Vector vortex beam hybrid array generation method based on metasurface

Abstract

A method for generating a vector vortex beam hybrid array based on a super-structure surface is characterized by comprising the following steps: S1, generating a laser beam through a laser, and generating a linearly polarized beam after passing through a polarizer; s2, enabling the linearly polarized light beam to enter the surface of the metasurface; and S3, the metasurface converts the left-handed circular polarization component and the right-handed circular polarization component of the incident light into scalar vortex beam arrays, and generates a vector vortex beam hybrid array in a momentum space through linear superposition. Extra optical elements are not needed, the system structure is compact, and optical aberration is not prone to occurring; independent regulation and control of polarization, orbital angular momentum, amplitude and phase of each light beam unit can be realized; and a flexible and efficient structured light field generation platform is provided for applications such as multi-particle control, high-dimensional quantum communication and high-capacity light information processing.

Description

Technical Field

[0001] This invention relates to a communication technology, particularly a micro-nano photonics and structured light field manipulation technology, specifically a method for generating a vector vortex beam hybrid array based on a metasurface. Background Technology

[0002] Structured light fields have broad application prospects in optical imaging, optical trapping, optical communication, optical encryption, laser material processing, and quantum information processing. Scalar vortex beams are a type of structured light field with a helical phase wavefront, carrying orbital angular momentum. Their beam center is a phase singularity, and the light intensity exhibits a ring-shaped distribution with a dark center. Vector vortex beams, on the other hand, possess both spatially varying polarization states and a helical phase wavefront. They are typically formed by the coherent superposition of two orthogonally polarized scalar vortex beams, carrying both spin and orbital angular momentum, thus offering greater advantages in information capacity and controllability.

[0003] Currently, research on the generation and control of vector vortex beams mainly focuses on three configurations: isolated single beams, arrays with the same vector vortex state, and hybrid arrays composed of multiple cylindrical vector beams. However, how to realize a controllable hybrid array with arbitrary vector vortex beams and independently control the core parameters of each unit (such as polarization state, orbital angular momentum, amplitude, and phase) remains a key challenge. The realization of such arrays will greatly expand the multidimensional control capabilities of structured light fields, increase information capacity, deepen the study of light-matter interaction mechanisms, and promote the development of technologies such as high-density data storage, parallel microfabrication, and multi-channel quantum communication.

[0004] The generation of existing vector vortex beam arrays mainly relies on the combination of spatial light modulators, Fourier lenses, and polarization optical elements in equally divided three-dimensional optical components. This involves spatially separating and generating orthogonally polarized scalar optical vortex arrays, which are then linearly superimposed. Such systems are structurally complex, and alignment errors between cascaded components can easily introduce additional aberrations, limiting their application in integrated, compact optical systems. Summary of the Invention

[0005] The purpose of this invention is to address the problems of complex optical paths and low integration in current technologies by proposing a method for generating vector vortex beam hybrid arrays based on metasurfaces, aiming to achieve the generation of vector vortex beam hybrid arrays with compact structure, flexible control, and controllable aberrations.

[0006] The technical solution of this invention is:

[0007] A method for generating a vector vortex beam hybrid array based on a metasurface, characterized by comprising the following steps:

[0008] S1. A laser beam is generated by a laser, and after passing through a polarizer, a linearly polarized beam is generated.

[0009] S2. Inject the linearly polarized beam onto the metasurface;

[0010] S3. The metasurface converts the left-hand circularly polarized component and the right-hand circularly polarized component of the incident light into scalar vortex beam arrays respectively, and generates a vector vortex beam hybrid array in momentum space through linear superposition.

[0011] Further: In step S3, the complex amplitude expression of the σ-polarization channel of the target vector vortex beam hybrid array in momentum space is:

[0012]

[0013] In the formula, (m,n) represents the row and column indices of the array. Coefficients It is a real-valued amplitude, determined by the higher-order Poincaré sphere polar coordinates; It is the initial constant phase, set by higher-order Poincaré spherical angular coordinates. Represents the topological spiral phase, where φ (m,n) =arg((x ′ -x ′m )+i(y ′ -y ′n )). σ=R and L represent the right-hand circular polarization state and the left-hand circular polarization state, respectively.

[0014] Furthermore, the metasurface provides the desired complex amplitude distribution through its nanostructure units, enabling independent phase and amplitude modulation of the orthogonal circularly polarized components. The complex amplitude optical field encoded on the metasurface is obtained through a three-step process: First, each vector vortex beam unit on the focal plane is modeled as a pure amplitude point source; second, the optical field propagating from each point source to the initial plane is calculated using inverse Fresnel diffraction, thereby generating a linear tilted phase; finally, the vortex phase, the initial phase, and the focusing phase are explicitly superimposed on the initial plane. The complex amplitude optical field distribution encoded on the metasurface is shown below:

[0015]

[0016] Where (x,y) represents the horizontal coordinates on the initial plane, and (r,θ) is the corresponding polar coordinate (r... 2 =x 2 +y 2 ,θ=atan2(y,x)), It is the amplitude coefficient on the initial plane, including the constant factor produced by inverse Fresnel diffraction. Focusing phase. The beam is focused onto the focal plane at z = f. Linear phase term. Then each vector vortex beam element is offset to a specified position (x) in the focal plane. ′m ,y ′n ).

[0017] Furthermore, the amplitude and phase of the complex amplitude optical field distribution encoded on the metasurface are as follows:

[0018]

[0019] Metasurface Structure Design

[0020] The basic unit of the metasurface is a "superpixel". Each superpixel is composed of a 2×2 square lattice, and two nanopillars are integrated in each lattice and arranged alternately to form a "diatomic" type metamolecule.

[0021] The nanostructure unit consists of high-refractive-index, low-loss dielectric nanopillars (such as hafnium oxide, titanium oxide, silicon, silicon nitride, silicon carbide, gallium nitride, or germanium) and a low-refractive-index substrate (such as silicon dioxide, aluminum oxide, or halogen glass). In the visible or near-infrared bands, a combination of silicon carbide rectangular nanopillars and a silicon dioxide substrate is preferred. By scanning the nanopillar height H, length L, width W, and lattice period P, structural units with high cross-polarization conversion efficiency are screened for constructing metasurfaces.

[0022] Taking silicon carbide nanopillars as an example, the metasurface preparation method of the present invention includes the following steps:

[0023] A1. A silicon carbide thin film of a specific thickness H is deposited on a fused silica substrate using plasma-enhanced chemical vapor deposition.

[0024] A2. Coat a layer of hexamethyldisilazane onto the silicon carbide film to enhance adhesion;

[0025] A3. A layer of positive electron beam photoresist and water-soluble conductive adhesive of a specific thickness are spin-coated onto the sample in sequence. The conductive adhesive is used to reduce the charging effect during subsequent electron beam exposure.

[0026] A4. Nanopatterns are exposed in photoresist using an electron beam exposure system and developed in o-xylene solution;

[0027] A5. Deposit a 30nm thick layer of aluminum on the photoresist sample using an electron beam evaporator, then immerse the sample in n-methylpyrrolidone at 80℃ for 10 minutes and perform gentle ultrasonic cleaning to complete the stripping process. This step will cause the pattern to be reversed from the photoresist to the metal aluminum hard mask.

[0028] A6. The sample was anisotropically dry etched using an inductively coupled plasma reactive ion etching machine until all the silicon carbide films without aluminum film coverage were etched, exposing the silicon dioxide substrate. The residual aluminum was removed in the stripping solution, and finally a metasurface composed of silicon carbide nanopillar arrays was obtained.

[0029] The beneficial effects of this invention are as follows:

[0030] (1) This invention provides a device and method for generating a vector vortex beam hybrid array based on a monolithic metasurface, which does not require additional optical components, has a compact system structure, and is less prone to optical aberrations;

[0031] (2) The metasurface has subwavelength scale pixel units, which support high degree of freedom wavefront manipulation and can realize independent control of polarization, orbital angular momentum, amplitude and phase of each beam unit.

[0032] (3) It provides a flexible and efficient structured light field generation platform for applications such as multi-particle manipulation, high-dimensional quantum communication, and high-capacity optical information processing. Attached Figure Description

[0033] Figure 1 This is a flowchart of the method for generating a vector vortex beam hybrid array based on a metasurface according to the present invention.

[0034] Figure 2 A schematic diagram of generating an arbitrary vector vortex beam hybrid array for a metasurface.

[0035] Figure 3 This is a schematic diagram of a device for generating a vector vortex beam hybrid array based on a metasurface.

[0036] Figure 4 This is a schematic diagram of a superpixel unit on a metasurface.

[0037] Figure 5 Transmission efficiency and phase diagrams for a series of rectangular silicon carbide pillars with different in-plane dimensions: a and b, and c and d, are the simulated transmission phases obtained after incident x- and y-polarized light, respectively. and And the transmission efficiencies Tx and Ty, where the incident wavelength is 630 nm.

[0038] Figure 6 The distribution of eight selected silicon carbide nanopillars of different sizes in the transmission phase and polarization conversion efficiency diagram of 5041 nanostructure units is shown.

[0039] Figure 7 The images shown are electron microscope images of the silicon carbide metasurface nanopillar array prepared in the examples: the left side is a top view and the right side is a side view.

[0040] Figure 8 This is a schematic diagram of the device for generating a vector vortex beam hybrid array based on metasurface devices and its measurement optical path in the embodiment.

[0041] Figure 9 To illustrate the results of generating three vector vortex beam intensity arrays on the metasurface and detecting different polarizations in this embodiment, we present: a. the positions of the three vector vortex beam arrays within the higher-order Poincaré sphere and their corresponding theoretical polarization distributions; b. and d. the intensity distributions of the three vector vortex beam arrays under conditions of no polarization analysis, X-polarization detection, Y-polarization detection, right-handed polarization detection, and left-handed polarization detection. The incident light used is X-ray polarized light.

[0042] Figure reference numerals: 11. Laser; 12. First linear polarizer; 13. Metasurface device; 14. Microscope objective; 15. Quarter wave plate; 16. Second linear polarizer; 17. Lens tube; 18. Imaging detector. Detailed Implementation

[0043] The present invention will be further described below with reference to the accompanying drawings and embodiments to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0044] like Figure 1 As shown, in one embodiment of the present invention, a method for generating a vector vortex beam hybrid array based on a metasurface includes the following steps:

[0045] S1. A laser beam is generated by a laser, and after passing through a polarizer, a linearly polarized beam is generated.

[0046] S2. Inject the linearly polarized beam onto the metasurface;

[0047] S3. The metasurface converts the left-hand circularly polarized component and the right-hand circularly polarized component of the incident light into scalar vortex beam arrays respectively, and generates a vector vortex beam hybrid array in momentum space through linear superposition.

[0048] like Figure 2 As shown, the monolithic metasurface proposed in this invention can generate a vector vortex beam hybrid array. The metasurface modulates the orthogonal circular polarization components of the incident ray-polarized beam to obtain scalar vortex beam arrays, and generates a target vector vortex beam hybrid array by linear superposition in momentum space.

[0049] In S3, the complex amplitude expression of the σ-polarization channel of the target vector vortex beam hybrid array in momentum space is:

[0050]

[0051] In the formula, (m,n) represents the row and column indices of the array. Coefficients It is a real-valued amplitude, determined by the higher-order Poincaré sphere polar coordinates α; It is the initial constant phase, set by the higher-order Poincaré spherical angular coordinate β. Represents the topological spiral phase, where φ (m,n) =arg((x′-x′) m )+i(y′-y′ n (σ = R and L represent the right-handed and left-handed circularly polarized states, respectively.)

[0052] Vector vortex beams have arbitrary polarization orders l p , l p =(l R -l L ) / 2.

[0053] In S3, the method for converting a linearly polarized beam into a set vector vortex beam array is as follows: a complex amplitude distribution is provided by a metasurface, which describes the generation of a scalar vortex beam array on a metasurface at the focal plane f, wherein the complex amplitude distribution is provided by nanostructure units at different positions on the metasurface.

[0054] Furthermore, the metasurface provides the desired complex amplitude distribution through its nanostructure units, enabling independent phase and amplitude modulation of the orthogonal circularly polarized components. The complex amplitude optical field encoded on the metasurface is obtained through a three-step process: First, each vector vortex beam unit on the focal plane is modeled as a pure amplitude point source; second, the optical field propagating from each point source to the initial plane is calculated using inverse Fresnel diffraction, thereby generating a linear tilted phase; finally, the vortex phase, the initial phase, and the focusing phase are explicitly superimposed on the initial plane. The complex amplitude optical field distribution encoded on the metasurface is shown below:

[0055]

[0056] Where (x,y) represents the horizontal coordinates on the initial plane, and (r,θ) is the corresponding polar coordinate (r... 2 =x 2 +y 2 ,θ=atan2(y,x)), It is the amplitude coefficient on the initial plane, including the constant factor produced by inverse Fresnel diffraction. Focusing phase. The beam is focused onto the focal plane at z = f. Linear phase term. Then each vector vortex beam element is offset to a specified position (x) in the focal plane.′m ,y ′n ).

[0057] Furthermore, the amplitude and phase of the complex amplitude optical field encoded on the metasurface are as follows:

[0058]

[0059] The metasurface is composed of a series of subwavelength nanostructure units, where two subwavelength nanostructures A and B constitute a "superpixel." Their transmission phases for a scalar vortex beam array polarized at specific wavelengths λ for X and Y are δ, respectively. Ax δ Ay and δ Bx δ By and in-plane rotation angle θ A θ B The following relationship must be satisfied:

[0060] Nanopillar A

[0061]

[0062] Nanopillar B

[0063]

[0064] like Figure 3 As shown, a device for generating a vector vortex beam array based on a metasurface is provided. The device includes: a laser 11 for generating a laser beam; a polarization control module consisting of a linear polarizer 12 for adjusting the incident laser beam to a linear polarization state; and a metasurface for directly converting the incident polarized beam into a scalar vortex beam array.

[0065] The nanostructure units of the metasurface consist of nanopillars with rectangular or elliptical cross sections and square or hexagonal glass substrates. Depending on the operating wavelength, the nanopillar materials are high-refractive-index, low-loss materials such as hafnium oxide, titanium oxide, silicon, silicon nitride, silicon carbide, gallium nitride, or germanium; the glass substrate materials are low-refractive-index, low-loss materials such as silicon dioxide, aluminum oxide, or halogen glasses (barium fluoride, calcium fluoride, magnesium fluoride, etc.).

[0066] Preferably, the nanopillars in the visible or near-infrared band are rectangular silicon carbide nanopillars with a height of H, a length of L, and a width of W. The glass substrate is a square silica substrate with a side length of P. The rectangular silicon carbide nanopillars and the square silica substrate constitute the nanostructure unit of the metasurface. By scanning the physical parameters H, L, W, and P, the nanostructure unit with high cross-polarization conversion efficiency is selected to form the metasurface used to generate a vector vortex beam array.

[0067] The method for preparing metasurfaces with silicon carbide nanopillars is as follows:

[0068] A1. A silicon carbide thin film of a specific thickness H is deposited on a fused silica substrate using plasma-enhanced chemical vapor deposition.

[0069] A2. Coat a layer of hexamethyldisilazane onto the silicon carbide film to enhance adhesion;

[0070] A3. A layer of positive electron beam photoresist and water-soluble conductive adhesive of a specific thickness (e.g., 200 nm) is spin-coated onto the sample in sequence, wherein the conductive adhesive is used to mitigate the charging effect during subsequent electron beam exposure.

[0071] A4. Expose nanopatterns in photoresist using an electron beam exposure system and develop them in o-xylene solution; preferably, the accelerating voltage is 125kV and the beam current is 1nA.

[0072] A5. Deposit a 30nm thick layer of aluminum on the photoresist sample using an electron beam evaporator, then immerse the sample in n-methylpyrrolidone at 80℃ for 10 minutes and perform gentle ultrasonic cleaning to complete the stripping process. This step will cause the pattern to be reversed from the photoresist to the metal aluminum hard mask.

[0073] A6. The sample was anisotropically dry etched using an inductively coupled plasma (ICP) reactive ion etching machine until all the silicon carbide films without aluminum film coverage were etched, exposing the silicon dioxide substrate. The residual aluminum was removed in the stripping solution, and finally a metasurface composed of silicon carbide nanopillar arrays was obtained.

[0074] In this embodiment, three metasurfaces were designed and fabricated to generate higher-order Poincaré spheres (HOPS) with polar axes l1 and l2, respectively. (l1,l2) Different vector vortex beam arrays are used on the metasurface, with a working wavelength λ of 630 nm. The metasurface diameter D = 500 μm and focal length f = 5 mm. Specifically, metasurface 1 operates along the HOPS... (1,-1) The meridian with azimuth β = 0 generates five equally spaced beam arrays, whose polar angle α values ​​continuously sweep from 0 to π; the metasurface 2 along the HOPS (1,-1) Five beam arrays are generated at the equator with α = π / 2, and their β values ​​continuously sweep from 0 to 2π; the metasurface 3 is a four-channel generator that simultaneously generates vector vortex beams corresponding to two different HOPS modes: where HOPS (2,-2) The modes at (π / 4, 0) and (3π / 4, 0) points in (α, β), and HOPS (3,-3) Modes in the same coordinate system.

[0075] The dual superatomic design of the metasurface is as follows: Figure 4 As shown, silicon carbide rectangular nanopillars A and B with a fixed height H = 850 nm are integrated in an alternating pattern within a square lattice on a quartz substrate (period U = 450 nm), with each 2×2 grid forming a superpixel. Numerical simulations were performed on 5041 nanostructure units of different lengths (L) and widths (W), ranging from 50 nm to 400 nm, using a finite-difference time-domain algorithm with a scan interval of 5 nm. Periodic boundary conditions were applied along the x and y axes, while perfectly matched layer boundary conditions were used along the z axis. Plane wave illumination with x and y polarization was sequentially applied from the substrate side, and the transmission phases of x and y polarized light with a wavelength of 630 nm for the 5041 different structural units were obtained. and ) and permeability (T x and T y ),like Figure 5 As shown.

[0076] The method for preparing the metasurface is as follows: First, a silicon carbide film with a thickness of 850 nm is deposited on a 500 μm thick fused silica substrate using plasma-enhanced chemical vapor deposition (PECVD). Then, a layer of hexamethyldisilazane is coated onto the silicon carbide film to enhance adhesion. Next, a 200 nm thick layer of positive electron beam photoresist and a thin layer of water-soluble conductive adhesive are spin-coated, where the conductive adhesive is used to mitigate the charging effect during subsequent electron beam exposure. Next, an electron beam exposure system with an accelerating voltage of 125 kV and a beam current of 1 nA is used to expose the nanostructure unit array pattern in the photoresist, followed by development in o-xylene solution. A 30 nm thick aluminum film is deposited on the sample using electron beam evaporation. The sample is then immersed in n-methylpyrrolidone at 80 °C for 10 minutes, followed by gentle ultrasonic cleaning to complete the lift-off process. This step causes the pattern to invert from the photoresist onto the aluminum hard mask. Anisotropic dry etching was performed on the sample using an inductively coupled plasma (ICP) reactive ion etching machine until the silicon carbide film without aluminum film coverage was completely etched, exposing the silicon dioxide substrate. The optimized anisotropic etching formulation was as follows: chamber pressure controlled at 13.5 mTorr, ICP generator RF power of 500 W, bias source RF power of 40 W, and C4F8 / SF6 ratio of 8 / 3. Finally, residual aluminum was removed in a stripping solution to obtain a metasurface device 14 composed of a silicon carbide nanopillar array. Figure 6 Electron microscope image of the prepared silicon carbide metasurface nanopillar array.

[0077] use Figure 7The experimental setup shown generates and measures a vector vortex beam array generated by three metasurfaces (MF1-MF3). The setup includes a laser 11, a first linear polarizer 12, a metasurface device 13, a microscope objective 14, a quarter-wave plate 15, a second linear polarizer 16, a tube lens 17, and an imaging detector 18, connected in sequence.

[0078] The first linear polarizer 12 is used to convert the polarization state of the incident light into linearly polarized light, which is then used to generate a vector vortex beam array. The position and theoretical polarization distribution of the beam array in the higher-order Poincaré sphere are as follows: Figure 9 As shown in a, the experimental results are as follows: Figure 9 The first column is shown in Figure b.

[0079] Using the aforementioned optical path, by adjusting the fast axis of the quarter-wave plate 14 to be parallel, perpendicular, +45 degrees, and -45 degrees to the transmission axis of the second linear polarizer 16, respectively, X, Y, right-hand circular polarization, and left-hand circular polarization detection can be obtained, as shown below. Figure 9 As shown in columns 2-5 of table b.

[0080] The experimental results above demonstrate that the metasurface platform can generate vector vortex beams with customized modal orders and complex polarization topologies (including radial and angular polarization states).

[0081] In the description of this invention, it should be understood that the terms "center," "thickness," "upper," "lower," "horizontal," "top," "bottom," "inner," "outer," and "radial," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying the relative importance or the number of technical features implicitly specified. Therefore, a feature defined by "first," "second," and "third" may explicitly or implicitly include one or more of that feature.

[0082] The above embodiments are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make several improvements and equivalent substitutions without departing from the principle of the present invention. All such improvements and equivalent substitutions to the claims of the present invention fall within the protection scope of the present invention.

[0083] All parts not covered in this invention are the same as or can be implemented using existing technologies.

Claims

1. A method for generating a vector vortex beam hybrid array based on a metasurface, characterized in that, It includes the following steps: S1. A laser beam is generated by a laser, and after passing through a polarizer, a linearly polarized beam is generated. S2. Inject the linearly polarized beam onto the metasurface; S3. The metasurface converts the left-hand circularly polarized component and the right-hand circularly polarized component of the incident light into scalar vortex beam arrays respectively, and generates a vector vortex beam hybrid array in momentum space through linear superposition.

2. The method according to claim 1, characterized in that, The target vector vortex beam hybrid array is a superposition of left-hand circularly polarized components (σ = L) and right-hand circularly polarized components (σ = R); the complex amplitude expression of the σ polarization channel value in momentum space is: In the formula, (m,n) represents the row and column indices of the array, and the coefficients are... It is a real-valued amplitude, determined by the higher-order Poincaré sphere polar coordinates; It is the initial constant phase, set by higher-order Poincaré spherical angular coordinates. Represents the topological spiral phase, where φ (m,n) =arg((x′-x′) m )+i(y′-y′ n )).

3. The method according to claim 1, characterized in that, The metasurface provides the required complex amplitude optical field through its nanostructure units, allowing for independent modulation of the phase and amplitude of orthogonal circularly polarized components. The described complex amplitude optical field is obtained through a three-step process: First, each vector vortex beam unit on the focal plane is modeled as a pure amplitude point source; second, the optical field propagating from each point source to the initial plane is calculated using inverse Fresnel diffraction, thereby generating a linear tilt phase; finally, the vortex phase, the initial phase, and the focusing phase are explicitly superimposed on the initial plane. The complex amplitude optical field distribution encoded by the metasurface is shown below. Where (x,y) represents the horizontal coordinates on the initial plane, and (r,θ) is the corresponding polar coordinate (r... 2 =x 2 +y 2 ,θ=atan2(y,x)), These are the amplitude coefficients on the initial plane, including constant factors generated by inverse Fresnel diffraction; focusing phase. Converging the beam to the focal plane at z = f; linear phase term Then each vector vortex beam element is offset to a specified position (x′) in the focal plane. m ,y′ n ).

4. The method according to claim 3, characterized in that, The amplitude and phase of the complex amplitude optical field encoded by the metasurface are as follows:

5. The method according to claim 4, characterized in that, The basic unit of the metasurface is a "superpixel". Each superpixel is composed of a 2×2 square lattice, and two nanopillars are integrated in each lattice and arranged alternately to form a "diatom" type metamolecule.

6. The method according to claim 5, characterized in that, The nanopillars (nanostructure units) are composed of high-refractive-index, low-loss dielectric nanopillars and low-refractive-index substrates. In the visible or near-infrared band, silicon carbide rectangular nanopillars are combined with silicon dioxide substrates. By scanning the height H, length L, width W and lattice period P of the nanopillars, structural units with high cross-polarization conversion efficiency are screened for constructing metasurfaces.

7. The method according to claim 6, characterized in that, The dielectric nanopillars are hafnium oxide, titanium oxide, silicon, silicon nitride, silicon carbide, gallium nitride, or germanium nanopillars.

8. The method according to claim 6, characterized in that, The low refractive index substrate is a silicon dioxide, aluminum oxide, or halogen glass substrate.

9. The method according to claim 1, characterized in that, The method for preparing metasurfaces using silicon carbide nanopillars includes the following steps: A1. A silicon carbide thin film of a specific thickness H is deposited on a fused silica substrate using plasma-enhanced chemical vapor deposition. A2. Coat a layer of hexamethyldisilazane onto the silicon carbide film to enhance adhesion; A3. A layer of positive electron beam photoresist and water-soluble conductive adhesive of a specific thickness are spin-coated onto the sample in sequence. The conductive adhesive is used to reduce the charging effect during subsequent electron beam exposure. A4. Nanopatterns are exposed in photoresist using an electron beam exposure system and developed in o-xylene solution; A5. Deposit a 30nm thick layer of aluminum on the photoresist sample using an electron beam evaporator, then immerse the sample in n-methylpyrrolidone at 80℃ for 10 minutes and perform gentle ultrasonic cleaning to complete the stripping process. This step will cause the pattern to be reversed from the photoresist to the metal aluminum hard mask. A6. The sample was anisotropically dry etched using an inductively coupled plasma reactive ion etching machine until all the silicon carbide films without aluminum film coverage were etched, exposing the silicon dioxide substrate. The residual aluminum was removed in the stripping solution, and finally a metasurface composed of silicon carbide nanopillar arrays was obtained.

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