Topological charge adjustable terahertz vortex light beam generation device based on electric control liquid crystal and preparation method of topological charge adjustable terahertz vortex light beam generation device

Abstract

The invention discloses a topological charge adjustable terahertz vortex light beam generation device based on electronic control liquid crystal and a preparation method thereof, and belongs to the technical field of adjustable terahertz vortex light beams. In order to achieve wide and accurate adjustment of generated vortex light beams, a first substrate layer, a rotary twisted electrode layer, a first polyimide orientation layer, an electric control liquid crystal layer, a second polyimide orientation layer, a uniform transparent electrode layer and a second substrate layer are sequentially arranged from top to bottom. The rotating and twisting electrode layer is composed of a series of discrete petal-shaped electrodes, and each petal-shaped electrode is connected with a multi-channel control power source through an electrode connecting line. The series of discrete petal-shaped electrodes are formed through a series of concentric fan-shaped rotation distortion and are used for generating electric field distribution to excite the electric control liquid crystal layer to generate vortex light beam phases. According to the invention, the generation of the vortex light beam is realized by adopting a relatively simple structure, the topological charge can be adjusted, the effect is obvious, and a related optical system can be simplified.

Description

Technical Field

[0001] The present invention belongs to the technical field of adjustable terahertz vortex beams, and in particular relates to a topological charge adjustable terahertz vortex beam generating device based on electrically controlled liquid crystal and a preparation method thereof. Background Art

[0002] The frequency of terahertz waves is between microwaves and infrared (0.1-10THz), and has broad application potential in security detection, communications, material analysis, medical imaging and other fields, making it an important field in scientific research and technological development. Liquid crystal patterning control technology is a passive control method for engineering design of terahertz wavefronts, which can achieve single or multiple control of the amplitude, phase and other properties of the terahertz light field. In recent years, with the continuous expansion of terahertz beam systems, people's demand for high-quality, integrated and diversified structured beam generating devices has been growing, which has promoted the development and update of customized engineering design solutions and the design of adjustable structured beam devices.

[0003] Terahertz vortex beams are a unique beam form in the terahertz band, which combines the characteristics of terahertz technology and vortex beams. This type of beam forms a complex light field distribution carrying orbital angular momentum (OAM) by introducing a specific spiral phase structure, allowing the beam to carry multiple discrete OAM states, providing a new dimension for information encoding, transmission and processing. Terahertz vortex beams not only inherit the advantages of terahertz waves such as strong penetration and sensitivity to material properties, but also have higher information carrying capacity and control accuracy due to their unique OAM characteristics. This feature makes terahertz vortex beams show great potential in high-speed, large-capacity communication systems, especially in data transmission scenarios that require high security and high efficiency, such as near-field communications and next-generation wireless network communications (6G).

[0004] At present, the main methods for generating terahertz vortex beams include traditional polymer lenses, half-wave plates spliced ​​in different optical axis directions, etc. The disadvantages of these solutions are large-scale devices, difficult processing, low efficiency, etc. The new solutions mainly include metasurfaces based on transmission phase or geometric phase, and light-oriented liquid crystal wave plates using geometric phase. The former uses metal or dielectric metasurfaces to introduce multi-order phase modulation factors to enable the generation of vortex beams under linear or circularly polarized terahertz plane wave incidence. The latter uses liquid crystal light orientation technology to control the arrangement of liquid crystal pointing angles to prepare spiral phase plates in the terahertz band. Although these solutions have improved the thinness of the device, they have the disadvantages of poor versatility and the inability to adjust the generated beam. At present, with the continuous development of terahertz beam systems, there is an urgent need for device solutions that are simple and convenient to process, highly integrated, thin, and can perform extensive and precise adjustment of the generated vortex beam. Summary of the invention

[0005] The problem to be solved by the present invention is to achieve simple and convenient processing, high integration, lightness and thinness, and the ability to perform extensive and precise adjustment of the generated vortex beam. A topological charge adjustable terahertz vortex beam generating device based on electrically controlled liquid crystal and a preparation method thereof are proposed.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions:

[0007] A topological charge adjustable terahertz vortex beam generating device based on electrically controlled liquid crystal, which is sequentially provided with a first substrate layer, a rotationally twisted electrode layer, a first polyimide alignment layer, an electrically controlled liquid crystal layer, a second polyimide alignment layer, a uniform transparent electrode layer, and a second substrate layer from top to bottom;

[0008] The rotationally twisted electrode layer is composed of a series of discrete petal electrodes, each of which is connected to a multi-channel control power supply via an electrode connecting line; a series of discrete petal electrodes are formed by a series of concentric fan-shaped rotational twists, and are used to generate an electric field distribution to excite the electrically controlled liquid crystal layer to generate a vortex beam phase.

[0009] Furthermore, the expression of the phase distribution provided by the rotationally twisted electrode layer is:

[0010]

[0011] in, is the phase distribution provided for the rotationally twisted electrode layer, H is the Heaviside step function, λ is the terahertz wavelength, f is the focal length parameter used to provide focusing to converge the vortex light, r is the radial coordinate of the point on the electrode layer, l is the topological charge of the vortex light, and i is the imaginary unit.

[0012] Furthermore, the first substrate layer and the second substrate layer are terahertz transparent quartz or silicon substrates; the number of petal electrodes in the rotationally twisted electrode layer is 12-48, and each petal electrode can be divided into two states of 1 and 0 based on power supply and no power supply.

[0013] Furthermore, the electrically controlled liquid crystal layer is used to cooperate with the rotationally twisted electrode layer to provide a phase delay of the sampled vortex beam, and the first polyimide orientation layer and the second polyimide orientation layer are antiparallel oriented to constrain the liquid crystal orientation near the upper and lower boundaries; the electrically controlled liquid crystal layer generates a single-value phase delay δ corresponding to the voltage through the birefringence effect of the liquid crystal, and the expression is:

[0014]

[0015] Where d is the thickness of the electrically controlled liquid crystal layer, θ is the change in the liquid crystal deflection angle with thickness, and n ⊥ and n ||are the refractive index when the polarization direction of the incident light is perpendicular to the pointing angle of the liquid crystal molecules and the refractive index when the polarization direction of the incident light is parallel to the pointing angle of the liquid crystal molecules, respectively; z is the thickness direction coordinate of the point in the electrically controlled liquid crystal layer;

[0016] The thickness of the electrically controlled liquid crystal layer depends on the birefringence of the liquid crystal, ensuring that the liquid crystal provides a phase shift of an angle of π after full deflection.

[0017] Furthermore, the uniform transparent electrode layer is grounded when powered, so as to provide a reference potential for the rotationally twisted electrode layer.

[0018] A method for preparing a topological charge adjustable terahertz vortex beam generating device based on electrically controlled liquid crystal, which is realized by relying on the topological charge adjustable terahertz vortex beam generating device based on electrically controlled liquid crystal, comprises the following steps:

[0019] S1. Depositing a 30 nm to 100 nm thick dimethyl sulfoxide-doped poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) terahertz transparent electrode layer on the second substrate layer by a thin film deposition process to obtain a uniform transparent electrode layer;

[0020] S2. Depositing a 30 nm to 100 nm thick dimethyl sulfoxide-doped poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) terahertz transparent electrode layer on the first substrate layer by a thin film deposition process, and then patterning the layer by a standard photolithography process to obtain a rotationally twisted electrode layer;

[0021] S3. Covering the second polyimide alignment layer and the first polyimide alignment layer on the uniform transparent electrode layer and the rotationally twisted electrode layer by spin coating, baking at high temperature after spin coating, and then performing rubbing alignment along the x-axis, and requiring that the rubbing alignment directions of the first polyimide alignment layer and the second polyimide alignment layer are antiparallel alignment;

[0022] S4. The thickness of the electrically controlled liquid crystal layer is calculated based on the birefringence of the liquid crystal, and then the liquid crystal box is assembled. The liquid crystal is filled between the first polyimide orientation layer and the second polyimide orientation layer and then sealed to obtain a topological charge adjustable terahertz vortex beam generating device based on electrically controlled liquid crystal.

[0023] Furthermore, the thin film deposition process in step S1 and step S2 is a spin coating process, wherein 5 Vol% to 15 Vol% DMSO is mixed into the PEDOT:PSS solution, followed by stirring for 1 to 1.5 hours, and then the stirred solution is filtered through a 0.45 μm syringe filter to obtain a uniformly mixed PEDOT:PSS doped solution to spin-coat a dimethyl sulfoxide-doped poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) terahertz transparent electrode layer, the spin coating speed is 2000 rpm to 8000 rpm, and the spin coating time is 30 s to 90 s.

[0024] Furthermore, the method for patterning in step S2 is to use a standard photolithography process and a lift-off stripping method to obtain a rotationally twisted electrode layer, and the specific implementation method is as follows:

[0025] First, the surface of the first substrate layer is rinsed with a deionized water solution, and then ultrasonically cleaned with deionized water, ethanol, and isopropanol for 10 minutes each to remove dust and oil on the surface, and then blown dry with dry high-purity nitrogen;

[0026] Spinning the cleaned first substrate layer with a photoresist at a speed of 2000 rpm to 6000 rpm for about 60 seconds;

[0027] After the photoresist is spin-coated, it is placed on a hot plate for pre-baking, with the temperature set to 100°C and the time set to 90s;

[0028] Then, a photolithography machine is used to expose and directly write the pattern designed on the mask to the photoresist to transfer the pattern;

[0029] After exposure, the sample was post-baked on a 105°C hot plate for 90 seconds. After post-baking, the treated sample was placed in a developer and developed for about 30 seconds to obtain a patterned photoresist layer.

[0030] Then, the first substrate layer with the transparent electrode spin-coated thereon was transferred to a hot stage and baked at 90° C. for 5 min to evaporate the water and completely form a film;

[0031] The photoresist is then stripped off, ultrasonically shaken in NMP for 20 seconds, and then blown dry with high-purity nitrogen to obtain a rotationally twisted electrode layer.

[0032] Furthermore, in step S3, commercial polyimide is spin-coated at a spin-coating speed of 2000 rpm to 4000 rpm for a spin-coating time of 30 s to 90 s, and after spin-coating, the substrate is baked at a high temperature of 200-240° C. for 2-2.5 h.

[0033] Furthermore, in step S4, based on the birefringence being 0.28, the thickness of the electrically controlled liquid crystal layer being 400 μm, and the maximum birefringence phase shift of the liquid crystal being π at a driving voltage of 5 V, a liquid crystal box is assembled, and the thickness of the liquid crystal layer is controlled to be 400 μm.

[0034] Beneficial effects of the present invention:

[0035] The present invention discloses a terahertz vortex beam generating device with adjustable topological charge based on electrically controlled liquid crystal, which is dedicated to meeting the urgent needs of terahertz structure beam modulation devices for miniaturization and integration. By using patterned liquid crystal driving technology, a terahertz vortex beam generating device with adjustable topological charge and a design method thereof are proposed. A transparent patterned electrode layer suitable for the terahertz frequency band is manufactured by patterned etching technology, which can form a specific rotationally distorted fan-shaped voltage distribution when powered on. Furthermore, a rotationally distorted fan-shaped phase pattern can be constructed in the liquid crystal layer through a carefully designed structural layout and thickness selection. By adjusting the power supply voltage sequence, the device can generate vortex beams with different topological charges. The advantages of this solution are that the device has a simple structure, low cost, high integration, and good compatibility with semiconductor processes. Only a relatively simple single-channel external circuit is required to achieve relatively accurate regulation of the topological charge of the vortex beam.

[0036] The terahertz vortex beam generating device with adjustable topological charge based on electrically controlled liquid crystal described in the present invention is aimed at the miniaturization and integration requirements of terahertz structure beam modulation devices. It can be realized only by a sandwich liquid crystal box structure and patterned electrodes. It has low cost, high integration, simple device preparation and processing technology, and is compatible with semiconductor technology. The terahertz patterned transparent electrode layer is prepared by a patterned etching process, and a specific light field distribution is achieved after power is turned on, realizing the customized design of the control device for a given light field. The topological charge of the generated vortex beam is adjustable, and the generation of the vortex beam and the adjustment of the topological charge are achieved by using a relatively simple structure. The effect is obvious and the related optical system can be simplified. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic structural diagram of a topological charge adjustable terahertz vortex beam generating device based on electrically controlled liquid crystal according to the present invention;

[0038] Figure 2 A diagram showing the connection relationship of the rotationally twisted electrode layer of the present invention;

[0039] Figure 3 This is a beam result diagram of the / 1{12}0{12} / electrode sequence of the present invention;

[0040] Figure 4 This is the light beam result diagram of the / 1{6}0{6}… / electrode sequence of the present invention. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the specific embodiments described are only part of the embodiments of the present invention, rather than all of the specific embodiments. The components of the specific embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations, and the present invention can also have other embodiments.

[0042] Therefore, the following detailed description of the specific embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents the selected specific embodiments of the present invention. Based on the specific embodiments of the present invention, all other specific embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0043] In order to further understand the content, features and effects of the present invention, the following specific implementation methods are given as examples, and the attached Figure 1 -Attached Figure 4 The detailed instructions are as follows:

[0044] Embodiment 1:

[0045] A topological charge adjustable terahertz vortex beam generating device based on electrically controlled liquid crystal, which is provided with a first substrate layer 1, a rotationally twisted electrode layer 2, a first polyimide alignment layer 3, an electrically controlled liquid crystal layer 4, a second polyimide alignment layer 5, a uniform transparent electrode layer 6, and a second substrate layer 7 in sequence from top to bottom;

[0046] The rotationally twisted electrode layer 2 is composed of a series of discrete petal electrodes 10, each petal electrode is connected to a multi-channel control power supply 9 via an electrode connecting line 8; a series of discrete petal electrodes 10 are formed by a series of concentric fan-shaped rotational twists, and are used to generate an electric field distribution to excite the electrically controlled liquid crystal layer 4 to generate a vortex beam phase.

[0047] Furthermore, the expression of the phase distribution provided by the rotationally twisted electrode layer 2 is:

[0048]

[0049] in, is the phase distribution provided for the rotationally twisted electrode layer 2, H is the Heaviside step function, λ is the terahertz wavelength, f is the focal length parameter used to provide focusing to converge the vortex light, r is the radial coordinate of the point on the electrode layer, l is the topological charge number of the vortex light, and i is the imaginary unit.

[0050] Furthermore, the first substrate layer 1 and the second substrate layer 7 are terahertz transparent quartz or silicon substrates; the number of petal electrodes 10 in the rotationally twisted electrode layer 2 is 12-48, and each petal electrode 10 can be divided into two states of 1 and 0 based on power supply and no power supply.

[0051] Furthermore, the degree of rotational distortion is determined by the design focal length of the device. The larger the focal length, the smaller the degree of rotational distortion. Each of the discrete petal electrodes of the rotationally twisted electrode layer can be independently powered, and the voltage can be independently adjusted. Each electrode can be divided into two states, "1" and "0", by being powered and not powered. Furthermore, the discrete petal electrodes have two rotation directions, depending on the positive and negative topological charge that needs to be generated. Here, the electrode has a clockwise rotation direction along the light-transmitting direction, which can generate a vortex beam with a positive topological charge. The number of petal electrodes of the designed device should not be too few or too many, and the effect should be better between 12 and 48. Too few will result in the inability to provide effective phase sampling, and too many will result in a reduction in the contrast of the liquid crystal phase.

[0052] Furthermore, the electrically controlled liquid crystal layer 4 is used to cooperate with the rotationally twisted electrode layer 2 to provide a phase delay of the sampled vortex beam, and the first polyimide orientation layer 3 and the second polyimide orientation layer 5 are antiparallel oriented to constrain the liquid crystal orientation near the upper and lower boundaries; the electrically controlled liquid crystal layer 4 generates a single-value phase delay δ corresponding to the voltage through the birefringence effect of the liquid crystal, and the expression is:

[0053]

[0054] Where d is the thickness of the electrically controlled liquid crystal layer, θ is the change in the liquid crystal deflection angle with thickness, and n ⊥ and n || are the refractive index when the polarization direction of the incident light is perpendicular to the pointing angle of the liquid crystal molecules and the refractive index when the polarization direction of the incident light is parallel to the pointing angle of the liquid crystal molecules, respectively; z is the thickness direction coordinate of the point in the electrically controlled liquid crystal layer 4;

[0055] The thickness of the electrically controlled liquid crystal layer 4 depends on the birefringence of the liquid crystal, ensuring that the liquid crystal provides a phase shift of an angle of π after full deflection.

[0056] Furthermore, the birefringence of the liquid crystal used is Δn=0.28, the thickness of the liquid crystal layer is 400um, and the wavelength of the terahertz wave is 118um, which can ensure that the maximum phase shift exceeds π. Combined with the power supply state of each electrode, the liquid crystal deflection phase shift in the "1" state needs to be precisely controlled at π, and the power supply voltage of the "1" state used here is 4.7V. The discrete petal-shaped electrodes cooperate with the liquid crystal to produce a phase distribution consistent with its shape, forming a vortex half-wave plate in the terahertz band.

[0057] Furthermore, the uniform transparent electrode layer 6 is grounded when powered, so as to provide a reference potential for the rotationally twisted electrode layer 2 .

[0058] Furthermore, the rotationally twisted electrode layer and the uniform transparent electrode layer require an amplitude transmittance of more than 70%, otherwise the quality of the output light beam may be poor.

[0059] The principle of this embodiment utilizes the electrically controlled phase modulation function of nematic liquid crystals, combined with terahertz transparent electrodes, to achieve customized phase modulation on the device. By generating a vortex beam phase distribution in the device, the incident light is converted into a vortex beam. By binarizing and restoring different vortex beam phase distributions, and combining the angular periodicity of the vortex light phase, the generation and conversion of multiple topological vortex beams can be integrated into one device.

[0060] The driving and vortex light switching effect of this embodiment is as follows: Figure 2 As shown, each electrode 1 is independently led out to a control power supply 3 through an electrode connection line 2 for independent voltage control. Figure 1 The uniform transparent electrode layer 6 in is grounded (0V) when powered, and is used as a reference potential. Here, the electrode array is driven by digital coding, and each electrode can be divided into two states, "1" and "0", by power supply and no power supply. The "1" state corresponds to the liquid crystal under the electrode providing a phase delay of π, and the "0" state corresponds to the liquid crystal under the electrode providing a phase delay of 0, and the phase delays corresponding to power on and no power on differ by π. By changing the voltage sequence, the topological charge of the vortex light generated in this embodiment can be controlled. Due to the constraints of the thickness of the liquid crystal and the periodicity of the vortex phase angle, the number of electrodes is 24, which can generate vortex light with topological charges of 1, 2, 3, 4, and 6, and the electrode sequences corresponding to each topological charge are: / 1{12}0{12} / , / 1{6}0{6}… / , / 11110000… / , / 111000… / , / 1100… / . Among them, 1{12} represents 12 consecutive 1s, and the same applies to other representations.

[0061] Figure 3 and Figure 4 The light beams corresponding to the electrode sequences of / 1{12}0{12} / and / 1{6}0{6}… / have topological charges of 1 and 2, respectively. Thus, by changing the switching sequence of the discrete electrodes, the phase distribution generated by the liquid crystal and consistent with the shape of the petal-shaped electrodes can be adjusted, thereby achieving the effect of changing the topological charge number generated by the device.

[0062] The terahertz transparent electrode layer described in this embodiment can be replaced with other films that can achieve high terahertz transmittance and high conductivity, such as graphene, carbon nanotubes, transparent conductive metal films, etc. The number of fan-shaped structures of the patterned transparent electrode layer described in this embodiment is not limited to this embodiment, for example, a higher number can be used, and the corresponding circuit can be matched.

[0063] Embodiment 2:

[0064] A method for preparing a topological charge adjustable terahertz vortex beam generating device based on electrically controlled liquid crystal is implemented based on the topological charge adjustable terahertz vortex beam generating device based on electrically controlled liquid crystal described in Example 1, and comprises the following steps:

[0065] S1. Depositing a 30 nm to 100 nm thick dimethyl sulfoxide-doped poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) terahertz transparent electrode layer on the second substrate layer by a thin film deposition process to obtain a uniform transparent electrode layer;

[0066] Further, the thin film deposition process in step S1 and step S2 is a spin coating process, 5Vol% to 15Vol% DMSO is mixed into the PEDOT:PSS solution, followed by stirring for 1 to 1.5 hours, and then the stirred solution is filtered through a 0.45 μm syringe filter to obtain a uniformly mixed PEDOT:PSS doped solution to spin-coat a dimethyl sulfoxide-doped poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) terahertz transparent electrode layer, the spin coating speed is 2000rpm to 8000rpm, and the spin coating time is 30s to 90s;

[0067] S2. Depositing a 30 nm to 100 nm thick dimethyl sulfoxide-doped poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) terahertz transparent electrode layer on the first substrate layer by a thin film deposition process, and then patterning the layer by a standard photolithography process to obtain a rotationally twisted electrode layer;

[0068] Furthermore, the method for patterning in step S2 is to use a standard photolithography process and a lift-off stripping method to obtain a rotationally twisted electrode layer, and the specific implementation method is as follows:

[0069] First, the surface of the first substrate layer is rinsed with a deionized water solution, and then ultrasonically cleaned with deionized water, ethanol, and isopropanol for 10 minutes each to remove dust and oil on the surface, and then blown dry with dry high-purity nitrogen;

[0070] Spinning the cleaned first substrate layer with a photoresist at a speed of 2000 rpm to 6000 rpm for about 60 seconds;

[0071] After the photoresist is spin-coated, it is placed on a hot plate for pre-baking, with the temperature set to 100°C and the time set to 90s;

[0072] Then, a photolithography machine is used to expose and directly write the pattern designed on the mask to the photoresist to transfer the pattern;

[0073] After exposure, the sample was post-baked on a 105°C hot plate for 90 seconds. After post-baking, the treated sample was placed in a developer and developed for about 30 seconds to obtain a patterned photoresist layer.

[0074] Then, the first substrate layer with the transparent electrode spin-coated thereon was transferred to a hot stage and baked at 90° C. for 5 min to evaporate the water and completely form a film;

[0075] The photoresist is then stripped off, ultrasonically shaken in NMP for 20 seconds, and then blown dry with high-purity nitrogen to obtain a rotationally twisted electrode layer.

[0076] S3. Covering the second polyimide alignment layer and the first polyimide alignment layer on the uniform transparent electrode layer and the rotationally twisted electrode layer by spin coating, baking at high temperature after spin coating, and then performing rubbing alignment along the x-axis, and requiring that the rubbing alignment directions of the first polyimide alignment layer and the second polyimide alignment layer are antiparallel alignment;

[0077] Furthermore, in step S3, commercial polyimide is spin-coated at a speed of 2000 rpm to 4000 rpm for a time of 30 s to 90 s, and after spin coating, the substrate is baked at a high temperature of 200-240° C. for 2-2.5 h;

[0078] S4. The thickness of the electrically controlled liquid crystal layer is calculated based on the birefringence of the liquid crystal, and then the liquid crystal box is assembled. The liquid crystal is filled between the first polyimide orientation layer and the second polyimide orientation layer and then sealed to obtain a topological charge adjustable terahertz vortex beam generating device based on electrically controlled liquid crystal.

[0079] Furthermore, in step S4, based on the birefringence being 0.28, the thickness of the electrically controlled liquid crystal layer being 400 μm, and the maximum birefringence phase shift of the liquid crystal being π at a driving voltage of 5 V, a liquid crystal box is assembled, and the thickness of the liquid crystal layer is controlled to be 400 μm.

[0080] Furthermore, the glue is sealed after the large birefringence nematic liquid crystal is filled. In practical applications, other nematic liquid crystals can also be used, and the thickness and driving voltage of the corresponding electrically controlled liquid crystal layer 4 need to be adjusted to meet the birefringence phase shift of the corresponding liquid crystal layer.

[0081] It should be noted that relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0082] Although the present application has been described above with reference to specific embodiments, various modifications may be made thereto and parts thereof may be replaced with equivalents without departing from the scope of the present application. In particular, as long as there is no structural conflict, the various features in the specific embodiments disclosed in the present application may be used in combination with each other in any manner, and the fact that these combinations are not exhaustively described in this specification is only for the sake of omitting space and saving resources. Therefore, the present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A topological charge adjustable terahertz vortex beam generating device based on electrically controlled liquid crystal, characterized in that: From top to bottom, a first substrate layer (1), a rotationally twisted electrode layer (2), a first polyimide alignment layer (3), an electrically controlled liquid crystal layer (4), a second polyimide alignment layer (5), a uniform transparent electrode layer (6), and a second substrate layer (7) are sequentially arranged; The rotationally twisted electrode layer (2) is composed of a series of discrete petal-shaped electrodes (10), each petal-shaped electrode being connected to a multi-channel control power supply (9) via an electrode connection line (8); the series of discrete petal-shaped electrodes (10) are formed by a series of concentric fan-shaped rotational twists, and are used to generate an electric field distribution to excite the electrically controlled liquid crystal layer (4) to generate a vortex light beam phase.

2. The device for generating a terahertz vortex beam with adjustable topological charge based on electrically controlled liquid crystal according to claim 1, characterized in that: The expression of the phase distribution provided by the rotationally twisted electrode layer (2) is: in, The phase distribution provided by the rotationally twisted electrode layer (2), H is the Heaviside step function, λ is the terahertz wavelength, f is the focal length parameter used to provide focusing to converge the vortex light, r is the radial coordinate of a point on the electrode layer, l is the topological charge number of the vortex light, and i is an imaginary unit.

3. A topological charge adjustable terahertz vortex beam generating device based on electrically controlled liquid crystal according to claim 1 or 2, characterized in that: The first substrate layer (1) and the second substrate layer (7) are terahertz-transparent quartz or silicon substrates; the number of petal-shaped electrodes (10) in the rotationally twisted electrode layer (2) is 12-48, and each petal-shaped electrode (10) can be divided into two states, 1 and 0, based on power supply and no power supply.

4. The topological charge adjustable terahertz vortex beam generating device based on electrically controlled liquid crystal according to claim 3, characterized in that: The electrically controlled liquid crystal layer (4) is used to cooperate with the rotationally twisted electrode layer (2) to provide a phase delay of the sampled vortex light beam. The first polyimide orientation layer (3) and the second polyimide orientation layer (5) are anti-parallel oriented to constrain the orientation of the liquid crystal near the upper and lower boundaries. The electrically controlled liquid crystal layer (4) generates a single-value phase delay δ corresponding to the voltage through the birefringence effect of the liquid crystal, and the expression is: Where d is the thickness of the electrically controlled liquid crystal layer, θ is the change in the liquid crystal deflection angle with thickness, and n ⊥ and n || are the refractive index when the polarization direction of the incident light is perpendicular to the pointing angle of the liquid crystal molecules and the refractive index when the polarization direction of the incident light is parallel to the pointing angle of the liquid crystal molecules, respectively; z is the thickness direction coordinate of a point in the electrically controlled liquid crystal layer (4); The thickness of the electrically controlled liquid crystal layer (4) depends on the birefringence of the liquid crystal, ensuring that the liquid crystal provides a phase shift of an angle of π after full deflection.

5. The topological charge adjustable terahertz vortex beam generating device based on electrically controlled liquid crystal according to claim 4, characterized in that: The uniform transparent electrode layer (6) is grounded when powered, and is used to provide a reference potential for the rotationally twisted electrode layer (2).

6. A method for preparing a topological charge adjustable terahertz vortex beam generating device based on electrically controlled liquid crystal, which is realized by relying on a topological charge adjustable terahertz vortex beam generating device based on electrically controlled liquid crystal as claimed in any one of claims 1 to 4, characterized in that: The steps include: S1. Depositing a 30 nm to 100 nm thick dimethyl sulfoxide-doped poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) terahertz transparent electrode layer on the second substrate layer by a thin film deposition process to obtain a uniform transparent electrode layer; S2. Depositing a 30 nm to 100 nm thick dimethyl sulfoxide-doped poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) terahertz transparent electrode layer on the first substrate layer by a thin film deposition process, and then patterning the layer by a standard photolithography process to obtain a rotationally twisted electrode layer; S3. Covering the second polyimide alignment layer and the first polyimide alignment layer on the uniform transparent electrode layer and the rotationally twisted electrode layer by spin coating, baking at high temperature after spin coating, and then performing rubbing alignment along the x-axis, and requiring that the rubbing alignment directions of the first polyimide alignment layer and the second polyimide alignment layer are antiparallel alignment; S4. The thickness of the electrically controlled liquid crystal layer is calculated based on the birefringence of the liquid crystal, and then the liquid crystal box is assembled. The liquid crystal is filled between the first polyimide orientation layer and the second polyimide orientation layer and then sealed to obtain a topological charge adjustable terahertz vortex beam generating device based on electrically controlled liquid crystal.

7. The method for preparing a topological charge adjustable terahertz vortex beam generating device based on electrically controlled liquid crystal according to claim 6, characterized in that: The thin film deposition process in step S1 and step S2 is a spin coating process, wherein 5 Vol% to 15 Vol% DMSO is mixed into a PEDOT:PSS solution, followed by stirring for 1 to 1.5 hours, and then the stirred solution is filtered through a 0.45 μm syringe filter to obtain a uniformly mixed PEDOT:PSS doped solution to spin-coat a dimethyl sulfoxide-doped poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) terahertz transparent electrode layer, the spin coating speed is 2000 rpm to 8000 rpm, and the spin coating time is 30 s to 90 s.

8. The method for preparing a topological charge adjustable terahertz vortex beam generating device based on electrically controlled liquid crystal according to claim 7, characterized in that: The method for patterning in step S2 is to use a standard photolithography process and a lift-off stripping method to obtain a rotationally twisted electrode layer. The specific implementation method is as follows: First, the surface of the first substrate layer is rinsed with a deionized water solution, and then ultrasonically cleaned with deionized water, ethanol, and isopropanol for 10 minutes each to remove dust and oil on the surface, and then blown dry with dry high-purity nitrogen; Spinning the cleaned first substrate layer with a photoresist at a speed of 2000 rpm to 6000 rpm for about 60 seconds; After the photoresist is spin-coated, it is placed on a hot plate for pre-baking, with the temperature set to 100°C and the time set to 90s; Then, a photolithography machine is used to expose and directly write the pattern designed on the mask to the photoresist to transfer the pattern; After exposure, the sample was post-baked on a 105°C hot plate for 90 seconds. After post-baking, the treated sample was placed in a developer and developed for about 30 seconds to obtain a patterned photoresist layer. Then, the first substrate layer with the transparent electrode spin-coated thereon was transferred to a hot stage and baked at 90° C. for 5 min to evaporate the water and completely form a film; The photoresist is then stripped off, ultrasonically shaken in NMP for 20 seconds, and then blown dry with high-purity nitrogen to obtain a rotationally twisted electrode layer.

9. The method for preparing a topological charge adjustable terahertz vortex beam generating device based on electrically controlled liquid crystal according to claim 8, characterized in that: In step S3, commercial polyimide is spin-coated at a spin-coating speed of 2000 rpm to 4000 rpm for a spin-coating time of 30 s to 90 s. After spin-coating, the substrate is baked at a high temperature of 200-240° C. for 2-2.5 h.

10. The method for preparing a topological charge adjustable terahertz vortex beam generating device based on electrically controlled liquid crystal according to claim 9, characterized in that: In step S4, based on the birefringence being 0.28, the thickness of the electrically controlled liquid crystal layer being 400 μm, and the maximum birefringence phase shift of the liquid crystal being π at a driving voltage of 5 V, a liquid crystal box is assembled, and the thickness of the liquid crystal layer is controlled to be 400 μm.

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