Microstructure for realizing scalar vortex and vector beam and design method thereof

Abstract

The application discloses a microstructure for realizing scalar vortex and vector light beams and a design method thereof. The microstructure comprises a substrate and microstructure units, wherein the substrate is divided into 2n regions (n is a positive integer), the 2n regions are rotationally distributed around a coordinate origin, and the microstructure units are arranged on each region, and the arrangement of the microstructure units satisfies that: in each region, all the microstructure units have the same rotation angle; and different regions have different rotation angles of the microstructure units. The microstructure designed by the application can realize different vortex response characteristics when different polarized light fields are used as excitation, has the advantages of high polarization conversion efficiency and small energy loss, and realizes the combination of traditional phase vortex and polarization vortex.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of physical optics, in particular to an artificial microstructure and a design method thereof. BACKGROUND

[0002] Based on the multi-degree-of-freedom light manipulation and light-matter interaction is an important direction of the study of optical physics in recent years. It is worth noting that the optical vortex is a unique light field, since Beth first observed the spin angular momentum (SAM) of the photon in 1936, the optical vortex has attracted great interest. Subsequently, Allen et al. proposed the concept of orbital angular momentum (OAM) in 1992. However, the study of optical vortex by human beings has not been completed, and its application prospect is broad, for example, the perfect optical vortex proposed by Ostroumov in 2013. In this context, the study on the generation of optical vortex in the field of materials has attracted great attention. Therefore, it is crucial to determine a proper material structure capable of intentionally manipulating the vortex beam.

[0003] The modulation of optical vortices can be achieved by two different methods, the first is to control the generation of light beams, for example, to design appropriate lasers. High topological charge contains more information, Dong et al. combined 3D printing technology to construct high topological charge vortex laser in 2023 (Dong Y, Pan G, Xun M, et al. Nanoprinted diffractive layer integrated vertical-cavity surface-emitting vortex lasers with scalable topological charge [J]. Nano Letters, 2023, 23(19): 9096-9104.). The second is to design artificial microstructures, i.e. metasurfaces, to achieve modulation in the process of light beam transmission. Metasurfaces are materials with special microstructures, which is the reason for their extraordinary optical properties. Currently, metasurfaces have been widely used in many fields of optics, such as anomalous refraction, high-efficiency reflection and phase control. Therefore, there have been many groundbreaking works in the field of metasurfaces, especially focusing on their influence on light field modulation, especially on optical vortices. For example, in 2017, Devlin et al. designed a metasurface structure (Devlin R C, Ambrosio A, Rubin N A, et al. Arbitrary spin-to-orbital angular momentum conversion of light [J]. Science, 2017, 358(6365): 896-901), proposed a method to convert arbitrary SAM states into total angular momentum states characterized by independent OAM superposition. In addition, Liu et al. used geometric phase metasurfaces combined with coding technology to achieve perfect vortex light (Liu, Mingze, et al. Broadband generation of perfect Poincaré beams via dielectric spin-multiplexed metasurface. Nature communications 12.1 (2021): 2230).

[0004] Despite extensive research on optical vortices, there are still key challenges that need immediate attention. One important aspect is related to the wide application of optical vortices in the field of quantum information, super-resolution microscopy and optical tweezers, which require the light beam to be in the near-infrared band. The 1.55um wavelength is known as the C-band, which plays a crucial role as a low-loss window in fiber communication, which has been widely recognized. Many common lasers, including erbium-doped fiber lasers, can emit monochromatic light in this band, which highlights the widespread use of this band. However, one cannot ignore the fact that silicon-based transmission fibers have a wide window from 1.4um to 1.65um, of which 1.4um is also an extremely critical monochromatic light frequency. In addition, Fu et al. found that ultrafast infrared lasers operating at a monochromatic 1.4um frequency can achieve the highest output energy conversion efficiency, which is recognized as the best method to effectively expand the energy of high-order harmonic photons (Fu Y, Takahashi E J, Midorikawa K. High-energy infrared femtosecond pulses generated by dual-chirped optical parametric amplification [J]. Optics Letters, 2015, 40(21): 5082-5085). In addition, phase vortices and polarization vortices have different application scenarios, so it is very meaningful to realize the construction of scalar vortices and vector beams. However, for many integrated on-chip systems, multiple functions often rely on the superposition of multiple super-surfaces, where each super-surface has its own micro-nano structure, which works independently on its own chip to lay the foundation for a single super-surface to achieve a certain function. Finally, by stacking these single-function super-surfaces, the combination of these single functions can be achieved to form a complex on-chip optical system. However, due to the superposition of multiple super-surfaces, there may be crosstalk problems between different microstructures on the final single integrated super-surface, and there may be large energy loss, as well as many inconveniences in actual processing. Therefore, it is of great significance to find an efficient artificial structure to construct a super-surface to realize near-infrared multifunctional optical vortices at 1.4um. SUMMARY

[0005] In view of the above prior art, the purpose of the present application is to provide a microstructure for realizing scalar vortices and vector beams and a design method thereof.

[0006] In order to achieve the above purpose, the present application provides the following technical solutions:

[0007] A microstructure for realizing scalar vortex and vector beam, the microstructure comprises a substrate and a microstructure unit, the substrate is divided into 2n regions, where n is a positive integer, 2n regions are distributed around the coordinate origin, and the microstructure unit is arranged on each region, and the arrangement of the microstructure unit satisfies: in each region, all microstructure units have the same rotation angle; different regions have different rotation angles of microstructure units.

[0008] Further, the rotation angle of the microstructure unit in each region is determined by the position of the region: the rotation angle of the microstructure unit in the ith region is And the phase compensation size of the phase plane brought by the microstructure unit is Where 1≤i≤2n.

[0009] Further, the substrate is divided into four regions, the negative direction of the X axis of the Cartesian coordinate system is selected as the starting direction of rotation, and the phase plane rotated counterclockwise satisfies The phase distribution.

[0010] Further, the microstructure unit is arranged on each of the four regions, the microstructure units in each region are periodically arranged, and the periods in the four regions are the same, but the rotation angles of the microstructure units are different, which are 0°, 45°, 90° and 135° respectively.

[0011] Further, the microstructure unit is a cross-shaped structure. The material of the microstructure unit is silicon, the height of the cross-shaped structure is 0.5um≤h2≤3um, the length in the X direction is 250nm≤dx≤320nm, the length in the Y direction is 410nm≤dy≤510nm, and the width is 140nm≤d≤160nm.

[0012] Further, the cross-shaped structure has a quasi-periodic interval of P=900um in the X direction and the Y direction.

[0013] Further, the material of the substrate is silicon dioxide, the thickness of the substrate is 1um≤h1≤3um, the length is 18um≤a≤30um, and the width is 18um≤b≤30um, where a=b.

[0014] The application also provides a design method for the microstructure for realizing the scalar vortex and the vector beam, which comprises the following steps: firstly, a substrate is selected; then, the substrate is divided into 2n regions, the 2n regions are distributed around a coordinate origin, the central angle of each region is 2π / 2n, n is a positive integer, and the counterclockwise or clockwise rotation direction is selected as the vortex phase direction; then, the rotation angle of the microstructure unit in each region is determined according to the relationship between the vortex phase and the designed rotation angle of the microstructure unit, and the microstructure units are arranged in the respective regions, so that each region has different phase compensation functions; the length dx of the X direction and the length dy of the Y direction of the microstructure unit are calculated by parametric scanning through a simulation software; subsequently, the optimal parameters are obtained by inputting the scanning calculation results into an evaluation function; finally, the microstructure units are arranged on the substrate according to the specified angle according to the optimal parameters, so that the microstructure for realizing the scalar vortex and the vector beam can be obtained.

[0015] Compared with the prior art, the application has the following beneficial effects:

[0016] (1) The application designs a single optical metasurface system composed of microstructures, which has the advantages of simple structure and easy implementation.

[0017] (2) The structure of the application can effectively realize complex vortex light fields under different polarization excitations: under the excitation of a circularly polarized light field, a scalar vortex with a circular polarization topological charge of 1 is generated; under the excitation of a linearly polarized light field, a vector beam, i.e., a linearly polarized vortex, is generated. The combination of traditional phase vortex and polarization vortex is realized.

[0018] (3) The application has the advantages of high polarization conversion efficiency and low energy loss. In particular, the metasurface system uses a three-dimensional cross structure, which has a transmission response of up to 98% for linearly polarized light; at the same time, in the design method, an evaluation function is used, so that the conversion efficiency of the structure for circularly polarized light is also as high as 98%. Therefore, the application can obtain a generation efficiency of the scalar vortex and the vector beam as high as 98%.

[0019] (4) The microstructure designed in the application is arranged to finally form a monolithic system-on-chip composed of only one kind of artificial microstructure, and there is no difference between these structures except for the rotation angle, so that the system-on-chip does not have the problems of system crosstalk and low efficiency caused by the monolithic system-on-chip composed of traditional superimposed metasurfaces.

[0020] (5) The system on chip structure formed by the single piece of the designed metasurface not only has the characteristics of simple structure and convenient processing, but also has the ability of generating high-efficiency scalar vortex and vector beam. Compared with the traditional optical fiber communication, the vortex light generated by the application has orbital angular momentum (OAM), further expands the communication channel, and provides a new way for large channel transmission. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments described in the present application, and other drawings can also be obtained by those skilled in the art according to these drawings.

[0022] Figure 1 The two artificial microstructure units with different rotation angles provided for the embodiments of the present application: (a) side view and (b) top view.

[0023] Figure 2 The physical properties of the artificial microstructure unit provided for the embodiments of the present application: (a) polarization conversion efficiency (RLT) distribution under circular polarization excitation, (b) transmittance distribution under linear polarization excitation (dx=160nm at this time), (c) structure of low transmission point, (d) distribution of two kinds of phase changes (dx=160nm at this time), (e) multipole expansion spectrum when the wavelength is 160nm, (f) field distribution of special complex polar state, (g) mode mainly with magnetic dipole, (h) relationship of multipole expansion spectrum T.

[0024] Figure 3 Field strength mode analysis of the structure unit with different rotation angles provided for the embodiments of the present application: (a) optical properties under circular polarization excitation, (b) optical properties under linear polarization excitation (X polarization is taken as an example).

[0025] Figure 4 (a) Microstructure rotation angle arrangement diagram and realized phase vortex and polarization vortex effect provided for the embodiments of the present application, (b) generated scalar vortex, (c) light field of the generated vector beam, (d) light field of the vector beam passing through a polarizer. DETAILED DESCRIPTION

[0026] In order to make those skilled in the art better understand the technical solutions of the present application, the present application will be further described in detail below with reference to the drawings.

[0027] The purpose of the present application is to realize scalar vortex and vector beam at the same time, and the technical idea can be derived by using geometric phase as a physical basis:

[0028] Geometric phase, also known as Pancharatnam-Berry (PB) phase, is a special phase existing in a non-uniform metasurface composed of a series of completely uniform artificial atoms, which has different rotation angles and is independent of the structure material. The change of the phase is only determined by the rotation angle. However, it is worth mentioning that the PB phase is a kind of phase modulation that only acts on circularly polarized light, as shown in formula 1-1:

[0029] J(θ)=M(θ) T ×T×M(θ) (1-1)

[0030] Where J(θ) represents the Jones matrix, and m(θ) represents the rotation matrix Where θ is the rotation angle of the structure. When considering the transmission case, T is the transmission matrix, that is, And in the matrix element t ij , represents the transmittance of i light to j light, so for most structures, t xy and t yx are both 0. By simplifying, formula 1-2 can be obtained:

[0031]

[0032] It is obvious that according to the calculation result, it can be found that the unit matrix is contained in part A, which means that any type of incident light will not change its any state, including the phase. However, the part that is really worth paying attention to is part B, which contains two matrices. As we all know, the Jones matrix of right-handed circularly polarized light is When it acts on J(θ), it will produce left-handed circularly polarized light, and the additional phase jump is only related to the rotation angle. Therefore, according to this idea, a structure that realizes scalar vortex can be constructed. When the incident light beam is circularly polarized in any state, a carefully designed structure can produce a phase jump on the surface, thereby forming a scalar vortex optical field.

[0033] In order to realize a vector beam, it is necessary to modulate the exit polarization state of the light field, which itself is a difficult problem, and it is more challenging to use only one metasurface to realize the existence of scalar vortex and vector beam at the same time. For this problem, in formula 1-1, it is known that the transmission coefficient matrix T actually contains the initial phase of the structure, as shown in formula 1-3:

[0034]

[0035] Where T xx is the amplitude of the x-polarized transmitted wave when x-polarized light is incident, is its phase. When T xx and T yy are close to 1 and Time, i.e. simplified as formula 1-4:

[0036]

[0037] According to the above results, the circularly polarized light and linearly polarized light are introduced respectively, and formula 1-5 is obtained. At this time, for the circularly polarized light, the emitted light is circularly polarized light, and there is a geometric phase θ that can be adjusted, that is, it can be used as the vortex phase of the vortex light to be constructed in the structure design; and for the incident linearly polarized light, the emitted light is still linearly polarized light, and the polarization direction is controlled by the vortex phase θ. According to the above derivation, scalar vortex and vector beams in the case of circular polarization and linear polarization can be realized respectively.

[0038]

[0039] Therefore, based on the above theoretical basis, the embodiment gives a design method of a microstructure for realizing scalar vortex and vector beams, which specifically includes the following steps: first, a substrate is selected, and in the embodiment, silicon dioxide is used as the substrate; then, the substrate is divided into 2n(n is a positive integer) regions, and the 2n regions are distributed in a rotating manner around the coordinate origin, wherein the size and shape of the regions are not necessarily the same, only the central angle is required to be the same, that is, for the 2n regions, the central angle of each region is 2π / 2n, and the counterclockwise (or clockwise) rotation direction is selected as the vortex phase direction; then, the relationship between the vortex phase derived according to formula 1-4 and the rotation angle of the artificial microstructure unit in each region is determined, and the rotation angles of the artificial microstructure units in each region are arranged in the respective regions so that each region has different phase compensation functions; in order to make the generation efficiency of the scalar vortex and the vector beam as high as possible, the length dx of the X direction and the length dy of the Y direction of the artificial microstructure unit are calculated by scanning and varying the parameters through a simulation software; subsequently, the optimal parameters can be obtained by inputting the scanning calculation results into an evaluation function; finally, the artificial microstructure units are arranged on the substrate according to the specified angles according to the optimal parameters, and the structure for realizing scalar vortex and vector beams of the application is obtained.

[0040] In each region, all the microstructure units have the same rotation angle; between different regions, the microstructure units have different rotation angles. The rotation angle of the microstructure unit in each region is determined by the position of the region, and the rotation angle of the microstructure in the i(th) (1≤i≤2n) region should be and the phase compensation size of the phase plane brought by the microstructure should be

[0041] The microstructure unit designed in this embodiment includes a cross-shaped pillar made of silicon, with the size of h1 = 1.2 um, h2 = 1 um, d = 150 nm, dx = 290 nm, dy = 460 nm, and the specific parameters are as shown in Figure 1 where θ is the rotation angle of the structure, which is determined by the phase plane of the vortex light. This parameter is the optimal structure solution for obtaining the highest scalar vortex and vector beam generation efficiency, which is obtained through physical analysis. This structure has relatively high transmission response for X and Y polarizations, which provides greater convenience for the construction of vector beams in the working waveband of 1.4 um.

[0042] As shown in (a) of Figure 2 , the R-L polarization light transmission rate (RLT) of dx and dy in the range of 160 nm to 700 nm is systematically scanned and calculated with a step of 10 nm. The results undoubtedly show that the polarization conversion efficiency changes between 0 and 1 as the structure parameters change. It is worth mentioning that since the circularly polarized light can be decomposed into linearly polarized components, and the structure of this embodiment satisfies the axial symmetry property of the X and Y axes, the results of linear polarization excitation exist symmetric solutions. This is the reason why the transmission spectrum is observed to be symmetric along the line (y = x). In addition, the scanning diagram shows two almost vertical singular points, resulting in abnormal mutations of the transmission rate, which is due to the Fano resonance caused by the periodic boundary condition. Figure 2 (b) of Figure 2 shows the linear polarization characteristics of a series of randomly selected bodies, and the results show that the structure of this embodiment is almost transparent to linear polarization. However, as shown in (c) of Figure 2 , this situation is due to the fact that the size of the structure has almost become rectangular, which is distributed in the x direction, so the transmission rate of y polarization has dropped sharply. Similarly, the propagation phase change of some structures is shown in (d) of , and it is found that any kind of polarization excitation can eventually cover the entire phase space.

[0043] It is well known that Mie scattering is crucial when the size of the structure is of the same order of magnitude as the incident excitation light field. Understanding the multipole characteristics of the structure is helpful for studying its intrinsic characteristics. In (e) of Figure 2 , the multipole expansion diagrams of some randomly selected structures are shown. In (f) of Figure 2 , due to the small gap between the strengths of the poles, the final structure is in a superposition state, and the field distribution is characterized by electric quadrupole (EQ) and magnetic dipole (MD). On the contrary, in (g) of Figure 2In (g), MD is dominant, so the magnetic dipole distribution is very obvious. The structural transmission system of the present application includes circular polarization and linear polarization transmission, which constitutes a complex analysis process. Fortunately, circularly polarized light is the superposition of linearly polarized light, so a novel transmittance concept is introduced in the whole system, denoted as T TOT , as shown in (h), T Figure 2 TOT = T RL + T xx + T yy By randomly selecting two instances, it can be seen that when dx is less than 350 nm, the microstructure is dominated by EQ in the transmission spectrum. This is clearly visible due to the presence of high-order electric quadrupoles in the dielectric system. In contrast, when dx exceeds 350 nm, MD is dominant. It is worth noting that a symmetrical relationship exists between the total transmittance curve T TOT and the total intensity of the superimposed comprehensive effect curve (Total Intensity, TOT), which lays the foundation for constructing evaluation indicators. It should be added that all the theoretical calculations described above in this embodiment are based on COMSOL Multiphysics 6.1 simulation software.

[0044] To find the optimal solution of the structure, it is obviously necessary for the structure to have high circular polarization conversion efficiency, high transmittance for linearly polarized light, and appropriate inherent propagation phase. Therefore, the present application proposes a structural evaluation function (SEF), as shown in equations 1-6:

[0045]

[0046] where x i , x j , x k , etc. represent the parameter values to be evaluated, s i , s j , s k ​m, n, p are the number of parameters to be evaluated under different weight values, representing the given standard target value. The evaluation function is characterized by an analytical function, which can be continuously extended according to the number of variables in the artificial structure design process and the weight between different variables. As found in the previous analysis, the changes of the three transmittances should have the same importance, so the values of the three transmittances should be calculated in the same term because they have the same weight value, while the phase change is much larger than the transmittance, so the two phase changes should have another weight value determined. The present application finally selects the third term and the first term to evaluate the structure to realize that the difference between the calculated phase and the standard phase and the difference between the calculated transmittance and the standard transmittance are in the same order of magnitude, thereby ensuring the accuracy of the evaluation function. Therefore, the present embodiment specifies three target transmittances, each set to 0.98, the propagation phase under X polarization is set to 0, and the propagation phase under Y polarization is set to 180. Based on SEF, the present application successfully analyzes all the structure parameters, and when the input structure parameter result is closer to 0, the effect of the structure is better, and according to this idea, the forward design of the structure is realized.

[0047] In Figure 3 two rotation angles are selected in (a) as a demonstration, it can be observed that no matter how many degrees the structure is rotated, the incident light field and the exit light field satisfy the BP phase characteristic, that is, the circularly polarized light is given an additional phase of twice the rotation angle. Without doubt, the phase difference between the incident plane and the exit plane of the optimal structure also strictly satisfies 2 times the change with the rotation angle. In the present application, linear polarization excitation is used to realize the vector light beam, and according to Figure 3 (b), taking X polarization as an example, the field intensity distribution of the structure rotated by 30° and 45° along the X axis is shown respectively. As can be seen from the figure, when the X polarization transmits through the structure, its polarization direction will be modulated by the rotation angle. Therefore, it provides a basis for our vector vortex structure.

[0048] Finally, the designed optimal microstructure is arranged on a substrate made of silicon dioxide, and the substrate of the present embodiment is a cuboid with side length a = b = 20 um, and the height h1 = 1.2 um. As shown in Figure 4 (a), the microstructure is divided into four regions, and the size of the regions is equal. The middle of the plate is taken as the coordinate origin, and the four regions correspond to the four quadrants of the Cartesian coordinate system, which correspond to four phase modulation regions in physics. The negative direction of the X axis of the Cartesian coordinate system is selected as the starting direction of rotation, that is, the third quadrant divided by the Cartesian coordinate system (it can also start from other quadrants as long as the phase change satisfies (0-2π) in the counterclockwise direction), and the phase plane rotated counterclockwise should satisfy The phase distribution of the first block area needs to compensate 0 phase (that is, the phase of the incident light beam is not affected), the second block area needs to compensate π / 2 phase (that is, the phase of the incident light beam is additionally increased by π / 2), the third block area needs to compensate π phase, and the fourth block area needs to compensate 3π / 2 phase. At this time, since the four areas are rotationally distributed, the fourth area and the first area are connected, thereby forming a complete (0-2π) phase change compensation surface. It should be noted that the larger the value of n, the higher the phase accuracy of the generated vortex light. The microstructures in each area present a 4x4 periodic distribution, wherein the periods of the X and Y directions are both P=800nm. In order to realize the phase vortex and polarization vortex counterclockwise from the third quadrant of the virtual Cartesian coordinate system, the microstructures in the actual space need to compensate for the phase and modulate the polarization state, so according to formulas 1-4, the corresponding microstructure arrangement in the four areas should have an angle with the Y axis. The angles of the microstructures in the four areas of the embodiment are 0°, 45°, 90° and 135° respectively. The structure can realize scalar vortex under circularly polarized excitation, and can also realize vector vortex under linearly polarized excitation.

[0049] Those skilled in the art can understand that, in addition to the example structures and parameters given in the above embodiments, other similar structures and sizes can also achieve the purpose of the present application, for example, changing dx and dy only results in a change in efficiency.

[0050] The above only describes some exemplary embodiments of the present application by way of illustration, and it is self-evident that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present application. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present application.

Claims

1. A microstructure for realizing scalar vortices and vector beams, characterized in that, The microstructure includes a substrate and microstructure units. The substrate is divided into 2n regions, where n is a positive integer. The 2n regions are distributed around the origin of the coordinate system. The microstructure units are arranged in each region, and the arrangement of the microstructure units satisfies the following conditions: all microstructure units in each region have the same rotation angle; different regions have different rotation angles of the microstructure units; and the material of the microstructure units is silicon. The microstructure unit is a cross structure with a height of 0.5um≤h2≤3um, a length in the X direction of 250nm≤dx≤320nm, a length in the Y direction of 410nm≤dy≤510nm, and a width of 140nm≤d≤160nm; the quasi-period of the interval in the X and Y directions is P=900nm.

2. The microstructure for realizing scalar vortices and vector beams according to claim 1, characterized in that, The rotation angle of the microstructural unit within each region is determined by the position of that region: the rotation angle of the microstructural unit within the i-th region is... Furthermore, the phase compensation magnitude of the phase plane brought about by the microstructure unit is Where 1≤i≤2n.

3. The microstructure for realizing scalar vortices and vector beams according to claim 2, characterized in that, The substrate is divided into four regions. The negative X-axis of the Cartesian coordinate system is selected as the starting direction of rotation. The phase plane of counterclockwise rotation satisfies... The phase distribution.

4. The microstructure for realizing scalar vortices and vector beams according to claim 3, characterized in that, The microstructure units are arranged in the four regions respectively. The microstructure units in each region are arranged periodically, and the period is the same in the four regions. However, the rotation angles of the microstructure units are different, namely 0°, 45°, 90° and 135°.

5. A microstructure for realizing scalar vortices and vector beams according to claim 1, characterized in that, The substrate is made of silicon dioxide, and its thickness is 1µm ≤ h1 ≤ 3µm, its length is 18µm ≤ a ≤ 30µm, and its width is 18µm ≤ b ≤ 30µm, where a = b.

6. The design method for a microstructure realizing scalar vortices and vector beams as described in claim 1, characterized in that, The method includes the following steps: First, a substrate is selected; then, the substrate is divided into 2n regions, which are distributed around the origin of the coordinate system. The central angle of each region is 2π / 2n, where n is a positive integer, and the counterclockwise or clockwise rotation direction is selected as the vortex phase direction; then, based on the relationship between the vortex phase and the rotation angle of the designed microstructure unit, the rotation angle of the microstructure unit in each region is determined, and the microstructure units are arranged in their respective regions so that each region has a different phase compensation function; using simulation software, the length dx in the X direction and the length dy in the Y direction of the microstructure unit are calculated using variable parameters; subsequently, the optimal parameters are obtained by inputting the scanning calculation results into an evaluation function; finally, the microstructure units are processed and arranged on the substrate at a specified angle according to the optimal parameters, thus obtaining the microstructure that realizes scalar vortices and vector beams.

7. The design method according to claim 6, characterized in that, The evaluation function is: Where x i x j x k s represents the parameter value that needs to be evaluated. i s j s k This represents a given standard target value, where m, n, and p are the number of parameters to be evaluated under different weight values.

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