Nonlinear perfect vector beam generating element and preparation method and application thereof

Abstract

The invention belongs to the technical field of non-linear optics, and particularly relates to a non-linear perfect vector light beam generating element and a preparation method and application thereof. The element comprises a first glass substrate, a first light-operated orientation layer, a ferroelectric nematic phase liquid crystal layer, a second light-operated orientation layer and a second glass substrate, the first glass substrate and the second glass substrate are oppositely arranged; a first light-operated orientation layer and a second light-operated orientation layer are respectively arranged on the inner sides of the first glass substrate and the second glass substrate; the first light-operated orientation layer and the second light-operated orientation layer are provided with nonlinear perfect vector light beam control patterns; and the nonlinear perfect vector light beam control pattern controls liquid crystal molecules in the ferroelectric nematic phase liquid crystal layer to be distributed in a concentric circle orientation mode of a plurality of cycles. Through direct orientation of the liquid crystal electric dipole, integration and miniaturization of a nonlinear perfect vector beam device and one-step direct generation of a nonlinear perfect vector beam are realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of nonlinear optics, and in particular relates to a nonlinear perfect vector light beam generating element, a preparation method and an application thereof. Background Art

[0002] Vector beams are structured light fields with programmable vector distribution characteristics, and have demonstrated their important application value in many fields such as optical communications, high-resolution imaging, and micromanipulation. Recently, the concept of a perfect vector beam has been proposed. The annular intensity distribution of this beam has no direct correlation with its topological charge, and the topological charge can be arbitrarily encoded. It is worth noting that perfect vector beams with different topological charge numbers form a series of orthogonal bases, ensuring that the complementary crosstalk between them is extremely low. Based on this feature, perfect vector beams can theoretically carry an unlimited number of topological charges during transmission, thereby providing new possibilities for significantly improving the communication capacity in the field of optical communications, and also making the storage and transmission of high-density optical information more efficient and reliable.

[0003] Currently, various methods have been proposed to generate such perfect vector beams, such as combining linear diffraction elements and using spatial light modulators. Current research primarily focuses on the generation and control of linear perfect vector beams. Simultaneous encoding of perfect vector beams during nonlinear frequency conversion has been less studied, primarily due to the difficulty in freely manipulating the orientation of the electric dipole. Simultaneous encoding of perfect vector beams during nonlinear frequency conversion has important theoretical and applied implications. It not only efficiently utilizes the degrees of freedom of optical frequency, improving the transmission capacity and flexibility of communication systems, but also reduces crosstalk between signals through its orthogonal basis properties, enhancing system robustness and stability. Furthermore, this technology provides new tools and methods for the design of novel photonic devices and fundamental scientific research on light-matter interactions, promoting technological innovation and development in optical communications, quantum information processing, and super-resolution imaging. For currently widely used uniaxial ferroelectric crystal elements, the phase matching conditions are sensitive to the polarization direction of the electric vector, so direct nonlinear frequency conversion will smear out their vector characteristics. Furthermore, implementation generally requires a complex optical system with multiple elements stacked on top of each other.

[0004] Therefore, it is of great significance to develop a new nonlinear perfect vector beam generating element. Summary of the Invention

[0005] The present invention aims to solve the current problems of the generation of nonlinear perfect vector beams, such as the need for a complex optical system with many superimposed components and the difficulty in controlling the orientation of electric dipoles. A nonlinear perfect vector beam generating element prepared by the structured orientation of liquid crystals is proposed, which can realize the integration and miniaturization of nonlinear perfect vector beam devices and the direct generation of nonlinear perfect vector beams.

[0006] The present invention also aims to provide a method for preparing the above-mentioned nonlinear perfect vector light beam generating element.

[0007] In order to solve the above technical problems, the present invention discloses a nonlinear perfect vector beam generating element, which includes a first glass substrate, a first optical alignment layer, a ferroelectric nematic liquid crystal layer, a second optical alignment layer, and a second glass substrate; the first glass substrate and the second glass substrate are arranged opposite each other; the first and second optical alignment layers are further provided on the inner sides of the first and second glass substrates, respectively; and spacer particles are provided between the first and second optical alignment layers.

[0008] The first and second optical alignment layers are provided with nonlinear perfect vector beam control patterns; the nonlinear perfect vector beam control patterns control the liquid crystal molecules in the ferroelectric nematic liquid crystal layer to be oriented and distributed in concentric rings of several periods.

[0009] Specifically, the spacer particles are used to control the distance between the first photo-alignment layer and the second photo-alignment layer;

[0010] Specifically, the first photo-controlled alignment layer, the second photo-controlled alignment layer and the spacer particles form a liquid crystal box after packaging; and the liquid crystal box forms a ferroelectric nematic liquid crystal layer after injecting a ferroelectric nematic liquid crystal material.

[0011] The present invention sets nonlinear perfect vector beam control patterns for the first and second photo-control alignment layers to correspond to nonlinear perfect vector beams with different topological charges, but is not limited to these topological charges, and includes nonlinear perfect vector beams corresponding to any topological charge.

[0012] Preferably, the nonlinear perfect vector beam control pattern controls the diameter of the nonlinear perfect vector beam by controlling the size of the ring period.

[0013] Preferably, the nonlinear perfect vector beam control pattern is composed of two concentric circular ring orientation distributions in a single period, and the orientation angle difference between adjacent circular rings is 90 degrees; the nonlinear perfect vector beam control pattern controls the intensity of the nonlinear perfect vector beam by controlling the width ratio of the two concentric circular rings in a single period.

[0014] Preferably, the nonlinear perfect vector beam control pattern has a single ring orientation rotation angle within a single period of the pattern being any angle; the nonlinear perfect vector beam control pattern controls the topological charge of the nonlinear perfect vector beam by controlling the single ring orientation rotation angle;

[0015] Specifically, in some embodiments of the present invention, by controlling the nonlinear perfect vector beam control pattern, the orientation rotation angles of a single circular ring molecule are controlled to be 360°, 540°, 720° and 1080°, respectively, thereby realizing nonlinear perfect vector beams with topological charges of 2, 3, 4 and 6, respectively.

[0016] The present invention also provides a method for preparing the above-mentioned nonlinear perfect vector beam generating element, which specifically comprises the following steps:

[0017] S1. The first glass substrate and the second glass substrate are ultrasonically cleaned and dried and then UV-ozone cleaned;

[0018] S2. Spin-coating a photo-alignment agent on the first glass substrate and the second glass substrate after cleaning in S1, and curing to form a first photo-alignment layer and a second photo-alignment layer;

[0019] S3. Apply spacer particles on both sides of the first optical alignment layer, and then place the second optical alignment layer on the package to form a liquid crystal cell;

[0020] S4. performing polarized UV exposure on the first optical alignment layer and the second optical alignment layer to form a nonlinear perfect vector beam control pattern;

[0021] S5. Injecting a ferroelectric nematic liquid crystal material into the liquid crystal box to form a ferroelectric nematic liquid crystal layer, thereby obtaining the nonlinear perfect vector light beam generating element.

[0022] Specifically, the photo-alignment agent is an azo-based photo-controlled alignment material SD1.

[0023] Specifically, the ferroelectric nematic liquid crystal material is a ferroelectric nematic liquid crystal material containing an intermediate polar phase;

[0024] Preferably, the ferroelectric nematic liquid crystal material is 4-((4-nitrophenoxy)carbonyl)-3-(trifluoromethyl)pheny 2-fluoro-4-methoxybenzoate.

[0025] Specifically, in S1, the ultrasonic cleaning includes ultrasonic cleaning with ethanol alcohol solution and ultrasonic cleaning with ultrapure water;

[0026] Preferably, the ultrasonic cleaning time of the ethanol alcohol lotion is 20 minutes; the ultrasonic cleaning of the ultrapure water is divided into two times, each time lasting 10 minutes.

[0027] Specifically, in S1, the drying temperature is 140° C. and the drying time is 40 minutes.

[0028] Specifically, in S1, the ultraviolet ozone cleaning is performed for 30 minutes.

[0029] Specifically, in S2, the spin coating has the following parameters: the rotation speed of the first spin coating is 3000 rpm, and the spin coating time is 40 seconds; the rotation speed of the second spin coating is 300 rpm, and the spin coating time is 10 seconds.

[0030] Specifically, in S2, the curing is carried out under the following conditions: curing at 100 degrees Celsius for 10 minutes.

[0031] Specifically, in S3, the spacer particles are silica microspheres.

[0032] Furthermore, the application of the above-mentioned nonlinear perfect vector beam generating element in generating a nonlinear perfect vector beam also falls within the protection scope of the present invention.

[0033] Specifically, in embodiments of the present invention, the nonlinear perfect vector beam generating element can simultaneously perform frequency doubling and vector field conversion on incident fundamental frequency Gaussian light. During the nonlinear frequency conversion, the original fundamental frequency Gaussian mode is converted into a perfect vector beam. Furthermore, by configuring different nonlinear perfect vector beam control patterns, nonlinear perfect vector beams with topological charges of 2, 3, 4, and 6 can be generated.

[0034] Beneficial effects: The present invention can realize the integration and miniaturization of nonlinear perfect vector beam devices and the one-step direct generation of nonlinear perfect vector beams by directly orienting the liquid crystal electric dipoles. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more apparent.

[0036] Figure 1 The structure diagram of the nonlinear perfect vector beam generating element prepared by the present invention;

[0037] Figure 2 Schematic diagram of the molecular orientation of the nonlinear perfect vector beam generating element prepared by the present invention;

[0038] Figure 3 The texture image of the nonlinear perfect vector beam generating element prepared by the present invention under a polarizing microscope;

[0039] Figure 4 Schematic diagram of the process of generating a nonlinear perfect vector beam prepared by the present invention;

[0040] Figure 5 Beam analysis of the nonlinear perfect vector beam prepared by the present invention with a topological charge equal to 2;

[0041] Figure 6Schematic diagram of the molecular orientation of the nonlinear perfect vector beam generating element corresponding to the nonlinear perfect vector beams with topological charges equal to 3, 4, and 6 prepared by the present invention;

[0042] Figure 7 The nonlinear perfect vector light beams with topological charges equal to 3, 4, and 6 prepared by the present invention. DETAILED DESCRIPTION

[0043] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It will be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all structures.

[0044] In the following examples, the synthesis route of the ferroelectric nematic liquid crystal material 4-((4-nitrophenoxy)carbonyl)-3-(trifluoromethyl)pheny 2-fluoro-4-methoxybenzoate (NJU001) is:

[0045]

[0046] The specific steps are:

[0047] Synthesis of A1: 8.5 g (50 mmol) of 2-fluoro-4-methoxybenzoic acid, 15 g (50 mmol) of benzyl 2-trifluoromethyl-4-hydroxybenzoate, 0.2 g of DMAP, and 100 ml of dichloromethane were added to a 250 ml three-necked flask. The mixture was cooled to 5°C while stirring, and then a solution of DCC (12.5 g (60 mmol) dissolved in 30 ml of dichloromethane) was added dropwise at a temperature of 5-10°C. After the addition was completed, the mixture was kept warm for 12 h, filtered, and the filtrate was washed with 50 ml of 1% hydrochloric acid. The dichloromethane layer was collected, dried over anhydrous magnesium sulfate, and concentrated to remove dichloromethane. 50 ml of ethanol was added for crystallization to obtain 18.4 g (41 mmol) of A1 in a yield of 82.14%.

[0048] Synthesis of A2: 15 g (33 mmol) of A1 and 50 ml of tetrahydrofuran were added to a 100 ml hydrogenation reactor, followed by 1 g of 5% palladium on carbon. After hydrogen substitution (0.1 MPa), the hydrogenation reaction was carried out for 12 h. The hydrogenation reactor was purged with nitrogen, the palladium on carbon was removed by filtration, and the tetrahydrofuran was removed by concentration. 50 ml of ethanol was added for crystallization to obtain 10.4 g (28.1 mmol) of A2, with a yield of 85.11%.

[0049] Synthesis of NJU001: 8 g (22 mmol) of A2, 3.4 g (24.5 mmol) of p-nitrophenol, 0.1 g of DMAP, and 100 ml of dichloromethane were added to a 250 ml three-necked flask. The temperature was lowered to 5°C, and a dichloromethane solution of DCC (5.53 g in 20 ml of DCM) was added dropwise. After the addition was complete, the mixture was incubated for 12 hours, filtered, and the filtrate was washed with 50 ml of 1% hydrochloric acid, dried over anhydrous magnesium sulfate, and concentrated to remove dichloromethane. The mixture was then purified by flash column chromatography and crystallized from ethanol to obtain 4.8 g (10 mmol) of NJU001. The content was 99.3%, and the yield was 44.8%.

[0050] Example 1

[0051] The embodiment of the present invention provides a nonlinear perfect vector beam generating element, Figure 1 The present invention provides a structural diagram of a liquid crystal element, which specifically includes a first glass substrate and a second glass substrate that are relatively staggered; the first and second glass substrates are also provided with a first optical alignment layer and a second optical alignment layer formed by spin-coating a photo-alignment agent and then curing the inner sides thereof; spacer particles are provided on both sides between the first and second optical alignment layers; after curing, a liquid crystal cell is formed between the first and second optical alignment layers and the spacer particles provided on both sides, and a ferroelectric nematic liquid crystal layer is formed after liquid crystal material is poured into the layer.

[0052] The embodiment of the present invention further provides a method for preparing a nonlinear perfect vector beam generating element, the specific steps of which are as follows:

[0053] First, ultrasonically clean the first and second glass substrates using anhydrous ethanol for 20 minutes. Then, ultrasonically clean them twice using ultrapure water, each time for 10 minutes. The cleaned substrates were placed in a drying oven set to 140°C for 40 minutes. Finally, the first and second glass substrates were cleaned using UV-ozone for 30 minutes.

[0054] Subsequently, the photo-alignment agent SD1 was spin-coated on the first and second glass substrates. The spin coating method was as follows: the first step of the spin coating was performed at a rotation speed of 3000 rpm for 40 seconds. The second step of the spin coating was performed at a rotation speed of 300 rpm for 10 seconds. After the photo-alignment layer prepared from the selected SD1 material was spin-coated on the first and second glass substrates, the first and second glass substrates were placed on a hot plate at a temperature of 100 degrees Celsius to cure the photo-alignment layer for 10 minutes. After curing, a first photo-alignment layer was formed on one side of the first glass substrate, and a second photo-alignment layer was formed on one side of the second glass substrate.

[0055] Silica microspheres and UV sealant are mixed as spacers. After mixing evenly, they are applied on both sides of the first optical alignment layer. Then, the second glass substrate with the second optical alignment layer is placed on the side facing the spacer particles for encapsulation. The first and second glass substrates are staggered and bonded ( Figure 1 ), and placed under ultraviolet light until the sealant is cured to form a liquid crystal cell. The cell thickness is controlled by changing the diameter of the silica microspheres, and the cell thickness of the liquid crystal cell of the embodiment is measured by interferometry.

[0056] The first photo-controlled alignment layer and the second photo-controlled alignment layer are oriented by polarized ultraviolet exposure. An azo-based photo-controlled alignment material SD1 is selected as the alignment agent for the first and second photo-controlled alignment layers. Under the irradiation of linearly polarized light, the photo-controlled alignment material molecules will align in a direction perpendicular to the direction of the linearly polarized light, and through interaction with the liquid crystal molecules, the liquid crystal molecules form a specifically designed ordered arrangement. The liquid crystal material is poured between the first and second glass substrates, and the new ferroelectric nematic liquid crystal material NJU001 is heated to 150 degrees Celsius and poured into the liquid crystal box through a capillary glass tube to obtain the nonlinear perfect vector beam generating element.

[0057] Figure 2 This is a schematic diagram of the liquid crystal molecule orientation of the nonlinear perfect vector beam generating element prepared by the present invention. The figure shows the liquid crystal molecule orientation distribution within the first period of the nonlinear perfect vector beam control pattern. Each period consists of two concentric circular rings of equal width, and the orientation angle difference between adjacent rings is 90 degrees. Figure 3 This is the texture image of the nonlinear perfect vector beam generating element prepared by the present invention under a polarizing microscope.

[0058] Optionally, the circular period of the nonlinear perfect vector beam control pattern is not limited to the distribution shown in the figure, and a nonlinear perfect vector beam control pattern with any period size will determine the diameter of the nonlinear perfect vector beam.

[0059] Optionally, the rotation angle of the single circular molecular orientation of the nonlinear perfect vector beam control pattern is not limited to 360 degrees as shown in the figure, and includes nonlinear perfect vector beams with different topological charges corresponding to any rotation angle.

[0060] Optionally, each period of the nonlinear perfect vector beam control pattern is not limited to being composed of two concentric circular ring orientation distributions of equal width, and includes any two concentric circular ring orientation distributions of unequal width to determine the intensity of the nonlinear perfect vector beam.

[0061] Figure 4This diagram illustrates the process of generating a beam using the nonlinear perfect vector beam generating element fabricated in the present invention. During cooling, the novel ferroelectric nematic liquid crystal NJU001 undergoes the following phase transitions: above 132°C, it assumes an isotropic state; between 132°C and 76°C, it assumes a nematic phase; between 76°C and 58°C, it assumes an intermediate polar phase; and below 58°C, it assumes a ferroelectric nematic phase. While the ferroelectric nematic phase typically makes it difficult to manipulate the orientation of electric dipoles, the present invention utilizes the intermediate polar phase of NJU001, enabling superior electric dipole control through optically controlled orientation, enabling the creation of various nonlinear perfect vector beam control patterns. After cooling to the intermediate polar phase, the temperature is maintained constant, and a lens is added after the nonlinear perfect vector beam generating element to produce a nonlinear perfect vector beam.

[0062] Optionally, the new ferroelectric nematic material NJU001 (4-((4-nitrophenoxy)carbonyl)-3-(trifluoromethyl)pheny 2-fluoro-4-methoxybenzoate), but not limited to this material, includes all materials of this type of ferroelectric nematic phase containing an intermediate polar phase. This type of material can have good photo-controlled orientation properties while maintaining a stable frequency-doubled signal.

[0063] Figure 5 This is a beam analysis of the nonlinear perfect vector beam prepared by the present invention when the topological charge is equal to 2. Setting the nonlinear perfect vector beam control pattern with a topological charge of 2, the emitted frequency-doubled perfect vector beam will be imaged at the focal position of the lens. When the topological charge of the emitted nonlinear perfect vector beam is equal to 2, placing a polarizer after the beam will cause the nonlinear perfect vector beam to become a four-lobed light spot.

[0064] Figure 6 This is a schematic diagram of the orientation of the nonlinear perfect vector beam generating element corresponding to the nonlinear perfect vector beams with topological charges equal to 3, 4, and 6 prepared by the present invention. The orientation rotation angles of a single circular ring molecule are 540°, 720°, and 1080°, respectively.

[0065] Figure 7 Nonlinear perfect vector beams with different topological charges prepared by the present invention. Setting the nonlinear perfect vector beam control pattern for topological charges of 3, 4, and 6 results in the outgoing frequency-doubled perfect vector beam forming an image at the lens focal point. When the outgoing nonlinear perfect vector beam has a topological charge of 3, 4, or 6, placing an analyzer after the beam results in the corresponding nonlinear perfect vector beam becoming a 6-, 8-, or 12-lobed spot.

[0066] Optionally, the present invention sets a nonlinear perfect vector beam with a topological charge equal to 2, 3, 4, or 6, but is not limited to these topological charge numbers, and includes nonlinear perfect vector beams corresponding to larger or smaller topological charges.

[0067] The present invention provides a nonlinear perfect vector beam generating element, its preparation method, and its application. Numerous methods and approaches exist for implementing this technical solution. The foregoing merely represents a preferred embodiment of the present invention. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are considered within the scope of protection of the present invention. Components not specified in this embodiment may be implemented using existing technologies.

Claims

1. A nonlinear perfect vector beam generating element, characterized in that: The element comprises a first glass substrate, a first light-controlled alignment layer, a ferroelectric nematic phase liquid crystal layer, a second light-controlled alignment layer and a second glass substrate; the first glass substrate and the second glass substrate are arranged opposite to each other; the first glass substrate and the second glass substrate are also provided with a first light-controlled alignment layer and a second light-controlled alignment layer on their inner sides respectively; and spacer particles are provided between the first light-controlled alignment layer and the second light-controlled alignment layer; The first light-controlled orientation layer and the second light-controlled orientation layer are provided with nonlinear perfect vector beam control patterns; the nonlinear perfect vector beam control patterns control the liquid crystal molecules in the ferroelectric nematic liquid crystal layer to be oriented and distributed in concentric rings of several periods.

2. The element according to claim 1, characterized in that The nonlinear perfect vector beam control pattern is composed of two concentric circular ring orientation distributions in a single period, and the orientation angle difference between adjacent circular rings is 90 degrees.

3. The element according to claim 1, characterized in that The nonlinear perfect vector beam control pattern has a single circular ring molecule orientation rotation angle within a single period of the pattern being any angle.

4. The method for preparing the nonlinear perfect vector beam generating element as claimed in any one of claims 1 to 3, characterized in that: The specific steps are: S1. Ultrasonic cleaning and drying of the first glass substrate and the second glass substrate followed by ultraviolet ozone cleaning; S2. Spin-coating a photo-alignment agent on the first glass substrate and the second glass substrate cleaned in S1, and curing to form a first photo-alignment layer and a second photo-alignment layer; S3. Applying spacer particles on both sides of the first light-controlled alignment layer, and then placing the second light-controlled alignment layer on the package to form a liquid crystal cell; S4. Orienting the first photo-controlled alignment layer and the second photo-controlled alignment layer by polarized ultraviolet exposure to form a nonlinear perfect vector beam control pattern; S5. Injecting ferroelectric nematic liquid crystal material into the liquid crystal box to form a ferroelectric nematic liquid crystal layer, thereby obtaining the nonlinear perfect vector light beam generating element.

5. The preparation method according to claim 4, characterized in that: The photo-alignment agent is an azo-based photo-controlled alignment material SD1.

6. The preparation method according to claim 4, characterized in that: The ferroelectric nematic liquid crystal material is a ferroelectric nematic liquid crystal material containing an intermediate polar phase.

7. The preparation method according to claim 6, characterized in that: The ferroelectric nematic liquid crystal material is 4-((4-nitrophenoxy)carbonyl)-3-(trifluoromethyl)pheny 2-fluoro-4-methoxybenzoate.

8. The preparation method according to claim 4, characterized in that: In S2, the spin coating has the following parameters: the rotation speed of the first step of spin coating is 3000 rpm, and the spin coating time is 40 seconds; the rotation speed of the second step of spin coating is 300 rpm, and the spin coating time is 10 seconds.

9. The preparation method according to claim 4, characterized in that: In S2, the curing is performed at 100 degrees Celsius for 10 minutes.

10. Use of the nonlinear perfect vector beam generating element as claimed in any one of claims 1 to 3 in generating a nonlinear perfect vector beam.

Images