Multi-polarization multiplexing terahertz coding metasurface based on vanadium dioxide

Abstract

The invention discloses a vanadium dioxide-based multi-polarization multiplexing terahertz coding metasurface, which comprises a bottom plate and a dielectric layer arranged on the upper surface of the bottom plate, a metal layer and vanadium dioxide are arranged on the upper surface of the dielectric layer, and the period p is equal to 150 microns; the metal layer comprises a square split ring and a cross ellipse arranged in the square split ring, and the vanadium dioxide is embedded in a gap of the square split ring. According to the multi-polarization multiplexing terahertz coding metasurface based on the vanadium dioxide, the ultra-fast conversion characteristic of the vanadium dioxide is utilized, and two phase regulation and control modes are combined, so that the metasurface has the characteristics of flexible design and diversified functions, the problems that the metasurface is fixed in function and single in polarization component are solved, and the metasurface has a wide application prospect. And the application prospect of the coding metasurface device is expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of coding supersurfaces, and in particular to a terahertz coding supersurface based on multi-polarization multiplexing of vanadium dioxide. Background Art

[0002] Metamaterials are artificial subwavelength unit array structures. Through careful design, these materials can exhibit unique physical properties that cannot be found in nature, such as negative dielectric constant, negative magnetic permeability, negative refractive index or zero refractive index. The electromagnetic properties of metamaterials can be described by equivalent dielectric constant and equivalent magnetic permeability. These two parameters determine the refractive index of the metamaterial, thereby determining the transmission mode of the incident wave. Through this design, the limitations of natural materials in dielectric constant and magnetic permeability can be broken. In theory, people can design metamaterials with arbitrary dielectric constant and magnetic permeability as needed to achieve various functions.

[0003] However, metamaterials need to control electromagnetic waves through phase accumulation in space, which means that a certain thickness is required in the propagation direction, which leads to many inconveniences in design and processing, such as large volume, heavy mass, and difficulty in integration. Metasurface, as a two-dimensional planar form of metamaterial, does not rely on phase and amplitude accumulation in the propagation direction to control electromagnetic waves, but achieves arbitrary control of electromagnetic waves through phase or amplitude changes occurring on the surface of the structure and accumulating these changes. Therefore, the metasurface only needs a single layer or ultra-thin multi-layer structure, which can be arranged in two dimensions on the cross section perpendicular to the transmission direction to realize its function.

[0004] In 2014, Professor Cui Tiejun's research group at Southeast University proposed the concepts of "digital coding metasurface" and "programmable coding metasurface", realizing the regulation of electromagnetic information in a digital way, connecting metasurfaces with information science. The digital states "0" and "1" of a one-bit digital coding metasurface represent the phases of 0 and π, respectively. The phase here is not an absolute phase value, but the phase difference between two coding states. The concept of coded metasurfaces can also be extended to two bits or even higher to achieve more flexible electromagnetic information regulation. When the coding pattern is constructed by different digital states to form different arrangements, the electromagnetic radiation function in space will also change accordingly, realizing functions such as multi-beam, single beam deflection, radar cross section reduction and vortex beam.

[0005] With the development of today's society, single-function polarization devices are difficult to meet the needs, such as beamforming, beam scanning, and near-field focusing, which all require real-time dynamic control. Therefore, giving metasurfaces the ability to dynamically adjust electromagnetic waves is a topic worthy of in-depth research in the current metasurface field.

[0006] VO2 is a typical phase change material that can undergo a significant Insulator-to-Metal Transition (IMT) under the action of external stimuli. At room temperature, VO2 is in an insulating state. When the temperature rises above its phase transition temperature of 341K (about 68°C), VO2 will be in a metallic state, and its lattice structure will change from a monoclinic rutile structure at low temperatures to a tetragonal rutile structure at high temperatures. This change causes its electrical conductivity to vary by 3-5 orders of magnitude.

[0007] In the prior art, some tunable metasurfaces combined with VO2 are used to achieve wavefront control of linear polarization and circular polarization. However, they are limited by the inherent limitations brought by the geometric phase, which makes it impossible to use the co-polarization component in the manipulation of circular polarization, and will cause the functional locking of left-handed and right-handed polarized light, which is not conducive to the multifunctional integration and multiplexing of metasurfaces in modern communication systems. Summary of the invention

[0008] The purpose of the present invention is to provide a terahertz coding metasurface based on multi-polarization multiplexing of vanadium dioxide to achieve the manipulation of linear polarization and circular polarization components.

[0009] To achieve the above-mentioned object, the present invention provides a terahertz coding metasurface based on multi-polarization multiplexing of vanadium dioxide, comprising a base plate and a dielectric layer arranged on the upper surface of the base plate, wherein the upper surface of the dielectric layer is provided with a metal layer and vanadium dioxide, and the period of the base plate and the dielectric layer is p=150 μm;

[0010] The metal layer comprises a square opening ring and a cross ellipse arranged inside the square opening ring, and the vanadium dioxide is embedded in the gap of the square opening ring.

[0011] Preferably, the transverse ellipse size of the cross ellipse is l x , the longitudinal ellipse size of the cross ellipse is l y , where l x With l y are all non-fixed values, l x With l y The length range is 10 to 100 μm.

[0012] Preferably, the vanadium dioxide is a phase change material, and the reversible transformation of vanadium dioxide from an insulating state to a metallic state is regulated by temperature, as follows:

[0013] When vanadium dioxide is in an insulating state, it adopts a propagation phase mode. When vanadium dioxide is in a metallic state, it has metallic properties. At this time, the length of the vanadium dioxide is l v , l v It is a non-fixed value, and its length range is 5 to 65 μm.

[0014] Preferably, when the vanadium dioxide is in a metallic state, the square open ring is closed to form an isotropic structure.

[0015] Preferably, the dielectric layer is polyimide, with a thickness of t1=30 μm, a dielectric constant of ε=3.5, and a tangent loss of tanδ=0.0027.

[0016] Preferably, the outer side length of the square open ring is l=140 μm, the inner width is g=20 μm, and the minor axis of the cross ellipse is w=10 μm.

[0017] To achieve the above-mentioned object, the present invention provides an application of a terahertz coding metasurface with multi-polarization multiplexing based on vanadium dioxide in a metasurface array of 24×24 units.

[0018] Preferably, when in the insulating state, when a y-polarized terahertz wave is vertically irradiated onto the metasurface array, the reflected y-polarized terahertz wave is split into two lobes along the x-direction at 31.9° at 0.315 THz;

[0019] When in a metallic state, when a left-handed circularly polarized terahertz wave is vertically irradiated onto the metasurface array, the reflected left-handed circularly polarized terahertz wave is divided into four lobes at 40° at 1.1 THz.

[0020] By changing the transverse and longitudinal phase difference of the cross ellipse, a metasurface with co-polarization control of linear polarization and circular polarization was designed. When VO2 is in the insulating state, it has the ability to convert y-polarized light into dual beams, and when VO2 is in the metallic state, it has the ability to convert left-handed circularly polarized light into four beams.

[0021] Preferably, when in the insulating state, when an x-polarized terahertz wave is vertically irradiated onto the metasurface array, the reflected terahertz wave is split into two lobes along the y direction at 29° at 0.315 THz;

[0022] When in a metallic state, when a left-handed circularly polarized terahertz wave is vertically irradiated onto the metasurface array, the reflected left-handed circularly polarized terahertz wave is deflected to 29°, and the reflected right-handed circularly polarized terahertz wave forms a vortex beam at 1.1 THz, with a phase spiral distribution of 360°, which is the characteristic of a +1-order vortex beam.

[0023] By changing the transverse and longitudinal phase difference of the cross ellipse, a metasurface for co-polarization and cross-polarization regulation of linear polarization and circular polarization is designed. In the VO2 insulating state, it has the ability to convert x-polarized light into dual beams. In the metallic state, it has the ability to convert left-handed circularly polarized light into a single-beam deflection and a right-handed circularly polarized vortex beam.

[0024] Preferably, when in the insulating state, when an x-polarized terahertz wave is vertically irradiated onto the metasurface array, the reflected terahertz wave is split into two lobes along the x-direction at 40.3° at 0.515 THz;

[0025] When in a metallic state, the electric field energy of the left-handed circular polarization of the metasurface array is focused at 40 μm on the focal plane, and the phase spiral changes by 360°; the electric field energy of the right-handed circular polarization is focused at 1200 μm on the focal plane, and the phase spiral changes by 720°.

[0026] By changing the transverse and longitudinal phase difference of the cross ellipse, a metasurface that decouples linear polarization and two orthogonal circular polarizations is designed. In the VO2 insulating state, it has the ability to convert x-polarized light into dual beams, and in the metallic state, it has the ability to convert two orthogonal circularly polarized lights into focused vortices with different focal planes and topological charges.

[0027] Therefore, the present invention adopts the above-mentioned terahertz coding metasurface based on multi-polarization multiplexing of vanadium dioxide, and the beneficial effects are as follows:

[0028] (1) The metasurface of the present invention is a sandwich structure composed of a phase change material, a metal layer and a dielectric layer. Using this structure, multiple coding metasurface arrays are designed, such as a metasurface for co-polarization regulation of linear polarization and circular polarization, a metasurface for co-polarization and cross-polarization regulation of linear polarization and circular polarization, and a metasurface for decoupling linear polarization and two orthogonal circular polarizations. Under temperature changes, VO2 has the characteristics of insulation-metal transition. In the insulating state, one-bit coding of linear polarization can be achieved, and in the metallic state, one-bit or two-bit coding of circular polarization can be achieved. Specifically, in the VO2 insulating state, the metasurface with co-polarization control of linear polarization and circular polarization has the ability to convert y-polarized light into dual beams, and in the VO2 metallic state, it has the ability to convert left-handed circularly polarized light into four beams; in the insulating state, the metasurface with co-polarization and cross-polarization control of linear polarization and circular polarization has the ability to convert x-polarized light into dual beams, and in the metallic state, it has the ability to convert left-handed circularly polarized light into a single-beam deflection and right-handed circularly polarized vortex beam; in the insulating state, the metasurface with decoupling of linear polarization and two orthogonal circular polarizations has the ability to convert x-polarized light into dual beams, and in the metallic state, it has the ability to convert two orthogonal circularly polarized lights into focused vortices with different focal planes and topological charges.

[0029] (2) The present invention can realize the multiplexing of different functions of linear polarization and circular polarization beams by adjusting the temperature to make VO2 change from an insulating state to a metallic state. In addition, by combining the propagation phase and the geometric phase in the circular polarization, the independent regulation of the co-polarization and cross-polarization component functions and the decoupling of left-handed and right-handed circularly polarized light can be realized, which solves the limitation that only the cross component and the locking of left-handed and right-handed circularly polarized light functions can be used in the circular polarization manipulation, is conducive to the integration of multiple functions, and expands the application prospects of coded metasurface devices.

[0030] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a top view of an embodiment of a terahertz coding metasurface based on multi-polarization multiplexing of vanadium dioxide according to the present invention;

[0032] Figure 2 is a side view of an embodiment of a terahertz coding metasurface based on multi-polarization multiplexing of vanadium dioxide according to the present invention;

[0033] Figure 3 1 is an amplitude and phase variation diagram of an embodiment of a terahertz coding metasurface for multi-polarization multiplexing based on vanadium dioxide of the present invention, wherein (a) is a schematic diagram of the amplitude of a one-bit coding metasurface when the VO2 length is changed to 5 and 25 μm for x polarization in the VO2 insulating state, (b) is a schematic diagram of the phase of a one-bit coding metasurface when the VO2 length is changed to 5 and 25 μm for x polarization in the VO2 insulating state, (c) is a schematic diagram of the amplitude of a one-bit coding metasurface when the VO2 length is changed to 5 and 65 μm for y polarization in the VO2 insulating state, (d) is a schematic diagram of the phase of a one-bit coding metasurface when the VO2 length is changed to 5 and 65 μm for y polarization in the VO2 insulating state, (e) is a schematic diagram of the amplitude variation when the lateral and longitudinal dimensions of the cross ellipse are changed in the VO2 metallic state, and (f) is a schematic diagram of the phase variation when the lateral and longitudinal dimensions of the cross ellipse are changed in the VO2 metallic state;

[0034] Figure 4 The present invention is a linear polarization and circular polarization co-polarization control diagram of a terahertz coding metasurface embodiment of multi-polarization multiplexing based on vanadium dioxide, wherein (a) is a metasurface with linear polarization and circular polarization co-polarization control, and in the VO2 insulating state, the units are periodically arranged as "000000111111···" along the x direction, (b) is a metasurface with linear polarization and circular polarization co-polarization control, and in the VO2 metallic state, the units are arranged in a checkerboard format as "0011 / 1100···", (c) is a metasurface with linear polarization and circular polarization co-polarization control, and in the VO2 insulating state, when y-polarized light is incident, the three-dimensional far-field simulation result has a frequency of 0.315 THz, and the output is dual beams, and (d) is a metasurface with linear polarization and circular polarization co-polarization control, and in the VO2 metallic state, when left-handed circularly polarized light is incident, the three-dimensional far-field simulation result has a frequency of 1.1 THz, and the output is four beams.

[0035] Figure 5The present invention is a terahertz coding metasurface embodiment of multi-polarization multiplexing based on vanadium dioxide, wherein (a) is a metasurface with linear polarization and circular polarization co-polarization and cross-polarization regulation, and in the VO2 insulating state, the units are periodically arranged as "00001111···" along the y direction, (b) is a metasurface with linear polarization and circular polarization co-polarization and cross-polarization regulation, and in the VO2 metallic state, the units are periodically arranged as "01230123···" along the x direction, and (c) is a metasurface with linear polarization and circular polarization co-polarization and cross-polarization regulation, and in the VO2 metallic state, the units are arranged as a vortex with a mode of +1. Light beam, (d) is the metasurface with linear polarization and circular polarization co-polarization and cross-polarization control. In the VO2 insulating state, when x-polarized light is incident, the three-dimensional far-field simulation result is at a frequency of 0.515 THz, and the output is a dual-beam. (e) is the metasurface with linear polarization and circular polarization co-polarization and cross-polarization control. In the VO2 metallic state, when left-handed circularly polarized light is incident, the three-dimensional far-field simulation result is at a frequency of 1.1 THz, and the output is a single-beam polarization. (f) is the metasurface with linear polarization and circular polarization co-polarization and cross-polarization control. In the VO2 metallic state, when left-handed circularly polarized light is incident, the three-dimensional far-field simulation result is at a frequency of 1.1 THz, and the output is a right-handed circularly polarized vortex beam.

[0036] Figure 6 It is a two-dimensional electric field distribution and phase distribution result of linear polarization and circular polarization co-polarization and cross-polarization regulation of a terahertz coding metasurface embodiment of the present invention based on multi-polarization multiplexing of vanadium dioxide, wherein (a) is the two-dimensional electric field distribution result of a vortex beam with a frequency of 1.1THz and a mode of +1 in the VO2 metallic state, and (b) is the simulation result of the two-dimensional phase distribution of a vortex beam with a frequency of 1.1THz and a mode of +1 in the VO2 metallic state;

[0037] Figure 7 It is a decoupling diagram of linear polarization and two orthogonal circular polarizations of a terahertz coding metasurface embodiment of multi-polarization multiplexing based on vanadium dioxide of the present invention, wherein, (a) is when VO2 is in an insulating state, the units are periodically arranged as "000111···" along the x direction, (b) is when VO2 is in a metallic state, the units are arranged as a focused vortex beam with a focus at 1200μm and a mode of +2, (c) is when VO2 is in a metallic state, the units are arranged as a focused vortex beam with a focus at 400μm and a mode of -1;

[0038] Figure 8This is a diagram of the decoupling results of linear polarization and two orthogonal circular polarizations of a terahertz coding metasurface embodiment of the present invention based on multi-polarization multiplexing of vanadium dioxide, wherein (a) is the three-dimensional far-field simulation result when x-polarized light is incident in the VO2 insulating state, the frequency is 0.515THz, and the output is a dual beam, (b) is the electric field distribution result of a focused vortex beam with a focus at 400μm and a mode of -1 when left-handed circularly polarized light is incident in the VO2 metallic state, the frequency is 1.1THz, and the output is right-handed circularly polarized light, (c) is the electric field distribution result of a focused vortex beam with a focus at 400μm and a mode of -1 when left-handed circularly polarized light is incident in the VO2 metallic state, The phase distribution result of the focused vortex beam with the focus at 400μm and mode as -1, the frequency is 1.1THz, and the output is right-handed circularly polarized light. (d) is in the VO2 metallic state, when right-handed circularly polarized light is incident, the focus is at 1200μm, the mode is +2, the frequency is 1.1THz, and the output is left-handed circularly polarized light. (e) is in the VO2 metallic state, when right-handed circularly polarized light is incident, the focus is at 1200μm, the mode is +2, the frequency is 1.1THz, and the output is left-handed circularly polarized light.

[0039] Reference numerals

[0040] 1. Vanadium dioxide; 2. Cross ellipse; 3. Square open ring; 4. Polyimide. DETAILED DESCRIPTION

[0041] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0042] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0043] Embodiment 1

[0044] like Figure 1 and Figure 2 As shown, a terahertz coding metasurface based on multi-polarization multiplexing of vanadium dioxide includes a base plate and a dielectric layer arranged on the upper surface of the base plate, and a metal layer and vanadium dioxide (VO2) 1 are arranged on the upper surface of the dielectric layer, with a period of p = 150μm. The dielectric layer is composed of polyimide, with a thickness of t1 = 30μm, a dielectric constant of ε = 3.5, and a tangent loss of tanδ = 0.0027. The metal layer includes a square opening ring 3 and a cross ellipse 2 arranged inside the square opening ring 3. Vanadium dioxide 1 is embedded in the gap of the square opening ring 3. The outer side length of the square opening ring 3 is l = 140μm, the inner width is g = 20μm, the short axis of the cross ellipse 2 is w = 10μm, and the thickness of the metal layer and the base plate is t2 = 0.2μm. The length of vanadium dioxide 1 is l v , the horizontal ellipse size of the cross ellipse 2 is l x, the longitudinal ellipse size of the cross ellipse 2 is l y , l x With l y All are variable.

[0045] A one-bit coding metasurface can be constructed in an insulating state for x-polarization, such as Figure 3 (a) and Figure 3 As shown in (b), when the length of VO2 is 5 and 25 respectively, it corresponds to the coding units 0 and 1. At a frequency of 0.515 THz, the reflection coefficient is above 0.8 and is almost equal, and the reflection phase is close to 180°. This satisfies the one-bit coding units "0" and "1". Similarly, a one-bit coding metasurface can also be constructed in an insulating state for y polarization. When the length of VO2 is 5 and 65 respectively, it corresponds to the coding units "0" and "1". As shown in (b), when the length of VO2 is 5 and 65 respectively, it corresponds to the coding units "0" and "1". Figure 3 (c) and Figure 3 As shown in (d), the reflection coefficients of the unit structures are almost equal, and the reflection phase difference is close to 180°. Figure 3 (e) and Figure 3 As shown in (f), by adjusting l x and l y , the reflection coefficients are all above 0.87 and the phase coverage range reaches 2π, and when VO2 is in a metallic state, the structure can be regarded as isotropic, and the reflection coefficient and phase change under x-polarization incidence are consistent with those under y-polarization incidence. These ensure that the subsequent diversified manipulation of circular polarization can be carried out.

[0046] For the metasurface with co-polarization control of linear polarization and circular polarization, when VO2 is in an insulating state, a one-bit coded metasurface can be realized for y polarization at a frequency of 0.315 THz. When VO2 is in a metallic state and the phase difference is 0°, a one-bit coded metasurface can be realized for the co-polarization component of circular polarization at 1.1 THz. Figure 3 (e) and Figure 3 (f) Select l x = l y =80μm, l x = l y =67μm two units to form a one-bit coding metasurface in the metallic state. In this embodiment, a metasurface array consisting of 24×24 units is designed. When in the insulating state, the coding sequence is as follows Figure 4 As shown in (a), Figure 4 (c) shows the far-field simulation results. The reflected y-polarized THz wave is split into two lobes along the x-direction at 31.9° at 0.315 THz. When in the metallic state, the coding sequence is as follows Figure 4 As shown in (b), Figure 4(d) shows the far-field simulation results. When the left-handed circularly polarized terahertz wave is vertically irradiated onto the coding metasurface, the reflected left-handed circularly polarized terahertz wave is divided into four lobes at 40° at 1.1 THz.

[0047] For the metasurface with linear polarization and circular polarization co-polarization and cross-polarization regulation, when VO2 is in an insulating state, a one-bit coded metasurface can be realized at 0.515THz for x-polarization. When VO2 is in a metallic state and the phase difference is 90°, a two-bit coded metasurface with co- and cross-polarization components can be realized at 1.1THz for circularly polarized light. The parameters are as follows:

[0048] serial number 1 2 3 4 <![CDATA[l x (μm)]]> 80 75 67 99 <![CDATA[l y (μm)]]> 99 80 75 67

[0049] The four units can realize two-bit encoding for the co-polarization and cross-polarization components of circular polarization. When in the insulating state, the coding sequence is as follows Figure 5 As shown in (a), Figure 5 (d) shows the far-field simulation results. When the x-polarized terahertz wave is irradiated vertically onto the coding metasurface, the reflected terahertz wave is split into two lobes along the y direction at 29° at 0.315 THz. When in the metallic state, the coding sequence of the co-polarized and cross-polarized components of the circular polarization is as follows Figure 5 (b) and Figure 5 (c) Figure 5 (e) and Figure 5 (f) shows the far-field simulation results. When the left-handed circularly polarized THz wave is irradiated vertically onto the coding metasurface, the reflected left-handed circularly polarized THz wave is deflected to 29°, and the reflected right-handed circularly polarized THz wave forms a vortex beam at 1.1 THz. Figure 6 (a) and Figure 6 (b) shows the near-field results of the electric field and phase. The electric field is distributed in a ring shape, and the phase is distributed in a 360° spiral shape, which is the characteristic of a +1-order vortex beam.

[0050] For the metasurface with decoupling of linear polarization and two orthogonal circular polarizations, when VO2 is in an insulating state, a one-bit coding metasurface can be realized at 0.515THz for x-polarization. When VO2 is in a metallic state and the phase difference is 180°, a two-bit coding metasurface with cross-polarization components can be realized at 1.1THz for circularly polarized light. The parameters are as follows:

[0051] serial number 1 2 3 4 5 6 7 <![CDATA[l x (μm)]]> 72 67 12 99 85 80 76 ly(μm) 85 80 76 75 72 67 12

[0052] The seven units can realize two-bit encoding for the two orthogonal cross-polarization components of circular polarization. When in the insulating state, the coding sequence is as follows Figure 7 As shown in (a), when in the metallic state, the encoding sequence of the reflected left-handed and right-handed components is as follows Figure 7 (b) and Figure 7 (c) as shown. Figure 8 (a) shows the far-field simulation results. Under x-polarized light incidence, dual beams deflected 40.3° along the x-direction can be generated at 0.515 THz. Figure 8 (b)-(e) show the near-field simulation results. The electric field energy of left-handed circular polarization is focused at 40μm on the focal plane, and the phase spiral changes by 360°; the electric field energy of right-handed circular polarization is focused at 1200μm on the focal plane, and the phase spiral changes by 720°.

[0053] Therefore, the present invention adopts the above-mentioned vanadium dioxide-based multi-polarization multiplexing terahertz coding metasurface, which can not only make it work in linear polarization and circular polarization modes before and after the VO2 phase change, but also can independently design the co-polarization and cross-polarization of circular polarization. It has great flexibility and versatility, can expand the utilization rate of space resources, and improve the information carrying capacity of equipment.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A terahertz coding metasurface based on multi-polarization multiplexing of vanadium dioxide, characterized by: It comprises a bottom plate and a dielectric layer arranged on the upper surface of the bottom plate, the upper surface of the dielectric layer is provided with a metal layer and vanadium dioxide, and the period of the bottom plate and the dielectric layer is p=150 μm; The metal layer comprises a square opening ring and a cross ellipse arranged inside the square opening ring, and the vanadium dioxide is embedded in the gap of the square opening ring.

2. The terahertz coding metasurface with multi-polarization multiplexing based on vanadium dioxide according to claim 1, characterized in that: The transverse ellipse size of the cross ellipse is l x , the longitudinal ellipse size of the cross ellipse is l y , where l x With l y are all non-fixed values, l x With l y The length range is 10 to 100 μm.

3. The terahertz coding metasurface based on multi-polarization multiplexing of vanadium dioxide according to claim 2, characterized in that: The vanadium dioxide is a phase change material, and the reversible transformation of vanadium dioxide from an insulating state to a metallic state is regulated by temperature, as follows: When vanadium dioxide is in an insulating state, it adopts a propagation phase mode. When vanadium dioxide is in a metallic state, it has metallic properties. At this time, the length of the vanadium dioxide is l v , l v It is a non-fixed value, and its length range is 5 to 65 μm.

4. The terahertz coding metasurface based on multi-polarization multiplexing of vanadium dioxide according to claim 3, characterized in that: When the vanadium dioxide is in a metallic state, the square open ring is closed to form an isotropic structure.

5. The terahertz coding metasurface based on multi-polarization multiplexing of vanadium dioxide according to claim 4, characterized in that: The dielectric layer is polyimide, with a thickness of t1 = 30 μm, a dielectric constant of ε = 3.5, and a tangent loss of tanδ = 0.0027.

6. The terahertz coding metasurface with multi-polarization multiplexing based on vanadium dioxide according to claim 5, characterized in that: The outer side length of the square open ring is l=140 μm, the inner width is g=20 μm, and the minor axis of the cross ellipse is w=10 μm.

7. Application of the vanadium dioxide-based multi-polarization multiplexing terahertz coding metasurface according to any one of claims 1 to 6 in a metasurface array of 24×24 units.

8. The terahertz coding metasurface with multi-polarization multiplexing based on vanadium dioxide according to claim 7, characterized in that: When in the insulating state, when a y-polarized terahertz wave is vertically irradiated onto the metasurface array, the reflected y-polarized terahertz wave is split into two lobes along the x-direction at 31.9° at 0.315 THz; When in a metallic state, when a left-handed circularly polarized terahertz wave is vertically irradiated onto the metasurface array, the reflected left-handed circularly polarized terahertz wave is divided into four lobes at 40° at 1.1 THz.

9. The terahertz coding metasurface with multi-polarization multiplexing based on vanadium dioxide according to claim 7, characterized in that: When in the insulating state, when an x-polarized terahertz wave is vertically irradiated onto the metasurface array, the reflected terahertz wave is split into two lobes along the y direction at 29° at 0.315 THz; When in the metallic state, when a left-handed circularly polarized terahertz wave is irradiated vertically onto the metasurface array, the reflected left-handed circularly polarized terahertz wave is deflected to 29°, and the reflected right-handed circularly polarized terahertz wave forms a vortex beam at 1.1 THz, with a phase spiral distribution of 360°, which is the characteristic of a +1-order vortex beam.

10. The terahertz coding metasurface with multi-polarization multiplexing based on vanadium dioxide according to claim 7, characterized in that: When in the insulating state, when an x-polarized terahertz wave is vertically irradiated onto the metasurface array, the reflected terahertz wave is split into two lobes along the x-direction at 40.3° at 0.515 THz; When in a metallic state, the electric field energy of the left-handed circular polarization of the metasurface array is focused at 40 μm on the focal plane, and the phase spiral changes by 360°; the electric field energy of the right-handed circular polarization is focused at 1200 μm on the focal plane, and the phase spiral changes by 720°.

Images