A continuous phase metasurface structure, spatial light modulator and preparation method

Abstract

The present invention relates to a continuous phase metasurface structure, a spatial light modulator, and a preparation method. The continuous phase metasurface structure includes: a substrate and a plurality of wedge-shaped metasurface units. When the continuous phase metasurface structure is configured as a substrate for the spatial light modulator, a continuous phase gradient is generated by the wedge-shaped metasurface units to achieve one or more operations including reflected / transmitted beam steering adjustment, near-submicron high-resolution oriented liquid crystal, and near-submicron high-resolution patterned alignment liquid crystal. The present invention meets the requirements for beam steering in practical applications such as lidar and optical communications by generating a continuous phase gradient and controlling the polarization direction of liquid crystal, especially without being constrained by deflection angles and sidelobe noise. The liquid crystal can also be oriented and pre-tilted, which makes the liquid crystal more orderly and enhances its optoelectronic performance when driven by an external field. At the same time, the generation and control of vector beams are achieved through high-resolution patterned alignment liquid crystal.

Description

Technical Field

[0001] The present invention relates to the field of light modulation technology, and in particular to a continuous phase metasurface structure, a spatial light modulator and a preparation method thereof. Background Art

[0002] Many applications, such as lidar, optical communications, holographic displays, and laser processing, require beam controllers to deflect or shape the beam. Current technologies for beam steering rely on macroscopic or microscopic mechanical means or liquid crystal spatial light modulators. Macroscopic mechanical beam deflection primarily utilizes the rotation of a mirror or multifaceted prism, or the vibration of a mirror to achieve beam scanning; microscopic mechanical devices primarily rely on microelectromechanical systems (MEMS) to control beam scanning. Liquid crystal spatial light modulators, on the other hand, utilize voltage-driven pixel blocks to control the phase of the liquid crystal, thereby constructing a pre-fabricated wavefront phase to deflect or shape the beam.

[0003] However, mechanical beam steering is slow, bulky, and expensive. Using liquid crystal pixel arrays to achieve beam steering results in diffraction sidelobes in the reflected / transmitted beams due to the large pixel area of the liquid crystal. In lidar applications, sidelobes reduce steering efficiency, cause false alarms, and introduce noise. Furthermore, sidelobes in free-space optical communications can also create crosstalk and eavesdropping channels, reducing security. While the use of an aperture can eliminate unnecessary diffraction instructions (sidelobes), this limits the angular scanning range. Therefore, eliminating diffracted beams is a challenge for beam steering devices.

[0004] Furthermore, LiDAR systems for autonomous vehicles use beam steering as a key component, but this application requires a large field of view (FOV) of 60° to 120° to scan the scene. Therefore, beam steering over a large FOV is a pressing challenge. However, most current work finds that achieving a large deflection range is challenging or that practical manufacturing methods struggle to meet the complex design requirements. Summary of the Invention

[0005] (1) Technical issues to be resolved

[0006] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a continuous phase metasurface structure, a spatial light modulator and a preparation method, which solve the technical problems of the existing beam steering devices being constrained by sidelobe noise and deflection angle.

[0007] (2) Technical solution

[0008] In order to achieve the above objectives, the main technical solutions adopted by the present invention include:

[0009] In a first aspect, an embodiment of the present invention provides a continuous phase metasurface structure, comprising:

[0010] substrate;

[0011] A plurality of wedge-shaped metasurface units with tunable continuous phases are arranged on the substrate;

[0012] Among them, when the continuous phase metasurface structure is configured as a substrate of a spatial light modulator, a continuous phase gradient is generated by the wedge-shaped metasurface unit to achieve one or more operations of reflected / transmitted beam steering adjustment, high-resolution orientation of liquid crystal at a near submicron level to make the liquid crystal produce a pretilt angle, and high-resolution patterned alignment of liquid crystal at a near submicron level.

[0013] Optionally,

[0014] The material of the substrate is silicon or ITO glass;

[0015] The material of the wedge-shaped metasurface unit is a noble metal material including gold, silver, aluminum and copper, or a dielectric material including TiO2, SiO2, Si and polymer.

[0016] In a second aspect, an embodiment of the present invention provides a method for preparing a continuous phase metasurface structure, which is applied to the continuous phase metasurface structure as described above, comprising:

[0017] The photoresist layer coated on the substrate is patterned by electron beam exposure, and the patterned photoresist layer is deposited based on a pre-set electron beam evaporation system and evaporation material;

[0018] A preset degumming solution is used to peel off the photoresist layer outside the deposited pattern, so that the deposited pattern remains on the substrate to form a wedge-shaped metasurface unit.

[0019] Optionally, patterning the photoresist layer coated on the substrate by electron beam exposure, and depositing the patterned photoresist layer based on a pre-set electron beam evaporation system includes:

[0020] Spin-coating a positive electron beam photoresist on the surface of the aluminum film plated on the substrate to prepare a photoresist layer with a thickness of 440 to 460 nm;

[0021] After pre-baking the substrate with the photoresist layer at 145-155° C. for 1.5-2.5 minutes, electron beam lithography exposure is performed at a dose of 350 μC / cm2 under the conditions of 1.5-2.5 nA current and 75-85 kV voltage;

[0022] The exposed substrate is placed in a developer for 58 to 62 seconds to obtain a photoresist pattern in the shape of a quadrangular prism with a trapezoidal bottom surface on the substrate;

[0023] After development, based on the pre-set electron beam evaporation system and the evaporation material, the vacuum degree is 5×10E-6Torr and the evaporation rate is controlled at Under the conditions of , performing a film deposition operation on the photoresist pattern in the shape of a quadrangular prism with a trapezoidal bottom surface;

[0024] As the coating deposition thickness increases to 70 nm, the short side openings of the quadrangular prism-shaped photoresist pattern with a trapezoidal bottom surface are sealed, and then the coating deposition operation is continued on the long side openings until a wedge-shaped metasurface unit of 175 to 185 nm is obtained.

[0025] In a third aspect, an embodiment of the present invention provides a reflective / transmissive spatial light modulator based on a continuous phase metasurface structure, comprising:

[0026] Two substrates arranged opposite to each other and a liquid crystal molecule layer arranged between the two substrates;

[0027] A substrate is an ITO glass plate with a rubbed alignment layer;

[0028] The other substrate is a continuous phase metasurface structure, comprising: a substrate and a wedge-shaped metasurface array disposed on the substrate, the wedge-shaped metasurface array comprising a plurality of wedge-shaped metasurface unit groups of different periods, each wedge-shaped metasurface unit group comprising a plurality of wedge-shaped metasurface units of the same period;

[0029] Among them, by applying corresponding voltage to the liquid crystal molecular layer between the two substrates, one or more operations of reflection / transmission beam steering adjustment, near-submicron level high-resolution oriented liquid crystal, and near-submicron level high-resolution graphic alignment liquid crystal can be achieved.

[0030] Optionally,

[0031] The desired beam deflection angle is obtained by adjusting the structural parameters of the continuous phase metasurface structure, including length, width, period, and thickness, and / or by assisting movement with a preset mechanical displacement device so that a wedge-shaped metasurface unit group with different periods is incident or transmitted by the incident light;

[0032] By implementing near sub-micron level high resolution alignment of liquid crystal, a certain pre-tilt angle is generated in the liquid crystal;

[0033] By implementing high-resolution patterned alignment liquid crystal operations at a near sub-micron level, a variety of vector beams and / or vortex beams are generated and controlled.

[0034] Optionally, the liquid crystal molecule layer includes a plurality of twisted nematic liquid crystals, and a gap between each liquid crystal is 4 to 6 μm.

[0035] In a fourth aspect, an embodiment of the present invention provides a method for manufacturing a reflective / transmissive spatial light modulator, which is applied to the reflective / transmissive spatial light modulator as described above, comprising:

[0036] A liquid crystal cell is formed by using an ITO glass plate with a rubbed alignment layer and the continuous phase metasurface structure;

[0037] Liquid crystal is poured into a liquid crystal cell at a preset temperature to form a reflective / transmissive spatial light modulator.

[0038] Optionally, forming a liquid crystal cell using an ITO glass plate with a rubbed alignment layer and the continuous phase metasurface structure includes:

[0039] The polyimide solution was spin-coated on a cleaned ITO glass plate, and then baked in an oven at 195-205°C for 1.8-2.2 hours to obtain a polyimide coating with a thickness of 95-105 nm;

[0040] rubbing the polyimide coating using a friction machine to obtain an ITO glass plate with a friction alignment layer;

[0041] The ITO glass plate with the rubbed alignment layer and the continuous phase metasurface structure are bonded together by UV-curing adhesive doped with ±5 micron diameter silicon oxide to form a liquid crystal cell;

[0042] Among them, the gap in the liquid crystal box is controlled between 4 and 6 μm by adding silicon oxide microspheres with a diameter of ±5 μm.

[0043] Optionally, pouring liquid crystal into a liquid crystal cell at a preset temperature to form a reflective / transmissive spatial light modulator includes:

[0044] Liquid crystal is poured into a liquid crystal box by capillary action at a clearing point temperature of 65 to 75° C., and then cooled to room temperature to obtain a reflective / transmissive spatial light modulator.

[0045] (3) Beneficial effects

[0046] The present invention meets the requirements for beam steering in practical applications such as lidar and optical communications by generating a continuous phase gradient and controlling the polarization direction with liquid crystal, especially no longer being constrained by deflection angle and sidelobe noise; and the proposed wedge-shaped metasurface unit can orient the liquid crystal and produce a pre-tilt angle, which makes the liquid crystal more orderly and enhances its photoelectric performance when driven by an external field; at the same time, it can also achieve high-resolution patterned alignment of the liquid crystal to achieve the purpose of generating and regulating vector beams. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 A schematic structural diagram of a continuous phase metasurface structure provided by an embodiment of the present invention;

[0048] Figure 2 A schematic diagram of the tunable continuous phase corresponding to wedge-shaped metasurface units of different periods of a continuous phase metasurface structure provided by an embodiment of the present invention;

[0049] Figure 3 (a)-(c) show the effects of oriented liquid crystals on wedge-shaped metasurfaces with heights of 120nm, 150nm, and 180nm, respectively; (d) the device for testing the pre-tilt angle of liquid crystals using the rotating crystal method; and (e) the incident angle and pre-tilt angle when the phase difference of oriented liquid crystals on wedge-shaped metasurfaces of different heights is the largest.

[0050] Figure 4 A schematic flow chart of a method for preparing a continuous phase metasurface structure provided by an embodiment of the present invention;

[0051] Figure 5 A schematic diagram of a specific process of step S1 of a method for preparing a continuous phase metasurface structure provided by an embodiment of the present invention;

[0052] Figure 6 Schematic diagram of the preparation process of a wedge-shaped metasurface unit of a reflective / transmissive spatial light modulator based on a continuous phase metasurface structure provided in an embodiment of the present invention.

[0053] Figure 7 A schematic diagram of the composition of a reflective / transmissive spatial light modulator based on a continuous phase metasurface structure provided by an embodiment of the present invention;

[0054] Figure 8 A schematic diagram of an array on a continuous phase metasurface structure of a reflective / transmissive spatial light modulator based on a continuous phase metasurface structure provided by an embodiment of the present invention;

[0055] Figure 9 (a) and (b) are the simulation and experimental test of the order contrast of the anomalous reflection when the spatial light modulator is in the off state (x-polarization); (c) and (d) are the simulation and experimental test of the order contrast of the anomalous reflection when the spatial light modulator is in the on state (y-deflection); (e) and (f) are the simulation and experimental test of the order deflection angle of the anomalous reflection of the spatial light modulator;

[0056] Figure 10 A schematic diagram of the liquid crystal alignment of a wedge-shaped metasurface unit of a continuous phase metasurface structure provided by an embodiment of the present invention;

[0057] Figure 11 A schematic flow chart of a method for preparing a reflective / transmissive spatial light modulator provided in an embodiment of the present invention;

[0058] Figure 12 This is a schematic diagram of a specific flow of step F1 of a method for preparing a reflective / transmissive spatial light modulator provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0059] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation methods in conjunction with the accompanying drawings.

[0060] like Figure 1 As shown, an embodiment of the present invention proposes a continuous phase metasurface structure, comprising: a substrate; a wedge-shaped metasurface unit with tunable continuous phase, which is arranged on the substrate; wherein, when the continuous phase metasurface structure is configured as a substrate of a spatial light modulator, a continuous phase gradient is generated by the wedge-shaped metasurface unit to achieve one or more operations of reflected / transmitted beam steering adjustment, micron-level high-resolution orientation of liquid crystal and pre-tilt angle of liquid crystal, and micron-level high-resolution patterned alignment of liquid crystal.

[0061] The wedge-shaped metasurface unit with a certain tilt angle provided by the present invention can make the liquid crystal have a certain pre-tilt angle when it is aligned. Figure 3 (e) in FIG. 5 shows the relevant pre-tilt angle test results.

[0062] The wedge-shaped metasurface elements of the present invention utilize subwavelength dimensions, avoiding the generation of other diffraction orders, including sidelobe noise. Conventional large pixels naturally produce many orders. Furthermore, while existing technologies have a strong zero-order diffraction, the wedge-shaped metasurface elements of the present invention utilize anomalous diffraction, concentrating energy primarily on anomalous orders.

[0063] The long axis direction of each subwavelength structure wedge-shaped metasurface unit provided by the present invention can independently align the liquid crystal. By encoding the rotation angle of each structure, high-resolution graphical alignment of the liquid crystal can be achieved, and by applying voltage, the generation or closing of alignment patterns such as vector beams or vortex beams can be achieved.

[0064] Therefore, the present invention meets the requirements for beam steering in practical applications such as lidar and optical communications by generating a continuous phase gradient and controlling the polarization direction of liquid crystal, especially no longer being constrained by deflection angle and sidelobe noise; and the proposed wedge-shaped metasurface unit can orient the liquid crystal and produce a pre-tilt angle, which makes the liquid crystal more orderly and enhances the optoelectronic performance when driven by an external field; at the same time, it can also graphically align the liquid crystal with high resolution to achieve the purpose of generating and regulating vector beams.

[0065] To better understand the above technical solutions, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. Rather, these embodiments are provided to enable a clearer and more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0066] Further, Figure 1 One side of the wedge shown in the figure is composed of two straight lines that are inclined in the same direction and converge to each other, and the other side is composed of two parallel straight lines that converge to each other; Figure 2 It shows the continuous phase that can be brought about by wedge-shaped metasurfaces of different periods (i.e., different sizes). The principle is that the continuous gradient structure (wedge shape) of different thicknesses and widths can also continuously modulate the phase of light.

[0067] Furthermore, the material of the substrate can be a silicon wafer (reflective type) or ITO glass (transmissive type); the material of the wedge-shaped metasurface unit can be a precious metal, such as gold, silver, aluminum, copper, etc., or a dielectric material, such as Si, SiO2, TiO2, polymer material (such as photoresist, etc.); it should also be noted that the use of precious metals is generally reflective, while the use of dielectric materials is transmissive.

[0068] refer to Figure 3 , Figure 3 The ac in the figure are polarizing microscope images of liquid crystal orientation of wedge-shaped metasurfaces with different h2 heights made on ITO glass. It can be seen that the orientation effect is good and high-resolution orientation of liquid crystal can be achieved. Figure 3 Where d is the test device for the pre-tilt angle of liquid crystal orientation. Figure 3 Where e is the incident angle and pretilt angle at the maximum optical path difference of the three liquid crystal cells made with metasurfaces of different heights. This shows that the wedge-shaped metasurface unit can achieve a pretilt angle of approximately 2.2°, which is the same as the pretilt angle achieved by existing technology (rubbing alignment) and can meet practical needs.

[0069] like Figure 4 As shown, an embodiment of the present invention provides a method for preparing a continuous phase metasurface structure, which is applied to the above-mentioned continuous phase metasurface structure, comprising:

[0070] S1. Patterning a photoresist layer applied to a substrate by electron beam lithography (EBL) is performed, and the patterned photoresist layer is deposited using a pre-configured EB evaporation system and evaporation materials. EBL can be used to fabricate subwavelength devices. The EB evaporation system is a conventional instrument, and the evaporation materials include both metals and non-metals.

[0071] Furthermore, if Figure 5 and Figure 6 As shown, step S1 includes:

[0072] S11. Spin-coat a positive electron beam photoresist (AR-P6200.13) on the surface of the aluminum film (100 nm) deposited on the substrate to prepare a photoresist layer with a thickness of 440 to 460 nm (preferably 450 nm).

[0073] S12. After pre-baking the substrate with the photoresist layer at 145-155°C (preferably 150°C) for 1.5-2.5 min (preferably 2 min), electron beam lithography exposure is performed at a dose of 350 μC / cm2 under the conditions of 1.5-2.5 nA (preferably 2 nA) current and 75-85 kV (80 kV) voltage.

[0074] S13. The exposed substrate is placed in an AR 600-546 developer and developed for 58 to 62 seconds (preferably 60 seconds) to obtain a photoresist pattern in the shape of a quadrangular prism with a trapezoidal bottom surface on the substrate (the specific photoresist pattern is a trapezoidal hole, and finally a wedge-shaped structure with a three-dimensional structure is obtained by depositing metal or non-metal).

[0075] S14, after development, based on the pre-set electron beam evaporation system and the evaporation material, the vacuum degree is 5×10E-6Torr and the evaporation rate is controlled at 0.4 to 0.6 (preferably 0.5). Under the conditions of , a film deposition operation is performed on a photoresist pattern in the shape of a quadrangular prism with a trapezoidal bottom surface.

[0076] S15. As the coating deposition thickness increases to 70nm, the short side of the photoresist pattern in the shape of a quadrangular prism with a trapezoidal bottom surface is sealed first, and then the long side is deposited. Finally, after lift-off, an adhesion layer (chromium adhesion layer) of 1.5 to 2.5nm (preferably 2nm) is obtained, which has no effect on the device performance but only enhances the adhesion of the subsequent coating and a wedge-shaped metasurface unit of 175 to 185nm (preferably 180nm).

[0077] refer to Figure 1 The parameters of the wedge-shaped metasurface unit are: Py = 300nm, Px = 900nm, L = 700nm, h1 = 70nm, h2 = 180nm, w1 = 40nm, and W2 = 240nm. When the thickness is equal to the side length plus 30nm, the edge is sealed. In the embodiment, the electron beam forms a trapezoidal shape, and the process is a gradual process. For example, a 40nm wide area will be sealed at a thickness of 70nm. Therefore, the glue thickness is 430nm, and the final deposition is 180nm.

[0078] S2. Use a preset degumming solution (AR 600-71) to peel off the photoresist layer outside the deposited pattern, so that the deposited pattern remains on the substrate to form a wedge-shaped metasurface unit.

[0079] like Figure 7 As shown, an embodiment of the present invention provides a reflection / transmission type spatial light modulator based on a continuous phase metasurface structure, comprising: two substrates arranged opposite to each other and a liquid crystal molecule layer arranged between the two substrates; one substrate is an ITO glass plate with a rubbed alignment layer; the other substrate is a continuous phase metasurface structure, such as Figure 8 As shown, the continuous phase metasurface structure includes a substrate and a wedge-shaped metasurface array disposed on the substrate. The wedge-shaped metasurface array includes multiple groups of wedge-shaped metasurface units with different periods, and each group of wedge-shaped metasurface units includes several wedge-shaped metasurface units with the same period. This reflective / transmissive spatial light modulator not only eliminates interference from sidelobe signals but also achieves the advantage of a large field of view.

[0080] Furthermore, by applying a corresponding voltage to the liquid crystal molecular layer between the two substrates, one or more of the following operations can be achieved: beam steering adjustment for reflection / transmission, high-resolution alignment of liquid crystals at the micron level, and high-resolution patterned alignment of liquid crystals at the micron level. The near-submicron level is defined as less than 2 microns. When a beam of linearly polarized light passes perpendicularly through the liquid crystal cell, its polarization direction rotates due to the twisting of the liquid crystal molecules. When a certain voltage is applied to the two substrates, the electric field causes the liquid crystal molecules to tilt, and the magnitude of the tilt angle affects the magnitude of the rotation angle of the linearly polarized light's vibration direction. When the liquid crystal cell is inserted between two polarizers, the magnitude of the applied electric field can be used to modulate the amplitude or phase of the light wave.

[0081] Furthermore,

[0082] By adjusting the structural parameters of the continuous phase metasurface structure including length, width, period, and thickness and / or by using a preset mechanical displacement device to assist in moving the wedge-shaped metasurface unit groups with different periods so that the incident light is incident or transmitted, the desired beam deflection angle can be obtained. Figure 9 As shown, the thickness parameters of the known continuous phase metasurface structure are 180nm, W1 is 40nm, W2 is 240nm, the wedge length L = Px-200nm, Py is fixed at 300nm, and the starting value of the period Px is 300nm. By changing the period Px of the wedge-shaped metasurface unit, different deflection angles can be achieved. At the same time, a mechanical displacement device can be used to assist in the movement so that groups of wedge-shaped metasurface units with different periods Px can be incident or transmitted by the incident light, thereby achieving adjustable beam deflection angle.

[0083] By implementing near-submicron-level high-resolution alignment of liquid crystals, the liquid crystals produce a certain pre-tilt angle.

[0084] By implementing high-resolution patterned liquid crystal operations at the near-submicron level, a variety of vector light beams and / or vortex light beams can be generated and controlled. By implementing high-resolution patterned liquid crystals, vector light beams containing one or more of radially polarized light, angularly polarized light, and vortices can be generated and controlled accordingly. The liquid crystal can be oriented along the long axis of each unit cell on the metasurface. Simply by encoding a pattern, the liquid crystal can be aligned in an orderly manner. Figure 10 , the wedge-shaped metasurface unit can realize high-resolution liquid crystal alignment functions, such as angular and radial orientation of liquid crystals.

[0085] Applying a voltage controls the deflection of the liquid crystal, building on the already achieved control of the incident light polarization, and further enabling the generation and elimination of vector beams. Specifically, the rotation angles of the metasurface units can be distributed according to the phase distribution of the vector light field, and the liquid crystals will also align at the preset angles of each metasurface unit, thus achieving vector beams. When a higher voltage is applied, the liquid crystal becomes isotropic, lacking the phase or polarization of the vector beam, and the control effect disappears.

[0086] It is worth mentioning that the gap between each liquid crystal in the liquid crystal molecule layer is 4 to 6 μm.

[0087] like Figure 11 As shown, an embodiment of the present invention provides a method for preparing a reflective / transmissive spatial light modulator, which is applied to the reflective / transmissive spatial light modulator described above, comprising:

[0088] F1. A liquid crystal cell is formed using an ITO glass plate with a rubbed alignment layer and a continuous phase metasurface structure.

[0089] Furthermore, if Figure 12 As shown, step F1 includes:

[0090] F11. Spin-coat a polyimide solution (PI, DL-5260, DALTON) onto a cleaned ITO glass plate, then bake in an oven at 195-205°C for 1.8-2.2 hours (preferably 200°C) to obtain a polyimide coating with a thickness of 95-105 nm (preferably 100 nm). The cleaning process includes ultrasonicating the ITO glass plate in acetone for 20 minutes and in IPA for 20 minutes, followed by drying.

[0091] F12. Use a friction machine (LHC-MC-V1, HCPE) to rub the polyimide coating (PI layer) to obtain ITO glass with a rubbed alignment layer.

[0092] F13. The ITO glass plate with the rubbed alignment layer and the continuous phase metasurface are bonded together using UV-curable adhesive NOA65 to form a liquid crystal cell. Specifically, NOA65, doped with ±5-micron diameter silicon oxide, is applied and bonded to the ITO glass plate and the continuous phase metasurface, then cured with UV light.

[0093] F2. Liquid crystal is poured into a liquid crystal cell at a preset temperature to form a reflective / transmissive spatial light modulator.

[0094] Furthermore, step F2 includes: pouring liquid crystal E7 into the liquid crystal cell by capillary action at a clearing point temperature of 65-75° C. (preferably 70° C.) until it cools to room temperature of 25° C. to obtain a reflective / transmissive spatial light modulator.

[0095] In summary, the present invention discloses a continuous phase metasurface structure, a spatial light modulator, and a preparation method. The wedge-shaped metasurface unit in the continuous phase metasurface structure can orient liquid crystals with high resolution and introduce a pre-tilt angle, which makes the liquid crystal more ordered when driven by an external field and enhances the optoelectronic performance; the wedge-shaped metasurface unit can pattern the liquid crystal with high resolution for the generation and control of vector light beams. At the same time, the reflective tunable continuous phase metasurface spatial light modulator mentioned in the present invention has a large field of view. By adjusting the structural parameters of the wedge-shaped metasurface unit or with the assistance of mechanical displacement, continuous phase metasurfaces of different periods can be switched, achieving a larger angular deflection of the light beam from -17.98° to -76.87° and from 17.98° to 76.87°. It can be seen that the efficiency ratio of abnormal reflection is as high as ~15. Therefore, the spatial light modulator proposed by the present invention can meet the requirements for light beam steering in practical applications such as lidar and optical communications, so that it is no longer constrained by deflection angle and sidelobe noise.

[0096] Since the systems / devices described in the above embodiments of the present invention are systems / devices used to implement the methods of the above embodiments of the present invention, those skilled in the art will be able to understand the specific structures and variations of these systems / devices based on the methods described in the above embodiments of the present invention, and thus will not be described in detail here. All systems / devices used in the methods of the above embodiments of the present invention are within the scope of protection of the present invention.

[0097] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0098] The present invention is described with reference to flowcharts and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions.

[0099] It should be noted that, in the claims, any reference signs placed between brackets shall not be construed as limiting the claims. The word "comprising" does not exclude the presence of components or steps not listed in the claims. The word "a" or "an" preceding a component does not exclude the presence of a plurality of such components. The invention may be implemented by means of hardware comprising several different components and by means of a suitably programmed computer. In claims enumerating several means, several of these means may be embodied by one and the same hardware. The use of the words first, second, third etc. is for convenience only and does not indicate any order. These words may be understood as part of the component name.

[0100] In addition, it should be noted that, in the description of this specification, the description of the terms "one embodiment", "some embodiments", "embodiment", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples, unless they are contradictory.

[0101] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments after learning the basic creative concept. Therefore, the claims should be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0102] Obviously, those skilled in the art may make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if such modifications and variations fall within the scope of the claims and their equivalents, the present invention shall also include such modifications and variations.

Claims

1. A continuous phase metasurface structure, characterized in that: include: substrate; A plurality of wedge-shaped metasurface units with tunable continuous phases are arranged on the substrate; When the continuous phase metasurface structure is configured as a substrate for a spatial light modulator, a continuous phase gradient is generated by the wedge-shaped metasurface unit to achieve one or more of the following operations: beam steering adjustment for reflection / transmission, high-resolution alignment of liquid crystals at near submicron level to generate a pretilt angle for the liquid crystals, and high-resolution patterned alignment of liquid crystals at near submicron level. The method for preparing the continuous phase metasurface structure includes: The method comprises the following steps: patterning a photoresist layer coated on a substrate by electron beam exposure, and depositing the patterned photoresist layer based on a pre-set electron beam evaporation system and an evaporation material, comprising: spin coating a positive electron beam photoresist on the surface of an aluminum film plated on the substrate to prepare a photoresist layer with a thickness of 440 to 460 nm; pre-baking the substrate with the photoresist layer at 145 to 155° C. for 1.5 to 2.5 minutes, and then performing electron beam lithography exposure at a dose of 350 μC / cm2 under conditions of a current of 1.5 to 2.5 nA and a voltage of 75 to 85 kV; placing the exposed substrate in a developer for development for 58 to 62 seconds to obtain a photoresist pattern in the shape of a quadrangular prism with a trapezoidal bottom surface on the substrate; and after development, performing a evaporation process based on a pre-set electron beam evaporation system and an evaporation material at a vacuum degree of 5×10E-6 Torr and an evaporation rate controlled at Under the conditions of , a coating deposition operation is performed on the photoresist pattern in the shape of a quadrangular prism with a trapezoidal bottom surface; as the coating deposition thickness increases to 70 nm, the short side openings of the photoresist pattern in the shape of a quadrangular prism with a trapezoidal bottom surface are sealed, and then the coating deposition operation is continued on the long side openings until a wedge-shaped metasurface unit of 175 to 185 nm is obtained; A preset degumming solution is used to peel off the photoresist layer outside the deposited pattern, so that the deposited pattern remains on the substrate to form a wedge-shaped metasurface unit.

2. The continuous phase metasurface structure according to claim 1, wherein: The material of the substrate is silicon or ITO glass; The material of the wedge-shaped metasurface unit is one of gold, silver, aluminum and copper, or one of TiO2, SiO2, Si and polymer.

3. A reflection / transmission spatial light modulator based on a continuous phase metasurface structure, characterized in that: include: Two substrates arranged opposite to each other and a liquid crystal molecule layer arranged between the two substrates; A substrate is an ITO glass plate with a rubbed alignment layer; The other substrate is a continuous phase metasurface structure, comprising: a substrate and a wedge-shaped metasurface array disposed on the substrate, the wedge-shaped metasurface array comprising a plurality of wedge-shaped metasurface unit groups of different periods, each wedge-shaped metasurface unit group comprising a plurality of wedge-shaped metasurface units of the same period; By applying a corresponding voltage to the liquid crystal molecular layer between the two substrates, one or more operations including reflected / transmitted beam steering adjustment, near-submicron-level high-resolution oriented liquid crystal, and near-submicron-level high-resolution patterned alignment liquid crystal can be achieved; The desired beam deflection angle is obtained by adjusting the structural parameters of the continuous phase metasurface structure, including length, width, period, and thickness, and / or by assisting movement with a preset mechanical displacement device so that a wedge-shaped metasurface unit group with different periods is incident or transmitted by the incident light; By implementing near sub-micron level high resolution alignment of liquid crystal, a certain pre-tilt angle is generated in the liquid crystal; By implementing high-resolution patterned alignment liquid crystal operations at a near sub-micron level, a variety of vector beams and / or vortex beams are generated and controlled.

4. The reflective / transmissive spatial light modulator based on a continuous phase metasurface structure according to claim 3, wherein: The liquid crystal molecule layer includes a plurality of twisted nematic liquid crystals, and the gap between each liquid crystal is 4 to 6 μm.

5. A method for preparing a reflective / transmissive spatial light modulator, applied to the reflective / transmissive spatial light modulator according to claim 3 or 4, characterized in that: include: A liquid crystal cell is formed by using an ITO glass plate with a rubbed alignment layer and the continuous phase metasurface structure; Liquid crystal is poured into a liquid crystal cell at a preset temperature to form a reflective / transmissive spatial light modulator.

6. The method for preparing a reflective / transmissive spatial light modulator according to claim 5, wherein: Filling a liquid crystal into a liquid crystal cell at a preset temperature to form a reflective / transmissive spatial light modulator includes: Liquid crystal is poured into a liquid crystal box by capillary action at a clearing point temperature of 65 to 75° C., and then cooled to room temperature to obtain a reflective / transmissive spatial light modulator.

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