Nonlinear geometric phase liquid crystal element, method of making and use thereof

Abstract

The application discloses a nonlinear geometric phase liquid crystal element and a preparation method and application thereof. The liquid crystal element comprises a first substrate, a first orientation layer, a liquid crystal layer, a second orientation layer and a second substrate arranged in sequence; the first substrate and the second substrate are ITO glass substrates; the first orientation layer and the second orientation layer are photo-controlled orientation layers; the first orientation layer and the second orientation layer are coated on the first substrate and the second substrate by spin coating; the first orientation layer of the first substrate and the second orientation layer of the second substrate are oppositely arranged; and the distance between the first orientation layer and the second orientation layer is controlled by a spacer. The application utilizes the characteristic that ferroelectric nematic phase liquid crystals respond to external stimuli such as orientation fields, heat and electricity to realize the application of dynamically adjustable nonlinear structure light field regulation in the field of soft matter nonlinear photonics.

Description

Technical Field

[0001] This invention belongs to the field of nonlinear optics technology, and more specifically, relates to a nonlinear geometric phase liquid crystal element, its preparation method, and its application. Background Technology

[0002] Liquid crystals possess unique anisotropic optical properties, self-assembly capabilities, and dynamic tunability, making them an ideal choice for structured light field manipulation in linear optics. A novel type of liquid crystal discovered in recent years—ferroelectric nematic liquid crystal—breaks the head-to-tail symmetry of traditional liquid crystals, exhibiting spontaneous polarization, a large dielectric constant, and a strong nonlinear optical response, making it highly suitable for programmable, dynamic structured light field manipulation in nonlinear optics. To date, ferroelectric nematic liquid crystals have been extensively studied in terms of high-performance materials, electro-optic properties, polar order characterization, and stimulus responsiveness. However, in the field of nonlinear optics, due to the difficulty in controlling the polarization direction, research on lithography-free, dynamically tunable three-dimensional nonlinear optical fluids for light field manipulation remains limited.

[0003] Nonlinear photonics, primarily focused on the manipulation of light / photons in nonlinear media, is the core of nonlinear optics and has greatly promoted the development of materials science, quantum computing, biomedical engineering, and information technology. Currently, many novel physical effects and functions, such as continuous control of nonlinear phases, nonlinear wavefront shaping, nonlinear vector element holography, three-dimensional lithium niobate nanodomain engineering, frequency-doubled beam generation, and ultrathin, high-dimensional, and multiphoton quantum light sources, have been realized with the advent of nonlinear optical materials. However, due to the limitations of crystal symmetry, polarization is restricted to reverse polarization and binary polarization. Furthermore, the geometry of materials after static fabrication largely limits dynamic tunability. These facts severely hinder the exploration of new nonlinear optical phenomena in dynamic light-matter interactions to achieve more advanced nonlinear photonic applications. Moreover, with the engineering progress of bulk nonlinear photonic crystals and nonlinear metasurfaces, the concept of the geometric phase of light has been extended from linear optics to nonlinear optics. Therefore, how to utilize dynamically tunable materials to achieve nonlinear structured light field manipulation applications based on nonlinear geometric phases is currently a research hotspot. Summary of the Invention

[0004] The purpose of this invention is to achieve multidimensional optical field manipulation (including linear and nonlinear structured optical field manipulation) by utilizing the structured orientation of liquid crystals, and to realize the application of dynamically tunable liquid crystal elements in the field of nonlinear soft matter photonics by utilizing the responsiveness of liquid crystals to orientation, chirality, thermal and electrical stimulation.

[0005] This invention provides a nonlinear geometric phase liquid crystal element and its fabrication method. By employing photo-controlled orientation and thermal annealing processes to precisely pattern the ferroelectric nematic liquid crystal, the liquid crystal geometric phase element converts the pumped fundamental Gaussian light into a spatially unique structured light field during nonlinear frequency conversion. Furthermore, the sample exhibits a response to external stimuli such as thermal and electric fields, enabling its application in dynamically reconfigurable nonlinear photonics.

[0006] The nonlinear geometric phase encoded ferroelectric nematic liquid crystal cell includes a first ITO glass substrate, a first photo-alignment agent, a liquid crystal layer, a second photo-alignment layer, and a second ITO glass substrate. The first and second photo-alignment layers are spin-coated onto the first and second ITO substrates, respectively. The first photo-alignment layer of the first ITO substrate and the second photo-alignment layer of the second ITO substrate are placed opposite each other, and the distance between the first and second photo-alignment layers is controlled by spacers or the like.

[0007] Optionally, the material of the alignment layer can be selected from surfactants, friction alignment agents, photocrosslinking materials, photodegradable materials, and photoinduced cis-trans isomers. In this invention, the alignment agents for the first and second alignment layers are both azo-based photo-controlled alignment materials SD1 and Brilliant Yellow. Under linearly polarized light irradiation, the molecules of the photo-controlled alignment material align in a direction perpendicular to the direction of linearly polarized light, and through interaction with the liquid crystal molecules, cause the liquid crystal molecules to form an ordered orientation, thereby achieving control over the orientation of the liquid crystal molecules. In practical operation, the material is not limited to this.

[0008] Optionally, the liquid crystal layer material uses ferroelectric nematic liquid crystal to achieve a thermo- and electrically switchable dynamic nonlinear optical response. Ferroelectric nematic liquid crystals exhibit different phase states during temperature changes, resulting in corresponding changes in the nonlinear optical response. Furthermore, ferroelectric nematic liquid crystals respond rapidly to electric fields; applying an electric field causes the nonlinear optical response to switch. The nonlinear geometric phase liquid crystal element described in this invention uses either ferroelectric nematic liquid crystal RM734 or DIO, but is not limited to these materials.

[0009] Optionally, one or more of the chiral dopants CB15, 4-((4-nitrophenoxy)carbonyl)phenyl(S)-2-(sec-butoxy)-4-methoxybenzoate, (S)-ring-3, ZLI811, BDH1281, R1011, R811, S811, S5011, and R5011 in the liquid crystal layer of the nonlinear geometric phase liquid crystal element can achieve a nonlinear optical response with spin selectivity. However, it is not limited to these materials and structures. By using different chiral dopants in the liquid crystal layer and designing accordingly based on functional requirements, a specific structure can be obtained.

[0010] Specifically, in some embodiments of the present invention, the helical twisting induced by the chiral agent can drive the liquid crystal to self-assemble into a helical q-superstructure, which can generate a nonlinear vortex beam with strong circular dichroism. The chiral dopant of the chiral q-superstructure liquid crystal layer described in the present invention is the right-handed dopant R811, with a doping concentration of 1.0 wt%, and the induced q-superstructure exhibits a right-handed helix.

[0011] To solve at least one of the above-mentioned technical problems, according to one aspect of the present invention, a method for fabricating a nonlinear geometric phase liquid crystal element is provided, comprising the following steps: sequentially setting a first substrate, a first alignment layer, a liquid crystal layer, a second alignment layer, and a second substrate;

[0012] The first and second substrates are configured as ITO glass substrates;

[0013] The first and second alignment layers are configured as optically controlled alignment layers;

[0014] The first alignment layer and the second alignment layer are spin-coated onto the first substrate and the second substrate, with the first alignment layer of the first substrate and the second alignment layer of the second substrate placed opposite each other, and the distance between the first alignment layer and the second alignment layer is controlled by a spacer.

[0015] Preferably, one of the azo-based photo-alignment material SD1 and brilliant yellow is selected as the alignment agent for the first and second alignment layers. Under the irradiation of linearly polarized light, the molecules of the photo-alignment material will align in a direction perpendicular to the direction of the linearly polarized light, and through the interaction with the liquid crystal molecules, the liquid crystal molecules will form a specially designed ordered arrangement.

[0016] Specifically, in the embodiments of the present invention, the nonlinear geometric phase liquid crystal element described herein can convert the pumped fundamental Gaussian light into a spatially special structured light field while simultaneously performing nonlinear frequency conversion. For example, a q-wave plate generates a frequency-doubled vortex light field, and the left / right circularly polarized channels of the output light field correspond to different vortex topological charges. Simultaneously, the element retains linear light field manipulation capability, realizing the ability to convert fundamental Gaussian light into fundamental vortex light. Furthermore, the intensity of the nonlinear optical response changes accordingly with temperature variations or the introduction of an external electric field, thereby satisfying the application requirements of the nonlinear geometric phase liquid crystal element described herein in the field of dynamically reconfigurable nonlinear photonics.

[0017] According to another aspect of the present invention, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the steps in the method for preparing the nonlinear geometric phase liquid crystal element of the present invention.

[0018] According to another aspect of the present invention, a computer device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps in the method for preparing the nonlinear geometric phase liquid crystal element of the present invention.

[0019] Compared with existing technologies, the beneficial effects of the above-mentioned method of the present invention are as follows: The present invention utilizes the characteristic of liquid crystals responding to external stimuli to realize the application of dynamically tunable nonlinear liquid crystal light field control in the field of nonlinear soft matter photonics. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments will be briefly described below. Obviously, the drawings described below only relate to some embodiments of the present invention and are not intended to limit the present invention.

[0021] Figure 1 This is a structural diagram of the liquid crystal element prepared according to the present invention;

[0022] Figure 2 This is a schematic diagram of the liquid crystal molecule orientation of the nonlinear geometric phase liquid crystal element prepared in this invention;

[0023] Figure 3 The image shows the texture of the nonlinear geometric phase liquid crystal element sample prepared in this invention under a polarizing microscope.

[0024] Figure 4 The fundamental frequency optical field modulated by the nonlinear geometric phase liquid crystal element prepared in this invention and the generated frequency-doubled optical field;

[0025] Figure 5 The intensity change of the linear / nonlinear structure optical field response of the nonlinear geometric phase liquid crystal element prepared in this invention during temperature change;

[0026] Figure 6 The intensity change of the linear / nonlinear structure optical field response of the nonlinear geometric phase liquid crystal element prepared in this invention when an external electric field is introduced;

[0027] Figure 7 This is a schematic diagram of the liquid crystal molecule orientation of the spin-selective nonlinear geometric phase liquid crystal element prepared according to the present invention.

[0028] Figure 8 The emitted light field distribution of the spin-selective nonlinear geometric phase liquid crystal element prepared according to the present invention. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention.

[0030] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0031] Example 1:

[0032] like Figure 1 As shown, this invention proposes a nonlinear geometric phase liquid crystal element, its fabrication method, and its application. Figure 1 The structure of the liquid crystal element prepared according to the present invention is shown in the figure, and the preparation steps are as follows:

[0033] The ITO glass substrate was ultrasonically cleaned using ITO cleaning solution for 30 minutes. It was then ultrasonically cleaned twice more with ultrapure water, each time for 10 minutes. The cleaned substrate was then placed in a drying oven at 120°C for 40 minutes. Finally, the glass substrate was subjected to ultraviolet ozone cleaning for 30 minutes.

[0034] Optionally, a photoalignment agent SD1 is spin-coated onto an ITO glass substrate. The spin-coating process is as follows: first, spin-coating at 800 rpm for 8 seconds; second, spin-coating at 3000 rpm for 40 seconds. The final photoalignment agent layer has a thickness of approximately 30 nanometers. After spin-coating the alignment agent, the glass substrate with the photoalignment agent SD1 is annealed at 100°C for 10 minutes.

[0035] Optionally, 4-micron silica or polystyrene microspheres are mixed with sealant as a spacer and uniformly applied to the edge of the glass substrate. The upper and lower substrates are then bonded together in a staggered manner and placed under ultraviolet light until the sealant cures, forming a liquid crystal cell. The cell thickness of the liquid crystal cell in this embodiment was measured to be approximately 4.1 microns using interferometry.

[0036] To achieve a structure that matches the orientation of the ferroelectric nematic liquid crystal molecules, a multi-step partially overlapping exposure was performed using a micro-projection exposure system based on digital micromirror devices. In this system, the light beams reflected from each micromirror are assigned a specific polarization state after passing through an electrically controlled polarizer before illuminating the surface of the liquid crystal cell. After a certain dose of light exposure, the photo-aligning agent molecules in the exposed area will form a patterned alignment. By rotating the polarizer in the system, different positions of the exposed pattern can be aligned with polarized light of different directions, thus resulting in different orientations of the photo-aligning agent molecules.

[0037] Figure 2This is a schematic diagram of the liquid crystal molecule orientation of the nonlinear geometric phase liquid crystal element prepared by the present invention. The first alignment layer and the second alignment layer are oriented by polarized ultraviolet exposure. Liquid crystal material is injected between the first substrate and the second substrate. The ferroelectric nematic liquid crystal material RM734 is heated to 190°C and injected into the liquid crystal cell through a capillary glass tube, so that the liquid crystal molecules are aligned according to the orientation direction of the first alignment layer and the second alignment layer. Figure 3 This is a texture image of the nonlinear geometric phase liquid crystal element sample prepared in this invention under a polarizing microscope.

[0038] Figure 4 This invention describes the modulation of the fundamental frequency light field and the generation of the frequency-doubled light field by the nonlinear geometric phase liquid crystal element prepared according to the present invention. The first and second alignment layers are oriented by polarized ultraviolet exposure. Ferroelectric nematic liquid crystal is then injected between the first and second substrates, aligning the liquid crystal molecules according to the orientation directions of the first and second alignment layers. The nonlinear geometric phase liquid crystal element of the present invention can frequency-double the wavelength of the pumped fundamental Gaussian light from the infrared region to the visible light region, carrying a nonlinear geometric phase. It converts the original infrared Gaussian mode beam into a hollow vortex visible beam, and the left / right circularly polarized components of the emitted light field correspond to different vortex topological charges. Simultaneously, the element retains linear light field modulation capability, realizing the ability to convert fundamental Gaussian light into fundamental vortex light. Therefore, the element can simultaneously modulate the fundamental frequency beam and generate the frequency-doubled beam, obtaining four different spatial modes of vortex light fields in their left / right circularly polarized components.

[0039] Figure 5 This invention describes the intensity changes of linear and nonlinear structured light fields in the nonlinear geometric phase liquid crystal element prepared by this invention during temperature changes. During cooling, the ferroelectric nematic liquid crystal RM734 undergoes the following phase transitions: isotropic above 182°C; nematic between 128°C and 182°C; and ferroelectric nematic between 40°C and 128°C. When the temperature changes from 40°C to 128°C, the liquid crystal is in the ferroelectric nematic phase, and the element simultaneously modulates the fundamental frequency beam and generates vortex light fields in four different spatial modes that produce frequency-doubled beams. At this time, the intensity of the frequency-doubled beam first decreases slowly, then rapidly, and finally becomes zero. When the temperature exceeds 128°C, the nonlinear optical response of the element disappears, and only the vortex beam spot generated by the fundamental frequency light is observed, while retaining linear optical modulation capability. Above 182°C, the liquid crystal element is in the isotropic state. Due to the disappearance of optical anisotropy, only the incident fundamental frequency spot is observed, and the element does not modulate the incident light. Thus, based on the operating temperature sequence of the component, the frequency, phase, and amplitude of the fundamental frequency optical field and the second harmonic optical field can be dynamically controlled by the component.

[0040] Figure 6 This invention describes the intensity change of the nonlinear optical response of the nonlinear geometric phase liquid crystal element prepared in this invention when an external electric field is introduced. When an alternating electric field is applied perpendicular to the nonlinear geometric phase liquid crystal element, the liquid crystal molecules rearrange under the influence of the electric field, and the intensity of the vortex light field of four different spatial modes that modulate the fundamental frequency beam and generate the frequency-doubled beam switches periodically with the electric field. When the voltage is 0V, the polarization direction of the nonlinear geometric phase liquid crystal element is parallel to the in-plane direction, and the intensity of the frequency-doubled beam of the two circularly polarized components and different spatial modes is the maximum. At the same time, the conversion efficiency of the right-hand circularly polarized component of the fundamental frequency beam modulated by optical anisotropy is the maximum. When the voltage is 0.5V, the polarization direction of the nonlinear geometric phase liquid crystal element is perpendicular to the in-plane direction, and the intensity of the frequency-doubled beam of the two circularly polarized components and different spatial modes is the minimum. At the same time, the optical anisotropy decreases, and the conversion efficiency of the right-hand circularly polarized component modulated by the fundamental frequency beam is the minimum. Thus, the element can dynamically control the frequency, phase, and amplitude of the fundamental frequency light field and the frequency-doubled light field according to the external electric field intensity.

[0041] Figure 7 This is a schematic diagram of the liquid crystal molecule orientation of the spin-selective nonlinear geometric phase liquid crystal element prepared according to the present invention. The first and second alignment layers are oriented by polarized ultraviolet exposure. A liquid crystal material doped with a chiral agent is then injected between the first and second substrates, causing the liquid crystal molecules to align according to the orientation directions of the first and second alignment layers.

[0042] Alternatively, the preparation method of ferroelectric nematic liquid crystal RM734 doped with the dextrorotatory chiral agent R811 is as follows:

[0043] Ferroelectric nematic liquid crystal RM734 and dextrorotatory chiral agent R811 were thoroughly mixed at a mass ratio of 1:99. Figure 8 This diagram illustrates the emitted light field distribution of the spin-selective nonlinear geometric phase liquid crystal element prepared according to the present invention. The emitted light field differs depending on the incident circularly polarized fundamental frequency light with different rotational directions. When right-handed circularly polarized fundamental Gaussian mode light is incident, the ferroelectric nematic liquid crystal element, doped with a right-handed chiral agent, efficiently converts the fundamental frequency light into frequency-doubled light. Furthermore, the left-handed and right-handed circularly polarized components of the frequency-doubled light carry different nonlinear geometric phases, generating visible vortex frequency-doubled beams with different spatial modes. When left-handed circularly polarized fundamental Gaussian mode light is incident, the element suppresses the process of converting the fundamental frequency light to the frequency-doubled light. Therefore, based on the circular polarization state of the incident fundamental frequency light and the chiral direction of the doped chiral agent, the element can control the frequency, phase, and amplitude of the frequency-doubled light field.

[0044] Example 2:

[0045] The computer-readable storage medium of this embodiment stores a computer program that, when executed by a processor, implements the steps in the method for preparing a nonlinear geometric phase liquid crystal element of Embodiment 1.

[0046] The computer-readable storage medium in this embodiment can be an internal storage unit of the terminal, such as the terminal's hard disk or memory; the computer-readable storage medium in this embodiment can also be an external storage device of the terminal, such as a plug-in hard disk, smart memory card, secure digital card, flash memory card, etc. equipped on the terminal; furthermore, the computer-readable storage medium can include both the terminal's internal storage unit and external storage devices.

[0047] The computer-readable storage medium of this embodiment is used to store computer programs and other programs and data required by the terminal. The computer-readable storage medium can also be used to temporarily store data that has been output or will be output.

[0048] Example 3:

[0049] The computer device of this embodiment includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the steps in the method for preparing a nonlinear geometric phase liquid crystal element according to Embodiment 1.

[0050] In this embodiment, the processor can be a central processing unit, or other general-purpose processors, digital signal processors, application-specific integrated circuits, off-the-shelf programmable gate arrays or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor, etc. The memory can include read-only memory and random access memory, and provides instructions and data to the processor. A portion of the memory can also include non-volatile random access memory. For example, the memory can also store device type information.

[0051] Those skilled in the art will understand that the content disclosed in the embodiments can be provided as a method, system, or computer program product. Therefore, this solution can take the form of a hardware embodiment, a software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this solution can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage and optical storage) containing computer-usable program code.

[0052] This solution is described with reference to flowchart illustrations and / or block diagrams of methods and computer program products according to embodiments of this solution. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing device to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing device, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0053] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0054] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0055] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc.

[0056] The examples described herein are merely preferred embodiments of the invention and are not intended to limit the concept and scope of the invention. Any modifications and improvements made by those skilled in the art to the technical solutions of the invention without departing from the design concept of the invention should fall within the protection scope of the invention.

Claims

1. A non-linear geometric phase liquid crystal element, characterized in that, The first substrate, the first orientation layer, the liquid crystal layer, the second orientation layer and the second substrate are sequentially arranged; The first substrate and the second substrate are ITO glass substrates; The first orientation layer and the second orientation layer are photoalignment layers; The first orientation layer and the second orientation layer are coated on the first substrate and the second substrate by spin coating, the first orientation layer of the first substrate and the second orientation layer of the second substrate are oppositely arranged, and the distance between the first orientation layer and the second orientation layer is controlled by a spacer; The material of the orientation layer is one of a surfactant, a rubbing orientation agent, a photo-crosslinking material, a photo-degradation material and a photo-induced cis-trans isomerization material; the orientation agent of the first orientation layer and the second orientation layer is one of azo photoalignment materials SD1 and brilliant yellow, and under the irradiation of linearly polarized light, the photoalignment material molecules are arranged along the direction perpendicular to the direction of the linearly polarized light, and through the interaction between the photoalignment material molecules and the liquid crystal molecules, the liquid crystal molecules form an ordered orientation; The liquid crystal layer adopts one or more of ferroelectric nematic liquid crystal RM734 and DIO, and the liquid crystal layer introduces one or more of chiral dopants CB15, 4-((4-nitrophenoxy)carbonyl)phenyl(S)-2-(sec-butoxy)-4-methoxybenzoate, (S)-ring-3, ZLI811, BDH1281, R1011, R811, S811, S5011 and R5011; When the temperature changes from 40℃ to 128℃, the liquid crystal is in a ferroelectric nematic phase state, the nonlinear geometric phase liquid crystal element simultaneously modulates a fundamental frequency light beam and generates a frequency-doubled light beam, and four different spatial mode vortex light fields are obtained from the left / right circularly polarized components of the modulated fundamental frequency light beam and the generated frequency-doubled light beam, and the four different spatial mode vortex light fields exist simultaneously, at this time, the intensity of the frequency-doubled light beam first slowly decreases, then rapidly decreases, and finally becomes zero; When an alternating current electric field is applied in a direction perpendicular to the nonlinear geometric phase liquid crystal element, the liquid crystal molecules are rearranged under the action of the electric field, and the intensity of the four different spatial mode vortex light fields of the nonlinear geometric phase liquid crystal element modulating the fundamental frequency light beam and generating the frequency-doubled light beam periodically switches with the electric field; when the voltage is 0V, the polarization direction of the nonlinear geometric phase liquid crystal element is parallel to the in-plane direction, the intensity of the frequency-doubled light beam of the two circularly polarized components and different spatial modes is maximum, and the conversion efficiency of the right circularly polarized component to the left circularly polarized component of the fundamental frequency light beam modulated by optical anisotropy is maximum; when the voltage is 0.5V, the polarization direction of the nonlinear geometric phase liquid crystal element is perpendicular to the in-plane direction, the intensity of the frequency-doubled light beam of the two circularly polarized components and different spatial modes is minimum, the optical anisotropy is reduced, and the conversion efficiency of the right circularly polarized component to the left circularly polarized component of the fundamental frequency light beam modulated by optical anisotropy is minimum.

2. The method of claim 1, wherein the non-linear geometric phase liquid crystal element is prepared by the steps of: The first substrate, the first orientation layer, the liquid crystal layer, the second orientation layer and the second substrate are sequentially arranged; The first substrate and the second substrate are ITO glass substrates; The first orientation layer and the second orientation layer are photoalignment layers; The first orientation layer and the second orientation layer are photoalignment layers; The first and second orientation layers are coated on the first and second substrates by spin coating, the first orientation layer surface of the first substrate and the second orientation layer surface of the second substrate are oppositely arranged, and the distance between the first and second orientation layers is controlled by spacers.

3. The preparation method according to claim 2, characterized in that, The azo photo-controllable orientation material is selected as the orientation agent of the first and second orientation layers, under the irradiation of linearly polarized light, the azo photo-controllable orientation molecules are arranged along the direction perpendicular to the linearly polarized light, and the liquid crystal molecules are made to form ordered orientation through the interaction between the liquid crystal molecules and the azo photo-controllable orientation molecules.

4. Use of the nonlinear geometric phase liquid crystal element according to claim 1 in the generation of nonlinear structured light fields.

5. A computer readable storage medium having stored thereon a computer program, characterized in that: The program is executed by the processor to implement the steps in the preparation method of the nonlinear geometric phase liquid crystal element according to any one of claims 2-3.

6. A computer device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The program is executed by the processor to implement the steps in the preparation method of the nonlinear geometric phase liquid crystal element according to any one of claims 2-3.

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