A terahertz liquid crystal tunable beam splitter and its fabrication method

Abstract

A terahertz liquid crystal tunable beam splitter and its fabrication method belong to the field of terahertz modulation device technology. This invention addresses the problem of universal integrated device applications in the terahertz field. The invention comprises a first quartz substrate, a wire-grid transparent electrode layer, a first polyimide alignment layer, an electro-controlled liquid crystal layer, a second polyimide alignment layer, a metal metasurface layer, and a second quartz substrate connected sequentially from top to bottom. The wire-grid transparent electrode layer is a strip array electrode structure, composed of a series of discrete array electrodes, each independently powered and with independently adjustable voltage. The metal metasurface layer is a hollow rectangular array structure, composed of a series of hollow rectangular structural units of the same size but different rotation angles, with the principal axis of each hollow rectangular structural unit arranged at a gradient rotation angle of 0–180°. The device structure of this invention is simple and low-cost.

Description

Technical Field

[0001] This invention belongs to the field of terahertz modulation device technology, specifically relating to a terahertz liquid crystal tunable beam splitter and its preparation method. Background Technology

[0002] Terahertz waves, with frequencies between microwaves and infrared (0.1-10 THz), have broad application potential in high-speed wireless communication, radar remote sensing, industrial and materials testing, and medical imaging, thus becoming an important field in scientific research and technological development. Terahertz metasurfaces and liquid crystal patterning control technologies, through subwavelength artificial structural units and refractive index gradients, respectively, enable single or multiple modulation and engineering design of amplitude, phase, polarization, and other characteristics, achieving diverse functions such as wavefront manipulation, mode conversion, and functional integration. In recent years, with the continuous expansion of terahertz beam systems, the demand for high-quality, integrated, diversified, and low-cost beam control devices has grown rapidly, driving the emergence of customized engineering design schemes and tunable beam device designs.

[0003] A terahertz beam splitter is a key device used to split a terahertz beam into two or more beams (such as reflected and transmitted beams). Its core function is to achieve energy distribution, interferometric measurement, or signal splitting in the optical path. It can be used in differential imaging systems to distribute energy to sample and reference channels, eliminate environmental noise, and improve imaging contrast. It can be used for beam splitting in terahertz interferometry, utilizing coherence to obtain parameters such as the sample's refractive index, thickness, and dielectric constant through phase difference measurement. As a free-space splitter, it distributes terahertz signals to a detector array, acquiring data from different channels in parallel, thus improving measurement speed.

[0004] Currently, the main devices used for terahertz beam splitting operations include: 1. Beam splitters based on polarization reflection characteristics, using refractive index materials or metal wire grid structures, relying on Fresnel reflection characteristics for beam splitting. However, the direction of the generated light is limited; only one beam can be in the same direction as the original beam, while the other beam is related to the incident angle, making flexible design impossible. Furthermore, the polarization of one of the split beams is not pure, often containing orthogonal polarizations, unless two orthogonally polarized beams are obtained under specific angle conditions such as the Buster angle. 2. Beam splitters based on metasurfaces, using geometric phase design to achieve beam splitting. They can achieve beam splitting at relatively large angles, but the splitting ratio cannot be adjusted, lacking tunability. 3. Adjustable beam splitters based on microelectromechanical systems (MEMS), using a MEMS to drive a cantilever beam or micromirror to dynamically adjust the splitting ratio. They offer a wide range of adjustable splitting ratios but are difficult to fabricate and costly. Summary of the Invention

[0005] The problem to be solved by this invention is to meet the demand for general-purpose integrated devices in the terahertz field, and a terahertz liquid crystal tunable beam splitter and its preparation method are proposed.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A terahertz liquid crystal tunable beam splitter includes a first quartz substrate, a wire grid transparent electrode layer, a first polyimide alignment layer, an electro-controlled liquid crystal layer, a second polyimide alignment layer, a metal metasurface layer, and a second quartz substrate.

[0008] The first quartz substrate, the wire grid transparent electrode layer, the first polyimide alignment layer, the electro-controlled liquid crystal layer, the second polyimide alignment layer, the metal metasurface layer, and the second quartz substrate are connected sequentially from top to bottom;

[0009] The wire grid transparent electrode layer is a strip array electrode structure, which consists of a series of discrete array electrodes. Each array electrode is independently powered and its voltage is independently adjustable.

[0010] The metal metasurface layer is a hollow rectangular array structure. The metal metasurface layer is composed of a series of hollow rectangular structural units of the same size but different rotation angles. The main axis of each hollow rectangular structural unit is arranged at an angle of 0 to 180° with a certain gradient rotation.

[0011] Furthermore, the spatial period of the array electrodes in the wire grid transparent electrode layer is set according to the deflection frequency, which is 150-650 micrometers; the width of each array electrode in the wire grid transparent electrode layer is 0.7-0.9 times the spatial period.

[0012] Furthermore, the number of array electrodes in the wire grid transparent electrode layer is 16-64.

[0013] Furthermore, the array electrodes in the wire grid transparent electrode layer are made of one of the following materials: indium tin oxide (ITO), DMSO-doped PEDOT:PSS, chromium, graphene, and carbon nanotubes, with a thickness of 5-50 nm.

[0014] Furthermore, the gradient in the metal metasurface layer is determined by the phase distribution interpolation of the unit position, and the change in rotation angle is 1 / 2 of the change in phase angle; the metal material in the metal hollow rectangle is one of gold, silver, and aluminum, and the thickness is 10-300nm.

[0015] Furthermore, based on the structural unit design in the metal metasurface layer, a terahertz liquid crystal adjustable beam splitter is designed to achieve a deflection angle at the operating frequency by realizing the deflection function.

[0016] Based on the geometric phase principle, the Jones matrix of the metallic metasurface layer is obtained. for:

[0017]

[0018] in, , These are the matrices for right-spin selection and left-spin selection, respectively. and θ represents the x-axis and y-axis transmittance of the structural unit, respectively; k is the wave vector of the incident terahertz wave; x is the coordinate of the beam along the x-axis on the metallic metasurface layer; and θ is the deflection angle of the beam on the metallic metasurface layer at a given wavelength. It is the identity matrix; The imaginary unit;

[0019] in, , .

[0020] Furthermore, the first and second quartz substrates are replaced with sapphire or poly(4-methylpentene-1) copolymer (TPX).

[0021] Furthermore, the orientation directions of the first polyimide orientation layer and the second polyimide orientation layer are antiparallel to each other and form a 45° angle with the extension direction of the array electrode. The thickness of the electro-controlled liquid crystal layer depends on the birefringence parameters of the liquid crystal used and ranges from 100 to 1000 micrometers.

[0022] Furthermore, the intensity distribution of the transmitted light beam obtained by the metal metasurface layer through the electro-controlled liquid crystal layer is as follows:

[0023]

[0024] in, The intensity of the left-biased beam. The intensity of the right-biased beam. This represents the proportion of left-handed circularly polarized light in the total incident terahertz waves;

[0025] The equivalent refractive index of the liquid crystal layer. The basis vectors representing left-handed circularly polarized light are: Let d represent the basis vector of right-handed circularly polarized light, d be the thickness of the liquid crystal layer, m represent the number of energized electrodes in the grid electrode layer, and N represent the total number of electrodes in the grid electrode layer. Represents the refractive index of the liquid crystal parallel to the orientation direction when no current is applied. Birefringence represents liquid crystals.

[0026] A method for fabricating a terahertz liquid crystal tunable beam splitter includes the following steps:

[0027] S1. Photoresist is spin-coated onto a clean first quartz substrate, followed by pre-baking, exposure, post-baking, and development to prepare the designed strip array structure;

[0028] S2. Deposit the array electrode material on the strip array structure obtained in step S1, and remove the residual photoresist to obtain the wire grid transparent electrode layer;

[0029] S3. Spin-coat photoresist onto a clean second quartz substrate, perform pre-baking, exposure, post-baking, and development to prepare the designed metasurface structure;

[0030] S4. Deposit a metal material on the metasurface structure obtained in step S3, and remove the residual photoresist to obtain a metal metasurface layer;

[0031] S5. Spin-coat polyimide orientation layers onto the wire gate transparent electrode layer and the metal metasurface layer respectively, and bake them at high temperature of 200℃-300℃ for 0.5-2h to obtain the first polyimide orientation layer and the second polyimide orientation layer respectively.

[0032] S6. The first polyimide orientation layer and the second polyimide orientation layer are rubbed and oriented in antiparallel directions and at 45° to the extension direction of the array electrode.

[0033] S7. Adhere the first polyimide alignment layer and the second polyimide alignment layer after the friction alignment in step S6, use gaskets for support on both sides, leave space in the central area, cover the space area, place the alignment layer inward, and obtain the liquid crystal cell.

[0034] S8. Fill the liquid crystal cell obtained in step S7 with liquid crystal to obtain an electro-controlled liquid crystal layer, and encapsulate it to obtain a terahertz liquid crystal adjustable beam splitter.

[0035] The beneficial effects of this invention are:

[0036] This invention discloses a terahertz liquid crystal tunable beam splitter, aiming to meet the urgent need for universal integrated devices in the terahertz field. Utilizing a metasurface platform and patterned liquid crystal driving technology, it achieves beam splitting while ensuring beam quality through the metasurface; and employs wire-grid transparent electrodes to generate an arrayed voltage distribution and liquid crystal phase modulation, enabling flexible distribution of beam splitting energy. The advantages of this invention lie in its simple device structure, low cost, high integration, and good compatibility with semiconductor processes.

[0037] This invention discloses a terahertz liquid crystal tunable beam splitter, addressing the miniaturization and integration needs of terahertz beam modulation devices. It can be implemented using only a sandwich liquid crystal cell structure with patterned electrodes, resulting in low cost, high integration, simple device fabrication, and compatibility with semiconductor processes. High beam splitting accuracy is maintained through beam separation achieved using a metasurface, and a terahertz wire grating transparent electrode layer is fabricated using a patterned fabrication process to achieve digital encoding control of the device. The dynamically adjustable beam splitting ratio and the orthogonal polarization of the two beams significantly enhance the flexibility and adaptability of terahertz systems, meeting the real-time energy distribution requirements of various scenarios such as spectral analysis, imaging, and communication. For example, in terahertz spectrometers, the intensity ratio of reference and signal light can be optimized as needed to improve measurement accuracy. This device supports multifunctional integrated system design, avoiding the drawbacks of frequent replacements required by traditional fixed beam splitters, reducing system complexity and cost, and promoting the development of portable terahertz devices. In coherent detection and interferometry, tunable beam splitting can enhance signal stability, facilitate the development of high-precision sensing and imaging technologies, and thus accelerate the practical application of terahertz technology in fields such as biomedical detection, security inspection, and materials analysis. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the structure of a terahertz liquid crystal adjustable beam splitter according to the present invention;

[0039] Figure 2 This is a partial enlarged view of the transparent electrode layer of the wire grid in a terahertz liquid crystal adjustable beam splitter according to the present invention;

[0040] Figure 3 This is an enlarged view of the structural unit of the metal metasurface layer in a terahertz liquid crystal tunable beam splitter according to the present invention.

[0041] Figure 4 This is a diagram showing the angular distribution of the terahertz liquid crystal adjustable beam splitter described in this invention without applied voltage.

[0042] Figure 5 This is a histogram showing the intensity ratio at 1.1 Thz for a terahertz liquid crystal tunable beam splitter according to the present invention under different coding sequences. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described specific embodiments are merely a part of the embodiments of the invention, and not all of them. The components of the specific embodiments of the invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations, and the invention may also have other embodiments.

[0044] Therefore, the following detailed description of specific embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected specific embodiments of the invention. All other specific embodiments obtained by those skilled in the art based on these specific embodiments without inventive effort are within the scope of protection of this invention.

[0045] To further understand the invention's content, features, and effects, the following specific embodiments are provided, along with accompanying drawings. Figure 1 - Appendix Figure 5 Detailed explanation is as follows:

[0046] Example 1:

[0047] A terahertz liquid crystal tunable beam splitter includes a first quartz substrate 1, a wire grid transparent electrode layer 2, a first polyimide alignment layer 3, an electro-controlled liquid crystal layer 4, a second polyimide alignment layer 5, a metal metasurface layer 6, and a second quartz substrate 7.

[0048] The first quartz substrate 1, the wire grid transparent electrode layer 2, the first polyimide alignment layer 3, the electro-controlled liquid crystal layer 4, the second polyimide alignment layer 5, the metal metasurface layer 6, and the second quartz substrate 7 are connected sequentially from top to bottom.

[0049] The wire grid transparent electrode layer 2 is a strip array electrode structure, which is composed of a series of discrete array electrodes. Each array electrode is independently powered and its voltage is independently adjustable.

[0050] The metal metasurface layer 6 is a metal hollow rectangular array structure. The metal metasurface layer 6 is composed of a series of metal hollow rectangular structural units of the same size but different rotation angles. The main axis of each metal hollow rectangular structural unit is arranged at an angle of 0 to 180° with a certain gradient rotation.

[0051] Furthermore, the spatial period of the array electrodes in the wire grid transparent electrode layer 2 is set according to the deflection frequency, which is 150-650 micrometers; the width of each array electrode in the wire grid transparent electrode layer 2 is 0.7-0.9 times the spatial period.

[0052] Furthermore, the number of array electrodes in the wire grid transparent electrode layer 2 is 16-64.

[0053] Furthermore, the array electrodes in the wire grid transparent electrode layer 2 are made of one of the following materials: indium tin oxide (ITO), DMSO-doped PEDOT:PSS, chromium, graphene, and carbon nanotubes, with a thickness of 5-50 nm.

[0054] Furthermore, the gradient in the metal metasurface layer 6 is determined by the phase distribution interpolation of the unit position, and the change in rotation angle is 1 / 2 of the change in phase angle; the metal material in the metal hollow rectangle is one of gold, silver, and aluminum, and the thickness is 10-300nm.

[0055] Furthermore, based on the structural unit design in the metal metasurface layer 6, a terahertz liquid crystal adjustable beam splitter is designed to achieve a deflection angle at the operating frequency by realizing the deflection function.

[0056] Based on the geometric phase principle, the Jones matrix of metal metasurface layer 6 is obtained. for:

[0057]

[0058] in, , These are the matrices for right-spin selection and left-spin selection, respectively. and θ represents the x-axis transmittance and y-axis transmittance of the structural unit, respectively; k is the wave vector of the incident terahertz wave; x is the coordinate of the beam along the x-axis on the metallic metasurface layer 6; and θ is the deflection angle of the beam on the metallic metasurface layer 6 at a given wavelength. It is the identity matrix; The imaginary unit;

[0059] in, , .

[0060] Furthermore, the first quartz substrate 1 and the second quartz substrate 7 are simultaneously replaced with sapphire or poly(4-methylpentene-1) copolymer TPX.

[0061] Furthermore, the orientation directions of the first polyimide orientation layer 3 and the second polyimide orientation layer 5 are antiparallel to each other, and the thickness of the electro-controlled liquid crystal layer 4 depends on the birefringence parameters of the liquid crystal used, ranging from 100 to 1000 micrometers.

[0062] Furthermore, the light intensity distribution of the metasurface transmitted beam obtained by the metal metasurface layer 6 through the electro-controlled liquid crystal layer 4 is as follows:

[0063]

[0064] in, The intensity of the left-biased beam. The intensity of the right-biased beam. This represents the proportion of left-handed circularly polarized light in the total incident terahertz waves;

[0065] The equivalent refractive index of the liquid crystal layer. The basis vectors representing left-handed circularly polarized light are: Let d represent the basis vector of right-handed circularly polarized light, d be the thickness of the liquid crystal layer, m represent the number of energized electrodes in the grid electrode layer, and N represent the total number of electrodes in the grid electrode layer. Represents the refractive index of the liquid crystal parallel to the orientation direction when no current is applied. Birefringence represents liquid crystals.

[0066] Furthermore, different voltages can be applied to different electrodes of the wire grid transparent electrode to adjust the deflection effect of the nearby liquid crystal, thereby controlling the proportion of deflected liquid crystal in the total liquid crystal area. At the same time, the wire grid transparent electrode has a high transmittance in the terahertz band.

[0067] Furthermore, the recommended period and width of the wire grid are 150-650 micrometers, and the suitable incident terahertz wave frequency is 2.5THz-0.6THz.

[0068] Furthermore, other parameters of the wire grid are designed, wherein the electrode width of the wire grid electrode in each cycle is 0.7-0.9 times the cycle, and the number of array electrodes is 16-64;

[0069] Furthermore, the wire grid is designed to extend in a direction parallel to the deflection plane to prevent unnecessary diffraction orders from being generated by the wire grid, which could affect the light intensity distribution within the deflection plane.

[0070] Furthermore, the design of the driving method allows each electrode to be powered independently, and the voltage can be adjusted independently. Each electrode can be divided into two states, "1" and "0", depending on whether it is powered or not.

[0071] Further driving can be achieved using overdrive technology, where the voltage of the "1" state is much greater than the liquid crystal threshold voltage.

[0072] Example 2:

[0073] A method for fabricating a terahertz liquid crystal tunable beam splitter includes the following steps:

[0074] S1. Photoresist is spin-coated onto a clean first quartz substrate, followed by pre-baking, exposure, post-baking, and development to prepare the designed strip array structure;

[0075] S2. Deposit the array electrode material on the strip array structure obtained in step S1, and remove the residual photoresist to obtain the wire grid transparent electrode layer;

[0076] S3. Spin-coat photoresist onto a clean second quartz substrate, perform pre-baking, exposure, post-baking, and development to prepare the designed metasurface structure;

[0077] S4. Deposit a metal material on the metasurface structure obtained in step S3, and remove the residual photoresist to obtain a metal metasurface layer;

[0078] S5. Spin-coat polyimide orientation layers onto the wire gate transparent electrode layer and the metal metasurface layer respectively, and bake them at high temperature of 200℃-300℃ for 0.5-2h to obtain the first polyimide orientation layer and the second polyimide orientation layer respectively.

[0079] S6. The first polyimide orientation layer and the second polyimide orientation layer are rubbed and oriented in antiparallel directions and at 45° to the extension direction of the array electrode.

[0080] S7. Adhere the first polyimide alignment layer and the second polyimide alignment layer after the friction alignment in step S6, use gaskets for support on both sides, leave space in the central area, cover the space area, place the alignment layer inward, and obtain the liquid crystal cell.

[0081] S8. Fill the liquid crystal cell obtained in step S7 with liquid crystal to obtain an electro-controlled liquid crystal layer, and encapsulate it to obtain a terahertz liquid crystal adjustable beam splitter.

[0082] Furthermore, the pattern preparation method described in steps S1 and S4 may be one or more of the following: ultraviolet exposure, laser direct writing, electron beam exposure, nanoimprinting, preferably ultraviolet exposure;

[0083] Furthermore, the deposition method described in steps S2 and S4 can be one or more of the following: magnetron sputtering, spin coating, electron beam evaporation, chemical vapor deposition, preferably magnetron sputtering;

[0084] Furthermore, the method for removing residual photoresist in steps S2 and S4 can be one or more of the following: acetone / NMP organic solvent dissolution / reactive ion etching, preferably NMP organic solvent dissolution.

[0085] Furthermore, the extension direction of the wire grid electrode is perpendicular to the gradient direction of the metal metasurface.

[0086] Furthermore, the thickness of the liquid crystal layer in the device depends on the birefringence of the liquid crystal used, ranging from 100 to 1000 micrometers, ensuring that the liquid crystal can provide a phase shift of more than π after complete deflection.

[0087] Example 3:

[0088] A terahertz liquid crystal tunable beam splitter includes a first quartz substrate 1, a wire grid transparent electrode layer 2, a first polyimide alignment layer 3, an electro-controlled liquid crystal layer 4, a second polyimide alignment layer 5, a metal metasurface layer 6, and a second quartz substrate 7.

[0089] The first quartz substrate 1, the wire grid transparent electrode layer 2, the first polyimide alignment layer 3, the electro-controlled liquid crystal layer 4, the second polyimide alignment layer 5, the metal metasurface layer 6, and the second quartz substrate 7 are connected sequentially from top to bottom.

[0090] The wire grid transparent electrode layer 2 is a strip array electrode structure, which is composed of a series of discrete array electrodes. Each array electrode is independently powered and its voltage is independently adjustable.

[0091] The metal metasurface layer 6 is a metal hollow rectangular array structure. The metal metasurface layer 6 is composed of a series of metal hollow rectangular structural units of the same size but different rotation angles. The main axis of each metal hollow rectangular structural unit is arranged at an angle of 0 to 180° with a certain gradient rotation.

[0092] Furthermore, the spatial period of the array electrodes in the wire-grid transparent electrode layer 2 is set to 312.5 micrometers according to the deflection frequency; the width of each array electrode in the wire-grid transparent electrode layer 2 is 250 micrometers. The wire-grid extension direction is parallel to the deflection plane to prevent unnecessary diffraction orders from being generated by the wire-grid, which could affect the light intensity distribution within the deflection plane.

[0093] Furthermore, the number of array electrodes in the wire grid transparent electrode layer 2 is 32.

[0094] Furthermore, the array electrode material in the wire grid transparent electrode layer 2 is one of indium tin oxide (ITO), DMSO-doped PEDOT:PSS, chromium, graphene, and carbon nanotubes.

[0095] Furthermore, the gradient in the metal metasurface layer 6 is determined by the phase distribution interpolation of the unit position, and the change in rotation angle is 1 / 2 of the change in phase angle; the metal material in the metal hollow rectangle is one of gold, silver, and aluminum.

[0096] Furthermore, the metal metasurface layer 6 is used to generate beam deflection and provide a reference potential for the wire grid transparent electrode layer. It is a hollowed-out rod pattern, and in this specific example, the deflection angle is designed to be 25° at 1.1 THz.

[0097] Furthermore, both the wire grid transparent electrode layer and the metal metasurface layer are fabricated on a quartz or silicon wafer with high transparency in the terahertz band. An insulating polyimide liquid crystal alignment layer is covered near the liquid crystal side to provide anchoring orientation for the liquid crystal layer. The orientation directions of the first polyimide alignment layer 3 and the second polyimide alignment layer 5 are antiparallel to each other and form a 45° angle with the extension direction of the array electrode.

[0098] Furthermore, the wire grid transparent electrode layer consists of a series of discrete strip electrodes, each of which can be powered independently and the voltage can be adjusted independently. Each electrode can be divided into two states, "1" and "0", depending on whether it is powered or not.

[0099] Furthermore, the thickness of the liquid crystal layer in the device depends on the birefringence of the liquid crystal used, ensuring that the liquid crystal can provide a phase shift greater than π after full deflection. The liquid crystal used here has a birefringence Δn = 0.28, a liquid crystal layer thickness of 800 micrometers, and an operating terahertz wave frequency of 1.1 THz, which can guarantee a maximum phase shift exceeding π.

[0100] Furthermore, the liquid crystal device is driven using overdrive technology. The power supply voltage for the "1" state is 10V, which is much higher than the threshold voltage of about 1.5V for liquid crystal, thus ensuring that the liquid crystal is sufficiently deflected.

[0101] Furthermore, by changing the switching sequence of the discrete electrodes, the proportion of phase change in the liquid crystal layer can be adjusted, thereby achieving the effect of changing the beam splitting ratio of the device. In addition, the switching sequence should satisfy periodicity to reduce the influence on the incident terahertz wave.

[0102] Each strip electrode is independently led out to control circuit 6 via a wire for independent voltage control. The device has two operating modes: voltage amplitude mode and digital encoding mode.

[0103] The voltage amplitude method supplies the same power to all electrodes of the electrode array. As the power supply voltage varies, the phase delay of the liquid crystal layer varies, which can control the beam splitting ratio in this embodiment.

[0104] The electrode array is driven by a digital encoding method. Each electrode can be divided into two states, "1" and "0," depending on whether it is powered on or not. The "1" state corresponds to a phase delay of π for the liquid crystal under that electrode, and the "0" state corresponds to a phase delay of 0 for the liquid crystal under that electrode. The phase delay difference between powered on and unpowered is π. The beam splitting ratio in this embodiment can be controlled by changing the voltage sequence. Taking 4-bit driving as an example, the corresponding electrode sequences are: … / 0000 / …、 … / 0001 / …、 … / 0011 / …、 … / 0111 / …、 … / 1111 / …, with corresponding left-side deflection light intensity ratios of 0.9, 0.68, 0.58, 0.52, and 0.4, and beam splitting ratios L:R of approximately 9:1, 2:1, 4:3, 1:1, and 2:3, respectively.

[0105] The terahertz transparent electrode layer described in this embodiment can be replaced with other thin films such as graphene, carbon nanotubes, or transparent conductive metal films that can achieve high terahertz transmittance and high conductivity. The number of fan-shaped structures in the wire-grid transparent electrode layer described in this embodiment is not limited to this embodiment; for example, a higher number can be used, along with appropriate circuitry.

[0106] It should be noted that relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0107] Although this application has been described above with reference to specific embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of this application. In particular, as long as there is no structural conflict, the features in the specific embodiments disclosed in this application can be combined with each other in any way. The lack of an exhaustive description of these combinations in this specification is merely for the sake of brevity and resource conservation. Therefore, this 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 terahertz liquid crystal adjustable beam splitter, characterized in that, It includes a first quartz substrate (1), a wire grid transparent electrode layer (2), a first polyimide alignment layer (3), an electro-controlled liquid crystal layer (4), a second polyimide alignment layer (5), a metal metasurface layer (6), and a second quartz substrate (7). The first quartz substrate (1), the wire grid transparent electrode layer (2), the first polyimide alignment layer (3), the electro-controlled liquid crystal layer (4), the second polyimide alignment layer (5), the metal metasurface layer (6), and the second quartz substrate (7) are connected sequentially from top to bottom; The wire grid transparent electrode layer (2) is a strip array electrode structure. The wire grid transparent electrode layer (2) is composed of a series of discrete array electrodes. Each array electrode is independently powered and its voltage is independently adjustable. The metal metasurface layer (6) is a metal hollow rectangular array structure. The metal metasurface layer (6) is composed of a series of metal hollow rectangular structural units of the same size but different rotation angles. The main axis direction of each metal hollow rectangular structural unit is arranged at an angle of 0 to 180° according to a certain gradient. Based on the structural unit design of the metal metasurface layer (6), a terahertz liquid crystal adjustable beam splitter is designed to achieve the deflection angle at the working frequency. Based on the geometric phase principle, the Jones matrix of the metallic metasurface layer (6) is obtained. for: in, , These are the matrices for right-spin selection and left-spin selection, respectively. and Let x and y be the transmittance of the structural unit, respectively; k be the wave vector of the incident terahertz wave; x be the coordinate of the beam along the x-axis on the metal metasurface layer (6); and θ be the deflection angle of the beam on the metal metasurface layer (6) at a given wavelength. It is the identity matrix; The imaginary unit; in, , ; The light intensity distribution of the transmitted light beam obtained by transmitting the metal metasurface layer (6) through the electro-controlled liquid crystal layer (4) is as follows: in, The intensity of the left-biased beam. The intensity of the right-biased beam. This represents the proportion of left-handed circularly polarized light in the total incident terahertz waves; The equivalent refractive index of the liquid crystal layer. The basis vectors representing left-handed circularly polarized light are: Let d represent the basis vector of right-handed circularly polarized light, d be the thickness of the liquid crystal layer, m represent the number of energized electrodes in the grid electrode layer, and N represent the total number of electrodes in the grid electrode layer. Represents the refractive index of the liquid crystal parallel to the orientation direction when no current is applied. Birefringence, representing liquid crystals; The different electrodes of the wire grid transparent electrode are subjected to different voltages to adjust the deflection effect of the nearby liquid crystal, thereby controlling the proportion of deflected liquid crystal in the total liquid crystal area. At the same time, the wire grid transparent electrode has a high transmittance in the terahertz band.

2. The terahertz liquid crystal adjustable beam splitter according to claim 1, characterized in that, The spatial period of the array electrodes in the wire grid transparent electrode layer (2) is set according to the deflection frequency, which is 150-650 micrometers; the width of each array electrode in the wire grid transparent electrode layer (2) is 0.7-0.9 times the spatial period.

3. A terahertz liquid crystal adjustable beam splitter according to claim 2, characterized in that, The number of array electrodes in the wire grid transparent electrode layer (2) is 16-64.

4. A terahertz liquid crystal adjustable beam splitter according to claim 3, characterized in that, The array electrode material in the wire grid transparent electrode layer (2) is one of indium tin oxide (ITO), DMSO-doped PEDOT:PSS, chromium, graphene, or carbon nanotubes, with a thickness of 5-50 nm.

5. A terahertz liquid crystal adjustable beam splitter according to claim 4, characterized in that, The gradient in the metal metasurface layer (6) is determined by the phase distribution interpolation of the unit position, and the rotation angle change is 1 / 2 of the phase angle change; the metal material in the metal hollow rectangle is one of gold, silver and aluminum, and the thickness is 10-300nm.

6. A terahertz liquid crystal adjustable beam splitter according to claim 5, characterized in that, The first quartz substrate (1) and the second quartz substrate (7) are simultaneously replaced with sapphire or poly(4-methylpentene-1) copolymer (TPX).

7. A terahertz liquid crystal adjustable beam splitter according to claim 6, characterized in that, The orientation directions of the first polyimide orientation layer (3) and the second polyimide orientation layer (5) are antiparallel to each other and at 45° to the extension direction of the array electrode. The thickness of the electro-controlled liquid crystal layer (4) depends on the birefringence parameters of the liquid crystal used and ranges from 100 to 1000 micrometers.

8. A method for fabricating a terahertz liquid crystal tunable beam splitter according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Photoresist is spin-coated onto a clean first quartz substrate, followed by pre-baking, exposure, post-baking, and development to prepare the designed strip array structure; S2. Deposit the array electrode material on the strip array structure obtained in step S1, and remove the residual photoresist to obtain the wire grid transparent electrode layer; S3. Spin-coat photoresist onto a clean second quartz substrate, perform pre-baking, exposure, post-baking, and development to prepare the designed metasurface structure; S4. Deposit a metal material on the metasurface structure obtained in step S3, and remove the residual photoresist to obtain a metal metasurface layer; S5. Spin-coat polyimide orientation layers onto the wire gate transparent electrode layer and the metal metasurface layer respectively, and bake them at high temperature of 200℃-300℃ for 0.5-2h to obtain the first polyimide orientation layer and the second polyimide orientation layer respectively. S6. The first polyimide orientation layer and the second polyimide orientation layer are rubbed and oriented in antiparallel directions and at 45° to the extension direction of the array electrode. S7. Adhere the first polyimide alignment layer and the second polyimide alignment layer after the friction alignment in step S6, use gaskets for support on both sides, leave space in the central area, cover the space area, place the alignment layer inward, and obtain the liquid crystal cell. S8. Fill the liquid crystal cell obtained in step S7 with liquid crystal to obtain an electro-controlled liquid crystal layer, and encapsulate it to obtain a terahertz liquid crystal adjustable beam splitter.

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