Geometric phase-based long-wave infrared arsenic selenide super lens and design method thereof

Abstract

The invention discloses a geometric phase-based long-wave infrared arsenic selenide superlens and a design method thereof, the superlens is composed of a substrate and an optical metasurface arranged on the substrate, and the optical metasurface is composed of a plurality of elliptic cylinders which rotate by an angle alpha and are arranged periodically. The method comprises the following steps: determining structural parameters of a microstructure unit; rotating the microstructure units by an angle alpha; according to the relation between the geometric phase and the alpha angle; adjusting the rotation angle alpha of the microstructure unit to enable the angle alpha to meet the geometric phase distribution of the microstructure unit, and determining the angle alpha of the microstructure unit; and forming a metasurface array according to the alpha angles of the microstructure units and preset periodic arrangement, and arranging the metasurface array on the upper surface of the substrate to obtain the super lens. According to the invention, high-efficiency and high-resolution imaging can be realized under long-wave infrared. The long-wave infrared arsenic selenide super lens based on the geometric phase and the design method thereof can be widely applied to the technical field of super lens design.

Description

Technical Field

[0001] The present invention relates to the technical field of superlens design, and in particular to a long-wave infrared arsenic selenide superlens based on geometric phase and a design method thereof. Background Art

[0002] Since the introduction of the metalens, many researchers have made many excellent research results because of its constituent micro-nanostructure units' ability to freely regulate the response of electromagnetic waves and its adaptability to micro-nanoprocessing technology. However, most metalenses work in the visible light band, and there are few reports on the research of metalenses in the long-wave infrared band. It is still a huge challenge to design a metalens that can work in the long infrared band to achieve high polarization conversion efficiency, high numerical aperture and high focusing efficiency, and at the same time have a large numerical aperture (high resolution) and high focusing efficiency. In addition, the optical metasurface arrays of most metalenses use a variety of different types of complex-shaped micro-nanostructure units, which will increase the difficulty of the processing technology. Even for simple rectangular nanocolumns, the angular problems will reduce the manufacturing tolerance during the processing. Summary of the invention

[0003] In order to solve the above technical problems, the purpose of the present invention is to provide a long-wave infrared arsenic selenide superlens based on geometric phase and a design method thereof, which can achieve high-efficiency and high-resolution imaging in long-wave infrared.

[0004] The first technical solution adopted by the present invention is: a long-wave infrared arsenic selenide superlens based on geometric phase, the superlens is composed of a substrate and an optical supersurface arranged on the substrate, the optical supersurface is composed of a plurality of elliptical cylinders rotated at an angle α and arranged periodically, wherein:

[0005] The substrate is used to support the optical metasurface;

[0006] The optical metasurface is used to adjust the amplitude, phase and polarization parameters of the incident light;

[0007] The elliptical cylinder is used to optimize the adjustment result of the optical metasurface.

[0008] Furthermore, the substrate and the optical metasurface are both made of As2Se3 chalcogenide glass.

[0009] Furthermore, the rotation angle α ranges from 0° to 180°.

[0010] Furthermore, the major semi-axis of the elliptical cylinder is a, the minor semi-axis of the elliptical cylinder is b, the height of the elliptical cylinder is h, and the arrangement period of adjacent elliptical cylinders is p.

[0011] The second technical solution adopted by the present invention is: a design method of a long-wave infrared arsenic selenide superlens based on geometric phase, comprising the following steps:

[0012] Determining structural parameters of the microstructure unit according to the shape of the microstructure unit of the optical metasurface, wherein the structural parameters include a major semi-axis, a minor semi-axis, a height, and a period;

[0013] According to the structural parameters of the microstructure unit, the microstructure unit is rotated by an angle α;

[0014] Determining the geometric phase distribution of the microstructure unit according to the relationship between the geometric phase and the angle α;

[0015] Based on the working parameters of the optical metasurface, adjusting the rotation angle α of the microstructure unit so that the angle α satisfies the geometric phase distribution of the microstructure unit, and determining the angle α of the microstructure unit;

[0016] According to the α angle of the microstructure unit, a super surface array is formed according to a preset periodic arrangement and arranged on the upper surface of the substrate to obtain a super lens.

[0017] Further, the step of determining the structural parameters of the microstructure unit according to the shape of the microstructure unit of the optical metasurface specifically includes:

[0018] Determining the shape of the microstructure unit of the optical metasurface according to the polarization conversion efficiency and geometric transmittance of the microstructure unit of the optical metasurface and taking into account the manufacturing tolerance;

[0019] Based on the shape of the microstructure unit of the optical metasurface, the major semi-axis and the minor semi-axis of the microstructure unit are fixed, and the height and period of the microstructure unit are scanned to obtain a first transmittance result of the microstructure unit;

[0020] Based on the shape of the microstructure unit of the optical metasurface, the height and period of the microstructure unit are fixed, and the major semi-axis and the minor semi-axis of the microstructure unit are scanned to obtain a second transmittance result of the microstructure unit;

[0021] The structural parameters of the microstructure unit are determined by combining the first transmittance result and the second transmittance result.

[0022] Furthermore, the scanning range of the long semi-axis of the microstructure unit is a∈[1.2 μm, 1.7 μm], and the scanning range of the short semi-axis of the microstructure unit is b∈[0.3 μm, 0.8 μm].

[0023] Furthermore, the working parameters of the optical metasurface include band, wavelength, focal length and radius, wherein the band l∈[8μm, 14μm], the wavelength λ=8-14μm, the focal length F=60μm, and the radius R=77.5μm.

[0024] Furthermore, the expression of the geometric phase distribution of the microstructure unit is specifically as follows:

[0025]

[0026] In the above formula, φ(·) represents the geometric phase distribution of the microstructure unit, λ represents the operating wavelength, x and y represent the coordinates of the center point of the elliptical cylinder of the microstructure unit, and F represents the focal length.

[0027] Further, the expression of the angle α of the microstructure unit is specifically as follows:

[0028]

[0029] In the above formula, α(·) represents the α angle of the microstructure unit, λ represents the working wavelength, x and y represent the coordinates of the center point of the elliptical cylinder of the microstructure unit, and F represents the focal length.

[0030] The beneficial effects of the method and system of the present invention are as follows: the present invention determines the shape and structural parameters of the micro-nano structural unit by numerically analyzing the micro-nano structural unit, and determines the rotation angle of the elliptical cylinder at different positions by utilizing the relationship that the size of the geometric phase is twice the rotation angle α, so that the manufactured superlens can achieve low-dispersion, high-efficiency focusing and high-quality imaging in the long-wave infrared band, and can achieve high-efficiency and high-resolution imaging in the long-wave infrared. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a structural schematic diagram of a long-wave infrared arsenic selenide superlens based on geometric phase of the present invention;

[0032] Figure 2 It is a schematic diagram of the process steps of a design method of a long-wave infrared arsenic selenide superlens based on geometric phase of the present invention;

[0033] Figure 3 It is a schematic diagram of the relationship between the structural parameters and transmittance of the micro-nano structural unit provided by a specific embodiment of the present invention and the conversion efficiency of the micro-nano structural unit with determined structural parameters in the long-wave infrared band;

[0034] Figure 4 is a schematic diagram of the geometric phase distribution result corresponding to the change of the rotation angle of the elliptical cylinder provided by a specific embodiment of the present invention;

[0035] Figure 5Schematic diagram of the electric field intensity in the xz plane corresponding to the superlens and the electric field intensity in the xy plane corresponding to the superlens provided by a specific embodiment of the present invention;

[0036] Figure 6 It is a schematic diagram of the electric field intensity distribution of the superlens in the z direction when x=0, the electric field intensity distribution in the x direction at the focus of the superlens when y=0, and the electric field intensity distribution in the y direction at the focus of the superlens when x=0 provided by a specific embodiment of the present invention. DETAILED DESCRIPTION

[0037] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The step numbers in the following embodiments are only provided for the convenience of explanation and description, and the order between the steps is not limited in any way. The execution order of each step in the embodiment can be adaptively adjusted according to the understanding of those skilled in the art.

[0038] First of all, it should be noted that a metasurface is an optical device composed of subwavelength-sized, anisotropic or isotropic micro-nano structures arrayed at subwavelength intervals on a substrate. It can flexibly and effectively control the phase, amplitude, polarization and other characteristics of electromagnetic waves through artificial design, so it has been applied in holographic imaging, vortex light generators, beam shaping, etc. The focusing metasurface, that is, the metalens, can be realized by realizing the 2π phase change of electromagnetic waves through the micro-nanostructures in the metasurface, so the metalens is made of optical elements that focus light on the metasurface. Specifically, the geometric dimensions and rotation angles of the subwavelength-scale micro-nanostructures are used to arbitrarily control the phase 0-2π, and arrange them according to certain rules to achieve the focusing of light and imaging of the scene. The metalens, also known as the super-structure lens, has the characteristics of lightness, miniaturization and multi-functional integration. It has been proven that it can gradually replace the bulky and expensive traditional imaging systems, especially in the long-wave infrared band, where the advantages of lightness and thinness of the metalens are more obvious.

[0039] Chalcogenide glasses are amorphous materials formed based on chalcogen elements. They have the advantages of excellent infrared transparency, good thermal optical properties, and low manufacturing cost. Chalcogenide glasses have good application scenarios in optical devices in the long infrared band due to their spectral transmittance range of long-wave infrared. Among them, arsenic selenide (As2Se3) is an amorphous compound. The transmittance range of selenium-based materials basically covers the entire long infrared window and has excellent infrared anti-reflection effect. At the same time, arsenic selenide also has a high nonlinear refractive index, so it has important application value in optical devices.

[0040] The core function of the metalens relies on phase control. There are several methods of phase control: resonant phase control, geometric phase control, and propagation phase control. The geometric phase is only related to the in-plane rotation angle of the micro-nanostructure. Therefore, the metalens constructed by the geometric phase has a wide spectrum, and geometric phase control is also the most widely used phase control mechanism.

[0041] Based on this, the embodiment of the present invention proposes a metalens based on geometric phase and capable of achieving high polarization conversion efficiency, high numerical aperture and high focusing efficiency in the long-wave infrared band. The micro-nano structure unit is numerically analyzed by using the finite difference time domain method (FDTD) to determine its shape and structural parameters. The rotation angle of the elliptical cylinder at different positions is determined by using the relationship that the size of the geometric phase is 2 times the rotation angle α, so that the manufactured metalens can achieve low dispersion, high efficiency focusing and high quality imaging in the long-wave infrared band, which provides a reference for geometric phase type high efficiency focusing and high quality imaging. In addition, the micro-nano structure in the present design has a simple shape and is easy to process and prepare.

[0042] Reference Figure 1 The present invention provides a long-wave infrared arsenic selenide superlens based on geometric phase, which is composed of a substrate and an optical supersurface arranged on the substrate, and the optical supersurface is composed of a plurality of elliptical cylinders rotated by an angle α and arranged periodically, wherein:

[0043] The substrate is used to support the optical metasurface;

[0044] Optical metasurfaces are used to adjust the amplitude, phase, and polarization parameters of incident light;

[0045] Elliptical cylinders are used to optimize the tuning results of optical metasurfaces.

[0046] In this embodiment, if Figure 1 As shown, Figure 1 (a) is a schematic diagram of the three-dimensional structure of the substrate and optical metasurface of the long-wave infrared arsenic selenide metalens with high numerical aperture and high focusing efficiency based on geometric phase of the present invention; Figure 1(b) is a schematic diagram of the three-dimensional structure of the micro-nano structure unit and a top view of the micro-nano structure unit, including a substrate and an optical metasurface arranged on the substrate, wherein the substrate is used to support the optical metasurface on the substrate, and the optical metasurface on the substrate can realize flexible regulation of parameters such as the amplitude, phase and polarization of the incident light; the metasurface includes a number of elliptical cylinders rotated by an angle α and arranged periodically, and the elliptical cylinder design provides a wealth of regulation means for the metasurface, enabling it to optimize the regulation ability of light in multiple dimensions, and the elliptical cylinders include elliptical cylinders with the same height, the same major semi-axis and the same minor semi-axis, wherein the parameters of the geometric dimensions of the elliptical cylinders include the major semi-axis a, the minor semi-axis b and the height h, wherein the elliptical cylinders are uniformly arranged in an array, the height is set to be the same, and the arrangement period of adjacent elliptical cylinders is also set to be the same, the substrate and the optical metasurface on the substrate are both made of As2Se3 chalcogenide glass, the angle α of the elliptical cylinder rotation ranges from 0° to 180°, and the metasurface is composed of a periodic arrangement of elliptical cylinders with the same semi-major axis a, the same minor semi-axis b and the same height h.

[0047] Among them, the substrate and the optical metasurface are both made of As2Se3 chalcogenide glass, the rotation angle α ranges from 0° to 180°, the major semi-axis of the elliptical cylinder a=1.5μm, the minor semi-axis of the elliptical cylinder b=0.8μm, the height of the elliptical cylinder h=5μm, and the arrangement period of adjacent elliptical cylinders is p=3.645μm.

[0048] It should also be noted that the elliptical columns are arranged uniformly and periodically in a circular array, with a height h of 5 μm and an arrangement period p of adjacent elliptical columns of 3.645 μm. The regular arrangement is conducive to achieving low dispersion. The material used for the elliptical columns is As2Se3 chalcogenide glass, which has the advantages of high transmittance, more moderate refractive index and smaller dispersion.

[0049] like Figure 3 As shown in (a), the micro-nano structure unit is numerically analyzed using the time-domain finite difference method, and the major semi-axis a and the minor semi-axis b of the elliptical cylinder are optimized by parameter scanning, and the structural parameters with high transmittance are selected. As a preferred embodiment, the major semi-axis a of the elliptical cylinder is 1.5 μm, and the minor semi-axis b is 0.8 μm. Figure 3 As shown in (b), after determining the structural parameters of the elliptical cylinder, scanning its major semi-axis a and minor semi-axis b, it can be seen that the elliptical cylinder has a very high polarization conversion efficiency in the long-wave infrared band.

[0050] Reference Figure 2 , a design method of a long-wave infrared arsenic selenide superlens based on geometric phase, comprising the following steps:

[0051] S100, determining structural parameters of the microstructure unit according to the shape of the microstructure unit of the optical metasurface, where the structural parameters include a major semi-axis, a minor semi-axis, a height, and a period;

[0052] Specifically, the shape of the microstructure unit of the optical metasurface is determined according to the polarization conversion efficiency and the transmittance of the geometric size of the microstructure unit of the optical metasurface, and taking into account the manufacturing tolerance; based on the shape of the microstructure unit of the optical metasurface, the major semi-axis and the minor semi-axis of the microstructure unit are fixed, and the height and the period of the microstructure unit are scanned to obtain a first transmittance result of the microstructure unit; based on the shape of the microstructure unit of the optical metasurface, the height and the period of the microstructure unit are fixed, and the major semi-axis and the minor semi-axis of the microstructure unit are scanned to obtain a second transmittance result of the microstructure unit; and the structural parameters of the microstructure unit are determined by combining the first transmittance result and the second transmittance result.

[0053] The scanning range of the long semi-axis of the microstructure unit is a∈[1.2 μm, 1.7 μm], and the scanning range of the short semi-axis of the microstructure unit is b∈[0.3 μm, 0.8 μm].

[0054] In this embodiment, the shape of the microstructure unit of the optical metasurface is determined to be an ellipse based on the polarization conversion efficiency of the microstructure unit, the transmittance of the geometric size, and taking into account the problem of reducing the manufacturing tolerance; the major semi-axis a and the minor semi-axis b of the elliptical cylinder are fixed, the height h and the period p of the elliptical cylinder are scanned, and the height h and the lattice constant (period) p of each microstructure unit are determined according to the transmittance results obtained by the scan, and then the major semi-axis a and the minor semi-axis b of the microstructure unit are scanned, and the structural parameters of the final micro-nano unit are determined by the transmittance results obtained by the scan.

[0055] S200, rotating the microstructure unit by an angle α according to the structural parameters of the microstructure unit;

[0056] Specifically, after determining the structural parameters of the microstructure unit, namely the major semi-axis a, the minor semi-axis b, the height h and the period p, the microstructure unit is rotated by an angle α to achieve full phase control of 0-2π.

[0057] S300, determining the geometric phase distribution of the microstructure unit according to the relationship between the geometric phase and the angle α;

[0058] Specifically, since the geometric phase is only related to the rotation angle of the micro-nanostructure, it is only necessary to rotate the angle of the nanocolumn by π to achieve a phase change of 2π, and determine the phase distribution that the elliptical columns at different positions in the superlens need to satisfy. This phase distribution is the geometric phase distribution.

[0059] S400, based on the working parameters of the optical metasurface, adjusting the rotation angle α of the microstructure unit so that the angle α satisfies the geometric phase distribution of the microstructure unit, and determining the angle α of the microstructure unit;

[0060] Specifically, according to the working band of the long-wave infrared arsenic selenide superlens determined by demand, the screened elliptical cylinder is rotated until its geometric phase satisfies the geometric phase distribution, and the rotation angle α is twice its geometric phase, and the rotation angle of the elliptical cylinder at different positions is determined.

[0061] like Figure 4 As shown, Figure 4 When the geometric dimensions of the elliptical cylinder are a=1.5μm, b=0.8μm, and h=5μm, as the rotation angle of the elliptical cylinder changes, the corresponding geometric phase distribution result diagram will show that the elliptical cylinder that determines the structural parameters is rotated by π, and the phase change is completely covered by 2π, that is, the size of the geometric phase is equal to twice the in-plane rotation angle.

[0062] The working parameters of the optical metasurface include band, wavelength, focal length and radius, where band l∈[8μm, 14μm], wavelength λ=8-14μm, focal length F=60μm, radius R=77.5μm, and then according to The calculated numerical aperture (NA) is 0.747.

[0063] In this embodiment, it is further necessary to explain that the phase distribution required by the metalens is:

[0064]

[0065] In the above formula, φ(·) represents the geometric phase distribution of the microstructure unit, λ represents the operating wavelength, x and y represent the coordinates of the center point of the elliptical cylinder of the microstructure unit, and F represents the focal length.

[0066] From the geometric phase, we know that the phase shift of φ(x, y) = 2α(x, y) can be achieved by rotating the elliptical cylinder at a given (x, y) coordinate by an angle of α(x, y). Therefore, it is obtained that each elliptical cylinder (x, y) is rotated by an angle, and the expression is:

[0067]

[0068] In the above formula, α(·) represents the α angle of the microstructure unit, λ represents the working wavelength, x and y represent the coordinates of the center point of the elliptical cylinder of the microstructure unit, and F represents the focal length.

[0069] S500, according to the α angle of the microstructure unit, a metasurface array is formed according to a preset periodic arrangement and arranged on the upper surface of the substrate to obtain a metalens.

[0070] Specifically, the elliptical cylinder is rotated by a corresponding angle α, and then arranged periodically to form a metasurface array, and finally the metasurface array is arranged on a substrate to obtain a superlens.

[0071] Finally, FDTD Solutions software was used to analyze the circularly polarized light with a wavelength of λ = 10 μm incident on Figure 1 (a) The designed metalens is simulated and the results are shown in Figure 5 shown.

[0072] The circularly polarized light is incident on the superlens along the positive direction of the z-axis, and after interacting with the micro-nanostructure, a cross-circularly polarized light convergence wavefront is formed, where Figure 5 (a) is the distribution of the output electric field of the superlens on the xz plane. Figure 5 (b) is the output electric field distribution of the focal plane (z=60 μm) of the metalens focus. It can be seen from the figure that the energy of the focused light spot is concentrated and the designed metalens has good focusing characteristics.

[0073] like Figure 6 (a) is the electric field intensity distribution diagram in the z direction when x=0. It can be seen from the figure that the electric field intensity energy peak is located at 59.7μm, which is only 0.5% different from the designed focal length F=60μm, achieving an almost consistent effect. Figure 6 (b) is the electric field intensity distribution diagram in the x direction at the focal plane y=0, Figure 6 (c) is the electric field intensity distribution diagram in the y direction at the focal plane x=0. The simulated full width at half maximum (FWHM) of the electric field intensity curve is measured and the FWHM value is obtained to be 6.12 μm. The calculated Rayleigh criterion value is compared with the FWHM of the designed superlens. The results show that the designed superlens can achieve near diffraction limit focusing and realize high-resolution imaging.

[0074] Finally, in order to characterize the focusing ability of the metalens, the focusing efficiency is defined as the ratio of the power within a circle with a diameter of 3×FWHM at the focus to the total power transmitted through the metalens. The electric field intensity distribution of the focal plane and the output surface obtained by simulation can obtain a focusing efficiency of up to 79%.

[0075] In summary, the embodiment of the present invention is based on the geometric phase of the metalens design method, and the circular polarized light is regulated by rotating the control unit structure by an angle of α. The metalens includes a substrate and an optical metasurface arranged on the substrate. The substrate and the metasurface are both made of As2Se3 chalcogenide glass. The metasurface is composed of a periodic arrangement of elliptical cylinders. The unit structure is simple and can reduce the requirements for processing conditions. The metalens constructed by the present invention is intended to solve the problem that the long-wave infrared metalens cannot have both high numerical aperture and high focusing efficiency at the same time, and the large-area experimental preparation tolerance is low.

[0076] Compared with the prior art, the embodiments of the present invention have the following advantages:

[0077] 1) As2Se3 chalcogenide glass is used to prepare the superlens. As2Se3 chalcogenide glass has the advantages of excellent infrared transmittance, small dispersion and low manufacturing cost, which effectively reduces the reflection and absorption loss in the long-wave infrared band. It is a preferred material for low-cost cooling infrared optical systems and long-wave infrared imaging systems.

[0078] 2) The phase is modulated based on the principle of geometric phase. The geometric phase is only related to the rotation angle of the micro-nano structure. The phase change of 2π can be achieved by rotating the angle of the nanocolumn by π. The shape of the micro-nano structure unit of the present invention adopts an elliptical column. The micro-nano structure unit has the same structural parameters. The structure of the manufactured super lens device is simple. Therefore, the super lens of the present invention has the advantages of simple processing technology and high manufacturing tolerance. And the super lens of the present invention can achieve the achromatic effect in the long-wave infrared band with only one layer of simple micro-nano structure.

[0079] 3) A long-wave infrared arsenic selenide superlens with high numerical aperture and high focusing efficiency is designed. The micro-nano structural unit (elliptical cylinder) is numerically analyzed using the time-domain finite difference method to determine the structural parameters of high transmittance and high polarization conversion efficiency. Then, according to the geometric phase distribution that the elliptical cylinder at different positions needs to satisfy, the rotation angle of the elliptical cylinder required at different positions is determined. The superlens designed by the present invention has the performance of high numerical aperture and high focusing efficiency, which is conducive to achieving high-efficiency and high-resolution imaging in the long-wave infrared.

[0080] The contents of the above method embodiments are all applicable to the present system embodiments. The functions specifically implemented by the present system embodiments are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0081] The above is a specific description of the preferred implementation of the present invention, but the invention is not limited to the embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A long-wave infrared arsenic selenide superlens based on geometric phase, characterized in that: The metalens is composed of a substrate and an optical metasurface arranged on the substrate, wherein the optical metasurface is composed of a plurality of elliptical cylinders rotated at an angle α and arranged periodically. Composition, of which: The substrate is used to support the optical metasurface; The optical metasurface is used to adjust the amplitude, phase and polarization parameters of the incident light; The elliptical cylinder is used to optimize the adjustment result of the optical metasurface.

2. According to claim 1, a long-wave infrared arsenic selenide superlens based on geometric phase, characterized in that: The substrate and the optical metasurface are both made of As2Se3 chalcogenide glass.

3. According to claim 2, a long-wave infrared arsenic selenide superlens based on geometric phase, characterized in that: The range of the rotation angle α is 0° to 180°.

4. According to claim 3, a long-wave infrared arsenic selenide superlens based on geometric phase, characterized in that: The major semi-axis of the elliptical cylinder is a, the minor semi-axis of the elliptical cylinder is b, the height of the elliptical cylinder is h, and the arrangement period of adjacent elliptical cylinders is p.

5. A design method for a long-wave infrared arsenic selenide superlens based on geometric phase, characterized in that: The following steps are involved: Determining structural parameters of the microstructure unit according to the shape of the microstructure unit of the optical metasurface, wherein the structural parameters include a major semi-axis, a minor semi-axis, a height, and a period; According to the structural parameters of the microstructure unit, the microstructure unit is rotated by an angle α; Determining the geometric phase distribution of the microstructure unit according to the relationship between the geometric phase and the angle α; Based on the working parameters of the optical metasurface, adjusting the rotation angle α of the microstructure unit so that the angle α satisfies the geometric phase distribution of the microstructure unit, and determining the angle α of the microstructure unit; According to the α angle of the microstructure unit, a super surface array is formed according to a preset periodic arrangement and arranged on the upper surface of the substrate to obtain a super lens.

6. The design method of a long-wave infrared arsenic selenide superlens based on geometric phase according to claim 5 is characterized in that: The step of determining the structural parameters of the microstructure unit according to the shape of the microstructure unit of the optical metasurface specifically includes: Determining the shape of the microstructure unit of the optical metasurface according to the polarization conversion efficiency and geometric transmittance of the microstructure unit of the optical metasurface and taking into account the manufacturing tolerance; Based on the shape of the microstructure unit of the optical metasurface, the major semi-axis and the minor semi-axis of the microstructure unit are fixed, and the height and period of the microstructure unit are scanned to obtain a first transmittance result of the microstructure unit; Based on the shape of the microstructure unit of the optical metasurface, the height and period of the microstructure unit are fixed, and the major semi-axis and the minor semi-axis of the microstructure unit are scanned to obtain a second transmittance result of the microstructure unit; The structural parameters of the microstructure unit are determined by combining the first transmittance result and the second transmittance result.

7. The design method of a long-wave infrared arsenic selenide superlens based on geometric phase according to claim 6 is characterized in that: The scanning range of the long semi-axis of the microstructure unit is a∈[1.2 μm, 1.7 μm], and the scanning range of the short semi-axis of the microstructure unit is b∈[0.3 μm, 0.8 μm].

8. The design method of a long-wave infrared arsenic selenide superlens based on geometric phase according to claim 7 is characterized in that: The working parameters of the optical metasurface include band, wavelength, focal length and radius, wherein the band l∈[8μm, 14μm], the wavelength λ=8-14μm, the focal length F=60μm, and the radius R=77.5μm.

9. The design method of a long-wave infrared arsenic selenide superlens based on geometric phase according to claim 8, characterized in that: The expression of the geometric phase distribution of the microstructure unit is specifically as follows: In the above formula, φ(·) represents the geometric phase distribution of the microstructure unit, λ represents the operating wavelength, x and y represent the coordinates of the center point of the elliptical cylinder of the microstructure unit, and F represents the focal length.

10. The design method of a long-wave infrared arsenic selenide superlens based on geometric phase according to claim 9, characterized in that: The expression of the angle α of the microstructure unit is specifically as follows: In the above formula, α(·) represents the α angle of the microstructure unit, λ represents the working wavelength, x and y represent the coordinates of the center point of the elliptical cylinder of the microstructure unit, and F represents the focal length.

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