface structure and a design method thereof. The design method of the metasurface structure comprises the following steps: determining materials of a substrate and a metasurface unit on the substrate, and the shape of the metasurface unit; determining a transmittance curve and / or a phase response curve of the metasurface unit in the first size range; judging whether a resonance peak exists in the transmittance curve and / or the phase response curve or not; if the resonance peak exists in the transmittance curve and / or the phase response curve, adjusting the material and the thickness of the covering layer to eliminate the resonance peak; if no resonance peak exists in the transmittance curve and / or the phase response curve, it is judged that the design method is completed. The metasurface structure solves the problem that in the prior art, a metasurface structure has harmonic peaks in phase response, and therefore transmittance is affected.

Description

Technical Field

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

[0002] Metasurface is an emerging optical element that has flourished in recent years. It includes a two-dimensionally arranged sub-wavelength unit structure that can freely control electromagnetic waves in multiple dimensions, such as amplitude, phase, and polarization. Metasurfaces are small in size and light in weight, which helps to reduce the size and weight of the optical system in which they are used. At present, metasurface structures have been widely used in imaging, beam shaping, holography, polarization measurement and other fields.

[0003] However, the current metasurface structures mainly achieve phase coverage of 0 to 2π by changing the structural size. There may be a resonance peak on the resulting phase delay response curve, which reduces the transmittance of the metasurface unit at the resonance peak and causes a dramatic change in the phase response, affecting the overall efficiency of the metasurface structure.

[0004] That is to say, the metasurface structure in the prior art has a problem that the phase response has a resonance peak, thereby affecting the transmittance. Summary of the invention

[0005] The main purpose of the present invention is to provide a metasurface structure and a design method thereof, so as to solve the problem in the prior art that the metasurface structure has a phase response with a resonance peak, thereby affecting the transmittance.

[0006] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, a design method of a metasurface structure is provided, comprising the following steps: determining the materials of a substrate and a metasurface unit on the substrate, and the shape of the metasurface unit; determining a transmittance curve and / or a phase response curve of the metasurface unit within a first size range; judging whether there is a resonance peak in the transmittance curve and / or the phase response curve; if there is a resonance peak in the transmittance curve and / or the phase response curve, adjusting the material and thickness of the covering layer to eliminate the resonance peak; if there is no resonance peak in the transmittance curve and / or the phase response curve, judging that the design method is completed.

[0007] Furthermore, the step of determining a transmittance curve and / or a phase response curve of the metasurface unit within a first size range includes: determining the height of the metasurface unit as a first height; and scanning the transmittance curve and / or the phase response curve of the metasurface unit within a first size range at the first height.

[0008] Further, in the step of scanning the transmittance curve and / or the phase response curve of the metasurface unit within the first size range at the first height, the first size range at the first height is set to satisfy a phase coverage of 2π.

[0009] Furthermore, the step of adjusting the material and thickness of the covering layer includes: selecting a material with a different refractive index from the metasurface unit as the material of the covering layer; establishing a superposition model of the metasurface unit and the covering layer; and using a rigorous coupled wave method scanning simulation to determine the thickness of the covering layer that can eliminate the resonance peak.

[0010] Further, in the step of selecting a material having a refractive index different from that of the metasurface unit as the material of the covering layer, the material of the covering layer is set to include one of SiO2 and SiN; and / or in the step of establishing an overlay model of the metasurface unit and the covering layer, the overlay model is set to include an overlay model formed by conformally covering at least one side of the upper surface and the lower surface of the metasurface unit with one or more covering layers.

[0011] Furthermore, the step of using a strict coupled wave method to scan and simulate to determine the thickness of the covering layer that can eliminate the resonance peak includes: using a strict coupled wave method to scan and simulate the transmittance curve and / or phase response curve of the metasurface unit of the covering layer at multiple thicknesses; determining the transmittance curve and / or phase response curve corresponding to the smallest resonance peak or no resonance peak among the multiple transmittance curves and / or multiple phase response curves and using it as a target graph; and taking the thickness of the covering layer corresponding to the target graph as the final thickness.

[0012] Further, in the step of scanning and simulating the transmittance curve and / or phase response curve of the metasurface unit of the cover layer at multiple thicknesses using the strict coupled wave method, it includes: determining the initial thickness h of the cover layer, and the initial thickness h satisfies: h = λ / (10*n cover ), λ is the working wavelength, n cover is the refractive index of the covering layer; the simulation thickness range is determined according to the initial thickness h; and a rigorous coupled wave method is used to scan the transmittance curve and / or phase response curve of the metasurface unit of the simulation covering layer within the simulation thickness range.

[0013] Furthermore, in the step of determining the materials of the substrate and the metasurface unit on the substrate, and the shape of the metasurface unit, the materials of the substrate and the metasurface unit on the substrate, and the shape of the metasurface unit are determined according to the working wavelength λ; and / or the metasurface unit is set to be columnar, and the cross-sectional shape of the columnar metasurface unit along the direction parallel to the substrate includes one of a circle, a polygon, a ring and a cross; and / or the material of the metasurface unit is set to include one of Si, αSi, TiO2, GaN and HfO2.

[0014] Further, in the step of determining the height of the super-surface unit as the first height, the first height is set to be greater than or equal to 400 nm and less than or equal to 1000 nm.

[0015] According to another aspect of the present invention, a metasurface structure is provided, which is the above-mentioned metasurface structure, and the metasurface structure includes: a substrate; a metasurface unit, wherein the metasurface units are multiple, and the multiple metasurface units are arranged in an array on the substrate; a covering layer, wherein a covering layer is arranged on the surface of at least part of the metasurface units on a side away from the substrate and / or on the surface of the metasurface units on a side facing the substrate, the covering layer has a different refractive index from the metasurface unit, and the covering layer is used to eliminate the resonance peak of the metasurface unit.

[0016] Applying the technical solution of the present invention, the design method of the metasurface structure includes the following steps: determining the materials of the substrate and the metasurface unit on the substrate, and the shape of the metasurface unit; determining the transmittance curve and / or the phase response curve of the metasurface unit within a first size range; judging whether there is a resonance peak in the transmittance curve and / or the phase response curve; if there is a resonance peak in the transmittance curve and / or the phase response curve, adjusting the material and thickness of the covering layer to eliminate the resonance peak; if there is no resonance peak in the transmittance curve and / or the phase response curve, judging that the design method is completed.

[0017] After determining the materials of the substrate and the metasurface unit on the substrate and the shape of the metasurface unit, the present application obtains the transmittance curve and / or phase response curve of the metasurface unit within the first size range through simulation, and determines whether there is a resonance peak in at least one of the transmittance curve and the phase response curve by observing at least one of the transmittance curve and the phase response curve. If there is a resonance peak in at least one of the transmittance curve and the phase response curve, the material and thickness of the covering layer are adjusted, so as to eliminate the resonance peak in the curve by using a covering layer of reasonable material and reasonable thickness, so as to obtain a metasurface structure without resonance peak, smooth phase response curve and transmittance curve, and at the same time, it can avoid the influence of the resonance peak on the light transmittance of the metasurface structure, which is conducive to ensuring the high transmittance of the metasurface structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0019] Figure 1 A flow chart showing a method for designing a super surface structure according to an optional embodiment of the present invention;

[0020] Figure 2 A partial schematic diagram of a super surface structure according to the first embodiment of the present invention is shown;

[0021] Figure 3 The transmittance curve and phase response curve of the metasurface structure without a cover layer of the first embodiment of the present invention are shown;

[0022] Figure 4 The transmittance curve and phase response curve of the super-surface structure with a 20 nm cover layer of the first embodiment of the present invention are shown;

[0023] Figure 5 The transmittance curve and phase response curve of the super-surface structure with a 50 nm cover layer of the first embodiment of the present invention are shown;

[0024] Figure 6 A partial schematic diagram of a super surface structure according to a second embodiment of the present invention is shown;

[0025] Figure 7 The transmittance curve and phase response curve of the metasurface structure without a cover layer of the second embodiment of the present invention are shown;

[0026] Figure 8 The transmittance curve and phase response curve of the super-surface structure of the second embodiment of the present invention with a covering layer of 10nm and 25nm are shown.

[0027] The above drawings include the following reference numerals:

[0028] 10. Substrate; 20. Metasurface unit; 30. Covering layer. DETAILED DESCRIPTION

[0029] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0030] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs.

[0031] In the present invention, unless otherwise specified, the directional words used, such as "up, down, top, bottom", usually refer to the directions shown in the drawings, or to the components themselves in the vertical, perpendicular or gravity directions; similarly, for ease of understanding and description, "inside and outside" refer to the inside and outside relative to the outline of each component itself, but the above-mentioned directional words are not used to limit the present invention.

[0032] In order to solve the problem in the prior art that the metasurface structure has a phase response with a resonance peak, thereby affecting the transmittance, the present invention provides a metasurface structure and a design method thereof.

[0033] like Figures 1 to 8As shown, the design method of the metasurface structure includes the following steps: determining the materials of the substrate 10 and the metasurface unit 20 on the substrate 10, and the shape of the metasurface unit 20; determining the transmittance curve, or the phase response curve, or the transmittance curve and the phase response curve of the metasurface unit 20 within the first size range; judging whether there is a resonance peak in at least one of the transmittance curve and the phase response curve; if there is a resonance peak in at least one of the transmittance curve and the phase response curve, adjusting the material and thickness of the covering layer 30 to eliminate the resonance peak; if there is no resonance peak in at least one of the transmittance curve and the phase response curve, determining that the design method is completed.

[0034] After determining the materials of the substrate 10 and the metasurface unit 20 on the substrate 10 and the shape of the metasurface unit 20, the present application obtains the transmittance curve, or the phase response curve, or the transmittance curve and the phase response curve of the metasurface unit 20 within the first size range through simulation, and determines whether there is a resonance peak in at least one of the transmittance curve and the phase response curve by observing at least one of the transmittance curve and the phase response curve. If there is a resonance peak in at least one of the transmittance curve and the phase response curve, the material and thickness of the covering layer 30 are adjusted, so as to eliminate the resonance peak in the curve by using a covering layer 30 of a reasonable material and a reasonable thickness, so as to obtain a metasurface structure without a resonance peak, a smooth phase response curve and a transmittance curve, and at the same time, it can avoid the influence of the resonance peak on the light transmittance of the metasurface structure, which is conducive to ensuring the high transmittance of the metasurface structure.

[0035] In summary, in order to address the problem of decreased transmittance caused by possible resonance peaks in current metasurface structures, the present invention proposes a design method for a metasurface structure, namely, a covering layer 30 is set on the metasurface unit 20, and the material and thickness of the covering layer 30 are determined by simulation, so as to destroy the conditions for the generation of the resonance peak and achieve a smooth phase response curve while maintaining a high transmittance, thereby avoiding the adverse effects of tolerances caused by the processing technology on the transmittance of the metasurface structure.

[0036] It should be noted that in the above step of determining whether there is a resonance peak in at least one of the transmittance curve and / or the phase response curve, it is possible to determine whether there is a resonance peak only in the phase response curve, or only in the transmittance curve, or both in the transmittance curve and the phase response curve. Figure 3 As shown in Figure 3 The transmittance curve and phase response curve of the metasurface unit 20 within the first size range are shown in the figure. The two curves are in the same figure, and it can be seen from the figure that the resonant peak position of the transmittance curve corresponds to the resonant peak position of the phase response curve. Therefore, in actual judgment, it is sufficient to judge one of the two.

[0037] Specifically, the above steps also include a coating process at the end, and the coating process includes: coating one or more covering layers 30 on at least one of the two side surfaces of each metasurface unit 20. The method of the present application does not need to add complex structures and process steps, and only needs to coat the covering layer 30 on at least one of the two side surfaces of the metasurface unit 20, and the operation is relatively convenient.

[0038] Specifically, in the step of determining the materials of the substrate 10 and the metasurface unit 20 on the substrate 10, and the shape of the metasurface unit 20, it specifically includes: determining the material of the substrate 10 and the materials of the multiple metasurface units 20 on the substrate 10 according to the working wavelength λ, where the working wavelength is the wavelength of the incident light received by the metasurface structure. For example, when the working wavelength is the wavelength of visible light, the substrate 10 can be made of glass; when the working wavelength is the wavelength of infrared light, the substrate 10 can be made of a single crystal silicon wafer. The material for setting the metasurface unit 20 includes one of Si, αSi, TiO2, GaN and HfO2, which can be selected according to different working wavelengths. αSi can be selected as the material of the metasurface unit 20 for the common 940nm working wavelength.

[0039] Then, the shape of the metasurface unit 20 is determined. The metasurface unit 20 is a micro-nano structure. In this case, the metasurface unit 20 can be set to be columnar. The cross-sectional shape of the columnar metasurface unit 20 along the direction parallel to the substrate 10 includes one of a circle, an ellipse, a polygon, a ring, and a cross; the polygon includes a square, a rectangle, and a regular polygon. In practical applications, the cross-sectional shape of the metasurface unit 20 can be a polarization-insensitive structure such as a circle, a square, a ring, a cross, a regular polygon, or a polarization-sensitive structure such as an ellipse or a rectangle. It can be set according to actual conditions, and a polarization-insensitive structure is preferred.

[0040] Specifically, the above-mentioned step of determining the transmittance curve and / or phase response curve of the metasurface unit 20 within the first size range includes:

[0041] First, the height of the metasurface unit 20 is determined as the first height. At this time, a height can be randomly selected or selected by the operator as the first height.

[0042] Then, scan the transmittance curve, or phase response curve, or transmittance curve and phase response curve of the metasurface unit 20 within the first size range at the first height. In this step, it is necessary to ensure that the first size range at the first height satisfies the phase coverage of 2π. The first height and the first size range can be reasonably adjusted according to this condition to obtain a reasonable height and first size range. At this time, in the transmittance and phase response diagram obtained, the horizontal axis represents the radius, the left vertical axis represents the transmittance, and the right vertical axis represents the phase. The two curves in the diagram are divided into a transmittance curve and a phase response curve. For reference Figure 3 as shown in .

[0043] It should be noted that when the super surface unit 20 is cylindrical and has a circular cross section, the first size range is the first radius range, where the radius is the radius of the circle; when the super surface unit 20 is rectangular or other multi-prism-shaped and has a polygonal cross section, the first size range is the first side length range, where the side length is the side length of the polygon. It can also be understood that the first size range includes one of the first radius range and the first side length range.

[0044] Specifically, in the step of determining the height of the metasurface unit 20 as the first height, the first height is set to be greater than or equal to 400nm and less than or equal to 1000nm. That is, the first height is selected within the range of 400nm-1000nm, and the optimal height can be determined by simulation.

[0045] Specifically, the step of adjusting the material and thickness of the cover layer 30 includes:

[0046] First, a material with a different refractive index from the metasurface unit 20 is selected as the material of the covering layer 30. By setting the refractive index of the covering layer 30 to be different from the refractive index of the metasurface unit 20, it is beneficial to ensure the reliability of the use of the covering layer 30 and to ensure that the covering layer 30 has the effect of destroying the resonance peak. The material that can be set for the covering layer 30 includes one of SiO2 and SiN. By rationally planning the material of the covering layer 30, the electromagnetic field distribution characteristics during resonance are changed, and the resonance peak conditions are destroyed. Using SiO2 or SiN as the material of the covering layer 30 can not only effectively eliminate the resonance peak, but also has good chemical stability and mechanical strength, and is suitable for optical sensors and optical communication equipment with harsh manufacturing environments. The chemical stability and mechanical strength of SiO2 or SiN can ensure the long-term stable operation of the metasurface structure and avoid performance degradation caused by environmental changes.

[0047] Then, a superposition model of the supersurface unit 20 and the covering layer 30 is established, that is, the covering layer 30 is superimposed on the upper surface and / or lower surface of the supersurface unit 20 to form a superposition model. In this step, setting the superposition model includes a superposition model formed by conformally covering one or more covering layers 30 on at least one side of the upper surface and the lower surface of the supersurface unit 20. Specifically, the superposition model includes a model consisting of the supersurface unit 20 and the covering layer 30 conformally covered on its surface. More specifically, the upper surface of the metasurface unit 20 refers to the side surface of the metasurface unit 20 away from the substrate 10, and the lower surface of the metasurface unit 20 refers to the side surface of the metasurface unit 20 facing the substrate 10. One or more covering layers 30 may be conformally covered only on the side surface of the metasurface unit 20 away from the substrate 10; one or more covering layers 30 may be provided only on the side surface of the metasurface unit 20 facing the substrate 10, that is, one or more covering layers 30 may be provided between the metasurface unit 20 and the substrate 10; one or more covering layers 30 may also be provided on both the upper and lower surfaces of the metasurface unit 20. The cross section of the covering layer 30 along the direction parallel to the substrate 10 has the same shape and area as the surface of the metasurface unit 20 where it is located, which can reduce the process complexity, and does not require additional exposure processes. Only a coating process is required to set the covering layer 30 on the metasurface unit 20.

[0048] In a preferred embodiment of the present application, the stacking model is a stacking model formed by conformally covering a covering layer 30 on both side surfaces of the super surface unit 20, where the two sides are the side of the super surface unit 20 facing the substrate 10 and the side away from the substrate 10.

[0049] Then, a strict coupled wave method scanning simulation is used to determine the thickness of the cover layer 30 that can eliminate the resonance peak. The thickness of the cover layer 30 is reasonably selected to ensure that the cover layer 30 at this thickness can effectively eliminate the resonance peak in the phase response curve, making the curve smoother and avoiding the reduction in transmittance caused by the resonance peak.

[0050] Specifically, the above-mentioned step of using the strict coupled wave method to scan and simulate to determine the thickness of the covering layer 30 that can eliminate the resonance peak includes: using the strict coupled wave method to scan and simulate the transmittance curve, or phase response curve, or transmittance curve and phase response curve of the metasurface unit 20 at multiple thicknesses of the covering layer 30, preferably scanning the transmittance curve and phase response curve of the metasurface unit 20 at multiple thicknesses. Thus, multiple transmittance curves, or multiple phase response curves, or multiple groups of transmittance curves and phase response curves are obtained, each group including a transmittance curve and a phase response curve corresponding to a thickness; then, the curve corresponding to the minimum resonance peak or no resonance peak among the multiple transmittance curves, or multiple phase response curves, or multiple groups of transmittance curves and phase response curves is determined and used as the target graph; the thickness of the covering layer 30 corresponding to the target graph is the final thickness. The thickness of the covering layer 30 here refers to the thickness of a single-layer covering layer 30. The optimal thickness of the cover layer 30 is determined through simulation, so as to ensure that the resonance peak in the phase response diagram of the metasurface unit 20 can be effectively eliminated after the cover layer 30 is set on the surface of the metasurface unit 20, thereby ensuring the performance stability of the metasurface unit 20.

[0051] Specifically, the step of determining the transmittance curve and / or phase response curve corresponding to the minimum resonance peak or no resonance peak among the multiple transmittance curves and / or multiple phase response curves and using the target graph includes one of the following:

[0052] Determine the transmittance curve corresponding to the smallest resonance peak or no resonance peak among the multiple transmittance curves and use it as the target graph;

[0053] Determine a phase response curve corresponding to the smallest resonance peak or no resonance peak among the multiple phase response curves and use it as a target graph;

[0054] A set of transmittance curves and phase response curves corresponding to the smallest resonance peak or no resonance peak among the multiple sets of transmittance curves and phase response curves is determined and used as a target graph.

[0055] In a specific embodiment of the present application, the above-mentioned step of using a strict coupled wave method to scan and simulate to determine the thickness of the covering layer 30 that can eliminate the resonance peak includes: using a strict coupled wave method to scan and simulate the transmittance curve and phase response curve of the metasurface unit 20 of the covering layer 30 at multiple thicknesses, thereby obtaining a one-to-one corresponding multiple transmittance curves and a plurality of phase response curves; determining the phase response curve corresponding to the smallest resonance peak or no resonance peak among the multiple phase response curves and using it as the target graph; and taking the thickness of the covering layer 30 corresponding to the target graph as the final thickness.

[0056] Specifically, in the step of scanning and simulating the transmittance curve and / or phase response curve of the metasurface unit 20 of the cover layer 30 at multiple thicknesses using the strict coupled wave method, the following steps are included: determining the initial thickness h of the cover layer 30, and the initial thickness h satisfies: h = λ / (10*n cover ), λ is the working wavelength, n cover is the refractive index of the cover layer 30. By reasonably constraining the initial thickness h of the single-layer cover layer 30, the working wavelength λ and the refractive index n of the cover layer 30 cover Satisfying the above relationship is conducive to the reasonable control of the material and refractive index of the covering layer 30 to meet the requirements, so as to better ensure that the covering has the effect of destroying the resonance peak. Then, the simulation thickness range is determined according to the initial thickness h. The simulation thickness range is a range of 20nm fluctuating around the center value of the initial thickness h, for example: simulation thickness range = [initial thickness h-20nm, initial thickness h+20nm], preferably simulation thickness range = [initial thickness h-10nm, initial thickness h+10nm]. It can be set according to the actual situation to ensure that the simulation thickness range is close to the initial thickness h, so that the optimal thickness can be quickly located. Then, the transmittance curve and phase response curve of the super surface unit 20 of the simulated covering layer 30 under the simulation thickness range are scanned by the strict coupled wave method to determine the optimal thickness of the covering layer 30.

[0057] In summary, by properly selecting the material and thickness of the cover layer 30, the resonance peak can be effectively suppressed, and the transmittance and phase control accuracy of the metasurface structure within a specific wavelength range can be improved, which is of great significance for the development of high-performance optical filters and optical switches. In optical filters, eliminating the resonance peak can achieve smoother transmission curves and phase curves, improve the selectivity and bandwidth performance of the filter, and enable it to play a key role in spectral analysis and optical communication systems.

[0058] In addition, the present application also provides a metasurface structure, which is the metasurface structure in the above method, and the metasurface structure includes a substrate 10, a metasurface unit 20 and a covering layer 30. There are multiple metasurface units 20, and the multiple metasurface units 20 are arranged in an array on one side surface of the substrate 10. The covering layer 30 is arranged on the side surface of at least some of the metasurface units 20 away from the substrate 10 and / or the side surface of the metasurface units 20 facing the substrate 10. The covering layer 30 has a different refractive index from the metasurface unit 20, and the covering layer 30 is used to eliminate the resonance peak of the metasurface unit 20.

[0059] By providing the substrate 10, the substrate 10 provides a housing position for a plurality of metasurface units 20, which is conducive to ensuring the reliability of each metasurface unit 20. The metasurface unit 20 is a micro-nano structure, and a covering layer 30 is provided on at least one of the side surface of the metasurface unit 20 away from the substrate 10 and the side surface of the metasurface unit 20 facing the substrate 10, so that the covering layer 30 can effectively destroy and eliminate the resonance peak in the phase response of the metasurface unit 20, thereby realizing a metasurface structure with a smooth phase response curve without a resonance peak, so that the device used by the metasurface structure is less sensitive to the tolerance during actual process processing.

[0060] Optionally, the covering layer 30 may be conformally arranged only on the surface of the side of the supersurface unit 20 away from the substrate 10; the covering layer 30 may be conformally arranged only on the surface of the side of the supersurface unit 20 facing the substrate 10, that is, the covering layer 30 is arranged between the supersurface unit 20 and the substrate 10; the covering layer 30 may also be arranged on both the surface of the side of the supersurface unit 20 facing the substrate 10 and the surface of the side away from the substrate 10, which can be arranged according to actual needs.

[0061] Specifically, the number of layers of the covering layer 30 on the same side of the metasurface unit 20 is one or more layers. Specifically, a single layer or multiple layers of the covering layer 30 may be arranged conformally only on the surface of the metasurface unit 20 away from the substrate 10; one or more layers of the covering layer 30 may be arranged conformally only on the surface of the metasurface unit 20 facing the substrate 10; one or more layers of the covering layer 30 may be arranged on both the surface of the metasurface unit 20 facing the substrate 10 and the surface of the metasurface unit 20 away from the substrate 10, and the arrangement may be made according to actual needs. When the covering layer 30 is arranged on both sides of the metasurface unit 20, the number of layers of the covering layer 30 on both sides may be the same or different.

[0062] In a preferred embodiment of the present application, each supersurface unit 20 is provided with a covering layer 30 on the surface on the side away from the substrate 10 and on the surface on the side facing the substrate 10, and the covering layer 30 on the two side surfaces of the supersurface unit 20 is a single layer.

[0063] Specifically, when the cover layer 30 is disposed on both side surfaces of the metasurface unit 20, the cover layers 30 on both side surfaces of the metasurface unit 20 have the same refractive index and the same or different thicknesses. That is to say, the cover layers 30 on both side surfaces of the metasurface unit 20 have the same refractive index, and the thicknesses can be set to be the same or different, which can be determined according to the effect obtained by actual simulation, so as to ensure that the combination of the two layers of cover layers 30 can effectively eliminate the resonance peak of the metasurface unit 20 where they are located.

[0064] In addition, the cross section of the cover layer 30 along the direction parallel to the substrate 10 has the same shape and area as the surface of the super surface unit 20 where it is located. In other words, the cover layer 30 is only arranged on the top surface and / or the bottom surface of the super surface unit 20, and is not arranged on the side surface, and the cover layer 30 has the same shape and area as the surface where it is located, which can reduce the complexity of the process, and does not require additional exposure process, and only needs to use the coating process to set the cover layer 30 on the surface of the super surface unit 20.

[0065] Specifically, the covering layer 30 includes one of a SiO2 layer and a SiN layer. By rationally planning the material of the covering layer 30, the electromagnetic field distribution characteristics during resonance are changed, and the resonance peak condition is destroyed. Using SiO2 or SiN as the material of the covering layer 30 can not only effectively eliminate the resonance peak, but also has good chemical stability and mechanical strength, and is suitable for optical sensors and optical communication equipment with harsh manufacturing environments. The chemical stability and mechanical strength of SiO2 or SiN can ensure the long-term stable operation of the metasurface structure and avoid performance degradation caused by environmental changes.

[0066] Specifically, the thickness of the cover layer 30 on the same side of the metasurface unit 20, the operating wavelength of the metasurface structure, and the refractive index of the cover layer 30 satisfy a linear relationship. For example, the thickness h of the cover layer 30 may satisfy: h = λ / (10*n cover ), λ is the working wavelength, n cover is the refractive index of the cover layer 30. By reasonably constraining the thickness h of the single-layer cover layer 30, the working wavelength λ and the refractive index n of the cover layer 30 cover The relationship between them is conducive to reasonably controlling the material and refractive index of the covering layer 30 to meet the requirements, thereby better ensuring that the covering has the effect of destroying the resonance peak.

[0067] Specifically, the height of the metasurface unit 20 is greater than or equal to 400nm and less than or equal to 1000nm. The optimal height can be determined by simulation. By rationally planning the height range of the metasurface unit 20, it is helpful to ensure that the size can meet the phase coverage of 2π. The metasurface unit 20 within this height range can provide a wider phase modulation range, which is suitable for designing broadband optical devices, such as broadband spectrum analyzers and multi-wavelength optical signal processors, and provides key technical support for the construction of high-performance optical communication networks.

[0068] In addition, the metasurface unit 20 is columnar, and the cross-sectional shape of the columnar metasurface unit 20 in the direction parallel to the substrate 10 includes one of a circle, an ellipse, a polygon, a donut and a cross. Polygons include squares, rectangles and regular polygons. In practical applications, the cross-sectional shape of the metasurface unit 20 can be a polarization-insensitive structure such as a circle, a square, a donut, a cross, a regular polygon, or a polarization-sensitive structure such as an ellipse or a rectangle. It can be set according to actual conditions, and a polarization-insensitive structure is preferred. By rationally planning the shape of the metasurface unit 20, more complex light field control can be achieved, which is suitable for high-precision beam deflection and focusing applications such as lidar and optical microscopes. In lidar, the design of the columnar metasurface unit 20 can achieve precise deflection and focusing of the laser beam, improve the detection accuracy and distance of the radar, and play an important role in the safe driving of self-driving cars and the precise positioning of drones.

[0069] In addition, the thickness of the cover layer 30 on the same side of the metasurface unit 20 is greater than or equal to 10nm and less than or equal to 55nm. Preferably, when a cover layer 30 is provided on both side surfaces of the metasurface unit 20, the thickness of the cover layer 30 on the same side of the metasurface unit 20 is greater than or equal to 10nm and less than or equal to 55nm. This is conducive to ensuring that the cover layer 30 within this thickness range can meet the function and role of destroying the resonance peak of the metasurface structure, while ensuring the light transmittance of the metasurface structure and the reliability of the use of the cover layer 30.

[0070] The method of the present application and the resulting supersurface structure are described in detail below in conjunction with two specific embodiments.

[0071] Embodiment 1

[0072] like Figures 2 to 5 As shown, the design method of the super surface structure and the super surface structure of embodiment 1 are described.

[0073] In this embodiment, the working wavelength λ of the metasurface structure is 940 nm. The material of the substrate 10 is determined to be D263T with a refractive index of 1.5137, the material of the metasurface unit 20 is determined to be αSi with a refractive index of 3.6, and the shape of the metasurface unit 20 is determined to be cylindrical.

[0074] like Figure 2As shown, the shape of the metasurface unit 20 of the metasurface structure of this embodiment is shown. The metasurface unit 20 of this embodiment is columnar and cylindrical in structure, and has polarization insensitivity. That is to say, the cross-sectional shape of the metasurface unit 20 along the direction parallel to the substrate 10 is circular. For ease of understanding, only one metasurface unit 20 is shown on the substrate 10 in the figure, but in actual application, there are multiple metasurface units 20 on the substrate 10 and they are arranged in a periodic array.

[0075] In this embodiment, the period of the metasurface unit 20 is 370nm, the height is 500nm, the first size range is the first radius range, the first radius range is greater than or equal to 40nm and less than or equal to 150nm, the first radius range needs to be determined in combination with the actual manufacturing process, and also needs to meet the period range and the phase difference of 2π. The scanning interval of the first radius is selected as 0.5nm, which can be adjusted according to the actual situation to ensure that possible resonance peaks are not missed.

[0076] When the metasurface unit 20 is not provided with a cover layer 30, the transmittance and phase response curves obtained by scanning using the strict coupled wave algorithm are as follows: Figure 3 As shown, Figure 3 In the figure, the horizontal axis represents the radius, the left vertical axis represents the transmittance, and the right vertical axis represents the phase. The two lines in the figure are the transmittance curve and the phase response curve. It can be seen from the figure that the metasurface unit 20 can cover a phase difference of 2π within the first size range of the scan at this height, and the phase vertical axis is from 0-6. However, it can be seen that there is a resonance peak in the phase response curve near the radius of 138nm, and the transmittance of the metasurface unit 20 drops below 80%. Although the unit structure at the resonance peak can be chosen to be avoided when designing the device, there are often tolerances in the actual device processing, causing the radius of the metasurface unit 20 to deviate from the design value. The metasurface unit 20 with a radius value of about 138nm, which does not have a resonance peak itself, may become a resonance peak due to tolerance. When the resonance peak occurs, not only the transmittance of the metasurface unit 20 is affected, but also the phase of the metasurface unit 20 will be severely affected, thereby affecting the efficiency and function of the metasurface structure.

[0077] Then, the material of the cover layer 30 is SiO2 with a refractive index of 1.4896. A cover layer 30 is set on the surface of the metasurface unit 20 away from the substrate 10 and the surface of the side facing the substrate 10, so that the metasurface unit 20 and the cover layers 30 on both sides form a stacked model. And the thickness of the cover layer 30 on the upper and lower surfaces of the metasurface unit 20 is controlled to be equal. Then, the strict coupled wave method is used to scan and simulate the transmittance curve and phase response curve of the metasurface unit 20 at multiple thicknesses of the cover layer 30. Figure 4The transmittance curve and phase response curve are shown when the thickness of the single-layer covering layer 30 on both sides of the metasurface unit 20 is 20 nm. It can be seen from the transmittance curve and the phase response curve that the intensity of the resonance peak is significantly weakened. Figure 5 The transmittance curve and phase response curve when the thickness of the single-layer cover layer 30 on both sides of the metasurface unit 20 is 50nm are shown. It can be seen from the figure that the resonance peak has basically disappeared, and the transmittance curve and the phase response curve are very smooth. At this time, it can be determined that the optimal thickness of the single-layer cover layer 30 is 50nm. Subsequently, the cover layer 30 of the optimal thickness can be set on the two side surfaces of each metasurface unit 20 through a coating process to complete the fabrication of the metasurface structure of this embodiment. The device constructed using the metasurface structure has better tolerance to tolerance.

[0078] Embodiment 2

[0079] like Figures 6 to 8 As shown, the design method of the super surface structure and the super surface structure of the second embodiment are described.

[0080] In this embodiment, the working wavelength λ of the metasurface structure is 940 nm. The material of the substrate 10 is determined to be D263T with a refractive index of 1.5137, the material of the metasurface unit 20 is determined to be αSi with a refractive index of 3.6, and the shape of the metasurface unit 20 is determined to be a cuboid.

[0081] like Figure 6 , which shows the shape of the metasurface unit 20 of the metasurface structure of this embodiment. The metasurface unit 20 of this embodiment is columnar, specifically quadrangular, and has polarization insensitivity. The cross-sectional shape of the metasurface unit 20 along the direction parallel to the substrate 10 is square. For ease of understanding, only one metasurface unit 20 is shown on the substrate 10 in the figure, but in actual applications, there are multiple metasurface units 20 on the substrate 10 and they are arranged in a periodic array.

[0082] In this embodiment, the period of the metasurface unit 20 is 370nm, the height is 520nm, the first size range is the first side length range, the first side length range is greater than or equal to 80nm and less than or equal to 300nm, the first side length range needs to be determined in combination with the actual manufacturing process, and also needs to meet the period range and the phase difference of 2π. The scanning interval of the first side length is selected as 0.5nm, which can be adjusted according to the actual situation to ensure that the possible resonance peak is not missed.

[0083] When the metasurface unit 20 is not provided with a cover layer 30, the phase response curve obtained by scanning using the strict coupled wave algorithm is as follows: Figure 7 As shown, Figure 7In the figure, the horizontal axis represents the side length, the left vertical axis represents the transmittance, and the right vertical axis represents the phase. The two lines in the figure are the transmittance curve and the phase response curve. It can be seen from the figure that the metasurface unit 20 can cover a phase difference of 2π within the first size range of the scan at this height, and the phase vertical axis is from 0-6. However, it can be seen that there is a resonance peak in the phase response curve near the side length of 236nm. Although the transmittance does not drop much at this point, there are mutations in both the transmittance and the phase. Although the metasurface unit 20 at the resonance peak can be chosen to be avoided when designing the device, there are often tolerances in the actual device processing, causing the side length of the metasurface unit 20 to deviate from the design value. The metasurface unit 20 with a side length value of about 236nm that does not have a resonance peak itself may become a resonance peak due to tolerance. When the resonance peak occurs, not only the transmittance of the metasurface unit 20 is affected, but also the phase of the metasurface unit 20 will be severely affected, thereby affecting the efficiency and function of the device.

[0084] Then, the material of the cover layer 30 is SiO2 with a refractive index of 1.4896. A cover layer 30 is disposed on the surface of the metasurface unit 20 away from the substrate 10 and the surface of the metasurface unit 20 facing the substrate 10, so that the metasurface unit 20 and the cover layers 30 on both sides form a stacked model. In this embodiment, the thickness of the cover layer 30 on the upper and lower surfaces of the metasurface unit 20 is not equal.

[0085] Then, a rigorous coupled wave method is used to scan and simulate the transmittance curve and phase response curve of the metasurface unit 20 with the cover layer 30 at multiple thicknesses. Figure 8 The transmittance curve and phase response curve are shown when the thickness of the cover layer 30 on the lower surface of the metasurface unit 20 is 10nm and the thickness of the cover layer 30 on the upper surface of the metasurface unit 20 is 25nm. It can be seen from the figure that the resonance peak has been completely eliminated. Subsequently, the cover layer 30 of the optimal thickness can be set on the two side surfaces of each metasurface unit 20 through a coating process to complete the fabrication of the metasurface structure of this embodiment. The device constructed using the metasurface structure has better tolerance to tolerance.

[0086] Obviously, the above-described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0087] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0088] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein.

[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for designing a metasurface structure, characterized in that: The steps include: Determining the materials of the substrate (10) and the metasurface unit (20) on the substrate (10), and the shape of the metasurface unit (20); Determining a transmittance curve and / or a phase response curve of the metasurface unit (20) within a first size range; Determining whether there is a resonance peak in the transmittance curve and / or the phase response curve; If the resonance peak exists in the transmittance curve and / or the phase response curve, the material and thickness of the cover layer (30) are adjusted to eliminate the resonance peak; if the resonance peak does not exist in the transmittance curve and / or the phase response curve, it is determined that the design method is completed.

2. The method for designing a supersurface structure according to claim 1, characterized in that: The step of determining a transmittance curve and / or a phase response curve of the metasurface unit (20) within a first size range comprises: Determining the height of the super surface unit (20) as a first height; Scanning the transmittance curve and / or the phase response curve of the metasurface unit (20) within a first size range at the first height.

3. The method for designing a super surface structure according to claim 2, characterized in that: In the step of scanning the transmittance curve and / or the phase response curve of the metasurface unit (20) within a first size range at the first height, the first size range at the first height is set to satisfy a phase coverage of 2π.

4. The method for designing a super surface structure according to claim 1, characterized in that: The step of adjusting the material and thickness of the covering layer (30) comprises: Selecting a material having a refractive index different from that of the metasurface unit (20) as the material of the covering layer (30); Establishing a superposition model of the supersurface unit (20) and the cover layer (30); The rigorous coupled wave method scanning simulation is adopted to determine the thickness of the cover layer (30) capable of eliminating the resonance peak.

5. The method for designing a super surface structure according to claim 4, characterized in that: In the step of selecting a material having a refractive index different from that of the metasurface unit (20) as the material of the cover layer (30), the material of the cover layer (30) is arranged to include one of SiO2 and SiN; and / or In the step of establishing a superposition model of the supersurface unit (20) and the covering layer (30), setting the superposition model includes forming a superposition model by conformally covering one or more layers of the covering layer (30) on at least one side of the upper surface and the lower surface of the supersurface unit (20).

6. The method for designing a super surface structure according to claim 4, characterized in that: The step of using a rigorous coupled wave method scanning simulation to determine the thickness of the cover layer (30) capable of eliminating the resonance peak comprises: Using a rigorous coupled wave method to scan and simulate the transmittance curve and / or phase response curve of the metasurface unit (20) of the cover layer (30) at multiple thicknesses; Determine the transmittance curve and / or the phase response curve corresponding to the minimum resonance peak or no resonance peak among the plurality of transmittance curves and / or the plurality of phase response curves and use it as a target graph; The thickness of the covering layer (30) corresponding to the target image is taken as the final thickness.

7. The method for designing a super surface structure according to claim 6, characterized in that: The step of scanning and simulating the transmittance curve and / or phase response curve of the metasurface unit (20) of the cover layer (30) at multiple thicknesses using a rigorous coupled wave method comprises: Determine the initial thickness h of the covering layer (30), and the initial thickness h satisfies: h=λ / (10*n cover ), λ is the working wavelength, n cover is the refractive index of the covering layer (30); Determine the simulation thickness range according to the initial thickness h; A strict coupled wave method is used to scan and simulate the transmittance curve and / or phase response curve of the metasurface unit (20) of the cover layer (30) within the simulation thickness range.

8. The method for designing a super surface structure according to any one of claims 1 to 7, characterized in that: In the step of determining the materials of the substrate (10) and the metasurface unit (20) on the substrate (10), and the shape of the metasurface unit (20), Determining the materials of the substrate (10) and the metasurface unit (20) on the substrate (10), and the shape of the metasurface unit (20) according to the operating wavelength λ; and / or The super surface unit (20) is arranged to be columnar, and the cross-sectional shape of the columnar super surface unit (20) along a direction parallel to the substrate (10) includes one of a circular shape, a polygonal shape, a circular ring shape and a cross shape; and / or The material of the super surface unit (20) includes one of Si, αSi, TiO2, GaN and HfO2.

9. The method for designing a super surface structure according to claim 2, characterized in that: In the step of determining the height of the super surface unit (20) as the first height, the first height is set to be greater than or equal to 400 nm and less than or equal to 1000 nm.

10. A super surface structure, characterized in that: The supersurface structure is the supersurface structure according to any one of claims 1 to 9, and the supersurface structure comprises: A substrate (10); A super surface unit (20), wherein the super surface unit (20) is multiple, and the multiple super surface units (20) are arranged in an array on the substrate (10), A covering layer (30), wherein the covering layer (30) is provided on at least a portion of a surface of the metasurface unit (20) away from the substrate (10) and / or on a surface of the metasurface unit (20) facing the substrate (10), the covering layer (30) and the metasurface unit (20) having a different refractive index, and the covering layer (30) is used to eliminate a resonance peak of the metasurface unit (20).

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