Metasurface structure

Abstract

The utility model provides a metasurface structure. The metasurface structure comprises a substrate; the metasurface unit array comprises a substrate, a plurality of metasurface units which are arranged on the substrate in an array mode, covering layers are arranged on the surfaces of the sides, away from the substrate, of at least part of the metasurface units and / or the surfaces of the sides, facing the substrate, of the metasurface units, and the refractive indexes of the covering layers are different from the refractive indexes of the metasurface units. The covering layer is used for eliminating the resonance peak of the metasurface unit. The metasurface structure solves the problem that in the prior art, phase response of a metasurface structure has harmonic peaks, and therefore transmittance is affected.

Description

TECHNICAL FIELD

[0001] The utility model relates to optical equipment technical field, specifically, relate to a kind of metasurface structure. BACKGROUND

[0002] Metasurface is the new optical element that vigorous development in recent years, it includes two-dimensional arrangement sub-wavelength unit structure, can carry out multidimensional free regulation to electromagnetic wave, such as amplitude, phase and polarization etc. Metasurface has the characteristics of small volume, light weight, help to reduce the volume and weight of optical system applied by it. At present, metasurface structure has been widely applied in imaging, beam shaping, holography, polarization measurement etc.

[0003] However, the current metasurface structure is mainly through changing structure size to realize 0~2π phase coverage, and there can be resonance peak on the phase retardation response curve obtained, so that the transmittance of metasurface unit at resonance peak is reduced, the phase response changes sharply, which affects the overall efficiency of metasurface structure.

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

[0005] The main purpose of the utility model is to provide a kind of metasurface structure, to solve the problem that the metasurface structure in the prior art has a resonance peak in phase response, thereby affecting the transmittance.

[0006] In order to achieve the above purpose, the utility model provides a kind of metasurface structure, metasurface structure includes: substrate;Metasurface unit, the metasurface unit is multiple, multiple metasurface units are arranged in array on substrate, covering layer, at least part metasurface unit is provided with covering layer on the side surface away from substrate and / or the side surface towards substrate, the refractive index of covering layer is different from that of metasurface unit, and the covering layer is used to eliminate the resonance peak of metasurface unit.

[0007] Further, the covering layer is provided on the side surface away from the substrate and the side surface towards the substrate of each metasurface unit.

[0008] Further, the refractive index of the covering layer on the two side surfaces of the metasurface unit is the same, the thickness is the same or different.

[0009] Further, the number of layers of the covering layer on the same side of the metasurface unit is one or more.

[0010] Further, the cross section of the covering layer along the direction parallel to the substrate is the same as the surface shape of the metasurface unit where it is located and has the same area.

[0011] Further, a linear relationship is satisfied between the thickness of the covering layer on the same side of the metasurface unit, the working wavelength of the metasurface structure and the refractive index of the covering layer.

[0012] Further, the height of the metasurface unit is greater than or equal to 400 nm and less than or equal to 1000 nm.

[0013] Further, the metasurface unit is columnar, and the cross-sectional shape of the columnar metasurface unit along a direction parallel to the substrate comprises one of a circle, an ellipse, a polygon, a circular ring and a cross.

[0014] Further, the thickness of the covering layer on the same side of the metasurface unit is greater than or equal to 10 nm and less than or equal to 55 nm.

[0015] Further, the covering layer comprises one of a SiO2 layer and a SiN layer.

[0016] The technical scheme of the present application is applied, by setting the substrate, the substrate provides accommodation positions for a plurality of metasurface units, which is beneficial to ensure the use reliability of each metasurface unit. The metasurface unit is a micro-nano structure, and the covering layer is arranged on at least one of the side surface of the metasurface unit away from the substrate and the side surface of the metasurface unit facing the substrate, so that the covering layer can effectively destroy and eliminate the resonance peak in the phase response of the metasurface unit, thereby realizing the smooth phase response curve of the metasurface structure without resonance, and making the device applied by the metasurface structure more insensitive to the tolerance during actual process processing. BRIEF DESCRIPTION OF DRAWINGS

[0017] The drawings accompanying the specification of the present application are used to provide a further understanding of the present application, and the schematic embodiments of the present application and the explanations thereof are used to explain the present application, and do not constitute an improper limitation on the present application. In the drawings:

[0018] Figure 1 A flow chart of a design method of a metasurface structure of one optional embodiment of the present application is shown;

[0019] Figure 2 A partial schematic view of the metasurface structure of the first embodiment of the present application is shown;

[0020] Figure 3 The transmittance curve and the phase response curve of the metasurface structure of the first embodiment of the present application without setting the covering layer are shown;

[0021] Figure 4 The transmittance curve and the phase response curve of the metasurface structure of the first embodiment of the present application with setting the covering layer of 20 nm are shown;

[0022] Figure 5The transmittance curve and the phase response curve of the super surface structure of the embodiment one of the utility model are shown in the figure.

[0023] Figure 6 The partial schematic view of the super surface structure of the embodiment two of the utility model is shown in the figure.

[0024] Figure 7 The transmittance curve and the phase response curve of the super surface structure of the embodiment two of the utility model are shown in the figure.

[0025] Figure 8 The transmittance curve and the phase response curve of the super surface structure of the embodiment two of the utility model are shown in the figure.

[0026] Among them, the above-mentioned drawing includes the following figure marks:

[0027] 10, substrate; 20, super surface unit; 30, cover layer. DETAILED DESCRIPTION

[0028] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The utility model will be described in detail below with reference to the drawings and in combination with embodiments.

[0029] It should be noted that, unless otherwise specified, all technical and scientific terms used in the present application have the same meaning as generally understood by those skilled in the art to which the present application belongs.

[0030] In the utility model, unless otherwise stated, the orientation words such as "up, down, top, bottom" are generally for the direction shown in the drawing, or for the component itself in the vertical, perpendicular or gravity direction; similarly, for the convenience of understanding and description, "inner, outer" refers to the inner and outer of the contour of each component itself, but the above-mentioned orientation words are not used to limit the utility model.

[0031] In order to solve the problem that the phase response of the existing super surface structure has resonance peak and thus affects the transmittance, the utility model provides a super surface structure.

[0032] As Figures 1 to 8As shown, the design method of the super surface structure includes the following steps: determining the materials of the substrate 10 and the super surface unit 20 on the substrate 10, and the shape of the super surface unit 20; determining the transmittance curve, or the phase response curve, or the transmittance curve and the phase response curve of the super surface unit 20 in 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 cover layer 30 to eliminate the resonance peak; and 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.

[0033] After determining the materials of the substrate 10 and the super surface unit 20 on the substrate 10, and the shape of the super surface unit 20, the application obtains the transmittance curve, or the phase response curve, or the transmittance curve and the phase response curve of the super surface unit 20 in the first size range through simulation, judges 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, adjusts the material and thickness of the cover layer 30 if there is a resonance peak in at least one of the transmittance curve and the phase response curve, and uses the cover layer 30 with reasonable material and thickness to eliminate the resonance peak in the curve to obtain the super surface structure with smooth phase response curve and transmittance curve without resonance peak, while avoiding the influence of the resonance peak on the light transmittance of the super surface structure and facilitating to ensure the high transmittance of the super surface structure.

[0034] In summary, in view of the problem that the resonance peak of the current super surface structure may cause the transmittance to decrease, the utility model provides a design method of the super surface structure, that is, the cover layer 30 is arranged on the super surface unit 20, the material and thickness of the cover layer 30 are determined through simulation, the condition for generating the resonance peak is destroyed, the smooth phase response curve is realized, the high transmittance is maintained, and the adverse influence of the tolerance caused by the processing technology on the transmittance of the super surface structure is avoided.

[0035] It should be noted that in the step of judging whether there is a resonance peak in at least one of the transmittance curve and / or the phase response curve, only the phase response curve can be judged, only the transmittance curve can be judged, or both the transmittance curve and the phase response curve can be judged. Figure 3 As shown in the reference Figure 3 The transmittance curve and the phase response curve of the super surface unit 20 in the first size range are shown in the reference

[0036] Specifically, the last step further includes a coating process, the coating process comprising: 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, which is relatively convenient to operate.

[0037] Specifically, in the step of determining the materials of the substrate 10 and the metasurface units 20 on the substrate 10, and the shape of the metasurface units 20, specifically comprising: determining the materials of the substrate 10 and the plurality of metasurface units 20 on the substrate 10 according to the working wavelength λ, wherein 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 glass; when the working wavelength is the wavelength of infrared light, the substrate 10 can be a single crystal silicon wafer. The material of the metasurface units 20 can be one of Si, αSi, TiO2, GaN and HfO2, which can be selected according to different working wavelengths. Commonly, 940nm working wavelength can select αSi as the material of the metasurface units 20.

[0038] Then, the shape of the metasurface units 20 is determined, the metasurface units 20 are micro-nano structures, at this time, the metasurface units 20 can be set to be columnar, and the cross-sectional shape of the columnar metasurface units 20 along the direction parallel to the substrate 10 includes one of a circle, an ellipse, a polygon, a circular ring and a cross; the polygon includes a square, a rectangle, a regular polygon. In actual application, the cross-sectional shape of the metasurface units 20 can be a polarization-insensitive structure such as a circle, a square, a circular ring, a cross and a regular polygon, or a polarization-sensitive structure such as an ellipse and a rectangle, which can be set according to actual conditions, and the polarization-insensitive structure is preferred.

[0039] Specifically, the above-mentioned step of determining the transmittance curve and / or the phase response curve of the metasurface units 20 in the first size range comprises:

[0040] First, the height of the metasurface units 20 is determined as the first height, at this time, a height can be randomly or manually selected as the first height.

[0041] Then, the scanning metasurface unit 20 scans the transmittance curve, or the phase response curve, or both the transmittance curve and the phase response curve in the first size range at the first height. In this step, the first size range at the first height needs to satisfy the phase coverage of 2π. The first height and the first size range can be adjusted to obtain a reasonable height and a reasonable first size range.At this time, the transmittance and phase response diagram obtained has two curves, one is the transmittance curve, and the other is the phase response curve. The horizontal axis represents the radius, the left vertical axis represents the transmittance, and the right vertical axis represents the phase. For reference, see Figure 3

[0042] It should be noted that when the metasurface unit 20 is in a cylindrical shape and the cross section is circular, the first size range is a first radius range, and the radius here is the radius of the circle. When the metasurface unit 20 is in a cuboid shape or other polygonal shape, and the cross section is a polygon, the first size range is a first edge length range, and the edge length here is the edge length of the polygon. It can also be understood that the first size range includes one of the first radius range and the first edge length range.

[0043] 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 400 nm and less than or equal to 1000 nm. That is, the first height is selected in the range of 400 nm-1000 nm, and the optimal height can be determined by simulation.

[0044] Specifically, the step of adjusting the material and thickness of the covering layer 30 includes:

[0045] First, a material different from the refractive index of the metasurface unit 20 is selected as the material of the covering layer 30. By setting the refractive index of the covering layer 30 different from the refractive index of the metasurface unit 20, the use reliability of the covering layer 30 is ensured, and the covering layer 30 has the effect of destroying the resonance peak. The material of the covering layer 30 can be one of SiO2 and SiN. By reasonably 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 not only effectively eliminates the resonance peak, but also has good chemical stability and mechanical strength, and is suitable for manufacturing optical sensors and optical communication equipment in harsh 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 due to environmental changes.

[0046] Then, a superstate unit 20 and a cover layer 30 are stacked to form a stacked model, that is, the cover layer 30 is stacked on the upper surface and / or the lower surface of the superstate unit 20 to form the stacked model. In this step, the stacked model includes at least one of the upper surface and the lower surface of the superstate unit 20 being covered with one or more cover layers 30. Specifically, the stacked model includes the superstate unit 20 and the cover layer 30 covering the surface of the superstate unit 20. More specifically, the upper surface of the superstate unit 20 refers to the surface of the superstate unit 20 away from the substrate 10, and the lower surface of the superstate unit 20 refers to the surface of the superstate unit 20 toward the substrate 10. One or more cover layers 30 can be arranged on only the surface of the superstate unit 20 away from the substrate 10, or on only the surface of the superstate unit 20 toward the substrate 10, or on both surfaces of the superstate unit 20. The cross section of the cover layer 30 along the direction parallel to the substrate 10 is the same as the surface shape of the superstate unit 20 and has the same area, which can reduce the process complexity and does not require additional exposure process, but only requires a film plating process to arrange the cover layer 30 on the superstate unit 20.

[0047] In the preferred embodiment of the present application, the stacked model is formed by covering the two surfaces of the superstate unit 20 with one cover layer 30, wherein the two surfaces refer to the surface of the superstate unit 20 toward the substrate 10 and the surface of the superstate unit 20 away from the substrate 10.

[0048] Then, the thickness of the cover layer 30 capable of eliminating the resonance peak is determined by rigorous coupled wave method scanning simulation. By reasonably selecting the thickness of the cover layer 30, the cover layer 30 at the thickness can effectively eliminate the resonance peak in the phase response curve, making the curve smoother and smoother, and avoiding the situation of reducing the transmittance caused by the resonance peak.

[0049] Specifically, the step of determining the thickness of the cover layer 30 capable of eliminating the resonance peak by scanning simulation using the rigorous coupled wave method comprises: scanning and simulating the transmittance curve, or the phase response curve, or the transmittance curve and the phase response curve of the metasurface unit 20 under multiple thicknesses of the cover layer 30 using the rigorous coupled wave method, and preferably scanning the transmittance curve and the phase response curve of the metasurface unit 20 under multiple thicknesses. Thus, multiple transmittance curves, or multiple phase response curves, or multiple sets of transmittance curves and phase response curves are obtained, each set 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 in the multiple transmittance curves, or the multiple phase response curves, or the multiple sets of transmittance curves and phase response curves is determined as the target graph; and the thickness of the cover layer 30 corresponding to the target graph is the final thickness. The thickness of the cover layer 30 here refers to the thickness of a single layer of the cover layer 30. By simulating to determine the optimal thickness of the cover layer 30, it is ensured that the resonance peak in the phase response graph of the metasurface unit 20 can be effectively eliminated after the cover layer 30 is arranged on the surface of the metasurface unit 20, and the performance stability of the metasurface unit 20 is ensured.

[0050] Specifically, in the step of determining the transmittance curve and / or the phase response curve corresponding to the minimum resonance peak or no resonance peak in the multiple transmittance curves and / or the multiple phase response curves as the target graph, one of the following is included:

[0051] The transmittance curve corresponding to the minimum resonance peak or no resonance peak in the multiple transmittance curves is determined as the target graph;

[0052] The phase response curve corresponding to the minimum resonance peak or no resonance peak in the multiple phase response curves is determined as the target graph;

[0053] A set of transmittance curve and phase response curve corresponding to the minimum resonance peak or no resonance peak in the multiple sets of transmittance curves and phase response curves is determined as the target graph.

[0054] In specific embodiments of the present application, the step of determining the thickness of the cover layer 30 capable of eliminating the resonance peak by scanning simulation using the rigorous coupled wave method comprises: scanning and simulating the transmittance curve and the phase response curve of the metasurface unit 20 under multiple thicknesses of the cover layer 30 using the rigorous coupled wave method, thereby obtaining a one-to-one correspondence between multiple transmittance curves and multiple phase response curves; determining the phase response curve corresponding to the minimum resonance peak or no resonance peak in the multiple phase response curves as the target graph; and taking the thickness of the cover layer 30 corresponding to the target graph as the final thickness.

[0055] Specifically, in the step of scanning the transmittance curve and / or phase response curve of the super surface unit 20 under multiple thicknesses of the cover layer 30 by using the rigorous coupled wave method, the step includes: determining an initial thickness h of the cover layer 30, the initial thickness h satisfies: h = λ / (10*n cover ), λ is the working wavelength, and 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 cover of the cover layer 30 to satisfy the above relationship, the material and the refractive index of the cover layer 30 can be reasonably controlled to meet the requirements, so that the function of destroying the resonance peak can be better guaranteed. Then, a simulation thickness range is determined according to the initial thickness h, the simulation thickness range is a range of 20 nm fluctuation above and below the center value of the initial thickness h, for example: the simulation thickness range = [initial thickness h-20nm, initial thickness h+20nm], and preferably the simulation thickness range = [initial thickness h-10nm, initial thickness h+10nm]. The simulation thickness range can be set according to actual conditions, as long as the simulation thickness range is close to the initial thickness h, which can quickly locate the optimal thickness. Then, the transmittance curve and the phase response curve of the super surface unit 20 under the simulation thickness range of the simulation cover layer 30 are scanned by using the rigorous coupled wave method, so as to determine the optimal thickness of the cover layer 30.

[0056] In summary, by reasonably selecting the material and thickness of the cover layer 30, the resonance peak can be effectively suppressed, the transmittance and phase control accuracy of the super surface structure in a specific wavelength range can be improved, which is of great significance for developing high-performance optical filters and optical switches. In the optical filter, the elimination of the resonance peak can realize a smoother transmission curve and phase curve, improve the selectivity and bandwidth performance of the filter, and make it play a key role in spectral analysis and optical communication systems.

[0057] In addition, the application also provides a super surface structure, the super surface structure is the super surface structure in the above method, the super surface structure includes a substrate 10, a super surface unit 20, and a cover layer 30, the super surface unit 20 is multiple, the multiple super surface units 20 are arranged in an array on one side surface of the substrate 10, at least part of the super surface units 20 are provided with the cover layer 30 on the side surface away from the substrate 10 and / or on the side surface of the super surface unit 20 facing the substrate 10, the cover layer 30 is different from the refractive index of the super surface unit 20, and the cover layer 30 is used for eliminating the resonance peak of the super surface unit 20.

[0058] By setting the substrate 10, the substrate 10 provides accommodation positions for the plurality of metasurface units 20, which is beneficial to ensure the use reliability of each metasurface unit 20. The metasurface unit 20 is a micro-nano structure, and the covering layer 30 is arranged 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 resonance peak, and making the device applied by the metasurface structure more insensitive to the tolerance in actual process processing.

[0059] Optionally, the covering layer 30 can be arranged on only the side surface of the metasurface unit 20 away from the substrate 10; the covering layer 30 can also be arranged on only the side surface of the metasurface unit 20 facing the substrate 10, that is, the covering layer 30 is arranged between the metasurface unit 20 and the substrate 10; or the covering layer 30 can be arranged on both the side surface of the metasurface unit 20 facing the substrate 10 and the side surface of the metasurface unit 20 away from the substrate 10, and the arrangement can be made according to actual needs.

[0060] Specifically, the number of layers of the covering layer 30 on the same side of the metasurface unit 20 is one or more. Specifically, one or more layers of the covering layer 30 can be arranged on only the side surface of the metasurface unit 20 away from the substrate 10; one or more layers of the covering layer 30 can also be arranged on only the side surface of the metasurface unit 20 facing the substrate 10; or one or more layers of the covering layer 30 can be arranged on both the side surface of the metasurface unit 20 facing the substrate 10 and the side surface of the metasurface unit 20 away from the substrate 10, and the arrangement can 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 the two sides is the same or different.

[0061] In one preferred embodiment of the present application, the covering layer 30 is arranged on both the side surface of the metasurface unit 20 facing the substrate 10 and the side surface of the metasurface unit 20 away from the substrate 10, and the number of layers of the covering layer 30 on the two sides of the metasurface unit 20 is one.

[0062] Specifically, when the covering layer 30 is arranged on both sides of the metasurface unit 20, the refractive index and the thickness of the covering layer 30 on the two sides of the metasurface unit 20 are the same or different. That is, the refractive index of the covering layer 30 on the two sides of the metasurface unit 20 is the same, and the thickness can be set to be the same or different, which can be determined according to the actual simulation effect, so as to ensure that the combination of the two layers of the covering layer 30 can effectively eliminate the resonance peak of the metasurface unit 20 where the covering layer 30 is located.

[0063] In addition, the cross section of the covering layer 30 along the direction parallel to the substrate 10 is the same as the surface shape of the metasurface unit 20 and has the same area. That is, the covering layer 30 is arranged only on the top surface and / or the bottom surface of the metasurface unit 20, and the side surface is not arranged. The covering layer 30 has the same shape and the same area as the surface on which the covering layer 30 is arranged, which can reduce the process complexity and does not need to increase the exposure process. Only the film plating process is needed to arrange the covering layer 30 on the surface of the metasurface unit 20.

[0064] Specifically, the covering layer 30 includes one of a SiO2 layer and a SiN layer. By reasonably 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 manufacturing optical sensors and optical communication equipment with harsh manufacturing environment. 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.

[0065] Specifically, the thickness of the covering layer 30 on the same side of the metasurface unit 20, the working wavelength of the metasurface structure, and the refractive index of the covering layer 30 satisfy a linear relationship. For example, the thickness h of the covering layer 30 can satisfy: h = λ / (10*n cover ), λ is the working wavelength, and n cover is the refractive index of the covering layer 30. By reasonably constraining the relationship among the thickness h of the single-layer covering layer 30, the working wavelength λ, and the refractive index n cover of the covering layer 30, the material and the refractive index of the covering layer 30 can be reasonably controlled to meet the requirements, so that the role of destroying the resonance peak can be better guaranteed.

[0066] Specifically, the height of the metasurface unit 20 is greater than or equal to 400 nm and less than or equal to 1000 nm. The optimal height can be determined by simulation. By reasonably planning the height range of the metasurface unit 20, it is beneficial to ensure that the size can meet the phase coverage of 2π. The metasurface unit 20 in 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.

[0067] In addition, the super surface unit 20 is in a columnar shape, and a cross-sectional shape of the columnar super surface unit 20 along a direction parallel to the substrate 10 includes one of a circular shape, an elliptical shape, a polygonal shape, a circular ring shape, and a cross shape. The polygonal shape includes a square shape, a rectangular shape, and a regular polygonal shape. In actual applications, the cross-sectional shape of the super surface unit 20 can be a polarization-insensitive structure such as a circular shape, a square shape, a circular ring shape, a cross shape, and a regular polygonal shape, or a polarization-sensitive structure such as an ellipse and a rectangle. The cross-sectional shape of the super surface unit 20 can be set according to actual conditions, and a polarization-insensitive structure is preferred. By reasonably planning the shape of the super surface unit 20, more complex light field regulation can be achieved, and the super surface unit 20 is suitable for high-precision beam deflection and focusing applications such as laser radars and optical microscopes. In a laser radar, the design of the columnar super surface unit 20 can achieve precise deflection and focusing of a laser beam, improve the detection accuracy and distance of the radar, and play an important role in the safe driving of an autonomous vehicle and the precise positioning of a drone.

[0068] In addition, the thickness of the covering layer 30 on the same side of the super surface unit 20 is greater than or equal to 10 nm and less than or equal to 55 nm. Preferably, when a layer of the covering layer 30 is arranged on both sides of the super surface unit 20, the thickness of the covering layer 30 on the same side of the super surface unit 20 is greater than or equal to 10 nm and less than or equal to 55 nm. In this way, the covering layer 30 within the thickness range can meet the function and role of destroying the resonance peak of the super surface structure, while ensuring the light transmittance of the super surface structure and the use reliability of the covering layer 30.

[0069] The method of the present application and the finally formed super surface structure will be described in detail below in conjunction with two specific embodiments.

[0070] Embodiment One

[0071] As shown in Figures 2 to 5 , the design method of the super surface structure of embodiment one and the super surface structure are described.

[0072] In this embodiment, the working wavelength λ of the super surface structure is 940 nm. The material of the substrate 10 is determined to be D263T, and the refractive index is 1.5137. The material of the super surface unit 20 is determined to be αSi, and the refractive index is 3.6. The shape of the super surface unit 20 is determined to be a cylindrical shape.

[0073] As shown in Figure 2As shown, the shape of the metasurface unit 20 of the metasurface structure of the present embodiment is shown, the metasurface unit 20 of the present embodiment is columnar and has a cylindrical structure, and has polarization-insensitive characteristics. That is, the cross-sectional shape of the metasurface unit 20 in a 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 applications, the metasurface units 20 on the substrate 10 are multiple and arranged in a periodic array.

[0074] In the present embodiment, the period of the metasurface unit 20 is 370 nm, the height is 500 nm, the first size range is a first radius range, the first radius range is greater than or equal to 40 nm and less than or equal to 150 nm, the first radius range needs to be determined in combination with the actual manufacturing process, and also needs to satisfy the period range and the phase difference of 2π. The scanning interval of the first radius is selected to be 0.5 nm, which can be adjusted according to actual conditions, in order to ensure that the resonant peak that may exist is not missed.

[0075] When the metasurface unit 20 is not provided with the cover layer 30, the transmittance and phase response curves of the metasurface unit 20 scanned by using the rigorous coupled wave algorithm are as shown in FIG. 3. Figure 3 Figure 3 In FIG. 3, 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 figure are the transmittance curve and the phase response curve, respectively. As can be seen from the figure, the metasurface unit 20 at this height can cover a phase difference of 2π in the scanned first size range, and the phase vertical axis is from 0 to 6. However, it can be seen that there is a resonant peak in the phase response curve near the radius of 138 nm, and the transmittance of the metasurface unit 20 drops to below 80%. Although the unit structure at the resonant peak position can be selected to avoid the resonant peak when designing, there is often a tolerance in the actual device processing, which causes the radius of the metasurface unit 20 to deviate from the design value. The metasurface unit 20 with a radius value near 138 nm that does not originally have a resonant peak may become a metasurface unit 20 with a resonant peak due to the tolerance. When the resonant peak occurs, not only the transmittance of the metasurface unit 20 is affected, but also the phase of the metasurface unit 20 is severely affected, thereby affecting the efficiency and function of the metasurface structure.

[0076] Then, the material of the cover layer 30 is selected to be SiO2, and the refractive index is 1.4896. A cover layer 30 is arranged on the side surface of the metasurface unit 20 away from the substrate 10 and the side surface facing the substrate 10, so that the metasurface unit 20 and the cover layers 30 on both sides form a superposition model. And the thicknesses of the cover layers 30 on the upper and lower surfaces of the metasurface unit 20 are controlled to be equal. Then, the transmittance curve and the phase response curve of the metasurface unit 20 with the cover layer 30 at multiple thicknesses are simulated by using the rigorous coupled wave method. Figure 4 ​The transmittance curve and the phase response curve of the single-layer cover layer 30 on the two side surfaces of the metasurface unit 20 when the thickness of the single-layer cover layer 30 is 20 nm are shown. It can be seen from the transmittance curve and the phase response curve that the strength of the resonance peak is obviously weakened. Figure 5 The transmittance curve and the phase response curve of the single-layer cover layer 30 on the two side surfaces of the metasurface unit 20 when the thickness of the single-layer cover layer 30 is 50 nm 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 50 nm. Subsequently, the cover layer 30 with the optimal thickness can be set on the two side surfaces of each metasurface unit 20 through a coating process, and the metasurface structure of the embodiment is completed. The device constructed by using the metasurface structure has better tolerance to tolerances.

[0077] Embodiment Two

[0078] As shown in Figures 6 to 8 , the design method of the metasurface structure of embodiment two and the metasurface structure are described.

[0079] In this embodiment, the working wavelength λ of the metasurface structure is 940 nm. It is determined that the material of the substrate 10 is D263T, and the refractive index is 1.5137. The material of the metasurface unit 20 is αSi, and the refractive index is 3.6. It is determined that the shape of the metasurface unit 20 is a cuboid.

[0080] As shown in Figure 6 , the shape of the metasurface unit 20 of the metasurface structure of this embodiment is shown. The metasurface unit 20 of this embodiment is in the form of a column, specifically a quadrangular prism, and has polarization-insensitive characteristics. The cross-sectional shape of the metasurface unit 20 in the direction parallel to the substrate 10 is a square. For ease of understanding, only one metasurface unit 20 is shown on the substrate 10 in the figure, but in actual application, the metasurface units 20 on the substrate 10 are multiple and arranged in a periodic array.

[0081] In this embodiment, the period of the metasurface unit 20 is 370 nm, and the height is 520 nm. The first size range is a first side length range, and the first side length range is greater than or equal to 80 nm and less than or equal to 300 nm. 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 to be 0.5 nm, which can be adjusted according to actual conditions, in order to ensure that no resonance peak is missed.

[0082] When the metasurface unit 20 is not provided with the cover layer 30, the phase response curve obtained by scanning using the rigorous coupled wave algorithm is as shown in Figure 7 Figure 7 ​In 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 curves in the figure are the transmittance curve and the phase response curve, respectively. As can be seen from the figure, the metasurface unit 20 at this height can cover a phase difference of 2π in the scanned first dimension range, and the phase vertical axis is from 0 to 6. However, it can be seen that there is a resonance peak in the phase response curve near the side length of 236 nm, although the transmittance does not decrease much, but both the transmittance and the phase have a sudden change. Although the designer can choose to avoid the metasurface unit 20 at the resonance peak, in actual device processing, there are often tolerances, which cause the side length of the metasurface unit 20 to deviate from the design value. The metasurface unit 20 with a side length near 236 nm that does not have a resonance peak may become one with a resonance peak due to tolerances. 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 is severely affected, thereby affecting the efficiency and function of the device.

[0083] Then, the material of the cover layer 30 is selected to be SiO2, and the refractive index is 1.4896. A cover layer 30 is arranged on the side surface of the metasurface unit 20 away from the substrate 10 and the side surface 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 thicknesses of the cover layers 30 on the upper and lower surfaces of the metasurface unit 20 are not equal.

[0084] Then, the transmittance curve and the phase response curve of the metasurface unit 20 with the cover layer 30 at multiple thicknesses are simulated by using the rigorous coupled wave method. Figure 8 The transmittance curve and the phase response curve when the thickness of the cover layer 30 on the lower surface of the metasurface unit 20 is 10 nm and the thickness of the cover layer 30 on the upper surface of the metasurface unit 20 is 25 nm are shown. As can be seen from the figure, the resonance peak has been completely eliminated. Subsequently, the cover layer 30 with the optimal thickness can be arranged on both side surfaces of each metasurface unit 20 by a plating process, and the metasurface structure of this embodiment is completed. The device constructed by using the metasurface structure has better tolerance to tolerances.

[0085] Obviously, the above-described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the scope of protection of the present application.

[0086] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments in accordance with the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, devices, components and / or combinations thereof, but do not preclude the presence or addition of one or more other features, steps, operations, devices, components and / or combinations thereof.

[0087] It should be noted that the terms "first", "second", and the like, herein do not necessarily have an either chronological or spatial relation to each other, but are used merely to distinguish a different single implementation from another unless specifically indicated otherwise. It should be understood that the use of the term "or" in the context of describing example embodiments is used to mean a selection of one or more of the alternatives. For example, the phrase "A / B or C" is satisfied by any one of the following alternatives: [A and B] or [C].

[0088] The preferred embodiments of the present application have been described above with the specific embodiments. The present application is not limited to the above embodiments. It will be appreciated by those skilled in the art that any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall fall within the scope of the present application.

Claims

1. A metasurface structure, characterized in that: The metasurface structure comprises: 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) is provided on at least a portion of the 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) has a different refractive index from that of the metasurface unit (20); and the covering layer (30) is used to eliminate the resonance peak of the metasurface unit (20).

2. The metasurface structure according to claim 1, wherein The covering layer (30) is provided on the surface of each super surface unit (20) on the side away from the substrate (10) and on the surface of the side facing the substrate (10).

3. The metasurface structure according to claim 2, wherein: The cover layers (30) on both side surfaces of the metasurface unit (20) have the same refractive index and the same or different thicknesses.

4. The metasurface structure according to claim 1, wherein The number of layers of the covering layer (30) on the same side of the super surface unit (20) is one or more layers.

5. The metasurface structure according to claim 1, wherein: The cross section of the covering layer (30) in a 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.

6. The metasurface structure according to claim 1, wherein: A linear relationship is satisfied among 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).

7. The metasurface structure according to any one of claims 1 to 6, characterized in that The height of the super surface unit (20) is greater than or equal to 400 nm and less than or equal to 1000 nm.

8. The metasurface structure according to any one of claims 1 to 6, characterized in that The super surface unit (20) is columnar, and the cross-sectional shape of the columnar super surface unit (20) in a direction parallel to the substrate (10) includes one of a circle, an ellipse, a polygon, a ring, and a cross.

9. The metasurface structure according to any one of claims 1 to 6, characterized in that The thickness of the cover layer (30) on the same side of the super surface unit (20) is greater than or equal to 10 nm and less than or equal to 55 nm.

10. The metasurface structure according to any one of claims 1 to 6, characterized in that The cover layer (30) includes one of a SiO2 layer and a SiN layer.

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