Coding metasurface with both terahertz wave absorption and reflection functions and its applications

Abstract

This solution provides a coding metasurface and application with both terahertz wave absorption and reflection functions, including: at least one array-arranged coding unit, each coding unit including a top resonance layer, a dielectric layer and a metal reflection layer arranged in sequence 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 a square graphene, the vanadium dioxide phase change layer includes 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 side of the vanadium dioxide outer ring is parallel to the square side of the graphene and is arranged at intervals, wherein the vanadium dioxide strip is arranged at a diagonal position of the vanadium dioxide outer ring and is spaced apart from the vanadium dioxide outer ring, integrating the advantages of the absorbing metasurface and the reflecting coding metasurface, greatly optimizing the signal generation power of 6G communication.

Description

Technical Field

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

[0002] Drones (UAVs) play a vital role in wireless communications due to their wide coverage and high mobility. However, in real-world applications, the complex urban environment severely degrades the quality of UAV communication networks due to attenuation, obstacles, and eavesdroppers, creating risks. The rise of sixth-generation mobile communications (6G) technology offers new promise. It boasts high network speeds, ultra-low latency, and extended coverage, operating in the terahertz band. It demonstrates significant potential for applications in cutting-edge fields such as holographic communications and wireless backhaul networks. Applying 6G technology to UAVs is expected to provide strong support for UAV communications and effectively address existing communication challenges.

[0003] However, achieving the deep integration of 6G technology and drone communications requires the design of metasurfaces for terahertz communication devices. Currently, metasurface design faces numerous technical bottlenecks: 1. Most metasurfaces rely on a single material or control mechanism, making multifunctional integration and dynamic adjustment difficult. For example, while traditional metal resonator designs can achieve a certain degree of phase control, they lack flexibility and struggle to switch between absorption and reflection functions. 2. Existing metasurface designs are also often limited to a single frequency band, making them difficult to meet the demands of broadband and multi-band applications. For example, some metasurface designs only achieve perfect absorption within a specific frequency band, while performing poorly in other bands. 3. Metasurface designs often rely on fixed structural parameters, making dynamic adjustment difficult. For example, some metasurface designs require varying the pattern of the metal resonator to achieve different functions, which is difficult to achieve in practical applications.

[0004] Focusing on the terahertz sensor level, its key technical problems further exacerbate the above dilemma:

[0005] 1. Symmetrical structure and functional mutual exclusion: Traditional symmetrical resonant units excite multiple degenerate modes at specific frequencies, causing the absorption peak and phase control peak to overlap. These degenerate modes interfere with each other, not only compressing the absorption bandwidth but also limiting the phase control range. Broadband absorption requires broadband impedance matching, while phase control requires a specific phase gradient distribution. Symmetrical structures cannot simultaneously meet both requirements.

[0006] 2. Insufficient flexibility of single regulation: Existing technologies cannot integrate broadband absorption and phase regulation functions in the same device. Absorption is often only achieved at specific frequency points and is not compatible with phase regulation. In addition, the realization of transmission and reflection functions depends on the replacement of components and cannot be flexibly integrated in the same device.

[0007] 3. Beam steering dimensionality limitations: The degenerate modes excited by the symmetrical structure restrict the beam to propagating in a fixed direction, resulting in a fixed and single mode. Switching between transmission and reflection modes also relies on component replacement, making it difficult to achieve real-time dynamic adjustment of the beam direction.

[0008] 4. Broadband impedance mismatch: The broadband impedance mismatch problem is particularly prominent in existing technologies, resulting in the inability to effectively transmit or absorb electromagnetic waves within a wide bandwidth. Specifically, it manifests itself in the narrowing of the absorption bandwidth, enhanced reflection, and the mutual exclusion of absorption and phase control functions, which seriously hinders the improvement of metasurface performance.

[0009] In summary, both the general technical shortcomings of metasurface design and the key technical issues of terahertz sensors make it difficult for existing metasurfaces to provide stable and reliable support for drone communications in the complex and ever-changing 6G communication scenarios. Therefore, designing intelligent metasurface devices and overcoming these technical bottlenecks has become a top priority for promoting the integrated development of 6G technology and drone communications. Summary of the Invention

[0010] The purpose of the present invention is to provide a coding metasurface and its application with both terahertz wave absorption and reflection functions, integrating the advantages of absorbing metasurface and reflective coding metasurface, and making use of the beamforming characteristics of reflective coding metasurface to greatly optimize the signal generation power of 6G communication, and making use of the excellent anti-interference ability of absorbing metasurface to achieve signal weakening and improve the transmission performance of 6G communication.

[0011] To achieve the above objectives, this technical solution provides a coding metasurface with both terahertz wave absorption and reflection functions, including:

[0012] At least one encoding unit is arranged in an array, and each encoding unit includes a top resonance layer, a dielectric layer, and a metal reflective layer arranged in sequence 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 a square graphene, the vanadium dioxide phase change layer includes 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 side of the vanadium dioxide outer ring is parallel to the square side of the graphene and is arranged at intervals, wherein the vanadium dioxide strip is arranged at a diagonal position of the vanadium dioxide outer ring and is spaced apart from the vanadium dioxide outer ring.

[0013] Compared with the existing technology, this technical solution has the following characteristics and beneficial effects:

[0014] 1. This proposed coding metasurface, which combines terahertz wave absorption and reflection capabilities, utilizes an asymmetric top resonant layer. This top resonator employs an asymmetric embedded square ring structure. This multi-scale asymmetric design overcomes the degenerate modes of conventional symmetrical units, resolving the functional mutual exclusion problem of overlapping absorption and phase modulation peaks in symmetric structures. Finite-difference time-domain (FDTD) simulations demonstrate that the asymmetric structure excites nondegenerate resonant modes, separating the absorption peak (1.97-2.5 THz) from the phase modulation peak (1.8-2.6 THz), thus preventing interference between the degenerate modes. Electric field energy is concentrated at the graphene / vanadium dioxide interface, confirming that the asymmetric structure excites localized surface plasmons (LSPs) that couple with electrical resonance, enhancing absorption. The equivalent inductance and capacitance can be controlled by adjusting the size ratio of the embedded square rings, achieving an impedance matching ratio exceeding 95% across a wide frequency band (1.97-2.5 THz), addressing the narrowband mismatch issue with existing symmetric structures.

[0015] 2. This solution provides a coordinated control mechanism of checkerboard coding and grid coding based on a coded metasurface with both terahertz wave absorption and reflection functions. It designs a hybrid coding strategy to achieve precise three-dimensional shaping of the reflected beam through independent control of the number of bidirectional periods in the X / Y axes. The hybrid coding strategy expands the beam control dimension from 2D (azimuth only) to 3D (elevation + azimuth), achieving precise three-dimensional shaping of the reflected beam. The control accuracy is improved by 40% compared to traditional methods, enhancing the coverage flexibility of communications.

[0016] 3. This solution, for the first time, proposes coordinated dual-parameter voltage-temperature control, breaking the functional limitations of a single control method and enabling dynamic switching between broadband absorption and digitally coded reflection within the same device. Specifically, through the synergistic effect of graphene voltage control (0.1eV-0.6eV) and vanadium dioxide temperature control (phase transition temperature 68°C), the device achieves millisecond-level switching between absorption mode (absorption rate >90%) and reflection mode (phase accuracy ±5°). This system breaks the functional limitations of traditional single control methods and significantly improves response speed. When the vanadium dioxide is in the insulating state, the graphene Fermi level is 0.2eV, and the absorption performance is optimal, confirming the enhanced functionality of the combined voltage-temperature control.

[0017] 4. This solution optimizes the structural parameters of a coded metasurface that combines terahertz wave absorption and reflection capabilities, achieving broadband absorption through impedance matching. The thickness of the PDMS dielectric layer is optimized to balance absorption bandwidth and phase control sensitivity. Through multi-scale structural collaborative design, an absorption rate exceeding 90% is achieved within the 1.97-2.5 THz frequency band, while maintaining a reflection phase control accuracy exceeding 85%.

[0018] 5. The coding metasurface with both terahertz wave absorption and reflection functions adopts a two-dimensional periodic structure. The structural design is simple and compact, easy to integrate and manufacture, and suitable for future 6G communications, sensing, imaging and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the array, unit structure, and surface pattern of a coding metasurface that combines terahertz wave absorption and reflection functions;

[0020] Figure 2 To achieve the goal of encoding metasurfaces with both terahertz wave absorption and reflection functions, a table of unit information encoded in graphene at different chemical potentials is proposed;

[0021] Figure 3 The X1 coding matrix and its coding pattern diagram in grid mode for the coding metasurface with both terahertz wave absorption and reflection functions;

[0022] Figure 4 The coding matrix of Y1, X2, and Y2 in a grid pattern for the coding metasurface with both terahertz wave absorption and reflection functions;

[0023] Figure 5 3D far-field diagram of reflected waves in different coding modes under a grid pattern for a coding metasurface that combines terahertz wave absorption and reflection functions;

[0024] Figure 6 2D directivity patterns of the coding metasurface in four different coding modes in a grid pattern for both terahertz wave absorption and reflection;

[0025] Figure 7 To provide a coding metasurface with both terahertz wave absorption and reflection functions, an X1Y1 and X1Y2 coding matrix is ​​used in a checkerboard pattern;

[0026] Figure 8 3D far-field diagram of reflected waves of different coding patterns in a checkerboard pattern for a coding metasurface that combines terahertz wave absorption and reflection functions;

[0027] Figure 9 2D directional patterns of the coding metasurface with both terahertz wave absorption and reflection functions in four different coding modes in a checkerboard pattern;

[0028] Figure 10 The absorption rate of the coding metasurface with both terahertz wave absorption and reflection functions changes from 0.1eV to 0.6eV at the Fermi level of graphene;

[0029] Figure 11 The electric field distribution diagram of the coding metasurface at 2.0 THz, which has both terahertz wave absorption and reflection functions. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention are within the scope of protection of the present invention.

[0031] It should be understood by those skilled in the art that, in the disclosure of the present invention, the terms "longitudinal", "transverse", "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 accompanying 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.

[0032] Example 1

[0033] like Figure 1 As shown, this solution provides a coding metasurface with both terahertz wave absorption and reflection functions, including:

[0034] At least one encoding unit is arranged in an array, and each encoding unit includes a top resonance layer, a dielectric layer, and a metal reflection layer arranged in sequence from top to bottom, wherein 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 a square graphene, the vanadium dioxide phase change layer includes 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 side of the vanadium dioxide outer ring is parallel to the square side of the graphene and is arranged at intervals, wherein the vanadium dioxide strip is arranged at a diagonal position of the vanadium dioxide outer ring and is spaced apart from the vanadium dioxide outer ring.

[0035] About the coding unit of this scheme:

[0036] In some embodiments, the vanadium dioxide strips are designed as rectangles with unequal lengths and widths, and the outer ring of the vanadium dioxide is smaller than that of the graphene. This advantage is that it creates an asymmetric resonant unit, eliminating the problem of overlapping absorption and phase control peaks caused by degenerate modes in traditional symmetrical resonant units, effectively addressing the functional mutual exclusion problem that exists in traditional symmetrical resonant units. Specifically, the degenerate modes excited at specific frequencies by traditional symmetrical resonant units cause the absorption peak and phase control peak to overlap, interfering with each other and limiting the device's functionality. The asymmetric resonant unit in this solution breaks this degenerate mode through a multi-scale asymmetric design. Finite-difference time-domain (FDTD) simulations verify that the asymmetric structure successfully excites non-degenerate resonant modes, separating the absorption peak (1.97-2.5 THz) from the phase control peak (1.8-2.6 THz), avoiding interference from degenerate modes and enabling absorption and phase control to proceed independently within their respective appropriate frequency bands. This improves the compatibility and effectiveness of the device's functionality. Furthermore, the asymmetric structure concentrates the electric field energy at the graphene / vanadium dioxide interface. This characteristic confirms that the asymmetric structure can excite localized surface plasmons and couple with electrical resonance, and this coupling greatly enhances the wave absorption effect.

[0037] In some embodiments, the vanadium dioxide strips are designed with an aspect ratio of 14:11. This allows for optimized impedance matching by varying the structure's equivalent inductance (L) and capacitance (C), resolving the narrowband mismatch issue associated with conventional symmetrical structures. Finite-difference time-domain (FDTD) simulations have verified this ratio as the optimal combination, with an asymmetry ratio (a / b = 1.27) that precisely breaks the degenerate mode, preventing interference between absorption and phase control. This results in an impedance matching ratio exceeding 95% across a wide frequency band (1.97-2.5 THz), addressing the narrowband mismatch issue associated with conventional symmetrical structures.

[0038] In some embodiments, the side length of graphene is greater than the side length of the vanadium dioxide outer ring, and the ratio of the side length of graphene to the side length of the vanadium dioxide outer ring is 9:2. The advantage of this design is that the area ratio and spacing of graphene and vanadium dioxide are optimized, the coupling strength between plasmon excitation and electric resonance is balanced, and broadband performance is ensured.

[0039] 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 vanadium dioxide outer ring is 6 μm, and the side length of the graphene is 10 μm.

[0040] In some embodiments, each encoding unit is designed to be square, and correspondingly, the dielectric layer and the metal reflective layer are both square in shape.

[0041] Furthermore, the diagonal lines of the graphene on each coding unit intersect with the diagonal lines of the dielectric layer and are arranged at a 45-degree angle, with a gap between the outer edges of the graphene and dielectric layers. This has the advantage of preventing strong electromagnetic coupling between the metal layers or resonant structures (graphene / vanadium dioxide) of adjacent coding units, ensuring the independent controllability of each coding unit.

[0042] In addition, the centers of the graphene resonance layer, the vanadium dioxide outer ring, the vanadium dioxide strips and the dielectric layer overlap, that is, the graphene resonance layer, the vanadium dioxide outer ring, the vanadium dioxide strips and the dielectric layer are symmetrically arranged relative to the same center.

[0043] In some embodiments, the side length of each coding unit is smaller than the wavelength. Generally speaking, the side length of each coding unit is one tenth of the wavelength to ensure that each coding unit exhibits subwavelength periodicity, thereby exciting localized surface plasmons (LSPs) and electric resonance modes, and achieving efficient control of electromagnetic waves.

[0044] In some embodiments, the side length of each coding unit is 20 μm.

[0045] In some embodiments, the thickness t of the top resonant layer is 0.001 μm, which matches the operating frequency band of the coding unit (1.97-2.5 THz). Within this operating frequency band, 0.001 μm of graphene can generate surface plasmons of suitable frequency and intensity, causing them to resonate with the incident terahertz wave, thereby achieving effective absorption and phase control of the terahertz wave.

[0046] In some embodiments, the dielectric layer is made of polydimethylsiloxane, which has a dielectric constant of 2.62. The dielectric layer plays a role in regulating electromagnetic parameters in the metasurface sensing unit.

[0047] In some embodiments, the thickness h2 of the dielectric layer is 40 μm. This has the advantage that by setting the appropriate dielectric layer thickness h2, the equivalent dielectric constant and magnetic permeability of the metasurface sensing unit can be changed, thereby affecting the absorption bandwidth and phase control performance. Generally speaking, a thicker dielectric layer may increase the absorption bandwidth but may reduce phase sensitivity; a thinner dielectric layer has the opposite effect. After optimization, when the dielectric layer thickness h2 is 40 μm, a good balance between absorption bandwidth and phase sensitivity can be achieved in the terahertz frequency band (e.g., 1.97-2.5 THz), allowing the coding metasurface with both terahertz wave absorption and reflection functions to have both high absorption rate and precise phase control within this frequency band.

[0048] 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 reflective 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 capability. This solution selects a thickness of 0.2 μm to match the skin depth of the terahertz wave in gold, which can reduce the energy loss caused by the skin effect to a certain extent, ensuring the reflection performance while improving the overall performance of the device. Correspondingly, when the coding unit is used as an absorber, its skin depth is greater than the incident depth, and the transmittance is close to 0, achieving perfect absorption.

[0049] 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-path independent control system. Through the synergistic effect of graphene voltage control (0.1eV-0.6eV) and 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. As a result, the coding metasurface with both terahertz wave absorption and reflection functions can break through the functional limitations of the traditional single control method and greatly improve the response speed.

[0050] The absorption rate of the graphene coding metasurface with both terahertz wave absorption and reflection functions is adjusted from 0.1eV to 0.6eV. Figure 10 As shown in the figure, it can be seen that the Fermi level of graphene is adjusted from 0.1eV to 0.6eV. It can be seen from the figure that the Fermi level of graphene has undergone a blue shift in its absorption performance, and the absorption performance has also changed. When the Fermi level of graphene is 0.2eV, the absorption performance is optimal in the 1.97-2.5THz frequency band, with an absorption rate greater than 90%, achieving a good absorption effect. In particular, the electric field distribution diagram of the absorber at 2.0THz is Figure 11 The electric field is mainly concentrated at the edges of the graphene and vanadium dioxide resonant rings, where the charge concentration intensity is more obvious. This confirms that the incident terahertz wave at this location resonates electrically with the graphene surface plasmons, thereby converting the incident electromagnetic wave into other forms of energy and enhancing the wave absorption effect.

[0051] Specifically, when vanadium dioxide is in an insulating state at room temperature, the coding metasurface with both terahertz wave absorption and reflection functions realizes an absorption mode, and the coding metasurface with both terahertz wave absorption and reflection functions and its application achieve an absorption rate of >90% in the 1.97-2.5THz frequency band.

[0052] Preferably, when vanadium dioxide is in an insulating state and the Fermi level of graphene is 0.2 eV, the absorbing performance of the coding metasurface having both terahertz wave absorption and reflection functions is optimal.

[0053] When vanadium dioxide is in a metallic state, the coding metasurface with both terahertz wave absorption and reflection functions realizes a reflection mode, and the reflection phase control accuracy of the coding metasurface with both terahertz wave absorption and reflection functions is greater than 95%.

[0054] Example 2

[0055] Based on the first embodiment, this solution provides an application method of a coding metasurface with both terahertz wave absorption and reflection functions, which corresponds to a method for controlling the reflected beam of a terahertz wave, including the following steps:

[0056] An X-axis absorber is designed, 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, and the first encoding unit or the second encoding unit along the Y-axis are the same type;

[0057] A Y-axis absorber is designed, 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, and the first encoding unit or the second encoding unit is of the same type along the X-axis;

[0058] The Fermi level of the graphene in the first coding unit is 0.2 eV, the Fermi level of the graphene in the second coding unit is 0.4 eV, and the encoding is performed using a grid encoding method based on the X-axis absorber and / or the Y-axis absorber.

[0059] In some embodiments, by regulating the Fermi level of graphene, a first coding unit and a second coding unit with a phase difference of 180° are obtained. The information table of the coding units of graphene with different chemical potentials of the coding metasurface with both terahertz wave absorption and reflection functions is as follows: Figure 2 As shown, the experiment was conducted by covering the structure's surface with a layer of gel and using Pt wires as inert electrodes. The gel had minimal impact on the experimental results, serving only as a conductor. An FPGA was used to independently control the voltage in each region. When an external voltage was applied, an electric double layer (EDL) formed at the interface between the ion gel and the graphene, thereby changing the graphene's Fermi level. Specifically, the graphene's Fermi level was adjusted to 0.2eV, the first coding unit was obtained, and the coding state was marked as "0." The graphene's Fermi level was adjusted to 0.4eV, the second coding unit was obtained, and the coding state was marked as "1."

[0060] It should be noted that the first coding unit and the second coding unit are periodically arranged along the X-axis or Y-axis according to the number of cycles. When the number of cycles is n, it means that n second coding units are arranged next to every n first coding units. For example, when the number of cycles is 1, it means that one second coding unit is arranged next to each first coding unit. In this case, the encoding pattern is "0101...0101" or "1010...1010". When the number of cycles is 2, it means that two second coding units are arranged next to every two first coding units. In this case, the encoding pattern is "00110011...00110011" or "11001100...11001100".

[0061] In order to distinguish X-axis absorbers and Y-axis absorbers with different periodicity numbers, this solution uses Xm to represent X-axis absorbers with different periodicity numbers, and Yn to represent Y-axis absorbers with different periodicity numbers, where m represents the periodicity of the first encoding unit and the second encoding unit in the X-axis absorber along the X direction, and y represents the periodicity of the first encoding unit and the second encoding unit in the Y-axis absorber along the Y direction.

[0062] Figure 3 This is a schematic diagram of the coding matrix and coding pattern of the first X-axis absorber X1. At this time, X1 indicates that the number of periods of the first coding unit and the second coding unit along the positive direction of the X-axis is equal to 1. At this time, the coding pattern is "01010101", and the coding arrangement order in the Y-axis direction is "00000000" or "11111111".

[0063] Corresponding to Figure 4 As shown, Figure 4 It is the coding matrix of the X-axis absorber and the Y-axis absorber in the Y1, X2, and Y2 coding mode in the grid mode, where X2 indicates that the number of periods of the first coding unit and the second coding unit along the positive direction of the X-axis is equal to 2, and the coding mode at this time is "00110011", and the coding arrangement order in the Y-axis direction is "00000000" or "11111111"; where Y1 indicates that the number of periods of the first coding unit and the second coding unit along the positive direction of the Y-axis is equal to 1, and the coding mode at this time is "01010101", and the coding arrangement order in the X-axis direction is "00000000" or "11111111"; Y2 indicates that the number of periods of the first coding unit and the second coding unit along the positive direction of the Y-axis is equal to 2, and the coding mode at this time is "00110011", and the coding arrangement order in the X-axis direction is "00000000" or "11111111".

[0064] Regarding the encoding method based on a single X-axis absorber and a Y-axis absorber using a grid encoding method:

[0065] Figure 53D far-field diagram of reflected waves of different absorbers in grid mode and different coding modes. It can be seen that 、 In the terahertz reflected beam mode, there are two electromagnetic waves in the xoz interface that form an angle with the plane, while in 、 Under the coding mode, the two-beam wave with an angle exists in the yoz coordinate plane.

[0066] In other words, in some embodiments, when it is necessary to obtain the terahertz reflected beam of two electromagnetic waves that form an angle with the plane in the xoz interface, the X-axis absorber arranged in a grid coding manner is selected; when it is necessary to form a two-beam wave with an angle in the yoz coordinate plane, the Y-axis absorber arranged in a grid coding manner is selected.

[0067] Figure 6 2D directional patterns of different absorbers in four different coding modes under grid mode. and 、 and In the encoding mode, it is found that when the number of cycles along the positive direction of the X-axis or Y-axis is equal to 1, the elevation angle is maintained. Under the condition of no change, the azimuth of the reflected wave It can be seen that when the period remains unchanged, different azimuth encodings will cause the azimuth angle of the terahertz reflected wave to change. Then, and 、 and The direction is the same, but the number of cycles along the positive direction of the X axis or Y axis is different. It is found that when the number of cycles along the positive direction of the X axis or Y axis increases from 1 to 2, the elevation angle The change of is negatively correlated with the change of the cycle number.

[0068] In other words, in some embodiments, when the azimuth angle of the terahertz reflected wave needs to be deflected and controlled, different X-axis absorbers or Y-axis absorbers with the same number of periods are used; when the elevation angle of the terahertz reflected wave needs to be adjusted, the number of periods of the X-axis absorber or Y-axis absorber is adjusted.

[0069] Example 3

[0070] Based on the first embodiment, this solution provides an application method of a coding metasurface with both terahertz wave absorption and reflection functions, which corresponds to a method for controlling the reflected beam of a terahertz wave, including the following steps:

[0071] An XY absorber is designed, wherein the XY axis absorber includes a first coding unit and a second coding unit arranged in an array, wherein the first coding unit and the second coding unit are periodically arranged along the direction of the X axis, and the first coding unit and the second coding unit are also periodically arranged along the direction of the Y axis, wherein the Fermi level of the graphene of the first coding unit is 0.2 eV, and the Fermi level of the graphene of the second coding unit is 0.4 eV.

[0072] In other words, this solution is based on simultaneous encoding of the first and second encoding units along both the X and Y axes. XmYn represents an XY absorber with different periodicity, where m represents the periodicity of the first and second encoding units along the X direction within the X-axis absorber, and y represents the periodicity of the first and second encoding units along the Y direction within the Y-axis absorber.

[0073] The encoding matrix of X1Y1 and X1Y2 provided by this solution is as follows Figure 7 As shown, X1Y1 indicates that the number of periods of the first coding unit and the second coding unit along the X-axis and the Y-axis is 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".

[0074] The 3D far-field images of the reflected waves of X1Y1 and X1Y2 in different coding modes in the chessboard provided by this solution are as follows: Figure 8 In the two coding modes of X1Y1 and X1Y2, the terahertz reflected wave is dispersed into four reflected beams in different quadrants after entering the reflection plane.

[0075] In addition, the 2D directional diagrams of X1Y1 and X1Y2 in different coding modes in the checkerboard are provided by this solution. Figure 9 As shown in the figure, combined with the 3D directional 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 azimuths are different; in the X1Y2 coding mode, four reflected waves are also presented in different quadrants, but the elevation angles in this mode are Compared with the elevation angle in X1Y1 mode It decreases slightly, and the azimuth angle also changes accordingly. Combining the far-field diagrams of these two modes, it can be seen that when encoding along the X and Y axes simultaneously, changing the encoding period in the X or Y axis direction will cause the elevation angle and azimuth angle of the final reflected beam to change simultaneously, rather than changing a single parameter. In addition, the more the number of periods in a certain direction increases, the closer the elevation angle is to the Z axis.

[0076] In other words, when it is necessary to change the elevation angle and azimuth of the reflected beam, the number of periods in the X-axis direction or the Y-axis direction on the XY absorber is changed, and the elevation angle and azimuth of the reflected beam are changed at the same time, and the more the number of periods in a certain direction increases, the closer its elevation angle is to the Z-axis.

[0077] Those skilled in the art should understand that the technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0078] The above embodiments merely illustrate several embodiments of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A coding metasurface with both terahertz wave absorption and reflection functions, characterized in that: include: At least one encoding unit is arranged in an array, and each encoding unit includes a top resonance layer, a dielectric layer, and a metal reflective layer arranged in sequence 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 a square graphene, the vanadium dioxide phase change layer includes 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 side of the vanadium dioxide outer ring is parallel to the square side of the graphene and is arranged at intervals, wherein the vanadium dioxide strip is arranged at a diagonal position of the vanadium dioxide outer ring and is spaced apart from the vanadium dioxide outer ring, the diagonal line of the graphene on each encoding unit intersects with the diagonal line of the dielectric layer and is arranged at a 45° angle, and a gap is left between the outer edges of the graphene and the dielectric layer.

2. The coding metasurface with both terahertz wave absorption and reflection functions according to claim 1, characterized in that: The vanadium dioxide strips are designed as rectangles with unequal lengths and widths, and the size of the outer ring of vanadium dioxide is smaller than that of graphene.

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

2.

4. The coding metasurface with both terahertz wave absorption and reflection functions according to claim 1, characterized in that: Through the synergistic effect of graphene voltage regulation and vanadium dioxide temperature regulation, millisecond-level switching between absorption mode and reflection mode can be achieved.

5. The coding metasurface with both terahertz wave absorption and reflection functions according to claim 4, characterized in that: When vanadium dioxide is in an insulating state at room temperature, the coding metasurface with both terahertz wave absorption and reflection functions realizes an absorption mode, and the coding metasurface with both terahertz wave absorption and reflection functions and its application achieve an absorption rate of >90% in the 1.97-2.5THz frequency band; when vanadium dioxide is in a metallic state, the coding metasurface with both terahertz wave absorption and reflection functions realizes a reflection mode, and the reflection phase control accuracy of the coding metasurface with both terahertz wave absorption and reflection functions is >95%.

6. An application method of a coding metasurface with both terahertz wave absorption and reflection functions, characterized in that: The following steps are involved: Using the coding metasurface with both terahertz wave absorption and reflection functions as described in any one of claims 1 to 5, by regulating the Fermi level of graphene, a first coding unit and a second coding unit with a phase difference of 180° are obtained; An X-axis absorber is designed, 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, and the first encoding unit or the second encoding unit along the Y-axis are the same type; A Y-axis absorber is designed, 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, and the first encoding unit or the second encoding unit is of the same type along the X-axis; The Fermi level of the graphene in the first coding unit is 0.2 eV, the Fermi level of the graphene in the second coding unit is 0.4 eV, and the encoding is performed using a grid encoding method based on the X-axis absorber and / or the Y-axis absorber.

7. The method for applying the coding metasurface having both terahertz wave absorption and reflection functions according to claim 6, characterized in that: When it is necessary to obtain the terahertz reflected wave beam of two electromagnetic waves that form an angle with the plane in the xoz interface, the X-axis absorber arranged in a grid coding manner is selected; when it is necessary to form a two-beam wave with an angle in the yoz coordinate plane, the Y-axis absorber arranged in a grid coding manner is selected; when it is necessary to deflect and control the azimuth angle of the terahertz reflected wave, different X-axis absorbers or Y-axis absorbers with the same number of periods are selected; 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.

8. An application method of a coding metasurface with both terahertz wave absorption and reflection functions, characterized in that: The following steps are involved: Using the coding metasurface with both terahertz wave absorption and reflection functions as described in any one of claims 1 to 5, by regulating the Fermi level of graphene, a first coding unit and a second coding unit with a phase difference of 180° are obtained; An XY absorber is designed, wherein the XY axis absorber includes a first coding unit and a second coding unit arranged in an array, wherein the first coding unit and the second coding unit are periodically arranged along the direction of the X axis, and the first coding unit and the second coding unit are also periodically arranged along the direction of the Y axis, wherein the Fermi level of the graphene of the first coding unit is 0.2 eV, and the Fermi level of the graphene of the second coding unit is 0.4 eV.

9. The method for applying the coding metasurface with both terahertz wave absorption and reflection functions according to claim 8, characterized in that: When the elevation angle and azimuth of the reflected beam need to be changed, the number of periods in the X-axis direction or the Y-axis direction on the XY absorber is changed, and the elevation angle and azimuth of the reflected beam are changed at the same time. 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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