Temperature controlled vortex beam comparator, method of making and implementing the same

Abstract

The application discloses a temperature-controlled vortex beam comparator, a preparation method thereof and an implementation device. The first orientation layer and the second orientation layer of the vortex beam comparator have a control pattern with a periodically and gradually distributed molecular director. The control pattern forms a plurality of spoke-shaped regions. The spoke extension lines of each region meet at the same point. In a direction perpendicular to the spoke, the director of the liquid crystal molecules in the cholesteric liquid crystal layer is periodically and gradually distributed from 0° to 180° to form a curved and gradually changed grating based on cholesteric liquid crystal. In the cholesteric liquid crystal layer, the mass of the first chiral agent is greater than that of the second chiral agent, and the sensitivity of the first chiral agent to temperature is greater than that 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. The device integration of the vortex beam processing and the efficiency of the comparison operation can be improved, and the adjustment and control ability of the processing waveband can be expanded.

Description

TECHNICAL FIELD

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

[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 the computing demand. At the physical implementation level, all-optical computing requires effective development and regulation of the full-dimensional properties of light beams. Vortex beams are a special kind of light beams whose phase properties exhibit a spiral distribution in the cross-section, and the characteristic parameter is 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 have wide applications in ultra-wideband communication, quantum information processing and optical computing. The comparison of vortex beams refers to directly comparing the topological charge of two input vortex beams 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 realized by cascading diffractive elements and polarizers, but it faces problems such as system complexity. Compared with traditional elements, novel materials based on superstructures have the advantages of compactness, integration and multifunctionality, however, these devices are difficult to process, and there are certain limitations in the adjustability of the working waveband. SUMMARY

[0004] The present application provides a temperature-controlled vortex beam comparator, a preparation method thereof and an implementation device, to improve the integration of vortex beam processing devices and the efficiency of comparison operations, and effectively expand the dynamic range and regulation capacity of the working waveband of the devices.

[0005] In a first aspect, an embodiment of the present application provides a temperature-controlled vortex beam comparator, comprising a first substrate, a second substrate arranged oppositely, and a cholesteric liquid crystal layer located between the first substrate and the second substrate.

[0006] The first substrate is provided with a first alignment layer on the side close to the second substrate, and the second substrate is provided with a second alignment layer on the side close to the first substrate; wherein 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 with periodically and gradually distributed molecular directors, the control pattern forms a plurality of spoke-shaped regions, the spoke extension lines of each region meet at the same point, and along the direction perpendicular to the spoke, the directors of the liquid crystal molecules in the cholesteric liquid crystal layer are periodically and gradually distributed from 0° to 180° to form a curved and gradually changed grating based on cholesteric liquid crystal.

[0007] The cholesteric liquid crystal layer comprises 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 the 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 of the center of the control pattern to the intersection point of the spoke extension line, x represents a first direction parallel to the first substrate, and y represents a second direction parallel to the first substrate, the first direction and the second direction being orthogonal.

[0009] Optionally, the change degree of the helical twisting power of the first chiral agent at different temperatures is different, and the change degree of the helical twisting power of the second chiral agent at different temperatures is different.

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

[0011] Optionally, the first chiral agent comprises a left-handed chiral agent or a right-handed chiral agent; and the second chiral agent comprises 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 both the right-handed chiral agent, the helical twisting power of the whole 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 the left-handed chiral agent and the right-handed chiral agent respectively, or the right-handed chiral agent and the left-handed chiral agent respectively, the helical twisting power of the whole 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 material of the first alignment layer and the second alignment layer comprises at least one of photo-crosslinking material, photo-degradable material and photo-isomerization material.

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

[0015] In a second aspect, the embodiments of the present application further provide a preparation method of a vortex beam comparator with temperature control, for preparing the vortex beam comparator of any of the embodiments 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 a second alignment layer on one side of the second substrate;

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

[0019] oppositely arranging the first substrate and the second substrate to prepare a cholesteric liquid crystal layer with temperature control between the first alignment layer and the second alignment layer to form the vortex beam comparator;

[0020] wherein, the first alignment layer is located on the side of the first substrate close to the second substrate, the second alignment layer is located on the 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 with periodic gradual distribution of molecular director, the control pattern forms a plurality of areas in the shape of spokes, the spoke extension lines of each area intersect at the same point, along the vertical direction of the spoke, the director of the liquid crystal molecules of the cholesteric liquid crystal layer has a periodic gradual distribution of 0°-180° to form a curved gradual grating based on cholesteric liquid crystal; the cholesteric liquid crystal layer with temperature control comprises 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 that of the second chiral agent, and the sensitivity of the first chiral agent to temperature is greater than that of the second chiral agent, 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, the first alignment layer is formed on one side of the first substrate, and the second alignment layer is formed on one side of the second substrate, comprising:

[0022] The orientation material is spin-coated 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 orientation material is spin-coated are annealed to form the first alignment layer and the second alignment layer with the same orientation direction.

[0024] Optionally, before the vortex beam comparator is formed, the first substrate and the second substrate are arranged oppositely, and a temperature-controlled cholesteric liquid crystal layer is prepared between the first alignment layer and the second alignment layer, comprising:

[0025] The achiral 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 the mass of the first chiral agent is greater than the mass of the second chiral agent in the cholesteric liquid crystal layer;

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

[0027] In a third aspect, the embodiments of the present application also provide an implementation device of a temperature-controlled vortex beam comparator, comprising a vortex beam generation unit, a beam splitting unit, a temperature control unit, a receiving unit and the vortex beam comparator of any one of the first aspect.

[0028] The vortex beam generation unit is configured 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 generation unit, the vortex beam comparator is located at the first output end of the beam splitting unit, and the receiving unit is located at the second output end of the beam splitting unit. The receiving unit comprises a lens and a beam camera.

[0030] The light beam reflected by the vortex beam comparator passes through the beam splitting unit, is transmitted through the lens and is received by the beam camera.

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

[0032] The embodiment of the present application provides a temperature-controlled vortex beam comparator and a preparation method and an implementation device thereof, the vortex beam comparator comprises a first substrate, a second substrate and a cholesteric liquid crystal layer located between the first substrate and the second substrate which are oppositely arranged; a first orientation layer is arranged on the side of the first substrate close to the second substrate, and a second orientation layer is arranged on the 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, the first orientation layer and the second orientation layer have a control pattern with periodically varying distribution of molecular director, the control pattern forms a plurality of spoke-shaped regions, the spoke extension lines of each region intersect at the same point, and in the direction perpendicular to the spoke, the director of the liquid crystal molecules in the cholesteric liquid crystal layer has a periodic variation distribution of 0-180 degrees to form a cholesteric liquid crystal-based curved gradient grating; the cholesteric liquid crystal layer comprises 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 that of the second chiral agent, and the sensitivity of the first chiral agent to temperature is greater than that of the second chiral agent, 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 the embodiment of the present application, the helical chirality of the cholesteric liquid crystal layer is determined by the first chiral agent, the helical pitch of the cholesteric liquid crystal layer is dynamically regulated by the temperature and mainly determined by the first chiral agent, and the second chiral agent is used to further adjust the pitch adjustment range under the temperature control. The device integration and the efficiency of the comparison operation of the vortex beam processing can be improved, and the control ability of the processing waveband can be expanded.

[0033] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present application, nor is it used to limit the scope of the present application. Other features of the present application will become apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

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

[0036] Figure 2 A liquid crystal molecule director direction diagram of a curved gradient grating provided by the embodiment of the present application;

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

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

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

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

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

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

[0043] Figure 9 A comparison result schematic diagram of a vortex beam combination with a sum of topological charges being zero provided by an embodiment of the present application;

[0044] Figure 10 A comparison result schematic diagram of two vortex beams with equal topological charges provided by an embodiment of the present application. DETAILED DESCRIPTION

[0045] In order to make the personnel in the art better understand the present application scheme, the technical scheme in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by the person skilled in the art without creative labor should belong to the scope of protection of the present application.

[0046] It should be noted that the terms "first", "second", and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not necessarily have to describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units 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 is provided for embodiments of the present application, referring to Figure 1 The vortex beam comparator includes oppositely arranged first substrate 10, second substrate 20 and cholesteric liquid crystal layer 30 between the first substrate 10 and the second substrate 20; the first substrate 10 is provided with a first orientation layer 11 on the side close to the second substrate 20, and the second substrate 20 is provided with a second orientation layer 21 on the side close to the first substrate 10; wherein the first orientation layer 11 and the second orientation layer 21 have the same orientation direction, the first orientation layer 11 and the second orientation layer 21 have a control pattern with periodically varying distribution of molecular director, the control pattern forms a plurality of spoke-shaped regions, the spoke extension lines of each region intersect at the same point, and along the direction perpendicular to the spoke, the director of the liquid crystal molecules in the cholesteric liquid crystal layer 30 is periodically varied from 0° to 180° to form a curved 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 that of the second chiral agent, 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, and the sensitivity of the first chiral agent to temperature is greater than that of 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 light beams with wavelengths within the reflection band, the cholesteric liquid crystal layer 30 reflects the circularly polarized component with the same rotation direction as the liquid crystal layer, so that the incident linearly polarized vortex beam is projected on a circularly polarized state substrate to form an interference superposition of two input vortex beams. The two superimposed vortex beams are further diffracted by the curved gradient grating to form a fringe pattern, indicating the number relationship of the topological charges of the two vortex beams. Specifically, the light intensity distribution of the obtained light spot mainly extends in the horizontal direction, indicating that the sum of the topological charges of the two vortex beams is positive; the light intensity distribution of the obtained light spot mainly extends in the vertical direction, indicating that the sum of the topological charges of the two vortex beams is negative; the light intensity distribution of the obtained light spot extends equally in the horizontal and vertical directions, indicating that the sum of the topological charges of the two vortex beams is equal to zero, i.e. the topological charges of the two vortex beams are opposite.

[0049] The mass of the first chiral agent is greater than the mass of the second chiral agent, and the first chiral agent is more sensitive to temperature than the second chiral agent, 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 integration of the vortex beam processing device, the efficiency of the comparison operation, and the control ability of the processing waveband.

[0050] Figure 2 A liquid crystal molecule director direction diagram of the expansion and contraction gradually changing grating is provided in the embodiment of the present application. Optionally, on the basis of the above embodiment, the distribution of the liquid crystal molecule director satisfies: Wherein, α represents the azimuth angle of the liquid crystal molecule director, Λ represents the grating period, D represents the relative displacement of the center of the control pattern to the intersection point of the spoke extension line, x represents the first direction parallel to the first substrate 10, y represents the second direction parallel to the first substrate 10, and the first direction x and the second direction y are orthogonal.

[0051] For example, in an embodiment, Λ = π / 150 and D = 4.5 mm.

[0052] Optionally, on the basis of the above embodiment, the change degree of the helical twisting power of the first chiral agent at different temperatures is different, and the change degree of the helical twisting power of the second chiral agent at different temperatures is different; under the same temperature change amount, the change degree of the helical twisting power of the first chiral agent is greater than the change degree of the helical twisting power of the second chiral agent.

[0053] Optionally, on the basis of the above embodiment, 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 right-handed chiral agents, the helical twisting power of the cholesteric liquid crystal layer 30 as a whole 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 a left-handed chiral agent and a right-handed chiral agent respectively, or a right-handed chiral agent and a left-handed chiral agent respectively, the helical twisting power of the cholesteric liquid crystal layer 30 as a whole 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 application can flexibly adjust the dynamic range of the Bragg reflection band of the cholesteric liquid crystal layer 30 under certain temperature control conditions. For example, in an embodiment, the temperature-controlled left-handed cholesteric liquid crystal is mixed by 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, S811 sensitive to temperature gives the cholesteric liquid crystal temperature control property, and R5011 not sensitive to temperature is used to adjust the adjustable range of the Bragg reflection band of the cholesteric liquid crystal. It should be noted that the above-mentioned liquid crystal material type, chiral agent type and mixing ratio are only exemplary descriptions, and in other embodiments, the liquid crystal material type, chiral agent type and mixing ratio can be adjusted according to actual needs, so that the temperature-controlled cholesteric liquid crystal has the required temperature control performance.

[0055] Optionally, on the basis of the above-mentioned embodiment, the material of the first alignment layer 11 and the second alignment layer 21 includes at least one of photo-crosslinking material, photo-degradation material and photo-isomerization material.

[0056] In the embodiment of the present application, the material of the first alignment layer 11 and the second alignment layer 21 is photo-controlled alignment material, which can produce anisotropic surface force under the irradiation of ultraviolet polarized light, and then induce the directional arrangement of liquid crystal molecules.

[0057] Optionally, on the basis of the above-mentioned embodiment, continuing to refer to Figure 1 , the vortex beam comparator further includes a spacer particle 31 located between the first alignment layer 11 and the second alignment layer 21, the spacer particle 31 is used to support the first substrate 10 and the second substrate 20, and form a filling space of the cholesteric liquid crystal layer 30; wherein, along the third direction z perpendicular to the first substrate 10 and the second substrate 20, the extension length of the spacer particle 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 particle 31 in the embodiment of the present application is greater than or equal to 10 times the pitch of the liquid crystal molecules in the cholesteric liquid crystal layer 30, which can form a curved grating with sufficient reflectivity.

[0059] It can be understood that, Figure 1 In the above-mentioned embodiment, only the positional relationship of the spacer particle 31 for supporting the first substrate 10 and the second substrate 20 is exemplarily shown, but not the actual size and proportion. Optionally, the spacer particle 31 includes at least one of quartz microspheres and quartz columns, which can be designed according to actual conditions in specific implementation.

[0060] Figure 3 A relationship diagram of the Bragg reflection band of the cholesteric liquid crystal layer provided in the embodiment of the present application is shown in the following figure, Figure 4A reflection micrograph of the cholesteric liquid crystal layer at different temperatures is provided for the embodiment of the present application. Referring to Figure 3 , the abscissa represents wavelength in nanometers, and the ordinate represents reflectivity of the cholesteric liquid crystal layer. When the temperature is raised from 23.6℃ to 40.0℃, the center 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 in the cooling process. Referring to Figure 4 , the reflection orthogonal polarization mode is used in the figure, the scale is 200μm, the planar texture of the cholesteric liquid crystal layer 30 presents a uniform color, and the slightly bright and dark stripes reflect the designed curved and gradually changed grating pattern. It can be seen from Figure 4 that the cholesteric liquid crystal layer is orange at 38.4℃, red at 34.5℃, and dark at 24.4℃, and the corresponding photonic band gaps are 599-647nm, 622-682nm, and 982-1117nm, respectively. It should be noted that Figure 3 only exemplarily shows a relationship diagram of the reflection band of a cholesteric liquid crystal layer controlled by temperature, Figure 4 only exemplarily shows a reflection micrograph of the cholesteric liquid crystal layer at different temperatures, but is not limited to the cholesteric liquid crystal material used in the present application. In other embodiments, cholesteric liquid crystal materials with other optical properties can be selected according to actual needs.

[0061] In the cholesteric liquid crystal layer 30 of the embodiment of the present application, 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 comparison operation, and the control ability of processing wavelength band. In addition, the scheme of the embodiment of the present application 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 alignment layer 11 and the second alignment layer 21 are photoalignment materials, which can undergo physical or chemical reactions under the irradiation of ultraviolet polarized light, thereby generating anisotropic surface force to induce the directional arrangement of liquid crystal molecules. The extension length of the spacer particle 31 is greater than or equal to 10 times the pitch of the liquid crystal molecules in the cholesteric liquid crystal layer 30, which can form a curved and gradually changed grating with sufficient reflectivity.

[0062] Figure 5 A flowchart of a preparation method of a vortex beam comparator controlled by temperature is provided for the embodiment of the present application, which is used to prepare the vortex beam comparator of any of the above embodiments, referring 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 can be a flexible substrate or a rigid substrate with high light transmittance (greater than or equal to 85%). For example, the first substrate and the second substrate can be made of quartz glass, ITO glass or ordinary glass, and the thickness of the substrate can be 1-2 mm.

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

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

[0067] S540, oppositely arranging the first substrate and the second substrate, and preparing a temperature-controlled cholesteric liquid crystal layer between the first alignment layer and the second alignment layer to form a vortex beam comparator.

[0068] The first alignment layer is located on the side of the first substrate close to the second substrate, and the second alignment layer is located on the side of the second substrate close to the first substrate. The first alignment layer and the second alignment layer have the same orientation direction. The first alignment layer and the second alignment layer have a control pattern with a periodic gradual distribution of molecular director. The control pattern forms a plurality of spoke-shaped regions, and the spoke extension lines of each region intersect at the same point. In the vertical direction of the spoke, the director of the cholesteric liquid crystal layer has a periodic gradual distribution of 0°-180° to form a curved gradual 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.

[0069] Figure 6 Another flowchart of a preparation method of a temperature-controlled vortex beam comparator is provided for the embodiments of the present application, 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] For example, the spin coating process can include: first adjusting the rotation speed to 600-900 rpm, controlling the first spin coating time to 5-10 seconds, and making the alignment material uniformly distributed on the surface of the substrate to be coated; and then adjusting the rotation speed to 2500-3500 rpm, controlling the second spin coating time to 30-50 seconds, and making the alignment material spread out.

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

[0074] For example, the annealing process can include: the annealing atmosphere is air, the annealing temperature is 80-120℃, and the annealing time is 8-12 minutes.

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

[0076] Optionally, step S520 in the above embodiment can 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 the achiral nematic liquid crystal main body, the first chiral agent and the second chiral agent according to a preset ratio to obtain the temperature-controlled cholesteric liquid crystal material.

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

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

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

[0082] S660, oppositely arranging the first substrate and the second substrate to prepare a temperature-controlled cholesteric liquid crystal layer between the first alignment layer and the second alignment layer to form a vortex beam comparator.

[0083] Optionally, step S540 in the above embodiment can further include steps S640 and S650.

[0084] The preparation method of the temperature-controlled vortex beam comparator provided by the embodiments of the present application is used to prepare the vortex beam comparator of any of the above embodiments, and therefore has the same beneficial effects. The content not described in detail in the embodiments of the present application can be referred to the vortex beam comparator provided by the above embodiments.

[0085] Figure 7 The structure diagram of an embodiment of a temperature-controlled vortex beam comparator provided by the embodiments of the present application is shown in FIG. 1. 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 outputs two vortex beams to be compared, the two vortex beams having orthogonal linear polarization states. The beam splitting unit 200 is located 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. 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, then through the lens 410, and is received by the beam camera 420. The temperature control unit 300 modulates 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 components along the negative Z-axis direction (Z-axis and...). Figure 1 A laser source 110, a polarizer 120, a half-wave plate 130, a first quarter-wave plate 140, a first q-wave plate 150, a second quarter-wave plate 160, a second q-wave plate 170, and a third quarter-wave plate 180 are arranged sequentially in the same direction as the Z-axis (perpendicular to the plane of the first substrate). A beam-splitting unit 200 is a beam-splitting prism. A beam splitting unit 200 is located in a direction perpendicular to the Z-axis (perpendicular to the plane of the first substrate). Figure 7 In the X direction, and Figure 1 The receiving unit 400, which is parallel to the beam splitter unit 200 and has the same X-direction as the beam splitter unit 200, receives the light. The receiving unit 400 includes a lens 410 and a beam camera 420. The arrangement of the optical components is only illustrative and is not intended to limit the embodiments of the present invention. To reduce stray light, an aperture stop 190 may also be provided in the optical path.

[0087] The laser source 110 is used to generate a laser beam. Figure 7The propagation direction of the light beams is represented by arrows. First, the incident laser is converted into left-handed circularly polarized incident light by the linear polarizer 120, the half-wave plate 130 and the first quarter-wave plate 140. Then, the light beam passes through the first q-plate 150, the second quarter-wave plate 160, the second q-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 determined by the topological charge parameters of the first q-plate 150 and the second q-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 beams are transmitted through the beam splitting unit 200 and irradiate the vortex beam comparator 500. When the wavelength of the incident light irradiating the vortex beam comparator 500 is within the Bragg reflection band of the cholesteric liquid crystal layer (the left-handed one in this embodiment), the linearly polarized vortex beam is projected on the circularly polarized state substrate to form the interference superposition of the two input vortex beams due to the Bragg reflection of the circularly polarized selective cholesteric liquid crystal. The superposed vortex beam is reflected and diffracted, irradiates the receiving unit 400 through the beam splitting unit 200, forms a far-field diffraction pattern through the lens 410, and the diffraction spot is recorded by the beam camera 420.

[0088] An exemplary Figure 8 A schematic diagram of the comparison result of a vortex beam combination with a positive sum of topological charges provided by an embodiment of the present application is shown. The topological charges l1 and l2 of the input vortex beams are +3 and -1 respectively, and the relative phase is 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 in the vortex beam comparator 500 contains the wavelength 1064 nm of the light beam to be detected. The experimental results and numerical simulation results of the diffraction spot of the beam camera 420 are shown in FIG. 6. The topological charges l1 and l2 of the input vortex beams are +3 and -1 respectively, and the relative phase is taken as 0, π / 2, π and 3π / 2 respectively. According to the expansion degree of the spot intensity distribution in the horizontal direction and the vertical direction, it can be judged that the spot is mainly expanded in the horizontal direction, and the sum of the topological charges of the two vortex beams is positive. The geometric moment analysis technique can provide a more quantitative criterion. Let β be the ratio of the second-order central moments of the intensity distribution in the horizontal direction and the vertical direction, and let the judgment constant β0 be 9 / 8. When the relative phase is taken as 0, π / 2, π and 3π / 2 respectively, the measured β is 1.57, 1.29, 1.79 and 1.42 respectively, all of which satisfy β>β0, indicating that the sum of the topological charges is positive. 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 are shown in FIG. 6. The topological charges l1 and l2 of the input vortex beams are +3 and -1 respectively, and the relative phase is taken as 0, π / 2, π and 3π / 2 respectively. According to the expansion degree of the spot intensity distribution in the horizontal direction and the vertical direction, it can be judged that the spot is mainly expanded in the horizontal direction, and the sum of the topological charges of the two vortex beams is positive. The geometric moment analysis technique can provide a more quantitative criterion. Let β be the ratio of the second-order central moments of the intensity distribution in the horizontal direction and the vertical direction, and let the judgment constant β0 be 9 / 8. When the relative phase is taken as 0, π / 2, π and 3π / 2 respectively, the measured β is 1.57, 1.29, 1.79 and 1.42 respectively, all of which satisfy β>β0, indicating that the sum of the topological charges is positive.

[0089] An exemplary, Figure 9This is a schematic diagram illustrating the comparison results of a combination of vortex beams with a sum of zero topological charges, provided in an embodiment of the present invention. For example, the topological charges l1 and l2 of the input vortex beam are +2 and -2, respectively, and their relative phase is adjustable. The temperature of the vortex beam comparator 500 is controlled at 24.4°C, so that the reflection band of the cholesteric liquid crystal layer therein contains the wavelength of the beam to be detected, 1064 nm. Combined with... Figure 7 and Figure 9 , Figure 9 represent Figure 7 The experimental and numerical simulation results of the diffraction spot of the beam camera 420 are presented. The topological charges l1 and l2 of the input vortex beam are +2 and -2, respectively, and the relative phase Δφ takes values ​​of 0, π / 2, π, and 3π / 2, respectively. The corresponding measured β values ​​are 0.98, 0.90, 0.92, and 1.05, respectively. In all cases, 1 / β0 < β < β0, indicating that the light intensity distribution is basically equal in the horizontal and vertical directions, and the sum of the topological charges is equal to zero. That is, the topological charges of the two vortex beams are opposites of each other.

[0090] For example, Figure 10 This is a schematic diagram illustrating the comparison results of two vortex beams with equal topological charges, provided in an embodiment of the present invention. The temperature of the vortex beam comparator 500 is controlled at 24.4°C, ensuring that the cholesteric liquid crystal layer's reflective band encompasses the wavelength of the beam to be detected, which is 1064 nm. Combined with... Figure 7 and Figure 10 , Figure 10 represent Figure 7 Experimental and numerical simulation results of the diffraction spot of the beam camera 420 are presented. In this example, the topological charges l1 and l2 of the two input vortex beams are equal, namely +3 and +3, -1 and -1, +2 and +2, and -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 embodiments of the present invention only exemplify the comparison of vortex beams under a partial combination of topological charge values ​​at a wavelength of 1064nm, but are not intended to limit the vortex beam comparator provided by the present invention. In other embodiments, suitable cholesteric liquid crystal materials can be prepared according to actual needs, so that the vortex beam comparator provided by the present invention is applicable to different wavelength ranges and has different temperature adjustability.

[0092] It should be understood that the various forms of flow shown above can be used to reorder, add, or remove steps. For example, the steps recited in the present application can be performed in parallel, in series, or in a different order, as long as the desired results of the technical solutions of the present application can be achieved, which are not limited herein.

[0093] The above detailed description does not constitute a limitation on the protection scope of the present application. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A temperature controlled vortex beam comparator, characterized by, The cholesteric liquid crystal layer is arranged between the first substrate and the second substrate; 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 the molecular director is 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, and the director of the liquid crystal molecules in the cholesteric liquid crystal layer is periodically and gradually distributed in the direction perpendicular to the spoke to form a curved and gradually changing 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 of claim 1, wherein, The distribution of the director of the liquid crystal molecules satisfies: wherein, α represents an azimuth angle of the director of the liquid crystal molecules, Λ represents a grating period, D represents a relative displacement from the center of the control pattern to the intersection point of the spoke extension line, x represents a first direction parallel to the first substrate, and y represents a second direction parallel to the first substrate, the first direction and the second direction being orthogonal.

3. The vortex beam comparator of claim 1, wherein, The change degree of the helical twisting power of the first chiral agent at different temperatures is different, and the change degree of the helical twisting power of the second chiral agent at different temperatures is different. Under the same temperature change, the change degree of the helical twisting power of the first chiral agent is greater than the change degree of the helical twisting power of the second chiral agent.

4. The vortex beam comparator of claim 3, wherein, 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 right-handed chiral agents, the helical twisting power of the cholesteric liquid crystal layer as a whole 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 a left-handed chiral agent and a right-handed chiral agent respectively, or a right-handed chiral agent and a left-handed chiral agent respectively, the helical twisting power of the cholesteric liquid crystal layer as a whole 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 of claim 1, wherein, The material of the first orientation layer and the second orientation layer includes at least one of photo-crosslinking material, photo-degradation material and photo-induced cis-trans isomerization material.

6. The vortex beam comparator of claim 1, wherein, The vortex beam comparator further includes a spacer particle between the first orientation layer and the second orientation layer, the spacer particle is used to support the first substrate and the second substrate to form a filling space of the cholesteric liquid crystal layer; wherein along a third direction perpendicular to the first substrate and the second substrate, the extension length of the spacer particle 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 producing a temperature-controlled vortex beam comparator, for producing a vortex beam comparator according to any one of claims 1 to 6, characterized in that The method comprises: providing a first substrate and a second substrate; forming a first orientation layer on one side of the first substrate and a second orientation layer on one side of the second substrate; orienting the first orientation layer and the second orientation layer to form a target pattern; The first substrate and the second substrate are arranged oppositely, 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 the side of the first substrate close to the second substrate, and the second alignment layer is located on the 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 director periodically and gradually changes. The control pattern forms a plurality of spoke-shaped regions. The spoke extension lines of each region intersect at the same point. In the vertical direction of the spoke, the director of the liquid crystal molecules in the cholesteric liquid crystal layer periodically and gradually changes from 0° to 180° to form a cholesteric liquid crystal-based curved and gradually changing grating. 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. 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 first alignment layer is formed on one side of the first substrate, and the second alignment layer is formed on one side of the second substrate. The orientation material is spin-coated on one side of the first substrate and one side of the second substrate. The first substrate and the second substrate on which the orientation material is spin-coated are annealed to form the first alignment layer and the second alignment layer with 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 oppositely, 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 following steps are further included: The non-chiral nematic liquid crystal host, the first chiral agent, and the second chiral agent are mixed in a predetermined ratio to obtain a temperature-controlled cholesteric liquid crystal material. The predetermined ratio is such that the mass of the first chiral agent is greater than the mass of the second chiral agent in the cholesteric liquid crystal layer. Spaced particles are formed between the first alignment layer and the second alignment layer. In the third direction perpendicular to the first substrate and the second substrate, the extension length of the spaced particles is greater than or equal to 10 times the pitch of the liquid crystal molecules in the cholesteric liquid crystal layer.

10. An implementation of a temperature controlled vortex beam comparator, characterized by, The vortex beam comparator includes a vortex beam generating unit, a beam splitting unit, a temperature control unit, a receiving unit, and any one of claims 1-6. The vortex beam generating unit is used to output two vortex beams to be compared. 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, and the receiving unit is located at the second output end of the beam splitting unit. The receiving unit includes a lens and a beam camera. The light beam reflected by the vortex beam comparator passes through the beam splitter unit, is received by the light beam camera through the lens; The temperature control unit is used for modulating the Bragg reflection band of the vortex beam comparator.

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