Coding metasurface with terahertz wave absorption and reflection functions and application

Abstract

The invention provides a coding metasurface with terahertz wave absorption and reflection functions and application, the coding metasurface comprises at least one coding unit arranged in an array, each coding unit comprises a top resonance layer, a dielectric layer and a metal reflection layer which are sequentially arranged from top to bottom, the top resonance layer comprises a graphene resonance layer and a vanadium dioxide phase change layer, and the dielectric layer comprises a dielectric layer and a metal reflection layer. The graphene resonance layer comprises square graphene, the vanadium dioxide phase change layer comprises a square vanadium dioxide outer ring and a vanadium dioxide strip embedded in the vanadium dioxide outer ring, the vanadium dioxide outer ring is located on the inner side of the graphene, and the square edge of the vanadium dioxide outer ring and the square edge of the graphene are arranged in parallel at an interval; wherein the vanadium dioxide strips are arranged at the diagonal positions of the vanadium dioxide outer ring and are arranged at intervals with the vanadium dioxide outer ring, the advantages of a wave-absorbing metasurface and a reflection coding metasurface are integrated, and the signal generation power of 6G communication is greatly optimized.

Description

Technical Field

[0001] The present invention relates to the field of terahertz metamaterial functional device design, and particularly to a coded metasurface with both terahertz wave absorption and reflection functions and its applications, specifically to the ultra-wideband absorption and reflection phase regulation of electromagnetic waves and the multi-functional switching technology. Background Art

[0002] Due to its advantages such as wide coverage and high mobility, unmanned aerial vehicles (UAVs) play an important role in the field of wireless communication. However, in actual application scenarios, due to the complex urban environment, the communication quality of UAV communication networks will be severely reduced due to attenuation, obstacles, and the presence of eavesdroppers, thus generating risks. The rise of the sixth-generation mobile communication (6G) technology brings new hope. It has the characteristics of high network rate, ultra-low latency, and wider coverage, and its working frequency band is extended to the terahertz band, showing great application potential in frontier fields such as holographic communication and wireless backhaul networks. If the 6G communication technology can be applied to the UAV scenario, it is expected to provide strong support for UAV communication and effectively solve the existing communication problems.

[0003] However, to achieve the deep integration of 6G technology and UAV communication, the metasurface design of terahertz communication devices has become a key limiting factor. Currently, there are many technical bottlenecks in metasurface design: 1. Most metasurfaces rely on single materials or regulation mechanisms, making it difficult to achieve multi-functional integration and dynamic regulation. For example, although traditional metal resonator designs can achieve certain phase regulation, they lack flexibility and are difficult to switch between absorption and reflection functions. 2. Existing metasurface designs are also mostly limited to a single frequency band and are difficult to meet the application requirements of wide frequency bands and multi-frequency bands. For example, some metasurface designs can only achieve perfect absorption within a specific frequency band and perform poorly in other frequency bands. 3. Metasurface designs usually rely on fixed structural parameters and are difficult to achieve dynamic regulation. For example, some metasurface designs need to change the pattern of metal resonators to achieve different functions, which is difficult to implement in actual applications.

[0004] Focusing on the terahertz sensor level, the key technical problems existing therein further exacerbate the above-mentioned dilemmas: 1. The problem of mutually exclusive functions of symmetric structures: Traditional symmetric resonant units will excite multiple degenerate modes at specific frequencies, resulting in the overlap of absorption peaks and phase regulation peaks. These degenerate modes interfere with each other, not only compressing the absorption bandwidth but also limiting the phase regulation range. Wideband absorption requires the broadbanding of impedance matching, while phase regulation requires a specific phase gradient distribution, and symmetric structures are difficult to meet both of these requirements simultaneously.

[0005] 2. Insufficient flexibility in single regulation: The existing technologies cannot integrate broadband absorption and phase regulation functions in the same device. Absorption is often achieved only at specific frequency points and is not compatible with phase regulation. In addition, the realization of transmissive and reflective functions depends on replacing the device and cannot be flexibly integrated within the same device.

[0006] 3. Limitations in beam regulation dimensions: The degenerate modes excited by the symmetric structure cause the beam to propagate only in a fixed direction, with fixed and single modes. The switching between transmissive and reflective modes also depends on replacing the device, making it difficult to achieve real-time dynamic adjustment of the beam direction.

[0007] 4. Broadband impedance mismatch: The problem of broadband impedance mismatch is particularly prominent in the existing technologies, resulting in the ineffective transmission or absorption of electromagnetic waves within a broadband. Specifically, it is manifested as the narrowing of the absorption bandwidth, the enhancement of reflection, and the mutual exclusion of functions such as absorption and phase regulation, seriously hindering the performance improvement of the metasurface.

[0008] In summary, whether it is the general technical shortcomings of metasurface design or the key technical problems of terahertz sensors, the existing metasurfaces are difficult to provide stable and reliable support for UAV communication in the complex and changeable 6G communication scenarios. Therefore, designing intelligent metasurface devices and breaking through these technical bottlenecks have become the top priority for promoting the integrated development of 6G technology and UAV communication. Summary of the Invention

[0009] The purpose of the present invention is to provide a coded metasurface with both terahertz wave absorption and reflection functions and its application. By integrating the advantages of the absorbing metasurface and the reflective coded metasurface, and leveraging the beam shaping characteristics of the reflective coded metasurface, the signal generation power of 6G communication can be greatly optimized. With the excellent anti-interference ability of the absorbing metasurface, signal attenuation can be achieved, improving the transmission performance of 6G communication.

[0010] To achieve the above objectives, the present technical solution provides a coded metasurface with both terahertz wave absorption and reflection functions, including: At least an array of coded units, each coded unit includes a top resonance layer, a dielectric layer, and a metal reflection layer arranged from top to bottom in sequence. The top resonance layer includes a graphene resonance layer and a vanadium dioxide phase change layer. The graphene resonance layer includes graphene in the shape of a square, and the vanadium dioxide phase change layer includes a vanadium dioxide outer ring in the shape of a square and a vanadium dioxide strip embedded inside the vanadium dioxide outer ring. The vanadium dioxide outer ring is located inside the graphene, and the square sides of the vanadium dioxide outer ring are parallel and spaced from the square sides of the graphene. The vanadium dioxide strip is arranged at the diagonal position of the vanadium dioxide outer ring and is spaced from the vanadium dioxide outer ring.

[0011] Compared with the existing technologies, the present technical solution has the following characteristics and beneficial effects: 1. The coded metasurface with both terahertz wave absorption and reflection functions designed in this solution adopts an asymmetric top resonant layer. The top resonator adopts an asymmetric embedded square loop structure. By using multi-scale asymmetric design to break the degenerate modes of traditional symmetric units, the problem of functional mutual exclusion where the absorption peak overlaps with the phase regulation peak in the symmetric structure is solved. Through finite-difference time-domain (FDTD) simulation, the asymmetric structure excites non-degenerate resonant modes, separating the absorption peak (1.97 - 2.5 THz) from the phase regulation peak (1.8 - 2.6 THz) to avoid interference from degenerate modes. The electric field energy is concentrated at the graphene / vanadium dioxide interface, verifying that the asymmetric structure excites the coupling of local surface plasmon polaritons and electrical resonance, enhancing the wave absorption effect. By adjusting the equivalent inductance and capacitance through the size ratio of the embedded square loop, an impedance matching rate > 95% is achieved within a wide frequency band (1.97 - 2.5 THz), solving the narrowband mismatch problem of the existing symmetric structure.

[0012] 2. This solution provides a cooperative regulation mechanism for checkerboard coding and grid coding based on the coded metasurface with both terahertz wave absorption and reflection functions, designs a hybrid coding strategy, and realizes the three-dimensional spatial precise shaping of the reflected beam through independent regulation of the X / Y axis bidirectional period number. The hybrid coding strategy expands the beam regulation dimension from 2D (only azimuth angle) to 3D (elevation angle + azimuth angle), realizes the three-dimensional spatial precise shaping of the reflected beam, and improves the regulation accuracy by 40% compared with the traditional method, enhancing the coverage flexibility of communication.

[0013] 3. This solution first proposes the cooperative regulation of voltage-temperature dual parameters, breaks through the functional limitations of a single regulation method, and realizes the dynamic switching between broadband wave absorption and digital coding reflection in the same device. Specifically, through the cooperative effect of graphene voltage regulation (0.1 eV - 0.6 eV) and vanadium dioxide temperature regulation (phase transition temperature 68 °C), the device realizes millisecond-level switching between the wave absorption mode (absorption rate > 90%) and the reflection mode (phase accuracy ±5°). This system breaks through the functional limitations of traditional single regulation methods and greatly improves the response speed. When vanadium dioxide is in the insulating state, the wave absorption performance is optimal when the Fermi level of graphene is 0.2 eV, verifying the enhanced function of voltage-temperature combined regulation.

[0014] 4. This solution optimizes the structural parameters of the coded metasurface with both terahertz wave absorption and reflection functions, realizes broadband wave absorption through impedance matching, optimizes the thickness of the dielectric layer PDMS, and balances the wave absorption bandwidth and phase regulation sensitivity. Through multi-scale structural cooperative design, a wave absorption rate > 90% is achieved in the frequency band of 1.97 - 2.5 THz, while maintaining the reflection phase regulation accuracy > 85%.

[0015] 5. The coding metasurface with both terahertz wave absorption and reflection functions adopts a two-dimensional periodic structure, with a simple and compact structure design, which is convenient for integrated manufacturing and is applicable to future 6G communication, sensing, imaging and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagrams of the array, unit structure and surface pattern of the coding metasurface with both terahertz wave absorption and reflection functions; Figure 2 Table of coding unit information of the coding metasurface with both terahertz wave absorption and reflection functions in different chemical potentials of graphene; Figure 3 Coding matrix of X1 and its coding pattern of the coding metasurface with both terahertz wave absorption and reflection functions in grid mode; Figure 4 Coding matrices of Y1, X2, and Y2 of the coding metasurface with both terahertz wave absorption and reflection functions in grid mode; Figure 5 3D far-field diagram of the reflected wave of the coding metasurface with both terahertz wave absorption and reflection functions in different coding modes in grid mode; Figure 6 2D direction diagrams of the coding metasurface with both terahertz wave absorption and reflection functions in four different coding modes in grid mode; Figure 7 Coding matrices of X1Y1 and X1Y2 of the coding metasurface with both terahertz wave absorption and reflection functions in checkerboard mode; Figure 8 3D far-field diagram of the reflected wave of the coding metasurface with both terahertz wave absorption and reflection functions in different coding modes in checkerboard mode; Figure 9 2D direction diagrams of the coding metasurface with both terahertz wave absorption and reflection functions in four different coding modes in checkerboard mode; Figure 10 Absorption rate of the coding metasurface with both terahertz wave absorption and reflection functions when the Fermi level of graphene changes from 0.1 eV to 0.6 eV; Figure 11 Electric field distribution diagram of the coding metasurface with both terahertz wave absorption and reflection functions at 2.0 THz. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present invention.

[0018] Those skilled in the art should understand that in the disclosure of the present invention, the orientation or positional relationship indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting the present invention.

[0019] Embodiment 1 As Figure 1 shown, this solution provides a coded metasurface with both terahertz wave absorption and reflection functions, including: At least an array of coded units, each coded unit includes a top resonance layer, a dielectric layer, and a metal reflection layer arranged in sequence from top to bottom. Among them, the top resonance layer is a vanadium dioxide phase change layer and a graphene resonance layer in sequence from top to bottom. The graphene resonance layer includes graphene in the shape of a square. The vanadium dioxide phase change layer includes a vanadium dioxide outer ring in the shape of a square and a vanadium dioxide strip embedded inside the vanadium dioxide outer ring. The vanadium dioxide outer ring is located inside the graphene, and the square sides of the vanadium dioxide outer ring are parallel and spaced from the square sides of the graphene. Among them, the vanadium dioxide strip is arranged at the diagonal position of the vanadium dioxide outer ring and is spaced from the vanadium dioxide outer ring.

[0020] Regarding the coded unit of this solution: In some embodiments, the vanadium dioxide strip is designed as a rectangle with unequal length and width, and the size of the vanadium dioxide outer ring is smaller than the size of the graphene. The advantage of this is to design an asymmetric resonance unit to break the problem that the absorption peak and the phase modulation peak overlap due to the degenerate mode in the traditional symmetric resonance unit, effectively solving the problem of mutual exclusion of functions existing in the traditional symmetric resonance unit. Specifically, the degenerate mode excited by the traditional symmetric resonance unit at a specific frequency causes the absorption peak and the phase modulation peak to overlap and interfere with each other, restricting the performance of the device functions. The asymmetric resonance unit of this solution breaks this degenerate mode through multi-scale asymmetric design. Verified by the finite-difference time-domain (FDTD) simulation, this asymmetric structure successfully excites a non-degenerate resonance mode, separating the absorption peak (1.97 - 2.5 THz) from the phase modulation peak (1.8 - 2.6 THz), avoiding the interference of the degenerate mode, enabling absorption and phase modulation to be independent in their respective appropriate frequency bands, improving the compatibility and effectiveness of the device functions, and the asymmetric structure makes the electric field energy concentrate at the graphene / vanadium dioxide interface. This characteristic confirms that the asymmetric structure can excite the coupling of local surface plasmon polaritons and electric resonance, and this coupling effect greatly enhances the wave absorption effect.

[0021] In some embodiments, the aspect ratio of the vanadium dioxide strip is designed to be 14:11. Furthermore, by changing the equivalent inductance (L) and capacitance (C) of the structure, the impedance matching can be optimized, thereby solving the narrow-band mismatch problem of the traditional symmetric structure. Through the finite-difference time-domain (FDTD) simulation, the above ratio relationship is verified as the optimal combination, and the degree of asymmetry (a / b = 1.27) just breaks the degenerate mode, avoiding the mutual interference between absorption and phase regulation, and achieving an impedance matching rate > 95% within a wide frequency band (1.97 - 2.5 THz), solving the narrow-band mismatch problem of the existing symmetric structure.

[0022] In some embodiments, the side length of the graphene is greater than the side length of the outer ring of the vanadium dioxide, and the ratio of the side length of the graphene to the side length of the outer ring of the vanadium dioxide is 9:2. The advantage of such a design is to optimize the area ratio and spacing between the graphene and the vanadium dioxide, balance the coupling strength between the surface plasmon polaritons and the electrical resonance, and ensure the broadband performance.

[0023] Specifically, in some embodiments, the long side of the vanadium dioxide strip is 3 μm and the short side is 1 μm, the side length of the outer ring of the vanadium dioxide is 6 μm, and the side length of the graphene is 10 μm.

[0024] In some embodiments, each coding unit is designed as a square. Correspondingly, both the dielectric layer and the metal reflection layer are square-shaped.

[0025] Furthermore, the diagonal of the graphene on each coding unit intersects with the diagonal of the dielectric layer and is inclined at 45°, and there is a gap between the outer edge of the graphene and the dielectric layer. The advantage of this is to avoid strong electromagnetic coupling between the metal layers or the resonant structures (graphene / vanadium dioxide) of adjacent coding units, and ensure the independent controllability of each coding unit.

[0026] In addition, the centers of the graphene resonant layer, the outer ring of the vanadium dioxide, the vanadium dioxide strip, and the dielectric layer overlap, that is, the graphene resonant layer, the outer ring of the vanadium dioxide, the vanadium dioxide strip, and the dielectric layer are symmetrically arranged with respect to the same center.

[0027] In some embodiments, the side length of each coding unit is less than the wavelength. Generally speaking, the side length of each coding unit is one-tenth of the wavelength, so as to ensure that each coding unit exhibits sub-wavelength periodicity, thereby exciting the localized surface plasmon polaritons (LSP) and the electrical resonance mode, and realizing the efficient regulation of electromagnetic waves.

[0028] In some specific embodiments, the side length of each coding unit is 20 μm.

[0029] In some embodiments, the thickness t of the top resonant layer is 0.001 μm, which matches the operating frequency band (1.97 - 2.5 THz) of the coding unit. Within this operating frequency band, 0.001 μm of graphene can generate surface plasmon polaritons with appropriate frequencies and intensities, causing them to resonate with the incident terahertz wave, thereby achieving effective absorption and phase modulation of the terahertz wave.

[0030] In some embodiments, the dielectric layer is made of polydimethylsiloxane, and the dielectric constant of polydimethylsiloxane is 2.62. The dielectric layer plays a role in adjusting the electromagnetic parameters in this metasurface sensing unit.

[0031] In some embodiments, the thickness h2 of the dielectric layer is 40 μm. The advantage of this is that by setting the appropriate thickness h2 of the dielectric layer, the equivalent dielectric constant and permeability of the metasurface sensing unit can be changed, thereby affecting the absorption bandwidth and phase modulation performance. Generally speaking, a thicker dielectric layer may increase the absorption bandwidth but may reduce the phase sensitivity; a thinner dielectric layer has the opposite effect. After optimization, when the thickness h2 of the dielectric layer is 40 μm, a better balance between the absorption bandwidth and phase sensitivity can be achieved in the terahertz frequency band (such as 1.97 - 2.5 THz), enabling the coding metasurface with both terahertz wave absorption and reflection functions to have a high absorption rate and achieve precise phase modulation within this frequency band.

[0032] In some embodiments, the metal layer is made of gold, and the thickness h1 of the metal layer is 0.2 μm. The thickness h1 of the metal reflection layer needs to be compatible with the upper dielectric layer and the top resonant layer. If the thickness h1 of the metal layer is too large, it may affect the electric field distribution and electromagnetic coupling effect of the upper structure; if the thickness h1 of the metal layer is too small, it may not provide sufficient reflection ability. In this scheme, a thickness of 0.2 μm is selected to match the skin depth of terahertz waves in gold, which can reduce the energy loss caused by the skin effect to a certain extent, ensure the reflection performance, and improve the overall performance of the device. Correspondingly, when this coding unit is used as an absorber, its skin depth is greater than the incident depth, and the transmittance is almost 0, achieving perfect absorption.

[0033] In addition, since the top resonant layer in the coding metasurface with both terahertz wave absorption and reflection functions in this scheme includes a graphene resonant layer and a vanadium dioxide phase change layer, this scheme can develop a dual-channel independent control system. Through the synergistic effect of the graphene voltage control (0.1 eV - 0.6 eV) and the vanadium dioxide temperature control (phase change temperature 68 °C), millisecond-level switching between the absorption mode (absorption rate > 90%) and the reflection mode (phase accuracy ±5°) can be achieved, thereby enabling the coding metasurface with both terahertz wave absorption and reflection functions to break through the functional limitations of traditional single control methods and greatly improve the response speed.

[0034] When the Fermi level of graphene in the coded metasurface with both terahertz wave absorption and reflection functions is adjusted from 0.1 eV to 0.6 eV, the absorption rate is as follows Figure 10 shown. It can be seen that when the Fermi level of graphene is changed from 0.1 eV to 0.6 eV, from the figure, it can be seen that the wave absorption performance of the adjusted graphene undergoes a blue shift, and the absorption performance also changes. When the Fermi level of graphene is 0.2 eV, the wave absorption performance is optimal in the frequency band of 1.97 - 2.5 THz, and the absorption rate is greater than 90%, achieving a good wave absorption effect. Particularly, the electric field distribution diagram of the absorber at 2.0 THz is Figure 11 , and the electric field is mainly concentrated on the edges of graphene and vanadium dioxide resonant rings, where the charge aggregation intensity is more obvious, which confirms that the incident terahertz wave at this place undergoes electrical resonance with the surface plasmon of graphene, thereby converting the incident electromagnetic wave into other forms of energy and enhancing the wave absorption effect.

[0035] Specifically, when vanadium dioxide is in the normal temperature insulating state, the coded metasurface with both terahertz wave absorption and reflection functions realizes the wave absorption mode, and the coded metasurface with both terahertz wave absorption and reflection functions and its application achieve a wave absorption rate > 90% in the frequency band of 1.97 - 2.5 THz.

[0036] Preferably, when vanadium dioxide is in the insulating state and the Fermi level of graphene is 0.2 eV, the wave absorption performance of the coded metasurface with both terahertz wave absorption and reflection functions is optimal.

[0037] When vanadium dioxide is in the metallic state, the coded metasurface with both terahertz wave absorption and reflection functions realizes the reflection mode, and the reflection phase regulation accuracy of the coded metasurface with both terahertz wave absorption and reflection functions > 95%.

[0038] Example Two Based on Example One, this solution provides an application method of a coded metasurface with both terahertz wave absorption and reflection functions, and a method for correspondingly regulating the reflected beam of terahertz wave, including the following steps: Design an X-axis absorber, where the X-axis absorber includes a first coding unit and a second coding unit arranged in an array, and the first coding unit and the second coding unit are periodically arranged along the X-axis direction, and are the same type of first coding unit or second coding unit along the Y-axis; Design a Y-axis absorber, where the Y-axis absorber includes a first coding unit and a second coding unit arranged in an array, and the first coding unit and the second coding unit are periodically arranged along the Y-axis direction, and are the same type of first coding unit or second coding unit along the X-axis; The Fermi level of graphene in the first coding unit is 0.2 eV, and the Fermi level of graphene in the second coding unit is 0.4 eV. Encoding is performed using a grid coding method based on the X-axis absorber and / or Y-axis absorber.

[0039] In some embodiments, by regulating the Fermi level of graphene, the first coding unit and the second coding unit with a phase difference of 180° are obtained. The information table of graphene with different chemical potential coding units for the coding metasurface with both terahertz wave absorption and reflection functions is as Figure 2 shown. The experiment is completed by covering a layer of gel on its surface and using Pt wire as an inert electrode. The gel has a minimal impact on the experimental effect and is only used for conduction. An FPGA can be used to independently control the voltage of each region. When an external voltage is applied, an electric double layer (EDL) is formed at the interface between the ionic gel and graphene, thereby achieving the purpose of changing the Fermi level of graphene. Specifically, the Fermi level of graphene is regulated to 0.2 eV to obtain the first coding unit and mark the coding state as "0", and the Fermi level of graphene is regulated to 0.4 eV to obtain the second coding unit and mark the coding state as "1".

[0040] It should be noted that the first coding unit and the second coding unit are periodically arranged along the X-axis or Y-axis. When the number of periods is n, it means that n second coding units are arranged on the side of every n first coding units. For example, when the number of periods is 1, it means that one second coding unit is arranged on the side of every first coding unit, and the coding pattern at this time is "0101...0101" or "1010...1010". When the number of periods is 2, it means that two second coding units are arranged on the side of every two first coding units, and the coding pattern at this time is "00110011...00110011" or "11001100...11001100".

[0041] To distinguish the X-axis absorbers and Y-axis absorbers with different numbers of periods, in this solution, Xm represents the X-axis absorbers with different numbers of periods, and Yn represents the Y-axis absorbers with different numbers of periods, where m represents the number of periods of the first coding unit and the second coding unit along the X direction in the X-axis absorber, and y represents the number of periods of the first coding unit and the second coding unit along the Y direction in the Y-axis absorber.

[0042] Figure 3 It is a schematic diagram of the coding matrix and coding pattern of the first X-axis absorber X1. At this time, X1 represents that the number of periods of the first coding unit and the second coding unit along the positive X-axis is equal to 1, and the coding pattern at this time is "01010101", and the coding arrangement order in the Y-axis direction is "00000000" or "11111111".

[0043] Correspondingly, as Figure 4 shown.Figure 4 The encoding matrix for the X-axis absorber and Y-axis absorber in the grid mode under the Y1, X2, Y2 encoding modes. Among them, X2 indicates that the number of periods of the first encoding unit and the second encoding unit along the positive X-axis is equal to 2. At this time, the encoding mode is "00110011", and the encoding arrangement order in the Y-axis direction is "00000000" or "11111111". Among them, Y1 indicates that the number of periods of the first encoding unit and the second encoding unit along the positive Y-axis is equal to 1. At this time, the encoding mode is "01010101", and the encoding arrangement order in the X-axis direction is "00000000" or "11111111". Y2 indicates that the number of periods of the first encoding unit and the second encoding unit along the positive Y-axis is equal to 2. At this time, the encoding mode is "00110011", and the encoding arrangement order in the X-axis direction is "00000000" or "11111111".

[0044] Regarding the encoding method based on a single X-axis absorber and Y-axis absorber using the grid encoding method: Figure 5 It is the 3D far-field diagram of the reflected wave of different absorbers in the grid mode under different encoding modes. It can be seen that 、 Under the mode, there are two electromagnetic waves with an angle with the plane in the x-o-z interface for the terahertz reflected beam, while in 、 Under the encoding mode condition, the dichotomous beam with an angle exists in the y-o-z coordinate plane.

[0045] In other words, in some embodiments, when it is necessary to obtain the terahertz reflected beam with two electromagnetic waves with an angle with the plane in the x-o-z interface, select the X-axis absorber arranged in the grid encoding method; when it is necessary to form a dichotomous beam with an angle in the y-o-z coordinate plane, select the Y-axis absorber arranged in the grid encoding method.

[0046] Figure 6 It is the 2D direction diagram of different absorbers in the grid mode under four different encoding modes. When comparing and 、 and encoding modes, it is found that when the number of periods along the positive X-axis or Y-axis is equal to 1, while keeping the elevation angle unchanged, the azimuth angle of the reflected wave will change. It can be seen that under the condition of keeping the period unchanged, different azimuth encodings will cause the deflection control of the azimuth angle of the terahertz reflected wave. Then for and 、 and Analyze the case where the directions are the same, but the number of periods along the positive X-axis or Y-axis is different. It is found that when the number of periods along the positive X-axis or Y-axis increases from 1 to 2, the elevation angle changes negatively with the change of the number of periods.

[0047] In other words, in some embodiments, when it is necessary to deflect and regulate the azimuth angle of the terahertz reflected wave, different X-axis absorbers or Y-axis absorbers with the same number of periods are used; when it is necessary to adjust the elevation angle of the terahertz reflected wave, the number of periods of the X-axis absorber or Y-axis absorber is adjusted.

[0048] Embodiment 3 Based on Embodiment 1, this solution provides an application method of a coded metasurface with both terahertz wave absorption and reflection functions, and a method for correspondingly regulating the reflected beam of terahertz waves, including the following steps: Design an XY absorber, where the XY-axis absorber includes a first coding unit and a second coding unit arranged in an array. The first coding unit and the second coding unit are periodically arranged along the X-axis direction, and the first coding unit and the second coding unit are also periodically arranged along the Y-axis direction. The Fermi level of graphene in the first coding unit is 0.2 eV, and the Fermi level of graphene in the second coding unit is 0.4 eV.

[0049] In other words, this solution is based on the simultaneous coding of the first coding unit and the second coding unit along the X-axis and Y-axis. Represent the XY absorbers with different numbers of periods as XmYn, where m represents the number of periods of the first coding unit and the second coding unit along the X-direction in the X-axis absorber, and y represents the number of periods of the first coding unit and the second coding unit along the Y-direction in the Y-axis absorber.

[0050] The coding matrices of X1Y1 and X1Y2 provided by this solution are as Figure 7 shown. X1Y1 means that the number of periods of the first coding unit and the second coding unit along the X-axis and Y-axis are both 1. The coding along the X-axis direction is "01010101" or "10101010", and the coding pattern along the Y-axis direction is "01010101" or "10101010"; similarly, the coding of the X1Y2 absorber along the X-axis direction is "01010101" or "10101010", and the coding pattern along the Y-axis direction is "0011001100110011" or "1100110011001100".

[0051] The 3D far-field diagrams of the reflected waves of different coding patterns of X1Y1 and X1Y2 provided by this solution in the checkerboard are Figure 8, in the two coding modes of X1Y1 and X1Y2, the terahertz reflected wave is dispersed into four reflected beamlets in different quadrants after entering the incident reflection plane.

[0052] In addition, the 2D direction diagrams of X1Y1 and X1Y2 provided by this solution in different coding modes in the checkerboard are as Figure 9 shown. Combining the 3D direction diagram and the 2D far-field diagram, it can be seen that in the X1Y1 mode, although the four reflected waves are in different quadrants, their elevation angles are the same and their azimuth angles are different; while in the X1Y2 coding mode, there are also four reflected waves located in different quadrants, but the elevation angle in this mode is slightly smaller than the elevation angle in the X1Y1 mode At this time, the azimuth angle also changes correspondingly. Combining the far-field diagrams of these two modes, it can be known that when coding simultaneously along the X-axis and Y-axis, changing the coding period in the single direction of the X-axis or Y-axis, the elevation angle and azimuth angle of the final reflected beamlet will change simultaneously, rather than a single parameter changing alone, and the more the number of periods in a certain direction increases, the closer the elevation angle is to the Z-axis.

[0053] In other words, when it is necessary to change the elevation angle and azimuth angle of the reflected beamlet, change the number of periods in the X-axis direction or Y-axis direction on the XY absorber, and the elevation angle and azimuth angle of the reflected beamlet change simultaneously, and the more the number of periods in a certain direction increases, the closer the elevation angle is to the Z-axis.

[0054] Those skilled in the art should understand that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combinations of these technical features do not conflict, they should be considered to be within the scope described in this specification.

[0055] The above embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A coded metasurface with both terahertz wave absorption and reflection functions, characterized in that Comprising: At least an array arrangement of encoding units, each encoding unit including a top resonance layer, a dielectric layer, and a metal reflection layer sequentially arranged from top to bottom, wherein the top resonance layer includes a graphene resonance layer and a vanadium dioxide phase change layer, the graphene resonance layer includes graphene presenting a square shape, the vanadium dioxide phase change layer includes a vanadium dioxide outer ring presenting a square shape and a vanadium dioxide strip embedded inside the vanadium dioxide outer ring, the vanadium dioxide outer ring is located inside the graphene, and the square sides of the vanadium dioxide outer ring are arranged parallel and spaced from the square sides of the graphene, wherein the vanadium dioxide strip is arranged at the diagonal position of the vanadium dioxide outer ring and is spaced from the vanadium dioxide outer ring.

2. The coded metasurface with both terahertz wave absorption and reflection functions according to claim 1, characterized in that, The vanadium dioxide strip is designed as a rectangle with unequal length and width, and the size of the vanadium dioxide outer ring is smaller than that of the graphene.

3. The coded metasurface with both terahertz wave absorption and reflection functions according to claim 1, characterized in that The aspect ratio of the length to the width of the vanadium dioxide strip is designed to be 14:11, and the ratio of the side length of the graphene to the side length of the vanadium dioxide outer ring is 9:

2.

4. The coded metasurface with both terahertz wave absorption and reflection functions according to claim 1, characterized in that, The diagonal of the graphene on each encoding unit intersects with the diagonal of the dielectric layer and is arranged at an inclination of 45°, and there is a gap between the outer edges of the graphene and the dielectric layer.

5. The coded metasurface having both terahertz wave absorption and reflection functions according to claim 1, wherein Through the synergistic effect of the regulation of the graphene voltage and the regulation of the vanadium dioxide temperature, a millisecond-level switching between the absorption mode and the reflection mode is realized.

6. The coded metasurface with both terahertz wave absorption and reflection functions according to claim 5, characterized in that, When the vanadium dioxide is in the normal-temperature insulating state, the encoding metasurface with both terahertz wave absorption and reflection functions realizes the absorption mode, and the encoding metasurface with both terahertz wave absorption and reflection functions and its application achieve an absorption rate > 90% in the 1.97 - 2.5 THz frequency band; when the vanadium dioxide is in the metallic state, the encoding metasurface with both terahertz wave absorption and reflection functions realizes the reflection mode, and the reflection phase regulation accuracy of the encoding metasurface with both terahertz wave absorption and reflection functions > 95%.

7. An application method of a coded metasurface with both terahertz wave absorption and reflection functions, characterized in that, Including the following steps: Design an X-axis absorber, wherein the X-axis absorber includes a first encoding unit and a second encoding unit arranged in an array, wherein the first encoding unit and the second encoding unit are periodically arranged along the X-axis direction, and along the Y-axis are the same type of first encoding unit or second encoding unit; Design a Y-axis absorber, wherein the Y-axis absorber includes a first encoding unit and a second encoding unit arranged in an array, wherein the first encoding unit and the second encoding unit are periodically arranged along the Y-axis direction, and along the X-axis are the same type of first encoding unit or second encoding unit; Wherein the Fermi level of the graphene of the first encoding unit is 0.2 eV, the Fermi level of the graphene of the second encoding unit is 0.4 eV, and encoding is performed based on the X-axis absorber and / or the Y-axis absorber using a grid encoding method.

8. The application method of the coded metasurface with terahertz wave absorption and reflection functions according to claim 7, characterized in that, When it is necessary to obtain terahertz reflection beams of two electromagnetic waves forming an angle with the plane in the x-o-z interface, select the X-axis absorber arranged in a grid encoding method; when it is necessary to form a dichotomous wave with an angle in the y-o-z coordinate plane, select the Y-axis absorber arranged in a grid encoding method; when it is necessary to deflect and regulate the azimuth angle of the terahertz reflection wave, select different X-axis absorbers or Y-axis absorbers with the same number of periods; when it is necessary to adjust the elevation angle of the terahertz reflection wave, adjust the number of periods of the X-axis absorber or the Y-axis absorber.

9. An application method of a coded metasurface with both terahertz wave absorption and reflection functions, characterized in that, Including the following steps: Design an XY absorber, where the XY-axis absorber includes first coding units and second coding units arranged in an array. The first coding units and the second coding units are periodically arranged along the X-axis direction, and the first coding units and the second coding units are also periodically arranged along the Y-axis direction. The Fermi level of the graphene in the first coding unit is 0.2 eV, and the Fermi level of the graphene in the second coding unit is 0.4 eV.

10. The application method of the coded metasurface with both terahertz wave absorption and reflection functions according to claim 9, characterized in that, When it is necessary to change the elevation angle and azimuth angle of the reflected beam, change the number of periods in the X-axis direction or the Y-axis direction on the XY absorber. The elevation angle and azimuth angle of the reflected beam change simultaneously, and the more the number of periods in a certain direction increases, the closer the elevation angle is to the Z-axis.

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