Temperature-controlled vortex beam comparator and preparation method and implementation device thereof

Abstract

The invention discloses a temperature-controlled vortex beam comparator and a preparation method and an implementation device thereof, a first orientation layer and a second orientation layer of the vortex beam comparator are provided with control patterns with molecule directors in periodic gradual change distribution, and the control patterns form a plurality of spoke-shaped areas. Spoke extension lines of all the areas intersect at the same point, and directors of liquid crystal molecules in the cholesteric liquid crystal layer are periodically and gradually distributed at 0-180 degrees in the direction perpendicular to the spokes so as to form the spread gradual change grating based on the cholesteric liquid crystals. In the cholesteric liquid crystal layer, the mass of the first chiral agent is greater than that of the second chiral agent, and the sensitive degree of the first chiral agent to the temperature is greater than that of the second chiral agent to the temperature, so that the first chiral agent plays a leading role in the structure of the cholesteric liquid crystal, and the second chiral agent plays an auxiliary role in the structure of the cholesteric liquid crystal. The device integration level of vortex beam processing and the efficiency of comparison operation can be improved, and the regulation and control capability of the processing wave band can be expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of vortex beams, and in particular to a temperature-controlled vortex beam comparator and a preparation method and an implementation device thereof. Background Art

[0002] In recent years, with the development of artificial intelligence technology, the computing resources required for model training and actual use have increased dramatically, which has put forward new requirements for the speed and energy consumption of computing technology. All-optical computing has the advantages of high processing rate, high parallelism, and low energy consumption, and is a feasible solution to meet computing needs. At the physical implementation level, all-optical computing requires the effective development and regulation of the full-dimensional properties of the light beam. Vortex beams are a special type of light beams whose phase properties are spirally distributed in the cross section, and their characteristic parameters are the topological charge of the phase spiral. In theory, the topological charge can take any integer, and the vortex beam mode constitutes an infinite-dimensional state space. Vortex beams are widely used in extremely wide bandwidth communications, quantum information processing, and optical computing. The comparison of vortex beams refers to the comparison of the quantitative relationship between the topological charges of two input vortex beams directly through optical transformation. This comparison operation is of great significance to all-optical computing based on vortex beams.

[0003] In the prior art, the comparison operation of vortex beams can be achieved by cascading diffraction elements and polarizers, but it faces problems such as system complexity. Compared with traditional components, novel materials such as metasurfaces have advantages such as compactness, integration, and multi-functions. However, these devices are difficult to process and have certain limitations in the adjustability of the working band. Summary of the invention

[0004] The present invention provides a temperature-controlled vortex beam comparator and a preparation method and an implementation device thereof, so as to improve the integration of vortex beam processing devices and the efficiency of comparison operations, and effectively expand the dynamic range and regulation capability of the device's operating band.

[0005] In a first aspect, an embodiment of the present invention provides a temperature-controlled vortex beam comparator, comprising a first substrate and a second substrate arranged opposite to each other, and a cholesteric liquid crystal layer located between the first substrate and the second substrate;

[0006] A first alignment layer is disposed on a side of the first substrate close to the second substrate, and a second alignment layer is disposed on a side of the second substrate close to the first substrate; wherein the first alignment layer and the second alignment layer have the same alignment direction, and the first alignment layer and the second alignment layer have control patterns in which molecular directors are periodically and gradually distributed, the control patterns form a plurality of spoke-shaped regions, and the extension lines of the spokes of each region intersect at the same point, and along a direction perpendicular to the spokes, the directors of the liquid crystal molecules in the cholesteric liquid crystal layer are periodically and gradually distributed from 0° to 180°, so as to form a splayed gradient grating based on cholesteric liquid crystal;

[0007] The cholesteric liquid crystal layer includes a first chiral agent and a second chiral agent; wherein, in the cholesteric liquid crystal layer, the mass of the first chiral agent is greater than the mass of the second chiral agent, and the sensitivity of the first chiral agent to temperature is greater than the sensitivity of the second chiral agent to temperature, so that the first chiral agent plays a leading role in the structure of the cholesteric liquid crystal, and the second chiral agent plays an auxiliary role in the structure of the cholesteric liquid crystal.

[0008] Optionally, the distribution of directors of the liquid crystal molecules satisfies: Wherein, α represents the azimuth angle of the director of the liquid crystal molecule, Λ represents the grating period, D represents the relative displacement from the center of the control pattern to the intersection of the extended lines of the spokes, x represents a first direction parallel to the first substrate, y represents a second direction parallel to the first substrate, and the first direction and the second direction are orthogonal.

[0009] Optionally, the helical twisting ability of the first chiral agent changes to different degrees at different temperatures, and the helical twisting ability of the second chiral agent changes to different degrees at different temperatures;

[0010] At the same temperature change, the degree of change of the helical twisting ability of the first chiral agent is greater than the degree of change of the helical twisting ability of the second chiral agent.

[0011] Optionally, the first chiral agent includes a left-handed chiral agent or a right-handed chiral agent; the second chiral agent includes a left-handed chiral agent or a right-handed chiral agent;

[0012] When the first chiral agent and the second chiral agent are both the left-handed chiral agent, or are both the right-handed chiral agent, the overall spiral twisting ability of the cholesteric liquid crystal layer is enhanced, and the dynamic range of the Bragg reflection band of the cholesteric liquid crystal layer is blue-shifted; when the first chiral agent and the second chiral agent are respectively the left-handed chiral agent and the right-handed chiral agent, or are respectively the right-handed chiral agent and the left-handed chiral agent, the overall spiral twisting ability of the cholesteric liquid crystal layer is weakened, and the dynamic range of the Bragg reflection band of the cholesteric liquid crystal layer is red-shifted.

[0013] Optionally, the materials of the first alignment layer and the second alignment layer include at least one of a photo-crosslinking material, a photo-degradable material and a photo-induced cis-trans isomerization material.

[0014] Optionally, the vortex beam comparator also includes spacer particles located between the first orientation layer and the second orientation layer, and the spacer particles are used to support the first substrate and the second substrate to form a filling space for the cholesteric liquid crystal layer; wherein, along a third direction perpendicular to the first substrate and the second substrate, an extension length of the spacer particles is greater than or equal to 10 times the pitch of the liquid crystal molecules in the cholesteric liquid crystal layer.

[0015] In a second aspect, an embodiment of the present invention further provides a method for preparing a temperature-controlled vortex beam comparator, which is used to prepare the vortex beam comparator described in any embodiment of the first aspect, comprising:

[0016] providing a first substrate and a second substrate;

[0017] forming a first alignment layer on one side of the first substrate, and forming a second alignment layer on one side of the second substrate;

[0018] orienting the first alignment layer and the second alignment layer to form a target pattern;

[0019] The first substrate and the second substrate are arranged opposite to each other, and a temperature-controlled cholesteric liquid crystal layer is prepared between the first alignment layer and the second alignment layer to form the vortex beam comparator;

[0020] The first alignment layer is located on a side of the first substrate close to the second substrate, and the second alignment layer is located on a side of the second substrate close to the first substrate. The first alignment layer and the second alignment layer have the same alignment direction. The first alignment layer and the second alignment layer have control patterns in which molecular directors are distributed in a periodic gradient. The control patterns form a plurality of spoke-shaped regions, and the extension lines of the spokes of each region intersect at the same point. Along the vertical direction of the spokes, the directors of the liquid crystal molecules of the cholesteric liquid crystal layer are distributed in a periodic gradient of 0°-180° to form a splayed gradient grating based on cholesteric liquid crystal. The temperature-controlled cholesteric liquid crystal layer includes a first chiral agent and a second chiral agent. In the cholesteric liquid crystal layer, the mass of the first chiral agent is greater than the mass of the second chiral agent, and the sensitivity of the first chiral agent to temperature is greater than the sensitivity of the second chiral agent to temperature, so that the first chiral agent plays a leading role in the structure of the cholesteric liquid crystal, and the second chiral agent plays an auxiliary role in the structure of the cholesteric liquid crystal.

[0021] Optionally, forming a first alignment layer on one side of the first substrate and forming a second alignment layer on one side of the second substrate includes:

[0022] Spin coating an alignment material on one side of the first substrate and one side of the second substrate;

[0023] The first substrate and the second substrate on which the alignment material is spin-coated are annealed to form the first alignment layer and the second alignment layer having the same alignment direction.

[0024] Optionally, before the first substrate and the second substrate are arranged opposite to each other and a temperature-controlled cholesteric liquid crystal layer is prepared between the first alignment layer and the second alignment layer to form the vortex beam comparator, the method further includes:

[0025] A non-chiral nematic liquid crystal host, the first chiral agent and the second chiral agent are mixed according to a preset ratio to obtain a temperature-controlled cholesteric liquid crystal material; wherein the preset ratio is such that in the cholesteric liquid crystal layer, the mass of the first chiral agent is greater than the mass of the second chiral agent;

[0026] Spacer particles are formed between the first alignment layer and the second alignment layer; wherein, along a third direction perpendicular to the first substrate and the second substrate, an extension length of the spacer particles is greater than or equal to 10 times the helical pitch of the liquid crystal molecules in the cholesteric liquid crystal layer.

[0027] In a third aspect, an embodiment of the present invention further provides an implementation device of a temperature-controlled vortex beam comparator, comprising a vortex beam generating unit, a beam splitting unit, a temperature control unit, a receiving unit, and the vortex beam comparator described in any embodiment of the first aspect;

[0028] The vortex beam generating unit is used to output two vortex beams to be compared, and the polarization states of the two vortex beams are a pair of orthogonal linear polarization states;

[0029] The beam splitting unit is arranged at the output end of the vortex beam generating unit, the vortex beam comparator is located at the first output end of the beam splitting unit, the receiving unit is located at the second output end of the beam splitting unit, and the receiving unit includes a lens and a beam camera;

[0030] The light beam reflected by the vortex beam comparator passes through the beam splitting unit and then through the lens to be received by the beam camera;

[0031] The temperature control unit is used to modulate the Bragg reflection band of the vortex beam comparator.

[0032] The embodiment of the present invention provides a temperature-controlled vortex beam comparator and a preparation method and an implementation device thereof. The vortex beam comparator includes a first substrate and a second substrate that are arranged opposite to each other, and a cholesteric liquid crystal layer located between the first substrate and the second substrate; a first orientation layer is arranged on a side of the first substrate close to the second substrate, and a second orientation layer is arranged on a side of the second substrate close to the first substrate; wherein the first orientation layer and the second orientation layer have the same orientation direction, and the first orientation layer and the second orientation layer have a control pattern in which molecular directors are periodically and gradually distributed, and the control pattern forms a plurality of spoke-shaped regions, The extended lines of the spokes in each region meet at the same point, and the directors of the liquid crystal molecules in the cholesteric liquid crystal layer are distributed in a periodic gradient of 0°-180° along the direction perpendicular to the spokes to form a splayed gradient grating based on cholesteric liquid crystal; the cholesteric liquid crystal layer includes a first chiral agent and a second chiral agent; wherein, in the cholesteric liquid crystal layer, the mass of the first chiral agent is greater than the mass of the second chiral agent, and the sensitivity of the first chiral agent to temperature is greater than the sensitivity of the second chiral agent to temperature, so that the first chiral agent plays a leading role in the structure of the cholesteric liquid crystal, and the second chiral agent plays an auxiliary role in the structure of the cholesteric liquid crystal. In an embodiment of the present invention, the helical chirality of the cholesteric liquid crystal layer is determined by the first chiral agent, and the helical pitch of the cholesteric liquid crystal layer is dynamically regulated by the temperature mainly by the first chiral agent, and the second chiral agent is used to further adjust the pitch adjustment range under temperature control. The device integration and the efficiency of the comparison operation of the vortex beam processing can be improved, and the control capability of the processing band can be expanded.

[0033] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0035] Figure 1 A cross-sectional view of a temperature-controlled vortex beam comparator provided by an embodiment of the present invention;

[0036] Figure 2 A schematic diagram of the direction of the liquid crystal molecule director of a splayed gradient grating provided by an embodiment of the present invention;

[0037] Figure 3 A relationship diagram of the Bragg reflection band of a cholesteric liquid crystal layer provided by an embodiment of the present invention being controlled by temperature;

[0038] Figure 4 A reflection micrograph of a cholesteric liquid crystal layer at different temperatures provided by an embodiment of the present invention;

[0039] Figure 5 A flow chart of a method for preparing a temperature-controlled vortex beam comparator provided by an embodiment of the present invention;

[0040] Figure 6 A flow chart of another method for preparing a temperature-controlled vortex beam comparator provided by an embodiment of the present invention;

[0041] Figure 7 A schematic structural diagram of an implementation device of a temperature-controlled vortex beam comparator provided by an embodiment of the present invention;

[0042] Figure 8 A schematic diagram of comparison results of a vortex beam combination with a positive sum of topological charges provided by an embodiment of the present invention;

[0043] Fig. 9 A schematic diagram of comparison results of a vortex beam combination with a topological charge sum of zero provided in an embodiment of the present invention;

[0044] Fig.10 A schematic diagram of the comparison results of two vortex light beams with equal topological charge provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0045] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0046] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0047] Figure 1 A cross-sectional view of a temperature-controlled vortex beam comparator provided by an embodiment of the present invention, with reference to Figure 1 The vortex beam comparator comprises a first substrate 10 and a second substrate 20 which are arranged opposite to each other, and a cholesteric liquid crystal layer 30 located between the first substrate 10 and the second substrate 20; a first orientation layer 11 is arranged on a side of the first substrate 10 close to the second substrate 20, and a second orientation layer 21 is arranged on a side of the second substrate 20 close to the first substrate 10; wherein the first orientation layer 11 and the second orientation layer 21 have the same orientation direction, and the first orientation layer 11 and the second orientation layer 21 have a control pattern in which the molecular director is periodically and gradually distributed, and the control pattern forms a plurality of spoke-shaped regions, and the spokes of each region are The extended lines intersect at the same point, and along the direction perpendicular to the spokes, the directors of the liquid crystal molecules in the cholesteric liquid crystal layer 30 are distributed in a periodic gradient of 0°-180° to form a splayed gradient grating based on cholesteric liquid crystal; the cholesteric liquid crystal layer 30 includes a first chiral agent and a second chiral agent; wherein, in the cholesteric liquid crystal layer 30, the mass of the first chiral agent is greater than the mass of the second chiral agent, and the sensitivity of the first chiral agent to temperature is greater than the sensitivity of the second chiral agent to temperature, so that the first chiral agent plays a leading role in the structure of the cholesteric liquid crystal, and the second chiral agent plays an auxiliary role in the structure of the cholesteric liquid crystal.

[0048] It can be understood that, since in the cholesteric liquid crystal layer 30, the mass of the first chiral agent is greater than the mass of the second chiral agent, the first chiral agent is more sensitive to temperature than the second chiral agent, therefore, the helical chirality of the cholesteric liquid crystal layer 30 is determined by the temperature-sensitive chiral agent component, and the dynamic regulation of the helical pitch of the cholesteric liquid crystal layer 30 by temperature is also mainly determined by the temperature-sensitive chiral agent component, and the temperature-insensitive chiral agent is used to further adjust the pitch adjustment range under temperature control. Therefore, the first chiral agent plays a leading role in the structure of the cholesteric liquid crystal, and the second chiral agent plays an auxiliary role in the structure of the cholesteric liquid crystal. It should be noted that the cholesteric liquid crystal layer 30 has a Bragg reflection band, and the wavelength range of the Bragg reflection band is positively correlated with the pitch. For a light beam with a wavelength within the reflection band, the cholesteric liquid crystal layer 30 reflects the circularly polarized component with the same hand direction as the liquid crystal layer, so that the incident linearly polarized vortex light beam is projected on the circularly polarized state substrate, forming an interference superposition of two input vortex light beams. The two superimposed vortex beams are further diffracted by the spreading gradient grating to form a stripe-shaped spot pattern, indicating the quantitative relationship between the topological charges of the two vortex beams. Specifically, if the intensity distribution of the resulting spot mainly expands in the horizontal direction, it means that the sum of the topological charges of the two vortex beams is a positive number; if the intensity distribution of the resulting spot mainly expands in the vertical direction, it means that the sum of the topological charges of the two vortex beams is a negative number; if the intensity distribution of the resulting spot expands equally in the horizontal and vertical directions, it means that the sum of the topological charges of the two vortex beams is equal to zero, that is, the topological charges of the two are opposite to each other.

[0049] In the cholesteric liquid crystal layer 30 of the embodiment of the present invention, the mass of the first chiral agent is greater than the mass of the second chiral agent, and the sensitivity of the first chiral agent to temperature is greater than the sensitivity of the second chiral agent to temperature, so that the first chiral agent plays a leading role in the structure of the cholesteric liquid crystal, and the second chiral agent plays an auxiliary role in the structure of the cholesteric liquid crystal, which can improve the device integration of vortex beam processing, the efficiency of comparative operation, and expand the control capability of the processing band.

[0050] Figure 2 A schematic diagram of the direction of the director of a liquid crystal molecule of a splayed gradient grating provided in an embodiment of the present invention. Optionally, based on the above embodiment, the distribution of the director of the liquid crystal molecule satisfies: Wherein, α represents the azimuth angle of the director of the liquid crystal molecule, Λ represents the grating period, D represents the relative displacement from the center of the control pattern to the intersection of the extended lines of the spokes, x represents a first direction parallel to the first substrate 10, y represents a second direction parallel to the first substrate 10, and the first direction x is orthogonal to the second direction y.

[0051] Exemplarily, in one embodiment, Λ=π / 150, D=4.5 mm.

[0052] Optionally, based on the above embodiments, the degree of change of the helical twisting ability of the first chiral agent at different temperatures is different, and the degree of change of the helical twisting ability of the second chiral agent at different temperatures is different; at the same temperature change, the degree of change of the helical twisting ability of the first chiral agent is greater than the degree of change of the helical twisting ability of the second chiral agent.

[0053] Optionally, based on the above embodiments, the first chiral agent includes a left-handed chiral agent or a right-handed chiral agent; the second chiral agent includes a left-handed chiral agent or a right-handed chiral agent; when the first chiral agent and the second chiral agent are both left-handed chiral agents, or both are right-handed chiral agents, the overall spiral twisting ability of the cholesteric liquid crystal layer 30 is enhanced, and the dynamic range of the Bragg reflection band of the cholesteric liquid crystal layer 30 is blue-shifted; when the first chiral agent and the second chiral agent are respectively a left-handed chiral agent and a right-handed chiral agent, or respectively a right-handed chiral agent and a left-handed chiral agent, the overall spiral twisting ability of the cholesteric liquid crystal layer 30 is weakened, and the dynamic range of the Bragg reflection band of the cholesteric liquid crystal layer 30 is red-shifted.

[0054] The embodiment of the present invention can flexibly adjust the dynamic range of the Bragg reflection band of the cholesteric liquid crystal layer 30 under certain temperature control conditions. Exemplarily, in a certain embodiment, the temperature-controlled left-handed cholesteric liquid crystal is mixed with nematic liquid crystal E7, left-handed chiral agent S811 and right-handed chiral agent R5011, and the mass ratio is E7:S811:R5011=1:0.3338:0.0039. Among them, the temperature-sensitive S811 gives the cholesteric liquid crystal temperature controllability, while the temperature-insensitive R5011 is used to adjust the adjustable range of the cholesteric liquid crystal Bragg reflection band. It should be noted that the above-mentioned liquid crystal material types, chiral agent types and mixing ratios are only exemplary descriptions. In other embodiments, the liquid crystal material types, chiral agent types and mixing ratios can be adjusted according to actual needs so that the temperature-controlled cholesteric liquid crystal has the required temperature control performance.

[0055] Optionally, based on the above embodiment, the materials of the first alignment layer 11 and the second alignment layer 21 include at least one of a photo-crosslinking material, a photo-degradable material and a photo-induced cis-trans isomerization material.

[0056] In the embodiment of the present invention, the materials of the first alignment layer 11 and the second alignment layer 21 are photo-controlled alignment materials, which can undergo physical or chemical reactions under the irradiation of ultraviolet polarized light to generate anisotropic surface forces, thereby inducing directional alignment of liquid crystal molecules.

[0057] Optionally, based on the above embodiment, continue to refer to Figure 1 The vortex beam comparator also includes spacer particles 31 located between the first orientation layer 11 and the second orientation layer 21, and the spacer particles 31 are used to support the first substrate 10 and the second substrate 20 to form a filling space for the cholesteric liquid crystal layer 30; wherein, along a third direction z perpendicular to the first substrate 10 and the second substrate 20, an extension length of the spacer particles 31 is greater than or equal to 10 times the pitch of the liquid crystal molecules in the cholesteric liquid crystal layer 30.

[0058] The extension length of the spacer particles 31 in the embodiment of the present invention is greater than or equal to 10 times the helical pitch of the liquid crystal molecules in the cholesteric liquid crystal layer 30 , and can form a splayed gradient grating with sufficient reflectivity.

[0059] Understandably, Figure 1 The spacer particles 31 are only used to exemplarily show the positional relationship between the first substrate 10 and the second substrate 20, rather than the actual size and proportion. Optionally, the spacer particles 31 include at least one of quartz microspheres and quartz columns, which can be designed according to actual conditions during implementation.

[0060] Figure 3 A diagram showing the relationship between the Bragg reflection band of a cholesteric liquid crystal layer and temperature control provided by an embodiment of the present invention, Figure 4A reflection micrograph of a cholesteric liquid crystal layer at different temperatures provided by an embodiment of the present invention. Figure 3 , the horizontal axis represents the wavelength in nanometers; the vertical axis represents the reflectivity of the cholesteric liquid crystal layer. When the temperature is increased from 23.6°C to 40.0°C, the central wavelength of the Bragg reflection band of the cholesteric liquid crystal layer 30 is blue-shifted from 2220nm to 608nm; the corresponding relationship can be repeated during the cooling process. Figure 4 , the figure adopts the reflective orthogonal polarization mode, the scale bar is 200μm, the plane texture of the cholesteric liquid crystal layer 30 presents a uniform color, and the stripes with slight brightness changes reflect the designed splayed gradient grating pattern. Figure 4 It can be seen that the cholesteric liquid crystal layer is orange at 38.4°C, red at 34.5°C, and gray at 24.4°C. The corresponding photonic band gaps are 599-647nm, 622-682nm, and 982-1117nm. It should be noted that Figure 3 FIG. 1 is a diagram showing, by way of example, how the reflection band of a cholesteric liquid crystal layer is controlled by temperature. Figure 4 The reflection micrographs of the cholesteric liquid crystal layer at different temperatures are shown only as examples, but are not intended to limit the cholesteric liquid crystal material used in the present invention. In other embodiments, cholesteric liquid crystal materials with other optical properties may be selected according to actual needs.

[0061] In the cholesteric liquid crystal layer 30 of the embodiment of the present invention, the mass of the first chiral agent is greater than the mass of the second chiral agent, and the sensitivity of the first chiral agent to temperature is greater than the sensitivity of the second chiral agent to temperature, so that the first chiral agent plays a leading role in the structure of the cholesteric liquid crystal, and the second chiral agent plays an auxiliary role in the structure of the cholesteric liquid crystal, which can improve the device integration of vortex beam processing, the efficiency of comparative operation, and expand the control ability of the processing band. In addition, the scheme of the embodiment of the present invention can also flexibly adjust the dynamic range of the Bragg reflection band of the cholesteric liquid crystal layer 30 under certain temperature control conditions. The materials of the first orientation layer 11 and the second orientation layer 21 are light-controlled orientation materials, which can undergo physical or chemical reactions under the irradiation of ultraviolet polarized light, generate anisotropic surface forces, and then induce the directional arrangement of liquid crystal molecules. The extension length of the spacer particles 31 is greater than or equal to 10 times the pitch of the liquid crystal molecules in the cholesteric liquid crystal layer 30, and can form a splayed gradient grating with sufficient reflectivity.

[0062] Figure 5 A flow chart of a method for preparing a temperature-controlled vortex beam comparator provided in an embodiment of the present invention, which is used to prepare the vortex beam comparator of any of the above embodiments, with reference to Figure 5 , the method comprises the following steps:

[0063] S510 , providing a first substrate and a second substrate.

[0064] The first substrate and the second substrate may be flexible substrates or rigid substrates with high light transmittance (greater than or equal to 85%). For example, the first substrate and the second substrate may be made of quartz glass, ITO glass or ordinary glass, and the thickness of the substrate may be 1-2 mm.

[0065] S520 , forming a first alignment layer on one side of the first substrate, and forming a second alignment layer on one side of the second substrate.

[0066] S530 , aligning the first alignment layer and the second alignment layer to form a target pattern.

[0067] S540, disposing the first substrate and the second substrate opposite to each other, preparing a temperature-controlled cholesteric liquid crystal layer between the first alignment layer and the second alignment layer, and forming a vortex beam comparator.

[0068] The first alignment layer is located on a side of the first substrate close to the second substrate, the second alignment layer is located on a side of the second substrate close to the first substrate, the first alignment layer and the second alignment layer have the same alignment direction, the first alignment layer and the second alignment layer have a control pattern in which the molecular directors are periodically and gradually distributed, the control pattern forms a plurality of spoke-shaped regions, the spoke extension lines of each region intersect at the same point, along the vertical direction of the spoke, the liquid crystal molecule directors of the cholesteric liquid crystal layer are periodically and gradually distributed from 0° to 180° to form a splayed gradient grating based on cholesteric liquid crystal; the temperature-controlled cholesteric liquid crystal layer includes a first chiral agent and a second chiral agent; in the cholesteric liquid crystal layer, the mass of the first chiral agent is greater than the mass of the second chiral agent, the sensitivity of the first chiral agent to temperature is greater than the sensitivity of the second chiral agent to temperature, so that the first chiral agent plays a leading role in the structure of the cholesteric liquid crystal, and the second chiral agent plays an auxiliary role in the structure of the cholesteric liquid crystal.

[0069] Figure 6 A flow chart of another method for preparing a temperature-controlled vortex beam comparator provided by an embodiment of the present invention, referring to Figure 6 , the method comprises the following steps:

[0070] S610 , providing a first substrate and a second substrate.

[0071] S621 , spin-coating an alignment material on one side of the first substrate and one side of the second substrate.

[0072] Exemplarily, the spin coating process may include: first adjusting the rotation speed to 600-900 rpm, controlling the first spin coating time to 5-10 seconds, so that the orientation material is evenly distributed on the surface of the spin-coated substrate; then adjusting the rotation speed to 2500-3500 rpm, controlling the second spin coating time to 30-50 seconds, so that the orientation material is spread.

[0073] S622 , annealing the first substrate and the second substrate on which the alignment material is spin-coated to form a first alignment layer and a second alignment layer having the same alignment direction.

[0074] Exemplarily, the annealing process may include: an annealing atmosphere of air, an annealing temperature of 80-120° C., and an annealing time of 8-12 minutes.

[0075] It should be noted that the above rotation speed and spin coating time are only exemplary descriptions. In other embodiments, the rotation speed and spin coating time can be adjusted according to actual needs so that the alignment film can control the alignment of cholesteric liquid crystal molecules.

[0076] Optionally, step S520 in the above embodiment may include step S621 and step S622.

[0077] S630 , aligning the first alignment layer and the second alignment layer to form a target pattern.

[0078] S640, mixing a non-chiral nematic liquid crystal host, a first chiral agent, and a second chiral agent according to a preset ratio to obtain a temperature-controlled cholesteric liquid crystal material.

[0079] The preset ratio is such that in the cholesteric liquid crystal layer, the mass of the first chiral agent is greater than the mass of the second chiral agent.

[0080] S650 , forming spacer particles between the first alignment layer and the second alignment layer.

[0081] Wherein, along a third direction perpendicular to the first substrate and the second substrate, an extension length of the spacer particles is greater than or equal to 10 times of a helical pitch of liquid crystal molecules in the cholesteric liquid crystal layer.

[0082] S660, disposing the first substrate and the second substrate opposite to each other, preparing a temperature-controlled cholesteric liquid crystal layer between the first alignment layer and the second alignment layer, and forming a vortex beam comparator.

[0083] Optionally, steps S640 and S650 may be included before step S540 in the above embodiment.

[0084] The method for preparing the temperature-controlled vortex beam comparator provided in an embodiment of the present invention is used to prepare the vortex beam comparator of any of the above-mentioned embodiments, and therefore has the same beneficial effects. For contents not described in detail in the embodiments of the present invention, reference can be made to the vortex beam comparator provided in the above-mentioned embodiments.

[0085] Figure 7 A schematic diagram of a structure of an implementation device of a temperature-controlled vortex beam comparator provided by an embodiment of the present invention, referring to Figure 7The device includes a vortex beam generating unit 100, a beam splitting unit 200, a temperature control unit 300, a receiving unit 400, and a vortex beam comparator 500 provided in any of the above embodiments. The vortex beam generating unit 100 is used to output two vortex beams to be compared, and the polarization states of the two vortex beams are a pair of orthogonal linear polarization states; the beam splitting unit 200 is arranged at the output end of the vortex beam generating unit 100, the vortex beam comparator 500 is located at the first output end of the beam splitting unit 200, and the receiving unit 400 is located at the second output end of the beam splitting unit 200, and the receiving unit 400 includes a lens 410 and a beam camera 420; the beam reflected by the vortex beam comparator 500 passes through the beam splitting unit 200, and then passes through the lens 410 and is received by the beam camera 420; the temperature control unit 300 is used to modulate the Bragg reflection band of the vortex beam comparator 500.

[0086] For example, continue to refer to Figure 7 The vortex beam generating unit 100 includes a negative direction of the Z axis (Z axis and Figure 1 The laser light source 110, the polarizer 120, the half-wave plate 130, the first quarter-wave plate 140, the first q-wave plate 150, the second quarter-wave plate 160, the second q-wave plate 170, and the third quarter-wave plate 180 are sequentially arranged, and the beam splitting unit 200 is a beam splitting prism; and the beam splitting unit 200 is located in a direction perpendicular to the Z direction ( Figure 7 In the X direction, Figure 1 The light is received by a receiving unit 400 that is parallel to the beam splitting unit 200 and has the same X direction as the beam splitting unit 200. The receiving unit 400 includes a lens 410 and a beam camera 420. The arrangement of the optical devices is only schematic and is not a limitation of the embodiments of the present invention. In order to reduce stray light, a stop 190 may also be provided in the light path.

[0087] The laser light source 110 is used to generate a laser beam. Figure 7The arrows exemplarily represent the propagation direction of the light beam. First, the incident laser is converted into left-handed circularly polarized incident light by a linear polarizer 120, a half-wave plate 130, and a first quarter-wave plate 140. Subsequently, the light beam passes through the first q-wave plate 150, the second quarter-wave plate 160, the second q-wave plate 170, and the third quarter-wave plate 180 in sequence to obtain a horizontally linearly polarized vortex beam and a vertically linearly polarized vortex beam. The topological charge values ​​of the two vortex beams are jointly determined by the topological charge parameters of the first q-wave plate 150 and the second q-wave plate 170. The relative phase of the two vortex beams is controlled by the optical axis direction of the second quarter-wave plate 160. Half of the vortex beam is transmitted through the beam splitting unit 200 and irradiated to the vortex beam comparator 500. When the wavelength of the incident light irradiated on the vortex beam comparator 500 is within the Bragg reflection band of the cholesteric liquid crystal layer (taking left-handed light as an example in this embodiment), due to the circularly polarized selective Bragg reflection effect of the cholesteric liquid crystal, the linearly polarized vortex beam is projected onto the circularly polarized state substrate, forming an interference superposition of the two input vortex beams. The superimposed vortex beam is reflected and diffracted, irradiated to the receiving unit 400 through the beam splitting unit 200, and forms a far-field diffraction pattern through the lens 410. The formed diffraction spot is recorded by the beam camera 420.

[0088] For example, Figure 8 A schematic diagram of the comparison results of a vortex beam combination with a positive sum of topological charges provided by an embodiment of the present invention. The topological charges l1 and l2 of the input vortex beam are +3 and -1 respectively, and their relative phases are adjustable. The temperature of the vortex beam comparator 500 is controlled to be 24.4°C so that the reflection band of the cholesteric liquid crystal layer contains the wavelength of the light beam to be detected, 1064nm. Figure 7 and Figure 8 , Figure 8 represent Figure 7 The experimental results and numerical simulation results of the diffraction spot of the beam camera 420 show that the topological charges l1 and l2 of the input vortex beam are +3 and -1 respectively, and the relative phase △φ takes the values ​​of 0, π / 2, π, and 3π / 2 respectively. According to the expansion degree of the light spot intensity distribution in the horizontal and vertical directions, it can be judged that the light spot mainly expands in the horizontal direction, and the sum of the topological charges of the two vortex beams is a positive number. The geometric moment analysis technology can be used to provide a more quantitative criterion. Let β be the ratio of the second-order central moment of the horizontal and vertical directions of the light intensity distribution, and set the judgment constant β0=9 / 8. When the relative phase △φ takes the values ​​of 0, π / 2, π, and 3π / 2 respectively, the corresponding measured β is 1.57, 1.29, 1.79, and 1.42 respectively, and β>β0, indicating that the sum of the topological charges is a positive number.

[0089] For example, Fig. 9A schematic diagram of the comparison result of a vortex beam combination with a zero sum of topological charges provided by an embodiment of the present invention. Exemplarily, the topological charges l1 and l2 of the input vortex beam are +2 and -2 respectively, and their relative phases are adjustable. The temperature of the vortex beam comparator 500 is controlled to be 24.4°C so that the reflection band of the cholesteric liquid crystal layer therein includes the wavelength 1064nm of the light beam to be detected. Figure 7 and Fig. 9 , Fig. 9 represent Figure 7 The experimental results and numerical simulation results of the diffraction spot of the beam camera 420 show that the topological charges l1 and l2 of the input vortex beam are +2 and -2 respectively, and the relative phase △φ is 0, π / 2, π, 3π / 2 respectively. The corresponding measured β is 0.98, 0.90, 0.92, and 1.05 respectively, and 1 / β0<β<β0 is satisfied. This shows that the expansion of the light intensity distribution in the horizontal and vertical directions is basically equal, and the sum of the topological charges is equal to zero, that is, the topological charges of the two vortex beams are opposite to each other.

[0090] For example, Fig.10 A schematic diagram of the comparison result of two vortex beams with equal topological charge provided by an embodiment of the present invention. The temperature of the vortex beam comparator 500 is controlled to be 24.4°C, so that the reflection band of the cholesteric liquid crystal layer contains the wavelength of the light beam to be detected, 1064nm. Figure 7 and Fig.10 , Fig.10 represent Figure 7 Experimental results and numerical simulation results of the diffraction spot of the beam camera 420. In this example, the topological charges l1 and l2 of the two input vortex beams are equal, respectively +3 and +3, -1 and -1, +2 and +2, -2 and -2, for a total of four examples. Among them, the spot of the first example mainly expands in the horizontal direction, and β=3.46>β0, indicating that the sum of the topological charges of the two vortex beams is positive; the spot of the second example mainly expands in the vertical direction, and β=0.84<1 / β0, indicating that the sum of the topological charges of the two vortex beams is negative; the spot of the third example mainly expands in the horizontal direction, and β=2.65>β0, indicating that the sum of the topological charges of the two vortex beams is positive; the spot of the fourth example mainly expands in the vertical direction, and β=0.62<1 / β0, indicating that the sum of the topological charges of the two vortex beams is negative.

[0091] It should be noted that the embodiment of the present invention only exemplarily shows the vortex beam comparison under some topological charge value combinations at a wavelength of 1064nm, but it is not a limitation of the vortex beam comparator provided by the present invention. In other embodiments, according to actual needs, suitable cholesteric liquid crystal materials are prepared so that the vortex beam comparator provided by the present invention is suitable for different wavelength ranges and has different temperature adjustability.

[0092] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0093] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A temperature-controlled vortex beam comparator, characterized in that: It comprises a first substrate and a second substrate which are arranged opposite to each other, and a cholesteric liquid crystal layer located between the first substrate and the second substrate; A first alignment layer is disposed on a side of the first substrate close to the second substrate, and a second alignment layer is disposed on a side of the second substrate close to the first substrate; wherein the first alignment layer and the second alignment layer have the same alignment direction, and the first alignment layer and the second alignment layer have control patterns in which molecular directors are periodically and gradually distributed, the control patterns form a plurality of spoke-shaped regions, and the extension lines of the spokes of each region intersect at the same point, and along a direction perpendicular to the spokes, the directors of the liquid crystal molecules in the cholesteric liquid crystal layer are periodically and gradually distributed from 0° to 180°, so as to form a splayed gradient grating based on cholesteric liquid crystal; The cholesteric liquid crystal layer includes a first chiral agent and a second chiral agent; wherein, in the cholesteric liquid crystal layer, the mass of the first chiral agent is greater than the mass of the second chiral agent, and the sensitivity of the first chiral agent to temperature is greater than the sensitivity of the second chiral agent to temperature, so that the first chiral agent plays a leading role in the structure of the cholesteric liquid crystal, and the second chiral agent plays an auxiliary role in the structure of the cholesteric liquid crystal.

2. The vortex beam comparator according to claim 1, characterized in that: The distribution of directors of the liquid crystal molecules satisfies: Wherein, α represents the azimuth angle of the director of the liquid crystal molecule, Λ represents the grating period, D represents the relative displacement from the center of the control pattern to the intersection of the extended lines of the spokes, x represents a first direction parallel to the first substrate, y represents a second direction parallel to the first substrate, and the first direction and the second direction are orthogonal.

3. The cholesteric liquid crystal layer according to claim 1, characterized in that: The helical twisting ability of the first chiral agent changes to different degrees at different temperatures, and the helical twisting ability of the second chiral agent changes to different degrees at different temperatures; At the same temperature change, the degree of change of the helical twisting ability of the first chiral agent is greater than the degree of change of the helical twisting ability of the second chiral agent.

4. The vortex beam comparator according to claim 3, characterized in that: The first chiral agent includes a left-handed chiral agent or a right-handed chiral agent; the second chiral agent includes a left-handed chiral agent or a right-handed chiral agent; When the first chiral agent and the second chiral agent are both the left-handed chiral agent, or are both the right-handed chiral agent, the overall spiral twisting ability of the cholesteric liquid crystal layer is enhanced, and the dynamic range of the Bragg reflection band of the cholesteric liquid crystal layer is blue-shifted; when the first chiral agent and the second chiral agent are respectively the left-handed chiral agent and the right-handed chiral agent, or are respectively the right-handed chiral agent and the left-handed chiral agent, the overall spiral twisting ability of the cholesteric liquid crystal layer is weakened, and the dynamic range of the Bragg reflection band of the cholesteric liquid crystal layer is red-shifted.

5. The vortex beam comparator according to claim 1, characterized in that: The materials of the first alignment layer and the second alignment layer include at least one of a photo-crosslinking material, a photo-degradable material, and a photo-induced cis-trans isomerization material.

6. The vortex beam comparator according to claim 1, characterized in that: The vortex beam comparator also includes spacer particles located between the first orientation layer and the second orientation layer, and the spacer particles are used to support the first substrate and the second substrate to form a filling space for the cholesteric liquid crystal layer; wherein, along a third direction perpendicular to the first substrate and the second substrate, an extension length of the spacer particles is greater than or equal to 10 times the pitch of the liquid crystal molecules in the cholesteric liquid crystal layer.

7. A method for preparing a temperature-controlled vortex beam comparator, used for preparing the vortex beam comparator according to any one of claims 1 to 6, characterized in that: include: providing a first substrate and a second substrate; forming a first alignment layer on one side of the first substrate, and forming a second alignment layer on one side of the second substrate; orienting the first alignment layer and the second alignment layer to form a target pattern; The first substrate and the second substrate are arranged opposite to each other, and a temperature-controlled cholesteric liquid crystal layer is prepared between the first alignment layer and the second alignment layer to form the vortex beam comparator; The first alignment layer is located on a side of the first substrate close to the second substrate, and the second alignment layer is located on a side of the second substrate close to the first substrate. The first alignment layer and the second alignment layer have the same alignment direction. The first alignment layer and the second alignment layer have control patterns in which molecular directors are distributed in a periodic gradient. The control patterns form a plurality of spoke-shaped regions, and the extension lines of the spokes of each region intersect at the same point. Along the vertical direction of the spokes, the liquid crystal molecule directors of the cholesteric liquid crystal layer are distributed in a periodic gradient of 0°-180° to form a splayed gradient grating based on cholesteric liquid crystal. The temperature-controlled cholesteric liquid crystal layer includes a first chiral agent and a second chiral agent. In the cholesteric liquid crystal layer, the mass of the first chiral agent is greater than the mass of the second chiral agent, and the sensitivity of the first chiral agent to temperature is greater than the sensitivity of the second chiral agent to temperature, so that the first chiral agent plays a leading role in the structure of the cholesteric liquid crystal, and the second chiral agent plays an auxiliary role in the structure of the cholesteric liquid crystal.

8. The preparation method according to claim 7, characterized in that: The step of forming a first alignment layer on one side of the first substrate and forming a second alignment layer on one side of the second substrate comprises: Spin coating an alignment material on one side of the first substrate and one side of the second substrate; The first substrate and the second substrate on which the alignment material is spin-coated are annealed to form the first alignment layer and the second alignment layer having the same alignment direction.

9. The preparation method according to claim 7, characterized in that: Before the first substrate and the second substrate are arranged opposite to each other and a temperature-controlled cholesteric liquid crystal layer is prepared between the first alignment layer and the second alignment layer to form the vortex beam comparator, the method further includes: A non-chiral nematic liquid crystal host, the first chiral agent and the second chiral agent are mixed according to a preset ratio to obtain a temperature-controlled cholesteric liquid crystal material; wherein the preset ratio is such that in the cholesteric liquid crystal layer, the mass of the first chiral agent is greater than the mass of the second chiral agent; Spacer particles are formed between the first alignment layer and the second alignment layer; wherein, along a third direction perpendicular to the first substrate and the second substrate, an extension length of the spacer particles is greater than or equal to 10 times the helical pitch of the liquid crystal molecules in the cholesteric liquid crystal layer.

10. An implementation device of a temperature-controlled vortex beam comparator, characterized in that: It comprises a vortex beam generating unit, a beam splitting unit, a temperature control unit, a receiving unit and a vortex beam comparator according to any one of claims 1 to 6; The vortex beam generating unit is used to output two vortex beams to be compared, and the polarization states of the two vortex beams are a pair of orthogonal linear polarization states; The beam splitting unit is arranged at the output end of the vortex beam generating unit, the vortex beam comparator is located at the first output end of the beam splitting unit, the receiving unit is located at the second output end of the beam splitting unit, and the receiving unit includes a lens and a beam camera; The light beam reflected by the vortex beam comparator passes through the beam splitting unit and then through the lens to be received by the beam camera; The temperature control unit is used to modulate the Bragg reflection band of the vortex beam comparator.

Images