A transmission range-extending liquid crystal phase shifter

Abstract

A transmission-range extended liquid crystal phase shifter belongs to the field of terahertz modulation device technology. It addresses the urgent need for universal integrated tunable devices in the terahertz technology field. This invention comprises, in sequence, a first substrate, a polarization-selective reflective layer, a first terahertz transparent electrode layer, a first liquid crystal alignment layer, a liquid crystal layer, a second liquid crystal alignment layer, a second terahertz transparent electrode layer, a selective polarization conversion metasurface upper layer, a dielectric layer, a selective polarization conversion metasurface lower layer, and a second substrate. The polarization-selective reflective layer is a metal strip array structure. The selective polarization conversion metasurface upper layer is composed of alternating rod-shaped structural units and blank units, and the selective polarization conversion metasurface lower layer is composed of alternating metal planar structural units and wire grid structural units. Each rod-shaped structural unit is located directly above a metal planar structural unit, and each blank unit is located directly above a wire grid structural unit. This invention provides a reliable path for precise control of the electromagnetic wave phase.

Description

Technical Field

[0001] This invention belongs to the field of terahertz modulation device technology, specifically relating to a transmission range extender liquid crystal phase shifter. Background Technology

[0002] Terahertz waves (THz) generally refer to electromagnetic radiation with frequencies ranging from 0.1 to 10 THz, falling between the microwave and infrared spectra. Due to its unique spectral resources and diverse interactions with matter, terahertz technology has demonstrated significant application potential in fields such as security detection, high-speed wireless communication, materials spectroscopy, and biomedical imaging, and has become one of the key cutting-edge areas of focus in current scientific research and industrial applications.

[0003] In terahertz beam modulation and communication systems, the phase shifter, as a core functional unit, plays a crucial role in precisely controlling the phase of electromagnetic waves. Its performance directly determines the system's beam pointing accuracy, response speed, and transmission efficiency. Phase-shifting devices based on liquid crystal materials utilize the birefringence effect induced by an applied electric field to change the orientation of liquid crystal molecules, achieving phase modulation. These devices have attracted continuous attention due to their low cost, mature fabrication process, and low driving voltage.

[0004] With the continuous expansion of terahertz technology in fields such as 6G mobile communication, high-resolution imaging, non-destructive testing, and precision medicine, transmissive liquid crystal phase shifters are gradually becoming key components of terahertz phased array systems due to their large phase modulation depth and excellent wavefront control capabilities. Integrating transmissive liquid crystal phase shifters into the array structure enables various complex functions such as dynamic beam scanning, multi-beam generation, and directional transmission of spatial signals.

[0005] Traditional terahertz functional devices, such as lenses, waveplates, and spatial light modulators, generally suffer from problems such as large size, fixed functions, and limited control efficiency, making it difficult to meet the urgent needs of modern high-performance systems for miniaturization, integration, and reconfigurability. In contrast, liquid crystal metasurface devices, with their subwavelength-scale unit structure, can flexibly and efficiently control the amplitude, phase, and polarization state of terahertz waves, providing a unique solution for achieving the thinning and integration of terahertz systems.

[0006] As a key component in terahertz beam manipulation and communication systems, phase shifters require high efficiency, large phase shift, and compact design. Liquid crystal-based devices utilize the principle of electrically controlled birefringence to achieve phase control and have attracted widespread attention due to their low cost and simple driving. However, these devices rely on the phase accumulation of a single propagation of the terahertz wave in the liquid crystal, and their modulation capability is fundamentally limited by the intrinsic birefringence of the liquid crystal material, typically between 0.15 and 0.3. To achieve sufficient phase modulation depth, a relatively thick liquid crystal layer must be used. Taking a 1 THz operating frequency as an example, to achieve a phase modulation of π radians, the required liquid crystal layer thickness is typically between 700 and 850 micrometers. This size not only significantly increases the overall size and response time of the device but also easily introduces electromagnetic coupling interference between channels, leading to a decrease in system transmission efficiency.

[0007] Although significant progress has been made in the synthesis of high birefringence liquid crystal materials in recent years, simply optimizing material properties is still insufficient to overcome the inherent design constraints between large phase shift and thin layer thickness while ensuring high transmission efficiency. Therefore, it is urgent to fully leverage the application potential of metasurface-liquid crystal hybrid structures in reconfigurable terahertz photonic devices to develop an effective design strategy to address the trade-off between thickness and performance in terahertz liquid crystal phase shifters.

[0008] In addition, common polarization conversion structure designs do not have significant polarization selectivity. Most existing polarization conversion metasurfaces are reflective, often employing a double-layer metasurface structure with a metal reflective plane and microstructures, and there is no significant difference in polarization conversion effect for the two polarization directions. Summary of the Invention

[0009] The problem this invention aims to solve is the urgent need for general-purpose integrated tunable devices in the field of terahertz technology, and proposes a transmission range extender liquid crystal phase shifter.

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] A transmission range extender liquid crystal phase shifter includes a first substrate, a polarization selective reflective layer, a first terahertz transparent electrode layer, a first liquid crystal alignment layer, a liquid crystal layer, a second liquid crystal alignment layer, a second terahertz transparent electrode layer, a selective polarization conversion metasurface upper layer, a dielectric layer, a selective polarization conversion metasurface lower layer, and a second substrate, which are connected in sequence.

[0012] The polarization-selective reflective layer is a metal strip array structure;

[0013] The upper layer of the selective polarization conversion metasurface is composed of alternating rod-shaped structural units and blank units, and the lower layer of the selective polarization conversion metasurface is composed of alternating metal planar structural units and wire grid structural units. Each rod-shaped structural unit is located directly above the metal planar structural unit, and each blank unit is located directly above the wire grid structural unit.

[0014] The metal strip array structure in the polarization selective reflective layer and the wire grid structure unit in the lower layer of the selective polarization conversion metasurface intersect perpendicularly.

[0015] Furthermore, the materials of the first substrate and the second substrate are one or more of fused silica, silicon, and sapphire, and the thickness is 200-500 micrometers.

[0016] Furthermore, the period of the metal strip array in the polarization selective reflective layer is 0.1-0.4 times the wavelength, and the width of the metal strip array in each period is 0.3-0.7 times the period; the material of the metal strip array is one of gold, silver, copper, aluminum, palladium, and platinum, and the thickness of the metal strip array is 10-200 nanometers.

[0017] Furthermore, the thickness of the first terahertz transparent electrode layer and the second terahertz transparent electrode layer is 10-300 nanometers, which is used to apply an electric field to the liquid crystal layer to drive the liquid crystal deflection while maintaining high transmittance of terahertz waves.

[0018] Furthermore, the friction depth of the first liquid crystal alignment layer and the second liquid crystal alignment layer is 0.3 mm, which is used to guide the liquid crystal molecules to form a uniform and orderly initial arrangement on the substrate surface, thereby ensuring that a controllable and uniform photoelectric response can be achieved under the action of an external electric field.

[0019] Furthermore, the liquid crystal layer is made of one of the following materials: nematic liquid crystal, cholesteric liquid crystal, blue liquid crystal, or electro-optic polymer, and the thickness of the liquid crystal layer is 100-1000 micrometers.

[0020] Furthermore, in the upper layer of the selective polarization conversion metasurface, the length of the rod-shaped structural unit is 0.8-1.2 times the unit period, the width is 0.1-0.4 times the period, and they are placed at 45° to achieve high-efficiency polarization conversion reflection of terahertz waves in a linear polarization state and high-efficiency transmission of orthogonally linear polarization states. In the lower layer of the selective polarization conversion metasurface, the period of the wire grid structure unit is 0.1-0.4 times the unit period, and the width of the wire grid in each period is 0.3-0.7 times the wire grid period.

[0021] The metal structures in the upper and lower layers of the selective polarization conversion metasurface are made of one of the following metals: gold, silver, copper, aluminum, palladium, and platinum, and the thickness of the metal structures is 10-200 nanometers.

[0022] Furthermore, the material of the dielectric layer is one of polyimide, polydimethylsiloxane, polymethylpentene, Teflon, silicon, quartz, and sapphire, and the thickness of the dielectric layer is 15-100 micrometers.

[0023] Furthermore, the optical path analysis of the aforementioned transmission range extender liquid crystal phase shifter is as follows:

[0024] Terahertz waves are incident with x-polarization. They first pass through the polarization-selective reflective layer and then through the liquid crystal layer in a state where the x-polarization is perpendicular to the orientation direction of the liquid crystal, which corresponds to the first path.

[0025] Subsequently, it is reflected as y-polarized by the upper layer of the selective polarization conversion metasurface, the dielectric layer, and the lower layer of the selective polarization conversion metasurface. It passes through the liquid crystal layer and reaches the polarization-selective reflection layer to obtain the first phase shift φ1. After reflection, it passes through the liquid crystal layer again as y-polarized and exits the upper layer of the selective polarization conversion metasurface, the dielectric layer, and the lower layer of the selective polarization conversion metasurface to obtain the second phase shift φ2, corresponding to the second path.

[0026] Based on the fact that the first and second paths have the same polarization but different directions, we obtain φ1=φ2=φ, where φ is the phase shift of a single pass through the liquid crystal, expressed as:

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

[0033] in, , These represent the refractive indices when the terahertz wave polarization direction is parallel to the liquid crystal optical axis and the refractive indices when the terahertz wave polarization direction is perpendicular to the liquid crystal optical axis, respectively. The parameters used in the calculation describe the deflection intensity of the liquid crystal molecules. The wavelength of a terahertz wave. The thickness of the liquid crystal layer. The maximum deflection angle of the pointer within the liquid crystal layer. The parameters for calculating the dielectric anisotropy of liquid crystals are as follows: Parameters for calculating the anisotropy of liquid crystal warp and flexural elasticity. This is the threshold voltage of the liquid crystal. , These represent the dielectric constants of the liquid crystal when parallel to the optical axis and when perpendicular to the optical axis, respectively. , For liquid crystal curvature and flexural elasticity coefficient, This refers to the voltage applied across the two ends of the liquid crystal layer.

[0034] The beneficial effects of this invention are:

[0035] This invention discloses a transmission-range extended liquid crystal phase shifter, overcoming the inherent design constraints between large phase shift and thin layer thickness while ensuring high transmission efficiency. By introducing a selective polarization conversion metasurface and a polarization-selective reflective layer into the sandwich liquid crystal phase shifter structure, multiple passages of terahertz waves through the liquid crystal layer are achieved. This results in a doubling of the phase shift while maintaining high transmittance, increasing the phase shift depth and thus reducing the driving voltage and crosstalk spacing. The selective polarization conversion metasurface of this invention enables efficient polarization conversion in one polarization direction and efficient transmission in another, providing a design model for metasurface liquid crystal devices. This invention allows for device fabrication using only a sandwich liquid crystal cell structure combined with ultraviolet lithography, resulting in low cost, high integration, simple fabrication process, and compatibility with semiconductor processes. The device achieves wide-range, reconfigurable phase modulation in the terahertz band, and its compact configuration provides a reliable path for precise phase control of electromagnetic waves in terahertz beam modulation and communication systems.

[0036] The transmission range extender liquid crystal phase shifter described in this invention also has the effect of extending the range for isotropic liquid crystals and nematic liquid crystals; this invention has efficient polarization conversion reflection for x-polarization and efficient polarization conversion transmission for y-polarization. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of a transmission range extender liquid crystal phase shifter according to the present invention;

[0038] Figure 2 This is a schematic diagram of the polarization selective reflective layer of the present invention;

[0039] Figure 3 This is a schematic diagram of the structure of the upper layer of the selective polarization conversion metasurface of the present invention;

[0040] Figure 4 This is a schematic diagram of the structure of the lower layer of the selective polarization conversion metasurface of the present invention;

[0041] Figure 5This is a schematic diagram illustrating the working principle of a transmission range extender liquid crystal phase shifter according to the present invention;

[0042] Figure 6 This is an electrically controlled phase-shift spectrum of a transmission range-extending liquid crystal phase shifter according to the present invention;

[0043] Figure 7 This is a transmittance spectrum of an electrically controlled transmission range extender liquid crystal phase shifter according to the present invention. Detailed Implementation

[0044] 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.

[0045] 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.

[0046] To further understand the invention's content, features, and effects, the following specific embodiments are provided, along with accompanying drawings. Figure 1 -Appendix Figure 7 Detailed explanation is as follows:

[0047] Example 1:

[0048] A transmission range extender liquid crystal phase shifter includes a first substrate 1, a polarization selective reflective layer 2, a first terahertz transparent electrode layer 3, a first liquid crystal alignment layer 4, a liquid crystal layer 5, a second liquid crystal alignment layer 6, a second terahertz transparent electrode layer 7, a selective polarization conversion metasurface upper layer 8, a dielectric layer 9, a selective polarization conversion metasurface lower layer 10, and a second substrate 11, which are connected in sequence.

[0049] The polarization selective reflective layer 2 is a metal strip array structure;

[0050] The upper layer 8 of the selective polarization conversion metasurface is composed of alternating rod-shaped structural units 8-1 and blank units 8-2, and the lower layer 10 of the selective polarization conversion metasurface is composed of alternating metal planar structural units 10-2 and wire grid structural units 10-1. Each rod-shaped structural unit 8-1 is located directly above the metal planar structural unit 10-2, and each blank unit 8-2 is located directly above the wire grid structural unit 10-1.

[0051] The metal strip array structure in the polarization selective reflective layer 2 and the wire grid structure unit 10-1 in the selective polarization conversion metasurface lower layer 10 intersect perpendicularly.

[0052] Furthermore, the materials of the first substrate 1 and the second substrate 11 are one or more of fused silica, silicon, and sapphire, and the thickness is 200-500 micrometers.

[0053] Furthermore, the period of the metal strip array in the polarization selective reflective layer 2 is 0.1-0.4 times the wavelength, and the width of the metal strip array in each period is 0.3-0.7 times the period; the material of the metal strip array is one of gold, silver, copper, aluminum, palladium, and platinum, and the thickness of the metal strip array is 10-200 nanometers.

[0054] Furthermore, the thickness of the first terahertz transparent electrode layer 3 and the second terahertz transparent electrode layer 7 is 10-300 nanometers, which is used to apply an electric field to the liquid crystal layer to drive the liquid crystal deflection while maintaining high transmittance of terahertz waves.

[0055] Furthermore, the first terahertz transparent electrode layer 3 and the second terahertz transparent electrode layer 7 can be made of dimethyl sulfoxide-doped PEDOT:PSS (poly(3,4-ethylenedioxythiophene):polystyrene sulfonate), indium tin oxide, porous graphene, vanadium dioxide, and other metallic or non-metallic terahertz transparent electrode materials.

[0056] Furthermore, the friction depth of the first liquid crystal alignment layer 4 and the second liquid crystal alignment layer 6 is 0.3 mm, which is used to guide the liquid crystal molecules to form a uniform and orderly initial arrangement on the substrate surface, thereby ensuring that a controllable and uniform photoelectric response can be achieved under the action of an external electric field.

[0057] Furthermore, the material of the liquid crystal layer 5 is selected from one of nematic liquid crystal, cholesteric liquid crystal, blue liquid crystal, and electro-optic polymer, and the thickness of the liquid crystal layer 5 is 100-1000 micrometers.

[0058] Furthermore, in the upper layer 8 of the selective polarization conversion metasurface, the length of the rod-shaped structural unit 8-1 is 0.8-1.2 times the unit period, the width is 0.1-0.4 times the period, and they are placed at 45° to achieve high-efficiency polarization conversion reflection of terahertz waves in a linear polarization state and high-efficiency transmission of orthogonally linear polarization states. In the lower layer 10 of the selective polarization conversion metasurface, the period of the wire grid of the wire grid structural unit 10-1 is 0.1-0.4 times the unit period, and the width of the wire grid in each period is 0.3-0.7 times the wire grid period.

[0059] The metal structures in the upper layer 8 and the lower layer 10 of the selective polarization conversion metasurface are made of one of the following metals: gold, silver, copper, aluminum, palladium, and platinum, and the thickness of the metal structure is 10-200 nanometers.

[0060] Furthermore, the material of the dielectric layer 9 is one of polyimide, polydimethylsiloxane, polymethylpentene, Teflon, silicon, quartz, and sapphire, and the thickness of the dielectric layer 9 is 15-100 micrometers.

[0061] Furthermore, the optical path analysis of the aforementioned transmission range extender liquid crystal phase shifter is as follows:

[0062] The terahertz wave is incident with x-polarization. It first passes through the polarization selective reflection layer 2 and then through the liquid crystal layer 5 with x-polarization perpendicular to the liquid crystal orientation direction, which corresponds to the first path.

[0063] Subsequently, the selective polarization conversion metasurface upper layer 8, dielectric layer 9, and selective polarization conversion metasurface lower layer 10 reflect the light as y-polarized light, which passes through the liquid crystal layer 5 and reaches the polarization selective reflection layer 2 to obtain the first phase shift φ1. After reflection, the light passes through the liquid crystal layer 5 again as y-polarized light and exits through the selective polarization conversion metasurface upper layer 8, dielectric layer 9, and selective polarization conversion metasurface lower layer 10 to obtain the second phase shift φ2, corresponding to the second path.

[0064] Based on the fact that the first and second paths have the same polarization but different directions, we obtain φ1=φ2=φ, where φ is the phase shift of a single pass through the liquid crystal, expressed as:

[0065]

[0066]

[0067]

[0068]

[0069]

[0070]

[0071] in, , These represent the refractive indices when the terahertz wave polarization direction is parallel to the liquid crystal optical axis and the refractive indices when the terahertz wave polarization direction is perpendicular to the liquid crystal optical axis, respectively. The parameters used in the calculation describe the deflection intensity of the liquid crystal molecules. The wavelength of a terahertz wave. The thickness of the liquid crystal layer. The maximum deflection angle of the pointer within the liquid crystal layer. The parameters for calculating the dielectric anisotropy of liquid crystals are as follows: Parameters for calculating the anisotropy of liquid crystal warp and flexural elasticity. This is the threshold voltage of the liquid crystal. , These represent the dielectric constants of the liquid crystal when parallel to the optical axis and when perpendicular to the optical axis, respectively. , For liquid crystal curvature and flexural elasticity coefficient, This refers to the voltage applied across the two ends of the liquid crystal layer.

[0072] Furthermore, the terahertz wave, passing twice with its y-polarization perpendicular to the direction parallel to the liquid crystal and modulated by the liquid crystal's electro-controlled birefringence, achieved a phase shift twice that of a single pass through the liquid crystal, reaching 177° at 0.8 THz (500 micrometers of liquid crystal layer), while maintaining high transmittance, such as... Figure 6 , Figure 7 As shown.

[0073] In summary, to meet the urgent need for general-purpose integrated tunable devices in the terahertz technology field, this implementation scheme proposes a transmission-range-extended liquid crystal phase shifter and its fabrication method, addressing the basic unit design requirements of terahertz liquid crystal devices. This device employs a sandwich structure, introducing a selective polarization conversion metasurface and a polarization-selective reflective layer to allow the terahertz wave to propagate multiple times within the liquid crystal layer, thereby achieving a doubling of the phase shift while maintaining high transmittance. This method effectively improves the phase shift depth and helps reduce the driving voltage and crosstalk spacing. This scheme possesses advantages such as simple structure, low cost, and high integration, and exhibits good compatibility with semiconductor processes.

[0074] This embodiment describes a transmission-range extended liquid crystal phase shifter, which operates in a transmission mode. It also extends the transmission range for nematic liquid crystals, theoretically doubling the transmission phase shift, and for isotropic liquid crystals, theoretically tripling the transmission phase shift. This embodiment employs a more complex selective polarization conversion metasurface, which is not only structurally complex but also functionally more complex. This embodiment exhibits highly efficient polarization conversion reflection for x-polarization and highly efficient polarization conversion transmission for y-polarization.

[0075] Example 2:

[0076] A method for fabricating a transmission range extender liquid crystal phase shifter as described in Embodiment 1 includes the following steps:

[0077] (1) The substrate was ultrasonically cleaned sequentially with deionized water, alcohol, acetone, alcohol, and deionized water for 5-15 minutes.

[0078] (2) Spin coat the photoresist onto the substrate using a spin coater. The spin coating time is 25-60 s and the spin coating speed is 1000-10000 rpm.

[0079] (3) Pre-baking and UV exposure were performed on the above samples. The baking time was 30-120 s, the baking temperature was 90-130 ℃, and the exposure time was 1-10 s.

[0080] (4) Harden the above sample, bake for 30-120 s, bake at 90-130 ℃;

[0081] (5) Deposit a metal layer on the sample above, followed by development for 5-60 s to complete the preparation of the lower layer of the selective polarization conversion metasurface;

[0082] (6) Prepare a dielectric layer and repeat steps (2)-(5) on it to complete the preparation of the selective polarization conversion metasurface upper layer;

[0083] (7) Repeat steps (2)-(5) to complete the preparation of the polarization-selective reflective surface;

[0084] In the preferred embodiment, the pattern structure is prepared by ultraviolet exposure, but laser direct writing, electron beam exposure, or nanoimprinting can also be used; the method for depositing metal materials is magnetron sputtering, but thermal evaporation, electron beam evaporation, or chemical vapor deposition can also be used.

[0085] (8) PEDOT:PSS was spin-coated as a terahertz transparent electrode on the samples in steps (6) and (7) using a spin coater. The spin coating time was 25-60 s and the spin coating speed was 1000-10000 rpm.

[0086] (9) Based on the sample prepared above, spin coating and friction orientation of polyimide orientation agent are performed. The spin coating time is 25-60 s and the spin coating speed is 2000-5000 rpm. High temperature baking is then performed. First, the temperature is kept at 100℃-150℃ for 0.5-1 h, and then the temperature is 240℃-300℃ for 0.5-2 h. The heating rate during the heating process does not exceed 2.5℃ / min. The friction orientation speed is 500-2000 rpm and the pressing depth is 0.2-1.5 mm.

[0087] (10) The sample obtained in step (9) is coated with UV adhesive on the edges of the upper and lower substrates, and a gasket is placed to control the thickness of the liquid crystal layer. The upper and lower substrates are then bonded together and then cured with UV.

[0088] In the preferred embodiment, UV curing is carried out in a UV curing chamber or UV crosslinker, with LED or mercury lamp as the light source, power of 10-30 W, and photopolymerization time of 1-10 min;

[0089] (11) Pour liquid crystal into the sample obtained in step (10), apply ultraviolet adhesive to the part that is not coated with ultraviolet adhesive, and perform liquid crystal ultraviolet polymerization and ultraviolet adhesive curing.

[0090] In the preferred embodiment, UV polymerization is carried out in a UV curing chamber or UV crosslinker, with an LED or mercury lamp as the light source, a power of 10-30 W, and a polymerization time of 5-30 min.

[0091] Example 3:

[0092] A method for fabricating a transmission range extender liquid crystal phase shifter as described in Embodiment 1 includes the following steps:

[0093] The substrate is made of fused silica with a thickness of 500 micrometers. The period of the polarization-selective reflective layer grating is 0.25 times the wavelength, and the grating width within each period is 0.5 times the period. The grating period of the grating sub-units in the selective polarization conversion metasurface is 0.25 times the sub-unit period, and the grating width within each period is 0.5 times the grating period.

[0094] The substrate was ultrasonically cleaned sequentially with deionized water, alcohol, acetone, alcohol again, and then deionized water for 10 min each. Photoresist was then spin-coated using a spin coater at 4000 rpm for 30 s. The sample was then pre-baked and exposed to UV light for 80 s at 120°C, followed by 8 s of exposure. A hard coating was then applied to the sample, baked for 80 s at 120°C. Gold was then deposited on the sample using magnetron sputtering to a thickness of 100 nm, followed by development for 40 s, completing the preparation of the lower layer of the selective polarization conversion metasurface. An 80 μm thick polyimide dielectric layer was then prepared, and the above photolithography steps were repeated on top of it to complete the preparation of the upper layer of the selective polarization conversion metasurface. The above steps were repeated on other samples to complete the preparation of the polarization-selective reflective surface.

[0095] Based on the preparation of selective polarization conversion metasurfaces and polarization selective reflective surfaces, PEDOT:PSS was spin-coated as a terahertz transparent electrode using a spin coater for 30 s at a speed of 3000 rpm. Subsequently, a polyimide alignment agent was spin-coated and rubbed for alignment, with a spin-coating time of 30 s at a speed of 3000 rpm, followed by high-temperature baking. The initial temperature was 100℃ for 0.5 h, followed by 250℃ for 1 h, with a heating rate of 2℃ / min. The rubbed alignment speed was 1000 rpm, and the indentation depth was 0.5 mm.

[0096] The prepared sample was used as the upper and lower substrate edges to coat with UV adhesive, maintaining an antiparallel orientation along the x-direction. Spacers were placed to control the liquid crystal layer thickness to 500 micrometers. The upper and lower substrates were then bonded together, followed by UV curing in a UV crosslinker for 5 minutes. Liquid crystal was then poured into the sample, and UV adhesive was applied to the uncoated areas, followed by UV curing.

[0097] 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.

[0098] 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 transmission range extender liquid crystal phase shifter, characterized in that, It includes a first substrate (1), a polarization selective reflective layer (2), a first terahertz transparent electrode layer (3), a first liquid crystal alignment layer (4), a liquid crystal layer (5), a second liquid crystal alignment layer (6), a second terahertz transparent electrode layer (7), a selective polarization conversion metasurface upper layer (8), a dielectric layer (9), a selective polarization conversion metasurface lower layer (10), and a second substrate (11) connected in sequence. The polarization selective reflective layer (2) is a metal strip array structure; The upper layer (8) of the selective polarization conversion metasurface is composed of alternating rod-shaped structural units (8-1) and blank units (8-2), and the lower layer (10) of the selective polarization conversion metasurface is composed of alternating metal planar structural units (10-2) and wire grid structural units (10-1). Each rod-shaped structural unit (8-1) is located directly above the metal planar structural unit (10-2), and each blank unit (8-2) is located directly above the wire grid structural unit (10-1). The metal strip array structure in the polarization selective reflective layer (2) and the wire grid direction in the wire grid structure unit (10-1) in the selective polarization conversion metasurface lower layer (10) intersect perpendicularly.

2. The transmission range extender liquid crystal phase shifter according to claim 1, characterized in that, The first substrate (1) and the second substrate (11) are made of one or more of fused silica, silicon, and sapphire, and have a thickness of 200-500 micrometers.

3. A transmission range extender liquid crystal phase shifter according to claim 2, characterized in that, The period of the metal strip array in the polarization selective reflective layer (2) is 0.1-0.4 times the wavelength, and the width of the metal strip array in each period is 0.3-0.7 times the period; the material of the metal strip array is one of gold, silver, copper, aluminum, palladium and platinum, and the thickness of the metal strip array is 10-200 nanometers.

4. A transmission range extender liquid crystal phase shifter according to claim 3, characterized in that, The thickness of the first terahertz transparent electrode layer (3) and the second terahertz transparent electrode layer (7) is 10-300 nanometers, which are used to apply an electric field to the liquid crystal layer to drive the liquid crystal deflection while maintaining high transmittance of terahertz waves.

5. A transmission range extender liquid crystal phase shifter according to claim 4, characterized in that, The friction depth of the first liquid crystal alignment layer (4) and the second liquid crystal alignment layer (6) is 0.3 mm, which is used to guide the liquid crystal molecules to form a uniform and orderly initial arrangement on the substrate surface, thereby ensuring that a controllable and uniform photoelectric response can be achieved under the action of an external electric field.

6. A transmission range extender liquid crystal phase shifter according to claim 5, characterized in that, The liquid crystal layer (5) is made of one of the following materials: nematic liquid crystal, cholesteric liquid crystal, blue liquid crystal, or electro-optic polymer. The thickness of the liquid crystal layer (5) is 100-1000 micrometers.

7. A transmission range extender liquid crystal phase shifter according to claim 6, characterized in that, The length of the rod-shaped structural unit (8-1) in the upper layer (8) of the selective polarization conversion metasurface is 0.8-1.2 times the unit period, the width is 0.1-0.4 times the period, and it is placed at 45°. It is used to achieve high-efficiency polarization conversion reflection of terahertz waves in a linear polarization state and high-efficiency transmission of orthogonal linear polarization state. The period of the wire grid of the wire grid structural unit (10-1) in the lower layer (10) of the selective polarization conversion metasurface is 0.1-0.4 times the unit period, and the width of the wire grid in each period is 0.3-0.7 times the wire grid period. The metal structures in the upper layer (8) and lower layer (10) of the selective polarization conversion metasurface are made of one of the following metals: gold, silver, copper, aluminum, palladium, and platinum. The thickness of the metal structure is 10-200 nanometers.

8. A transmission range extender liquid crystal phase shifter according to claim 7, characterized in that, The material of the dielectric layer (9) is one of polyimide, polydimethylsiloxane, polymethylpentene, Teflon, silicon, quartz, and sapphire, and the thickness of the dielectric layer (9) is 15-100 micrometers.

9. A transmission range extender liquid crystal phase shifter according to claim 8, characterized in that, The optical path analysis of the aforementioned transmission range extender liquid crystal phase shifter is as follows: The terahertz wave is incident with x-polarization. It first passes through the polarization selective reflection layer (2) and then through the liquid crystal layer (5) with x-polarization perpendicular to the liquid crystal orientation direction, which corresponds to the first path. Subsequently, it is reflected as y-polarized through the upper layer (8) of the selective polarization conversion metasurface, the dielectric layer (9), and the lower layer (10) of the selective polarization conversion metasurface. It passes through the liquid crystal layer (5) and reaches the polarization selective reflection layer (2) to obtain the first phase shift φ1. After reflection, it passes through the liquid crystal layer (5) again as y-polarized and exits through the upper layer (8) of the selective polarization conversion metasurface, the dielectric layer (9), and the lower layer (10) of the selective polarization conversion metasurface to obtain the second phase shift φ2, corresponding to the second path; Based on the fact that the first and second paths have the same polarization but different directions, we obtain φ1 = φ2 = φ, where φ is the phase shift of a single pass through the liquid crystal, expressed as: in, , These represent the refractive indices when the terahertz wave polarization direction is parallel to the liquid crystal optical axis and the refractive indices when the terahertz wave polarization direction is perpendicular to the liquid crystal optical axis, respectively. The parameters used in the calculation describe the deflection intensity of the liquid crystal molecules. The wavelength of a terahertz wave. The thickness of the liquid crystal layer. The maximum deflection angle of the pointer within the liquid crystal layer. The parameters for calculating the dielectric anisotropy of liquid crystals are as follows: Parameters for calculating the anisotropy of liquid crystal warp and flexural elasticity. This is the threshold voltage of the liquid crystal. , These represent the dielectric constants of the liquid crystal when parallel to the optical axis and when perpendicular to the optical axis, respectively. , For liquid crystal curvature and flexural elasticity coefficient, This refers to the voltage applied across the two ends of the liquid crystal layer.

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