Vanadium dioxide dual-function terahertz metasurface and coding metasurface for 6G communication

Abstract

The present invention provides a vanadium dioxide dual-function terahertz metasurface and a coding metasurface for 6G communication. The vanadium dioxide dual-function terahertz metasurface includes at least one metasurface unit structure, wherein each metasurface unit structure includes a silicon layer, an intermediate dielectric layer and a phase change layer which are sequentially arranged from top to bottom, the silicon layer is a square silicon column with the same side length, and the four corner positions of the square silicon column are corner blocks with the same side length, the maximum length of the corner blocks located on the same side of the square silicon column constitutes the structural side length of the square silicon column, the phase change layer is a block with the same side length made of vanadium dioxide, when at room temperature, the vanadium dioxide of the phase change layer is in a dielectric state, and the metasurface unit structure transmits a terahertz beam; when at high temperature, the vanadium dioxide of the phase change layer is in a metallic state, and the metasurface unit structure reflects the terahertz beam, and a terahertz coding metasurface is designed based on the vanadium dioxide dual-function terahertz metasurface, which can be applied to the field of 6G communication.

Description

Technical Field

[0001] The present invention relates to the field of electromagnetic metasurface technology and terahertz beam control, and in particular to a vanadium dioxide dual-function terahertz metasurface and a coding metasurface for 6G communication. Background Art

[0002] Terahertz coding metasurface is a research field that combines terahertz technology and metamaterial concepts. The frequency band of terahertz waves is between microwaves and infrared light, and has broad application prospects in security inspection, nondestructive testing, communications, astronomy and other fields. Coding metasurface refers to the use of the concept of digital coding to design metasurfaces, and the coding function of electromagnetic waves is realized through the combination of different units. This design method simplifies the design process of metamaterials and makes the manipulation of electromagnetic waves more flexible. The terahertz coding metasurface obtained by applying coding technology to the terahertz band can realize efficient modulation and processing of terahertz waves. For example, in terahertz imaging and communication systems, coding metasurfaces can be used to improve the signal processing capabilities of the system or enhance the security of the system. In addition, due to the high frequency characteristics of terahertz waves, the use of coding metasurfaces can also explore new multifunctional integrated solutions, such as multiplexing, beamforming and other advanced functions.

[0003] At present, most of the metasurfaces studied are generally reflective metasurfaces, and the application of reflective metasurfaces is limited in some fields, such as indoor signal transmission and near-field projection enhancement, so a transmissive metasurface is needed to complement the shortcomings and defects of reflective metasurfaces. Although there are a small number of prior arts that disclose the design of dual-function metasurfaces, such as the prior art CN111665588A discloses a dual-function polarizer based on a vanadium dioxide and Dirac semimetal composite metasurface, each device structure unit includes a silicon dioxide layer and a vanadium dioxide layer from top to bottom, two Dirac semimetal U-shaped structures are arranged above the silicon dioxide layer, and a wire grid is arranged below the vanadium dioxide layer, but this scheme focuses on the dual excitation control of transmission and reflection polarization through the Fermi level control of the Dirac semimetal, which is applied to polarization conversion and wave plate design, and requires additional electrical control or material adjustment and relies on electrical control elements.

[0004] In addition, most of the current two-bit coded metasurface sensors are designed for 5G millimeter wave communications and satellite communications, focusing on reflection control and gain enhancement of high-frequency signals, and emphasizing electronic programmability and dynamic phase adjustment. For example, the prior art CN115513669B realizes electronic phase adjustment by loading diodes between metal layers. However, the phase difference of this coded metasurface sensor relies on the state change of the diode and different metal layer combinations. The phase is controlled by switching the switching state of the diode, which requires high precision manufacturing of the diode and the metal layer, and may have large losses and complex manufacturing processes at high frequencies. It cannot be applied to various terahertz beam steering (such as splitting, deflection, OAM vortex beam generation) in the 6G communication field.

[0005] In summary, the dual-function metasurface structure and operation control method of the prior art are relatively complex, and do not focus on the design of a simple dual-function metasurface sensor with switching between transmission and reflection; the phase control method of the coded metasurface in the prior art is complex and has not been well applied to terahertz beam control in the field of 6G communications. Summary of the invention

[0006] The purpose of the present invention is to provide a vanadium dioxide dual-function terahertz metasurface and a coded metasurface for 6G communication, and to design a dual-function terahertz metasurface unit that changes the transmission and reflection states by temperature control. At the same time, based on the dual-function terahertz metasurface unit, a terahertz coded metasurface with different codes is designed to realize terahertz beam control in the field of 6G communication.

[0007] To achieve the above objectives, the present technical solution provides a 6G communication vanadium dioxide dual-function terahertz metasurface, comprising: at least one metasurface unit structure, wherein each metasurface unit structure comprises a silicon layer, an intermediate dielectric layer and a phase change layer arranged in sequence from top to bottom, the silicon layer is a square silicon column with the same side length, and the four corners of the square silicon column are corner blocks with the same side length, the maximum length of the corner blocks on the same side of the square silicon column constitutes the structural side length of the square silicon column, the phase change layer is a block with the same side length made of vanadium dioxide, when at room temperature, the vanadium dioxide in the phase change layer is in a dielectric state, and the metasurface unit structure transmits the terahertz beam; when at high temperature, the vanadium dioxide in the phase change layer is in a metallic state, and the metasurface unit structure reflects the terahertz beam.

[0008] Secondly, the present solution provides a terahertz coding metasurface, which achieves a 2-bit coding effect, including: four groups of coding units composed of a square array of metasurface unit structures, the metasurface unit structures in the same coding unit are the same, and the structural side lengths of the metasurface unit structures in different coding units are different, and the normalized phases of the four groups of coding units are 0°, 90°, 180°, and 270°, respectively.

[0009] On the third aspect, the present scheme provides a terahertz coding metasurface, which achieves a 1-bit coding effect, including: two groups of coding units composed of a square array of metasurface unit structures, the metasurface unit structures in the same coding unit are the same, the structural side lengths of the metasurface unit structures in different coding units are different, and the phase difference between the two groups of coding units is 180°.

[0010] In a fourth aspect, the present scheme provides an application method of a terahertz coding metasurface for beam steering, comprising the following steps: arranging a first coding unit, a second coding unit, a third coding unit, and a fourth coding unit in sequence as a periodic coding unit, arranging at least two periodic coding units along the X-axis direction and the Y-axis direction, respectively, and the number of periodic coding units in the X-axis direction and the Y-axis direction is the same.

[0011] In a fifth aspect, the present invention provides an application method of a terahertz coding metasurface, comprising the following steps: calculating the phase difference of the OAM beam and introducing a spiral phase, and setting different coding units at different positions according to the phase difference.

[0012] Compared with the prior art, this technical solution has the following characteristics and beneficial effects:

[0013] 1. The vanadium dioxide dual-function terahertz metasurface for 6G communication in this solution uses vanadium dioxide as a phase change material, and controls the transmission and reflection modes of terahertz waves by adjusting the external temperature. When vanadium dioxide is in a dielectric state, the device acts as a transmission metasurface, which can achieve beam splitting and deflection in the 1.3THz frequency band; and when vanadium dioxide is in a metallic state, the device acts as a reflection metasurface, achieving similar functions in the 1THz frequency band. This innovation greatly expands the modulation range of electromagnetic waves in space and realizes flexible switching of functions.

[0014] Second, the terahertz coding metasurface of this scheme introduces the binary concept in computers into the design of metasurface units, designs a 2-bit coding metasurface, and designs 4 different coding units by optimizing structural parameters, corresponding to phase differences of 0°, 90°, 180° and 270°. Through Fourier convolution calculation, the complex beam control problem is simplified to a coding design problem, which can extend the direction of the reflected beam to 8 directions and realize precise control of electromagnetic waves. This coding design not only simplifies the design process of traditional metasurfaces, but also expands the phase control capability through high-bit coding, improving the flexibility and efficiency of metasurfaces in practical applications.

[0015] 3. The terahertz coding metasurface of this scheme can also be expanded to generate OAM (orbital angular momentum) vortex beams. A vortex beam coding metasurface that can generate a topological charge number of 1 is designed. This beam has the characteristics of high directivity and low divergence angle, which provides important support for 6G wireless communication and terahertz beam control. This innovation not only expands the types of beams, but also provides flexible beam control methods, which is suitable for application scenarios of enhancing signal coverage and reducing blind spots. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a structural diagram of a vanadium dioxide dual-function terahertz metasurface for 6G communication according to an embodiment of the present invention.

[0017] Figure 2 It is the unit amplitude phase diagram of different coding units.

[0018] Figure 3 The two-beam and four-beam 3D images of the terahertz-coded metasurface in the reflection state of 1 bit.

[0019] Figure 4 The two-beam and four-beam 3D images of the terahertz-coded metasurface in the transmission state of 1 bit.

[0020] Figure 5 It is a schematic diagram of the Fourier convolution calculation process.

[0021] Figure 6 is a schematic diagram of the OAM beamforming image. DETAILED DESCRIPTION

[0022] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0023] Those skilled in the art should understand that, in the disclosure of the present invention, the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0024] It is to be understood that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the element may be multiple, and the term "one" should not be understood as a limitation on the quantity.

[0025] Embodiment 1

[0026] This solution provides a 6G communication vanadium dioxide dual-function terahertz metasurface that can change the working mode of transmitting or reflecting terahertz beams through temperature. The vanadium dioxide dual-function terahertz metasurface has dual functions of transmission and reflection. The state of vanadium dioxide is changed by temperature regulation to achieve the transmission and reflection switching of terahertz waves, support the splitting, deflection and generation of vortex beams of multiple beams, and greatly expand the modulation space of electromagnetic waves in space. In addition, the terahertz metasurface provided by this solution can realize passive dynamic function switching, and is simpler in the control scheme and is suitable for a wide range of terahertz applications.

[0027] like Figure 1 As shown, the vanadium dioxide dual-function terahertz metasurface for 6G communication provided by this solution includes: at least one metasurface unit structure, wherein each metasurface unit structure includes a silicon layer, an intermediate dielectric layer, and a phase change layer arranged in sequence from top to bottom, the silicon layer is a square silicon column with the same side length, and the four corners of the square silicon column are corner blocks with the same side length, and the phase change layer is a block with the same side length made of vanadium dioxide.

[0028] Each supersurface unit structure of the vanadium dioxide dual-function terahertz supersurface for 6G communication provided by this solution is a three-layer structure, the top layer is a square silicon column, the middle layer is an intermediate dielectric layer, and the lower layer is a phase change layer using vanadium dioxide as a phase change material. When the ambient temperature is at room temperature, the vanadium dioxide in the phase change layer is in a dielectric state, and the supersurface unit structure can transmit the terahertz beam to realize the transmission function; when the ambient temperature is at a high temperature, the vanadium dioxide in the phase change layer is in a metallic state, and the supersurface unit structure can reflect the terahertz beam to realize the reflection function, thereby realizing the transmission and reflection of passive terahertz beams through temperature control.

[0029] In other words, when at room temperature, the vanadium dioxide in the phase change layer is in a dielectric state, and the metasurface unit structure transmits the terahertz beam; when at high temperature, the vanadium dioxide in the phase change layer is in a metallic state, and the metasurface unit structure reflects the terahertz beam. In some embodiments, when the ambient temperature is 68°C, the vanadium dioxide in the phase change layer is in a metallic state.

[0030] This scheme uses square silicon pillars as the top layer of the metasurface unit structure. The dielectric constant of the square silicon pillars is ε =11.9. "Silicon" as the structural material of the top layer can provide a high dielectric constant, which is conducive to regulating the phase of electromagnetic waves. At the same time, the processing of silicon materials is relatively mature. The square silicon pillars required for this scheme can be formed by electronic etching or photolithography technology. The shape design of the silicon pillars can meet the phase requirements of different coding units of the subsequent terahertz coding metasurface, thereby realizing flexible control of the terahertz beam.

[0031] The material of the intermediate dielectric layer of this scheme is polytetrafluoroethylene, the dielectric constant of polytetrafluoroethylene is ε =2.65, and the tangent loss is 0.001. The reason why polytetrafluoroethylene is selected as the intermediate dielectric layer of the metasurface unit structure is that polytetrafluoroethylene is an ideal plate material because it is a dielectric substrate working at high frequencies, and its dielectric constant is required to be small and stable, and it has good corrosion resistance, pressure resistance, and high temperature resistance.

[0032] In some embodiments, the square silicon pillar includes corner blocks located at four corners and side lines connecting adjacent corner blocks, wherein the four corner blocks have the same size, the side lines have the same width, and the width of the corner blocks is greater than the width of the side lines. Figure 1 As shown, the maximum length of the corner squares on the same side of the square silicon column constitutes the structural side length L of the square silicon column. In other words, the structural side length L of the square silicon column is the sum of the length of the side line and the lengths of the two corner squares.

[0033] In some embodiments, the height H3 of the square silicon column is 20 μm, the height H2 of the intermediate dielectric layer is 20 μm, the height H1 of the phase change layer is 0.5 μm, the square side length P of the phase change layer is 120 μm, and when the vanadium dioxide in the phase change layer is in a dielectric state, the conductivity of the phase change layer is 50 S / m. The vanadium dioxide dual-function terahertz metasurface for 6G communication can be used as a transmission metasurface, which can realize beam splitting and deflection in the 1.3THz frequency band; when the vanadium dioxide in the phase change layer is in a metallic state, the conductivity of the phase change layer is 20000 S / m. The vanadium dioxide dual-function terahertz metasurface for 6G communication can be used as a reflection metasurface, which can realize beam splitting and deflection in the 1THz frequency band. It should be noted that the vanadium dioxide dual-function terahertz metasurface for 6G communication designed in this scheme meets the transmission phase theory and simulation optimization results, which can ensure that the performance meets expectations when simulating in the terahertz frequency band, and greatly expands the modulation range of electromagnetic waves in space, realizing flexible switching of the dual functions of transmission and reflection.

[0034] Embodiment 2

[0035] As shown in Example 1, the vanadium dioxide dual-function terahertz metasurface for 6G communication can realize beam splitting and deflection functions in the terahertz band. This solution introduces binary in computers into the metasurface design to obtain a terahertz coding metasurface that can realize binary coding. For a 1-bit coded metasurface, it contains two different coding elements, 0 and 1, and requires the phase difference between the two to reach 180°. Based on this concept, this solution discretizes the phase within the range of 2π, thereby expanding higher bit coding. The phase difference required for any bit coding satisfies 2π / 2N, where N represents the number of designed bits.

[0036] This solution provides a terahertz coding metasurface that can achieve a 2-bit coding effect, including: four groups of coding units composed of a square array of metasurface unit structures, the metasurface unit structures in the same coding unit are the same, the structure side lengths of the metasurface unit structures in different coding units are different, and the normalized phases of the four groups of coding units are 0°, 90°, 180°, and 270° respectively. It should be noted that the size of each metasurface unit structure is determined by the size P of the phase change layer, so the size of each metasurface unit structure is the same, only the structure side lengths of the metasurface unit structures are different. Specifically, the coding unit whose structural side length of the super surface unit structure is 30 μm is defined as the first coding unit, the coding unit whose structural side length of the super surface unit structure is 45 μm is defined as the second coding unit, the coding unit whose structural side length of the super surface unit structure is 62 μm is defined as the third coding unit, and the coding unit whose structural side length of the super surface unit structure is 72 μm is defined as the fourth coding unit, wherein the normalized phases of the first coding unit, the second coding unit, the third coding unit and the fourth coding unit are 0°, 90°, 180° and 270° respectively. As mentioned above, although the structural side length of the super surface unit structure on each coding unit is different, the size of the super surface unit structure is the same, and the size of each coding unit is the same.

[0037] It should be noted that the supersurface unit structure in each coding unit is exactly the same, and the specific structure of the supersurface unit structure is shown in Example 1, where the structural side length of the supersurface unit structure refers to the maximum length of the corner squares located on the same side of the square silicon column.

[0038] Since a single metasurface unit structure is difficult to show periodic characteristics, this solution needs to arrange the metasurface unit structure in an n*n square array to improve the periodicity. In the embodiment of this solution, each coding unit is composed of a 3*3 square array of metasurface unit structures. In other words, each coding unit is composed of 9 identical metasurface unit structures repeatedly arranged. These identical metasurface unit structures achieve consistent phase and amplitude properties through the same structural parameters. This repeated design ensures the functional consistency and performance controllability of the entire terahertz coding metasurface, and can also increase the area of ​​interaction between electromagnetic waves and matter.

[0039] In some embodiments, each group of coding units in the terahertz coding metasurface provided by the present solution that can achieve a 2-bit coding effect contains at least one coding unit, and four groups of coding units are arranged in a set order.

[0040] It should be noted that the phase property of electromagnetic waves is a value that cycles with a period of 2π. The different structural side lengths L of the square silicon column affect the resonance conditions and propagation paths of the electromagnetic waves, and the phase values ​​of the responses of the coding units are different. If an initial value is set to a phase value of 0, then in a 2-bit terahertz coding metasurface, the phase difference is 2π / 4, which is equal to 90°, and then the normalized phases of each coding unit are given as 0°, 90°, 180°, and 270°. As mentioned above, the geometric scale of the coding unit is directly related to the wavelength of the electromagnetic wave. Different structural side lengths make the coding unit produce different phase responses to the wavelength adjustment. Therefore, this scheme can adjust the degree of phase modulation of the unit to the electromagnetic wave by changing the structural side length of the square silicon column of each coding unit.

[0041] Four discrete phase states are required for the 2-bit coding effect, usually 0°, 90°, 180° and 270°. These phase states represent four different coding states (0, 1, 2, 3). Each coding unit corresponds to a specific phase. These discrete phases allow precise control of the reflected phase of electromagnetic waves through specially designed coding units. Corresponding to the coding units of this scheme, the first coding unit corresponds to coding state 0, with a phase of 0°; the second coding unit corresponds to coding state 1, with a phase of 90°; the third coding unit corresponds to coding state 2, with a phase of 180°; the fourth coding unit corresponds to coding state 3, with a phase of 270°. The normalized phase table corresponding to the four coding units of the terahertz coding metasurface of this scheme is shown in Table 1:

[0042] Table 1 Normalized phase table of coding unit

[0043] .

[0044] This scheme simulates and verifies the designed terahertz coding metasurface and obtains the reflection amplitude curves of different coding units as shown in the following figure: Figure 2 As shown in (a) in the figure, the reflection phase curve is Figure 2 As shown in (b) in the figure, the transmission amplitude curve is Figure 2 As shown in (c) in the figure, the transmission phase curve is Figure 2 As shown in (d), from the reflection amplitude curve, it can be seen that the coding unit designed in this scheme can achieve a reflectivity of more than 80% in the range of 0.7-1.2 THz, and from the reflection phase curve, it can be seen that the coding unit designed in this scheme can also reach 90° (±10°) in a relatively uniform range of 0.7-1.2 THz, which perfectly meets the design principle of 2-bit reflection coding metasurface. From the transmission amplitude curve and the transmission phase curve, it can be seen that when the phase change layer switches the conductivity property, the electromagnetic properties of the device change, which is manifested in that each coding unit of the device can achieve a transmittance of more than 80% in the range of 1.22-1.38 THz. At the same time, the phase difference between each coding unit also well maintains the conditions required for 2-bit coding.

[0045] This scheme introduces the binary concept in computers into the design of metasurface units, designs a 2-bit coded metasurface, and designs four different coding units by optimizing structural parameters, corresponding to phase differences of 0°, 90°, 180° and 270°. This coding design not only simplifies the design process of traditional metasurfaces, but also expands the phase control capability through high-bit coding, thereby improving the flexibility and efficiency of metasurfaces in practical applications.

[0046] Embodiment 3

[0047] This solution also provides a terahertz coding metasurface that achieves a 1-bit coding effect, which can realize dual functions of reflection or transmission, including: two groups of coding units composed of a square array of metasurface unit structures, the metasurface unit structures in the same coding unit are the same, the structural side lengths of the metasurface unit structures in different coding units are different, and the phase difference between the two groups of coding units is 180°.

[0048] In some embodiments, the coding units are arranged in sequence to obtain a terahertz coding metasurface.

[0049] In some embodiments, the first coding unit and the third coding unit, or the second coding unit and the fourth coding unit can be arranged in sequence to obtain a terahertz coding metasurface.

[0050] Exemplarily, this scheme designs a terahertz coding metasurface composed of a first coding unit and a third coding unit arranged in sequence, and 8 first coding units and third coding units are periodically arranged in sequence along the X-axis direction to obtain a terahertz coding metasurface. At this time, the coding state of the terahertz coding metasurface is arranged as "02020202...", and is composed of a total of 24*24 metasurface unit structures. The perimeter Γ of each metasurface unit structure is equal to P×3×2, that is, 720 μm.

[0051] The ambient temperature is controlled to 68°C. At this time, the phase change layer is in a metallic state, and the corresponding vanadium dioxide conductivity is 20000S / m. At this time, the designed terahertz coding metasurface works in reflection mode. The simulation verification shows that under 1THz, the three-dimensional far-field diagram of the coded binary beam "02020202..." in the x-axis direction is as follows Figure 3 As shown in (a), at 1 THz, the three-dimensional far-field image of the chessboard-coded four-beam is as follows Figure 3 as shown in (b).

[0052] The ambient temperature is controlled to be room temperature. At this time, the phase change layer is in the dielectric state with a conductivity of 50 S / m. At this time, the designed terahertz coding metasurface works in the transmission mode. The simulation verification shows that at 1.3 THz, the three-dimensional far-field image of the transmission coding metasurface is arranged periodically along the x-axis in the coding mode of "02020202..." as shown in the figure. Figure 4 As shown in (a), at 1.3 THz, the three-dimensional far-field image of the chessboard-coded four-beam is as follows Figure 4 as shown in (b).

[0053] Embodiment 4

[0054] As described above, Example 2 provides a terahertz coding metasurface that can achieve a 2-bit coding effect. Since the electromagnetic field not only propagates linear momentum but also angular momentum, the incident wave can be flexibly adjusted through the coding metasurface to obtain OAM waves. That is, the terahertz coding metasurface that can achieve a 2-bit coding effect provided by this scheme can convert the incident plane wave into a wavefront with a specific phase gradient, thereby generating an OAM beam, and the coding metasurface beam deflection angle can be changed through phase encoding with different gradients, thereby achieving beam control.

[0055] Specifically, this solution provides an application method of a terahertz coding metasurface for beam steering, comprising the following steps:

[0056] The first coding unit, the second coding unit, the third coding unit, and the fourth coding unit are arranged in sequence as a periodic coding unit; at least two periodic coding units are arranged along the X-axis direction and the Y-axis direction, respectively, and the number of periodic coding units in the X-axis direction and the Y-axis direction is the same. It should be noted that the coding states of the first coding unit, the second coding unit, the third coding unit, and the fourth coding unit represent 0, 1, 2, and 3, respectively. In this scheme, the coding units are periodically arranged along the X-axis direction and the Y-axis direction in the order of "01230123...", and then multiple reflected wave azimuths can be obtained by Fourier convolution superposition of the codes in the X-axis direction and the Y-axis direction.

[0057] In this scheme, since the normalized phase angles of the first coding unit, the second coding unit, the third coding unit, and the fourth coding unit are 0°, 90˚, 180˚, and 270˚, respectively, the azimuth angle of the reflected wave can be expanded to 8 through Fourier convolution superposition. This scheme uses a 2-bit terahertz coding metasurface to achieve more sophisticated beam deflection control by changing the coding period and applying convolution operations. This diversified beam control capability provides more abundant options for the application of terahertz waves in wireless communications and radar stealth.

[0058] For example, in this scheme, 4 periodic coding units are arranged along the X-axis direction and the Y-axis direction, respectively. Then, the calculated phase angles of the X-code and the Y-code are 0° and 270°, respectively. It can be clearly seen that the azimuth angle φ of the beam after Fourier superposition is equal to the superposition of the x and y coding modes 315°. The specific arrangement is as follows: Figure 5 shown.

[0059] In addition, the present invention provides an application method of a terahertz coding metasurface for generating an OAM beam, comprising the following steps: calculating the phase difference of the OAM beam and introducing a spiral phase, and setting different coding units at different positions according to the phase difference.

[0060] It should be noted that the above-mentioned method of applying the terahertz coding metasurface to beam steering is to form multiple azimuth angles to achieve control of the terahertz beam, while this application method is to apply the terahertz coding metasurface to OAM waves to illustrate that the terahertz coding metasurface of this scheme has multifunctional properties.

[0061] Specifically, in order to generate an OAM beam with topological charge l=1, this scheme can use four coding units with phase differences Δϕ=0,π / 2,π,3π / 2 corresponding to 0, 1, 2, 3. The phase distribution diagram of the vortex wave metasurface with topological charge L=1 is shown as follows: Figure 6 As shown in (a), this scheme arranges the coding units according to the phase difference of the phase distribution to obtain the OAM vortex beam metasurface.

[0062] In some embodiments, in order to obtain an OAM beam generating a topological charge l=1, the present scheme sets different coding units at different positions according to the phase difference to obtain an OAM vortex beam metasurface, wherein the OAM vortex beam metasurface is a square consisting of a first region, a second region, a third region and a fourth region with phase differences of 0, π / 2, π, 3π / 2, respectively, wherein the first region is provided with a first coding unit composed of a square array of metasurface unit structures, the second region is provided with a second coding unit composed of a square array of metasurface unit structures, the third region is provided with a third coding unit composed of a square array of metasurface unit structures, and the fourth region is provided with a fourth coding unit composed of a square array of metasurface unit structures, the first region, the second region, the third region and the fourth region are arranged counterclockwise to obtain a square, and the areas of the first region, the second region, the third region and the fourth region are the same.

[0063] In some embodiments, the first region is a first coding unit in which the metasurface unit structure is arranged in a 10*10 matrix, the second region is a second coding unit in which the metasurface unit structure is arranged in a 10*10 matrix, the third region is a third coding unit in which the metasurface unit structure is arranged in a 10*10 matrix, and the fourth region is a fourth coding unit in which the metasurface unit structure is arranged in a 10*10 matrix. In this way, a 20×20 OAM vortex beam metasurface with a topological charge L=1 and a phase difference of Δφ=π / 2 is formed, realizing unit combinations with four phase differences of 0, 1, 2, and 3. The 20*20 here refers to the metasurface unit structure.

[0064] The OAM vortex beam metasurface with topological charge L=1 designed in this scheme is shown in Figure 6 As shown in (b), Figure 6 (b) shows the image of the vortex beam generated by terahertz wave excitation at 1 THz. From the simulation results, it can be clearly identified that its main feature is that the central beam amplitude is zero, which is a typical OAM characteristic beam with high directivity and small divergence angle. In addition, at a distance of 500 μm from the plane of the OAM vortex beam metasurface, the electric field phase distribution of the designed OAM metasurface is simulated and obtained as shown in the figure Figure 6 As shown in (c), it can be seen that the transmission of the L = 1 OAM vortex beam metasurface generated by our proposal is reliable and stable.

[0065] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other various forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, all technical solutions that are the same or similar to those of the present application fall within the protection scope of the present invention.

Claims

1. A vanadium dioxide dual-function terahertz metasurface for 6G communication, characterized in that: include: At least one super surface unit structure, wherein each super surface unit structure comprises a silicon layer, an intermediate dielectric layer and a phase change layer arranged in sequence from top to bottom, the silicon layer is a square silicon column with the same side length, and the square silicon column comprises corner blocks located at four corner positions and side lines connecting adjacent corner blocks, wherein the four corner blocks have the same size, the side lines have the same width, and the width of the corner blocks is greater than the width of the side lines, the maximum length of the corner blocks located on the same side of the square silicon column constitutes the structural side length of the square silicon column, the phase change layer is a block with the same side length made of vanadium dioxide, when at room temperature, the vanadium dioxide in the phase change layer is in a dielectric state, and the super surface unit structure transmits a terahertz beam; when at a high temperature, the vanadium dioxide in the phase change layer is in a metallic state, and the super surface unit structure reflects a terahertz beam.

2. The vanadium dioxide dual-function terahertz metasurface for 6G communication according to claim 1, characterized in that: The height of the square silicon column is H3 = 20 μm, the height of the intermediate dielectric layer is H2 = 20 μm, the height of the phase change layer is H1 = 0.5 μm, and the square side length P of the phase change layer is 120 μm.

3. The vanadium dioxide dual-function terahertz metasurface for 6G communication according to claim 1, characterized in that: The material of the middle dielectric layer is polytetrafluoroethylene.

4. A terahertz coding metasurface, characterized in that: include: Four groups of coding units are composed of a square array arrangement of the supersurface unit structures according to any one of claims 1 to 3, the supersurface unit structures in the same coding unit are the same, and the structural side lengths of the supersurface unit structures in different coding units are different, the normalized phases of the four groups of coding units are 0°, 90°, 180°, and 270°, respectively, the first coding unit corresponds to coding state 0, and the phase is 0°; the second coding unit corresponds to coding state 1, and the phase is 90°; the third coding unit corresponds to coding state 2, and the phase is 180°; the fourth coding unit corresponds to coding state 3, and the phase is 270°.

5. The terahertz coding metasurface according to claim 4, characterized in that: Among them, the coding unit with a structural side length of 30μm of the supersurface unit structure is defined as the first coding unit, the coding unit with a structural side length of 45μm of the supersurface unit structure is defined as the second coding unit, the coding unit with a structural side length of 62μm of the supersurface unit structure is defined as the third coding unit, and the coding unit with a structural side length of 72μm of the supersurface unit structure is defined as the fourth coding unit.

6. The terahertz coding metasurface according to claim 4, characterized in that: Each coding unit is composed of a metasurface unit structure arranged in a 3*3 square matrix.

7. A terahertz coding metasurface, characterized in that: include: Two groups of coding units composed of a square array arrangement of metasurface unit structures according to any one of claims 1 to 3, the metasurface unit structures in the same coding unit are the same, the structural side lengths of the metasurface unit structures in different coding units are different, the phase difference between the two groups of coding units is 180°, the first coding unit corresponds to coding state 0, the phase is 0°; the second coding unit corresponds to coding state 1, the phase is 90°; the third coding unit corresponds to coding state 2, the phase is 180°; the fourth coding unit corresponds to coding state 3, the phase is 270°, the first coding unit and the third coding unit, or the second coding unit and the fourth coding unit are arranged in sequence to obtain a terahertz coding metasurface.

8. An application method of the terahertz coding metasurface according to claim 5, applied to beam steering, characterized in that: The following steps are involved: The first coding unit, the second coding unit, the third coding unit, and the fourth coding unit are arranged in sequence as a periodic coding unit, at least two periodic coding units are arranged along the X-axis direction and the Y-axis direction, and the number of periodic coding units in the X-axis direction and the Y-axis direction is the same.

9. An application method of the terahertz coding metasurface according to claim 5, characterized in that: The following steps are involved: The phase difference of the OAM beam is calculated and the spiral phase is introduced, and different coding units are set at different positions according to the phase difference.

10. The application method of the terahertz coding metasurface according to claim 9, characterized in that: The following steps are involved: An OAM vortex beam metasurface is obtained by setting different coding units at different positions according to the phase difference, wherein the OAM vortex beam metasurface is a square composed of a first region, a second region, a third region and a fourth region with phase differences of 0, π / 2, π, 3π / 2 respectively, wherein a first coding unit composed of a square array of metasurface unit structures is arranged in the first region, a second coding unit composed of a square array of metasurface unit structures is arranged in the second region, a third coding unit composed of a square array of metasurface unit structures is arranged in the third region, and a fourth coding unit composed of a square array of metasurface unit structures is arranged in the fourth region, the first region, the second region, the third region and the fourth region are arranged counterclockwise to obtain a square, and the areas of the first region, the second region, the third region and the fourth region are the same.

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