Reconfigurable terahertz coding metasurface based on dual tunable materials and application

Abstract

The scheme provides a reconfigurable terahertz coding metasurface based on double adjustable materials and application, comprising: at least one metasurface structure unit, each metasurface structure unit comprising a vanadium dioxide layer, a graphene layer, a silicon dielectric layer, a polyimide intermediate layer and a metal bottom plate arranged in sequence from top to bottom, wherein the vanadium dioxide layer is composed of a first circular ring and a second circular ring arranged concentrically, the first circular ring is divided into four identical first circular arcs, a first interval section is arranged between adjacent first circular arcs, the second circular ring is divided into four identical second circular arcs, a second interval section is arranged between adjacent second circular arcs, and the first interval section and the second interval section are arranged alternately, the reflection and wave absorption functions can be integrated, the geometric symmetry is converted into electromagnetic parameter symmetry to dynamically adapt to environmental fluctuations, and then the anti-interference ability and stable operation ability of the terahertz communication system in a complex environment are improved.

Description

Technical Field

[0001] This invention relates to the field of terahertz communication technology, and in particular to a reconfigurable terahertz coded metasurface based on dual tunable materials and its applications. Background Technology

[0002] With the continuous evolution of communication technology, the sixth-generation mobile communication 6G system is expanding into the terahertz frequency band. Terahertz communication, with its advantages of ultra-high bandwidth and high-speed transmission, has become one of the key technological directions for realizing the vision of 6G communication. In terahertz communication systems, metasurfaces, as core components, play an important role in electromagnetic wave modulation and signal processing, and their performance directly affects the reliability, efficiency, and applicable scenarios of terahertz communication.

[0003] Traditional metasurfaces either employ a single operating mode, making it impossible to dynamically adjust their electromagnetic properties according to environmental fluctuations and adapt to complex communication scenarios; or they have fixed absorption frequency bands and narrow bandwidths, making it difficult to maintain stable absorption performance under multi-band interference caused by environmental fluctuations; at the same time, their phase modulation accuracy is inherently limited, leading to beam deflection errors, affecting the efficiency of multi-user spatial multiplexing, and the lack of environmental adaptability makes it difficult to eliminate network coverage blind spots, thus restricting the reliability of terahertz communication.

[0004] In addition, in practical terahertz communication applications, the interference of external environmental fluctuations on the metasurface control effect is particularly prominent, becoming a key bottleneck restricting the performance of traditional metasurfaces. During actual transmission, the incident angle of terahertz waves is easily shifted due to factors such as the movement of communication terminals and obstruction by obstacles. Traditional metasurfaces are mostly designed based on fixed incident angles and lack angle adaptability. Even a small shift in the incident angle will significantly reduce its control efficiency, resulting in beam deviation and a decrease in communication performance. Summary of the Invention

[0005] The purpose of this invention is to provide a reconfigurable terahertz coded metasurface based on dual tunable materials, optimize the structural design of the terahertz coded metasurface to integrate reflection and absorption functions, and transform geometric symmetry into electromagnetic parameter symmetry to dynamically adapt to environmental fluctuations, thereby improving the anti-interference capability and stable operation capability of the terahertz communication system in complex environments.

[0006] To achieve the above objectives, this technical solution provides a reconfigurable terahertz coded metasurface based on dual tunable materials, comprising: at least one metasurface structural unit, each metasurface structural unit comprising, from top to bottom, a vanadium dioxide layer, a graphene layer, a silicon dielectric layer, a polyimide intermediate layer, and a metal substrate, wherein the vanadium dioxide layer is composed of a first ring and a second ring arranged concentrically, the first ring being divided into four identical first arcs, with a first interval segment between adjacent first arcs, the second ring being divided into four identical second arcs, with a second interval segment between adjacent second arcs, and the first interval segment and the second interval segment being staggered, and both the first ring and the second ring being made of vanadium dioxide.

[0007] Secondly, this solution provides a 1-bit encoding method based on a reconfigurable terahertz encoded metasurface with dual tunable materials, comprising the following steps:

[0008] Two types of metasurface structural units with a phase difference of π are alternately arranged along the x-direction, and / or two types of metasurface structural units with a phase difference of π are alternately arranged along the y-direction, wherein the metasurface structural units are in reflection mode.

[0009] Thirdly, this scheme provides a 2-bit encoding method based on a reconfigurable terahertz encoded metasurface with dual tunable materials, including the following steps:

[0010] Four types of metasurface structural units with a phase difference of π / 2 are alternately arranged along the x-direction, and / or four types of metasurface structural units with a phase difference of π / 2 are alternately arranged along the y-direction, wherein the metasurface structural units are in reflection mode.

[0011] Compared with existing technologies, this technical solution has the following characteristics and beneficial effects:

[0012] 1. By innovatively combining the electromagnetic properties of graphene and vanadium dioxide, and through dual regulation of electrical signals and temperature, synchronous dynamic control of the electromagnetic wave reflection phase (0°~270° continuously adjustable) and amplitude is achieved, breaking through the limitations of traditional metasurfaces with single functions.

[0013] 2. A 2-bit coded metasurface based on four-state phase difference is proposed. A multi-period coding mode is constructed by combining the convolution theorem. For the first time, omnidirectional flexible control of terahertz beams in azimuth (0°~315°) and elevation (0°~26°) is realized, supporting single-beam directional reflection, multi-beam splitting and anomalous deflection.

[0014] 3. By integrating reflection and absorption functions into the same metasurface structure and achieving mode switching through vanadium dioxide conductivity switching, the reflection efficiency is >70% in the 5.4-5.6THz frequency band and the absorption rate is >99% in the 1.2 / 2.6THz frequency band, solving the problems of non-line-of-sight transmission and co-channel interference in 6G communication. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a reconfigurable terahertz coded metasurface based on dual tunable materials.

[0016] Figure 2 These are reflection amplitude and phase diagrams of metasurface structural units at different graphene Fermi levels.

[0017] Figure 3 This is a three-dimensional far-field scattering map of different 1-bit coding modes at a frequency of 5.4 THz.

[0018] Figure 4 It is a two-dimensional scattering diagram of different 1-bit coding modes at a frequency of 5.4 THz.

[0019] Figure 5 This is a three-dimensional far-field scattering map of different 1-bit coding modes at a frequency of 5.4 THz.

[0020] Figure 6 It is a two-dimensional scattering diagram of different 1-bit coding modes at a frequency of 5.4 THz.

[0021] Figure 7 It is a far-field three-dimensional heat dissipation diagram of the metasurface with the encoding mode of “000000000”.

[0022] Figure 8 It is X 2bit Encoding mode and Y 2bit Three-dimensional far-field simulation scattering diagram of the coded mode at 5.4THz.

[0023] Figure 9 It is X 2bit Encoding mode and Y 2bit The result of convolutional stacking of the encoding modes at 5.4THz.

[0024] Figure 10 It is the absorption rate curve of the metasurface structural unit in the microwave absorption mode. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0026] Those skilled in the art should understand that, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting this invention.

[0027] Example 1

[0028] like Figure 1 As shown, this design provides a reconfigurable terahertz coded metasurface based on dual tunable materials, comprising: at least one metasurface structural unit, each metasurface structural unit comprising, from top to bottom, a vanadium dioxide layer, a graphene layer, a silicon dielectric layer, a polyimide intermediate layer, and a metal substrate, wherein the vanadium dioxide layer is composed of a first ring and a second ring arranged concentrically, the first ring being divided into four identical first arcs, with a first interval segment between adjacent first arcs, the second ring being divided into four identical second arcs, with a second interval segment between adjacent second arcs, and the first interval segment and the second interval segment being staggered, the first ring and the second ring being made of vanadium dioxide.

[0029] This design utilizes a dual-tunable material-based reconfigurable terahertz coded metasurface. Instead of traditional metal patch patterns, the metasurface's functionality is switched by adjusting the conductivity of vanadium dioxide using temperature control, and its equivalent electromagnetic parameters are altered by adjusting the Fermi level of graphene using a bias voltage controlled by an FPGA. This allows for continuous control of the phase of reflected or transmitted electromagnetic waves.

[0030] In addition, the first and second rings of the reconfigurable terahertz coded metasurface based on dual tunable materials designed in this scheme both adopt an evenly divided symmetrical structure. The geometric symmetry of the symmetrical structure can be directly converted into the symmetry of the electromagnetic parameters, thereby reducing the interference of external environmental fluctuations (such as small temperature changes, incident wave angle shifts, and small material parameter errors) on the control effect.

[0031] Specifically, the center of the vanadium dioxide layer in the metasurface structural unit overlaps with the center of the graphene layer, and the entire vanadium dioxide layer is disposed on the graphene layer. Similarly, the center of the graphene layer overlaps with the center of the silicon dielectric layer, and the entire graphene layer is disposed on the silicon dielectric layer.

[0032] In some embodiments, the cross-sections of both the silicon dielectric layer and the graphene layer of the metasurface structure unit are square, and the cross-section of the graphene layer is smaller than that of the silicon dielectric layer.

[0033] In some specific embodiments, the side length P of the silicon dielectric layer of the metasurface structural unit is 22 μm, and the side length d of the graphene layer is 19.8 μm.

[0034] As mentioned earlier, the vanadium dioxide layer in this design consists of a first ring and a second ring arranged concentrically. Both the first and second rings are divided into four identical circular arcs to generate electromagnetic coupling within the metasurface structural unit. It should be noted that the circular shape of the first and second rings matches the "circular polarization propagation" characteristics of terahertz waves, and the segmented design of the rings further enhances the precise control of electromagnetic parameters.

[0035] In some embodiments, the four first intervals on the first ring have the same width, and the width w1 of the first interval is 2.2 μm.

[0036] In some embodiments, the four second intervals on the second ring have the same width, and the width w2 of the second interval is 2.2 μm.

[0037] It should be noted that the staggered arrangement of the first and second interval segments in this scheme means that the first and second interval segments are located on different radial directions of the first or second ring, that is, the radial directions of the first and second interval segments do not overlap.

[0038] In some embodiments, the first ring has a certain thickness, the outer radius R1 of the first ring is 6.6 μm, and the inner radius r1 of the first ring is 4.4 μm.

[0039] In some embodiments, the second ring also has a certain thickness, the outer radius R2 of the second ring is 3.3 μm, and the inner radius r1 of the first ring is 2.2 μm.

[0040] In some embodiments, the temperature of vanadium dioxide is adjusted to 80°C, at which point vanadium dioxide is in a metallic state, and the reconfigurable terahertz-encoded metasurface based on the dual tunable material is in reflection mode, which can be used to reflect terahertz waves. Correspondingly, when the reconfigurable terahertz-encoded metasurface based on the dual tunable material is in reflection mode, the conductivity σ of the first and second rings of the vanadium dioxide layer is 200000 S / m.

[0041] In some embodiments, the temperature of vanadium dioxide is controlled at 50~60℃. At this temperature, vanadium dioxide is in a dielectric state, and the reconfigurable terahertz coded metasurface based on the dual tunable material is in an absorbing mode, which can be used as a multi-band absorber. Correspondingly, when the reconfigurable terahertz coded metasurface based on the dual tunable material is in an absorbing mode, the conductivity σ of the first and second rings of the vanadium dioxide layer is 50 S / m.

[0042] In some embodiments, the graphene layer is a graphene film, and the thickness of the graphene layer is the thickness of a single carbon atom, that is, the thickness of the graphene layer is 0.34 nm.

[0043] Furthermore, the silicon dielectric layer in this design allows for the application of different voltage signals, providing a basis for altering the Fermi level of the graphene film. The polyimide interlayer, with a dielectric constant of 3.5, possesses excellent mechanical properties, chemical stability, and electrical insulation, serving as a supporting structure for the metasurface structural unit and meeting the wavelength matching requirements for terahertz waves. The metal layer enhances the response to terahertz signals, while the presence of the metal substrate ensures that most of the electromagnetic energy is reflected.

[0044] As mentioned earlier, this scheme generates metasurface structural units with different phases by controlling the Fermi level of the graphene layer. Specifically, when the metasurface structural unit is in reflection mode, controlling the Fermi level of the graphene layer to 0.01, 0.13, 0.26, and 0.38 yields four metasurface structural units with different phases, and the phase difference between adjacent metasurface structural units is 1 / 2π. Furthermore, two metasurface structural units with a phase difference of π form a 1-bit code, and two metasurface structural units with a phase difference of 1 / 2π form a 2-bit code.

[0045] Furthermore, such as Figure 2 As shown, this scheme modulates the bias voltage of the metasurface structural unit, and through CST simulation, generates four digital states "00", "01", "10" and "11" in binary form at different graphene Fermi levels. The simulation results of their reflection phase and amplitude are as follows. Figure 2 As shown in (a) and (b), it can be seen that the reflection amplitude of all states is above 0.7 at the operating frequency, which ensures good overall reflection efficiency. The phase responses of the four digital states of the metasurface structure unit are -798.3°, -695.4°, -609.0° and -523.9°, respectively. Obviously, the phase difference between the states of adjacent metasurface structure units is almost 90°±10°, which makes the device a 2-bit digital metasurface.

[0046] Specifically, when the metasurface structural unit is in reflection mode, when the Fermi level Ef of the graphene layer is adjusted to 0.01, the absolute phase of the metasurface structural unit is -798.3°, and the encoding state of the metasurface structural unit is defined as "00"; when the Fermi level Ef of the graphene layer is adjusted to 0.13, the absolute phase of the metasurface structural unit is -695.4°, and the encoding state of the metasurface structural unit is defined as "01"; when the Fermi level Ef of the graphene layer is adjusted to 0.26, the absolute phase of the metasurface structural unit is -609.0°, and the encoding state of the metasurface structural unit is defined as "10"; when the Fermi level Ef of the graphene layer is adjusted to 0.38, the absolute phase of the metasurface structural unit is -523.9°, and the encoding state of the metasurface structural unit is defined as "11". The reflection phase of the metasurface structural unit at different Fermi levels of the graphene layer is shown in Table 1 below.

[0047] Table 1. Reflection Phase Table of Metasurface Structure Units at Fermi Levels of Different Graphene Layers

[0048] .

[0049] When the metasurface structure unit is in the absorption mode, the absorption rate curve of the metasurface structure unit in the absorption mode is as follows: Figure 10 As shown, in absorption mode, the metasurface structure unit exhibits two absorption peaks, with absorption rates exceeding 99% at 1.2 THz and 2.6 THz. Further adjustments to the Fermi level of the graphene can further refine the frequency of these absorption peaks. As the Fermi level Ef gradually increases from 0.2 eV to 0.5 eV, the absorption peak at 2.6 THz gradually exhibits a blue shift, reaching its maximum absorption rate at 0.3 eV.

[0050] As mentioned earlier, the reconfigurable terahertz coded metasurface based on dual tunable materials in this scheme has a reflection efficiency of >70% in the 5.4-5.6THz frequency band and an absorption rate of >99% in the 1.2 / 2.6THz frequency band.

[0051] Example 2

[0052] This solution provides a 1-bit encoding scheme based on the reconfigurable terahertz coded metasurface based on dual tunable materials designed in Embodiment 1. Correspondingly, this solution provides a 1-bit encoding method based on the reconfigurable terahertz coded metasurface based on dual tunable materials, including the following steps:

[0053] Two types of metasurface structural units with a phase difference of π are alternately arranged along the x-direction, and / or two types of metasurface structural units with a phase difference of π are alternately arranged along the y-direction, wherein the metasurface structural units are in reflection mode.

[0054] In some embodiments, the conductivity of vanadium dioxide is adjusted to σ = 200000 S / m to obtain a metasurface structural unit in reflection mode.

[0055] The method of alternating metasurface structural units with a phase difference of π along the x-direction is called x-axis encoding, and the method of alternating metasurface structural units with a phase difference of π along the y-direction is called y-axis encoding. When the 1-bit encoding method of the reconfigurable terahertz encoded metasurface based on dual tunable materials encodes only along the x-axis or along the y-axis, it is a 1-bit traditional encoding mode. When the 1-bit encoding method of the reconfigurable terahertz encoded metasurface based on dual tunable materials encodes along both the x-axis and the y-axis, it is a 1-bit checkerboard encoding mode.

[0056] When two symmetrical reflected waves need to be generated in the xoz plane, metasurface structural units with a phase difference of π are alternately arranged along the x-direction, i.e., encoding along the x-axis; when two symmetrical reflected waves need to be generated in the yoz plane, metasurface structural units with a phase difference of π are alternately arranged along the y-direction, i.e., encoding along the y-axis. Furthermore, the deflection angle of the reflected waves can be changed by adjusting the number of metasurface structural units in the basic unit.

[0057] When four reflected waves need to be generated, metasurface structural units with a phase difference of π are alternately arranged along the x-direction at least once, and simultaneously, metasurface structural units with a phase difference of π are alternately arranged along the y-direction at least once. Furthermore, the number of metasurface structural units in the basic unit can be adjusted.

[0058] Specifically, as mentioned earlier, when the metasurface structural unit is in reflection mode, the phase difference between the metasurface structural unit with a Fermi level of 0.01 and the metasurface structural unit with a Fermi level of 0.26 in the graphene layer is π; the phase difference between the metasurface structural unit with a Fermi level of 0.13 and the metasurface structural unit with a Fermi level of 0.38 in the graphene layer is π.

[0059] In some embodiments, the base unit contains at least one metasurface structure unit, and the encoding period is the same as the number of metasurface structure units in the base unit. For example, when the encoding period is single-cycle encoding, the base unit contains only one metasurface structure unit.

[0060] Since the phase difference between metasurface structure units during 1-bit encoding is π, the encoding state of one metasurface structure unit is defined as "0", and the encoding state of the other metasurface structure unit is defined as "1". For example, when performing single-cycle encoding along the x-axis, the metasurface structure units alternate along the x-axis in the pattern "01010101", which can be defined as X1; when performing double-cycle encoding along the x-axis, the metasurface structure units alternate along the x-axis in the pattern "0011001100110011", which can be defined as X2; similarly, when performing single-cycle encoding along the y-axis, the metasurface structure units alternate along the y-axis in the pattern "01010101", which can be defined as Y1; when performing double-cycle encoding along the y-axis, the metasurface structure units alternate along the y-axis in the pattern "0011001100110011", which can be defined as Y... 2。

[0061] like Figure 3 and Figure 4 As shown, Figure 3 These are three-dimensional far-field scattering maps of different 1-bit encoding methods at a frequency of 5.4 THz. Figure 4 This is a two-dimensional scattering diagram of different 1-bit encoding methods at a frequency of 5.4 THz. It can be seen that the encoding modes X1 and X2 generate two symmetrical reflected waves in the xoz plane, with corresponding beam deflection angles of 17° and 8°, respectively. Figure 4 The two-dimensional scattering energy diagram shows that the deflection angle matches the numerical calculation result. The corresponding encoding modes of Y1 and Y2 also produce two symmetrical reflected waves in the y-0-z plane, with the corresponding beam deflection angles of 18° and 8°, which also conform to the theoretical numerical calculation.

[0062] like Figure 5 and Figure 6 As shown, Figure 5 These are three-dimensional far-field scattering maps of different 1-bit encoding methods at a frequency of 5.4 THz. Figure 6 These are two-dimensional scattering patterns of different 1-bit encoding methods at a frequency of 5.4 THz.

[0063] When single-cycle encoding is performed along the x-axis and simultaneously along the y-axis, the metasurface structural units are arranged alternately along the x-axis and y-axis in the pattern "01010101", which can be defined as the X1Y1 encoding mode. Similarly, when single-cycle encoding is performed along the x-axis and simultaneously along the y-axis in the pattern "01010101", the metasurface structural units are arranged alternately along the x-axis in the pattern "01010101" and along the y-axis in the pattern "0011001100110011", which can be defined as the X1Y2 encoding mode. Similarly, when performing double-cycle encoding along the x-axis and single-cycle encoding along the y-axis, the metasurface structural units are arranged alternately along the y-axis in the pattern "01010101" and alternately along the x-axis in the pattern "0011001100110011". This can be defined as the X2Y1 encoding mode. When performing double-cycle encoding along the x-axis and double-cycle encoding along the y-axis, the metasurface structural units are arranged alternately along the x-axis and y-axis in the pattern "01010101". This can be defined as the X2Y2 encoding mode. It can be clearly seen that all checkerboard coding patterns can generate four reflected waves. However, the deflection angles of the four reflected waves are different depending on the coding combination in the X and Y directions. The corresponding reflection deflection angles for the X1Y1 coding pattern are (θ, φ) = (26°, 45° / 135° / 225° / 315°). Comparing this to the reflection wave deflection angles for the X1Y1 coding pattern (θ, φ) = (13°, 45° / 135° / 225° / 315°), it can be seen that changing the number of coding cycles can change the deflection angle of the reflected waves, which is still applicable in the checkerboard coding pattern. The deflection angles for the X1Y2 encoding mode are (θ, φ) = (22°, 26° / 152° / 206° / 332°), and for the X2Y1 encoding mode are (θ, φ) = (20°, 64° / 114° / 244° / 294°). This shows that when the number of encoding cycles differs in different directions, the deflection angle in a particular direction can be changed independently, providing greater freedom in controlling beam deflection. This scheme can control the deflection angle θ within the range of 0°-26° through different encoding methods.

[0064] Furthermore, if there are only single-phase metasurface structural units along the x-axis or y-axis, there is no phase change in the encoding mode, resulting in specular reflection. This almost completely reflects electromagnetic waves perpendicular to the incident plane, with only one main reflection beam and a reflection deflection angle of θ = 0°. For example... Figure 7 As shown, the far-field three-dimensional heat dissipation diagram of the metasurface is generated using the X0 encoding mode with the encoding method "000000000". Figure 7 As shown.

[0065] Example 3

[0066] This solution provides a 2-bit encoding scheme based on the reconfigurable terahertz encoding metasurface based on dual tunable materials designed in Embodiment 1. The 2-bit encoding scheme can use four encoding units with a 90° phase difference to combine into more encoding modes, compensating for the shortcomings of 1-bit encoding, carrying more information, and bringing more degrees of encoding freedom. Correspondingly, this solution provides a 2-bit encoding method based on the reconfigurable terahertz encoding metasurface based on dual tunable materials, including the following steps:

[0067] Four types of metasurface structural units with a phase difference of π / 2 are alternately arranged along the x-direction, and / or four types of metasurface structural units with a phase difference of π / 2 are alternately arranged along the y-direction, wherein the metasurface structural units are in reflection mode.

[0068] In some embodiments, the conductivity of vanadium dioxide is adjusted to σ = 200000 S / m to control the four metasurface structural units to be in reflection mode.

[0069] In some embodiments, the base unit contains at least one metasurface structure unit, and the encoding period is the same as the number of metasurface structure units in the base unit. For example, when the encoding period is single-cycle encoding, the base unit contains only one metasurface structure unit.

[0070] When a single reflected wave needs to be generated, four types of metasurface structural units with a phase difference of π / 2 are selected as the basic units and alternately arranged along the x-direction, or four types of metasurface structural units with a phase difference of π / 2 are selected as the basic units and alternately arranged along the y-direction. The azimuth angle of the reflected wave is controlled by the number of metasurface structural units in the basic units.

[0071] When it is necessary to adjust the elevation and azimuth angles of a single reflected wave, four types of metasurface structural units with a phase difference of π / 2 are selected as basic units and alternately arranged along the x-direction, and four types of metasurface structural units with a phase difference of π / 2 are alternately arranged along the y-direction. The phase information and encoding sequence of each metasurface structural unit are convolved to obtain the synthetic reflection field of the entire metasurface. The azimuth angle of the reflected wave is adjusted by the number of metasurface structural units in the basic units. In some embodiments, the azimuth angle of the reflected wave is flexibly adjustable omnidirectionally from 0° to 315° and the elevation angle is 0° to 26°.

[0072] For example, if the first metasurface structural unit has a phase of 0° and the second unit has a phase of 270° (equivalent to -90°), the complex field representation of their convolution is:

[0073] The first one:

[0074] The second one:

[0075] Adding them together gives the total field (a simple superposition in a given observation direction, ignoring propagation phase difference):

[0076]

[0077] Find the modulus and phase (bit-by-bit):

[0078] mold:

[0079] Phase:

[0080] Therefore, after two equal-amplitude metasurface structural units are superimposed in this direction, the phase becomes 45°, the amplitude increases to 1 / 3 of the original unit amplitude. This means that local interference combines "0° and 270°" into a wave with a -45° phase and amplified amplitude.

[0081] In some embodiments, the reconfigurable terahertz coded metasurface based on dual tunable materials of this scheme generates eight azimuth angles of 0°, 90°, 180°, 270°, and 315°.

[0082] Specifically, when the metasurface structural units are in reflection mode, the phase difference between the metasurface structural units with Fermi levels of 0.01, 0.13, 0.26, and 0.38 in the graphene layer is set to π / 2. Therefore, these four metasurface structural units are used for 2-bit encoding, and the encoding states are defined as 0, 1, 2, and 3, respectively. For example, the encoding pattern of the four metasurface structural units with a phase difference of π / 2, which are set as basic units and alternately set along the x-direction, is X. 2bit Encoding mode: If there is only one metasurface structure unit in the basic unit, then X 2bit In the encoding pattern, the metasurface structural units are arranged in the manner of "01230123"; similarly, the encoding pattern of four types of metasurface structural units with a phase difference of π / 2, which are used as basic units and alternately arranged along the x-direction, is Y. 2bit Encoding mode: If there is only one metasurface structure unit in the basic unit, then Y 2bit In the encoding pattern, the metasurface structure units are arranged in the manner of "01230123", corresponding to X. 2bit Encoding mode and Y 2bit The three-dimensional far-field simulation scattering pattern of the encoding mode at 5.4 THz is shown below. Figure 8 As shown,

[0083] X 2bit Encoding mode and Y 2bit The result of convolutional stacking of the encoding modes at 5.4THz is as follows: Figure 9As shown, in this instance, X 2bit-1 Encoding mode and Y 2bit-1 The result of the encoding pattern concatenation, before convolution, X 2bit-1 Encoding mode and Y 2bit-1 The azimuth angles φ of the encoding modes are 0° and 270° respectively. It is clear that the azimuth angle φ of the final superimposed beam is equal to X. 2bit-1 Encoding mode and Y 2bit-1 The superposition of the coding patterns is 315°, and the elevation angle is 9°. Therefore, it is easy to obtain that for the four directions of 0°, 90°, 180°, and 270°, the azimuth angle of the reflected wave can be expanded to eight using convolution calculations, where X... 2bit-1 The encoding mode is represented as: ;

[0084] Y 2bit-1 The encoding mode is represented as:

[0085] ;

[0086] The convolutional stack is represented as:

[0087] .

[0088] Those skilled in the art should understand that the technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been 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.

[0089] The above embodiments are merely illustrative of several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A reconfigurable terahertz coded metasurface based on dual tunable materials, characterized in that, include: At least one metasurface structural unit, each metasurface structural unit comprising, from top to bottom, a vanadium dioxide layer, a graphene layer, a silicon dielectric layer, a polyimide intermediate layer, and a metal substrate, wherein the vanadium dioxide layer is composed of a first ring and a second ring arranged concentrically, the first ring being divided into four identical first arcs, with a first interval between adjacent first arcs, the second ring being divided into four identical second arcs, with a second interval between adjacent second arcs, and the first and second intervals being alternately arranged, the first and second rings being made of vanadium dioxide, and when the metasurface structural unit is in reflection mode, the Fermi level of the graphene layer is adjusted to 0.01, 0.13, 0.26, and 0.38, respectively, to obtain four metasurface structural units with different phases, and the phase difference between adjacent metasurface structural units is 1 / 2π.

2. The reconfigurable terahertz coded metasurface based on dual tunable materials according to claim 1, characterized in that, The four first intervals on the first ring have the same width, w1, which is 2.2 μm. The four second intervals on the second ring have the same width, w2, which is 2.2 μm. The outer radius R1 of the first ring is 6.6 μm, and the inner radius r1 of the first ring is 4.4 μm. The second ring also has a certain thickness, with an outer radius R2 of 3.3 μm and an inner radius r1 of 2.2 μm for the first ring.

3. The reconfigurable terahertz coded metasurface based on dual tunable materials according to claim 1, characterized in that, By controlling vanadium dioxide to be in a metallic state, a reconfigurable terahertz-encoded metasurface based on a dual-tunable material is put into a reflection mode, which can be used to reflect terahertz waves. By controlling vanadium dioxide to be in a dielectric state, a reconfigurable terahertz-encoded metasurface based on a dual-tunable material is put into an absorption mode, which can be used as a multi-band absorber.

4. The reconfigurable terahertz coded metasurface based on dual tunable materials according to claim 1, characterized in that, The reflection efficiency is >70% in the 5.4-5.6THz frequency band, and the absorption rate is >99% in the 1.2 / 2.6THz frequency band.

5. A 1-bit encoding method based on a reconfigurable terahertz coded metasurface with dual tunable materials, characterized in that, Includes the following steps: Two metasurface structural units with a phase difference of π are alternately arranged along the x-direction, and / or two metasurface structural units with a phase difference of π are alternately arranged along the y-direction, wherein the metasurface structural units are in reflection mode. The metasurface structural units include, from top to bottom, a vanadium dioxide layer, a graphene layer, a silicon dielectric layer, a polyimide intermediate layer, and a metal substrate. The vanadium dioxide layer is composed of a first ring and a second ring arranged concentrically. The first ring is divided into four identical first arcs, with a first interval between adjacent first arcs. The second ring is divided into four identical second arcs, with a second interval between adjacent second arcs. The first interval and the second interval are alternately arranged. Both the first ring and the second ring are made of vanadium dioxide. When the metasurface structural units are in reflection mode, the Fermi level of the graphene layer is adjusted to 0.01, 0.13, 0.26, and 0.38, respectively, to obtain four metasurface structural units with different phases, and the phase difference between adjacent metasurface structural units is 1 / 2π.

6. The 1-bit encoding method based on a reconfigurable terahertz coded metasurface using dual tunable materials according to claim 5, characterized in that, When it is necessary to generate two symmetrical reflected waves in the xoz plane, metasurface structural units with a phase difference of π are alternately arranged along the x direction, i.e., encoding is performed along the x-axis; when it is necessary to generate two symmetrical reflected waves in the yoz plane, metasurface structural units with a phase difference of π are alternately arranged along the y direction, i.e., encoding is performed along the y-axis.

7. The 1-bit encoding method based on a reconfigurable terahertz coded metasurface using dual tunable materials according to claim 5, characterized in that, When four reflected waves need to be generated, metasurface structural units with a phase difference of π are alternately arranged along the x-direction, and simultaneously metasurface structural units with a phase difference of π are alternately arranged along the y-direction.

8. A 2-bit encoding method based on a reconfigurable terahertz encoded metasurface with dual tunable materials, characterized in that, Includes the following steps: Four types of metasurface structural units with a phase difference of π / 2 are alternately arranged along the x-direction, and / or four types of metasurface structural units with a phase difference of π / 2 are alternately arranged along the y-direction, wherein the metasurface structural units are in reflection mode; The metasurface structure unit includes, from top to bottom, a vanadium dioxide layer, a graphene layer, a silicon dielectric layer, a polyimide intermediate layer, and a metal substrate. The vanadium dioxide layer consists of a first ring and a second ring arranged concentrically. The first ring is divided into four identical first arcs, with a first interval between adjacent first arcs. The second ring is divided into four identical second arcs, with a second interval between adjacent second arcs. The first and second intervals are staggered. Both the first and second rings are made of vanadium dioxide. When the metasurface structure unit is in reflection mode, the Fermi level of the graphene layer is adjusted to 0.01, 0.13, 0.26, and 0.38, respectively, resulting in four metasurface structure units with different phases. The phase difference between adjacent metasurface structure units is 1 / 2π.

9. The 2-bit encoding method for a reconfigurable terahertz coded metasurface based on dual tunable materials according to claim 8, characterized in that, When a single reflected wave needs to be generated, four types of metasurface structural units with a phase difference of π / 2 are selected as the basic units and alternately arranged along the x-direction, or four types of metasurface structural units with a phase difference of π / 2 are selected as the basic units and alternately arranged along the y-direction; when the elevation and azimuth angles of a single reflected wave need to be adjusted, four types of metasurface structural units with a phase difference of π / 2 are selected as the basic units and alternately arranged along the x-direction, and four types of metasurface structural units with a phase difference of π / 2 are selected as the basic units and alternately arranged along the y-direction, and the phase information and encoding sequence of each metasurface structural unit are convolved.

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