Graphene three-bit multifunctional encoding metasurface based on geometric phase

Abstract

The application provides a graphene three-bit multifunctional encoding metasurface based on geometric phase, which adopts a three-layer structure, and a composite structure containing graphene and an "I" type metal arm is arranged on the top. By rotating the angle of the metal arm, eight three-bit encoding units with a phase difference of 45 degrees are constructed based on the geometric phase principle. In the reflection mode, by encoding and arranging the units, high-precision beam control such as beam splitting, abnormal deflection and vortex beam generation can be realized. Meanwhile, by electrically controlling the Fermi level of graphene, the dynamic switching of the working mode of the metasurface can be realized: when the Fermi level is 0eV, the metasurface is in the high-efficiency reflection mode, and the reflection amplitude is higher than 80%; when the Fermi level rises to 1.0eV, the metasurface is switched to the high-efficiency absorption mode, and the absorption rate can reach 98.9% at 1.42THz. The application realizes the unification of high-precision beam control and dynamic function reconstruction.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electromagnetic metasurfaces, specifically to the sub-field of beam control and wave-absorbing materials in the terahertz frequency band, and is particularly suitable for dynamic multi-functional coded metasurface design based on geometric phase regulation, which can be applied to 6G communication, radar detection, terahertz stealth, and energy collection scenarios. BACKGROUND

[0002] A metasurface is a two-dimensional planar artificial electromagnetic material composed of unit structures with subwavelength sizes arranged periodically or non-periodically, which can flexibly regulate the amplitude, phase, polarization, and other characteristics of electromagnetic waves with extremely high efficiency. In recent years, digital coding and information science theory have been introduced into metasurface design, forming digital coded metasurfaces, which encode different electromagnetic responses into binary codes such as "0" and "1", and control electromagnetic beams by designing different coding sequences to achieve beam splitting, beam deflection, radar cross section (RCS) reduction, and other functions.

[0003] However, existing coded metasurface technology still faces many challenges. First, in terms of beam fine regulation, most designs are limited to 1-bit or 2-bit phase coding, with low phase resolution (e.g., 180° or 90°), resulting in large phase quantization errors, which makes it difficult to meet the high-precision control requirements of beam pointing and waveforms in future wireless communication and high-resolution imaging fields. Second, in terms of functionality, once a traditional metasurface is prepared, its electromagnetic function is usually fixed and cannot be changed, such as only being able to achieve reflected beam regulation or only being used as a wave-absorbing body. This single-function characteristic limits its adaptability and application potential in complex and variable electromagnetic environments.

[0004] To overcome these limitations, the industry is exploring multi-functional reconfigurable metasurface technology that can achieve multi-bit high-precision coding and dynamically switch between different working modes (such as reflection and absorption). SUMMARY

[0005] The embodiment of the application provides a graphene three-bit multi-functional coded metasurface based on geometric phase, which aims to overcome the problems of existing coded metasurface technology, such as insufficient phase resolution leading to limited beam control accuracy, and single function, which cannot dynamically switch between multiple working modes such as reflection and wave absorption.

[0006] The core technology of the application is mainly to combine the geometric phase regulation of static rotating unit structures with the dynamic electric regulation of graphene Fermi level, to realize a multi-functional metasurface that can perform 3-bit high-precision phase coding and flexibly switch between efficient reflection and efficient absorption modes.

[0007] In a first aspect, the present application provides a graphene three-bit multifunctional encoding metasurface based on geometric phase, comprising:

[0008] a metal ground layer;

[0009] a dielectric layer disposed on the metal ground layer;

[0010] and an array layer composed of a plurality of unit structures, the array layer being disposed on the dielectric layer;

[0011] wherein each unit structure comprises a metal resonant patch and a graphene layer;

[0012] The plurality of unit structures are selected from at least two or more base units and arranged, the base units having the same geometric structure, but each having a preset, different rotation angle of the metal resonant patch relative to a reference axis, to produce different phase responses to the incident circularly polarized electromagnetic wave based on the geometric phase principle;

[0013] The Fermi energy level of the graphene layer can be electrically controlled by an externally applied bias voltage, so that the metasurface can be switched between at least the following two working modes:

[0014] Reflection mode: at the first Fermi energy level, the metasurface exhibits high reflection characteristics, and the arrangement of the unit structures in the array layer produces a preset phase gradient distribution to the incident electromagnetic wave, so as to realize the manipulation of the reflected beam;

[0015] Absorption mode: at the second Fermi energy level, the metasurface exhibits high absorption characteristics, and the reflection of the incident electromagnetic wave is significantly suppressed.

[0016] Further, the metal resonant patch is an anisotropic structure, and its shape is an "I" type structure.

[0017] Further, the base units include eight types, each having a rotation angle of the metal resonant patch with a step interval of 22.5°, which together constitute a 3-bit encoding unit to realize phase coverage of 0 to 360° for reflected electromagnetic waves.

[0018] Further, the metasurface operates in the terahertz frequency band.

[0019] Further, in the reflection mode, the metasurface can independently control the phase encoding of left and right circularly polarized waves.

[0020] Further, in the reflection mode, by arranging unit structures with different phase responses in a specific encoding sequence, the metasurface is used to realize at least one of the following functions: beam splitting, anomalous beam deflection, or vortex beam generation.

[0021] Further, the metasurface is used to generate a vortex beam, and the arrangement of the unit structure is as follows:

[0022] At least four basic units with a phase difference of 90° are arranged in a spiral manner in space to generate a vortex beam carrying orbital angular momentum.

[0023] Further, by Fourier convolution superimposing a phase distribution for generating a vortex beam with a gradient phase sequence, the metasurface is used to simultaneously generate multiple vortex beams propagating in different directions.

[0024] Further, the first Fermi energy level is 0eV, and in the reflection mode, the reflection amplitude of the metasurface is higher than 80%.

[0025] Further, the second Fermi energy level is 1.0eV, and in the absorption mode, the electromagnetic wave absorption rate of the metasurface at a specific frequency point is higher than 95%.

[0026] The main contributions and innovations of the present application are as follows:

[0027] 1. Multi-functional dynamic switching is achieved: The present application utilizes the electrically adjustable characteristics of graphene Fermi energy level, and by applying an external bias voltage, the metasurface can be dynamically switched between high-efficiency reflection mode (reflection amplitude is higher than 80% when Fermi energy level is 0eV) and high-efficiency absorption mode (absorption rate is as high as 98.9% at 1.42THz when Fermi energy level is 1.0eV), greatly enhancing the adaptability of the device to complex electromagnetic environments.

[0028] 2. The precision and information capacity of beam control are improved: The present application proposes a 3-bit encoding scheme based on geometric phase, and by rotating the "I" type metal structure, 8 independent phase states are realized at an angle interval of 22.5°, completely covering the phase range of 360°. This design not only improves the resolution of phase control and the accuracy of beam control, but also realizes independent 3-bit encoding of left-handed and right-handed circularly polarized waves, significantly improving the information processing capacity and control freedom compared to traditional single-polarization metasurfaces.

[0029] 3. The diversity and advancement of beam applications are enhanced: The present application not only realizes conventional beam splitting and abnormal deflection, but also proposes a new method for generating and manipulating multiple vortex beams. By combining the Fourier convolution theorem, a single vortex beam can be split into multiple preset directions (for example, the main beam is deflected by 20°), breaking through the limitations of traditional vortex single-path transmission. This innovation provides the possibility for spatial multi-channel coverage, has great potential in improving terahertz communication capacity and radar multi-target detection capability, and highly meets the application requirements of future technologies such as 6G.

[0030] The details of one or more embodiments of the application are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the application will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF DRAWINGS

[0031] The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the application. In the drawings:

[0032] Figure 1 is a graph of a graphene three-bit multifunctional encoding metasurface structure based on geometric phase according to an embodiment of the application, wherein (a) is an image of eight unit rotation angles, (b) is a top view of a single metasurface unit;

[0033] Figure 2 is a graph of the reflection phase (brown line) and amplitude (blue line) of eight units under LCP (a and c) and RCP (b and d) incidence at 1.35 THz under different Fermi levels according to an embodiment of the application;

[0034] Figure 3 is a graph of the phase distribution of graphene at different rotation angles at 0 eV according to an embodiment of the application;

[0035] Figure 4 is an image of a two-beam encoding metasurface along the x-axis 01010101… encoding according to an embodiment of the application, wherein (a) is a three-dimensional far-field reflection image, (b) is a normalized reflection amplitude curve;

[0036] Figure 5 is an image of an abnormal beam reflection metasurface along the x-axis 01230123… encoding according to an embodiment of the application, wherein (a) is a three-dimensional far-field image, (b) is a normalized amplitude curve;

[0037] Figure 6 is an image of an abnormal beam reflection metasurface along the x-axis 01234567… encoding according to an embodiment of the application, wherein (a) is a three-dimensional far-field image, (b) is a normalized amplitude curve;

[0038] Figure 7 is an image of a vortex wave beam generation according to an embodiment of the application, wherein (a) is a single vortex wave image, (b) is a vortex wave image after convolution theorem superposition, (c) is a schematic diagram of a convolution superposition calculation phase distribution;

[0039] Figure 8 is an electromagnetic wave absorption graph of an encoding unit under different graphene Fermi levels according to an embodiment of the application. DETAILED DESCRIPTION

[0040] The exemplary embodiments will be described in detail herein with reference to the attached drawings. The description of the exemplary embodiments is intended to apply to all alternative embodiments, as would be understood by one skilled in the art. In other words, descriptions of some embodiments in the specification do not necessarily apply to all embodiments. Similarly, the description "comprises," "comprising," "attached," or "coupled" and variations thereof are used generically and do not exclude the presence of zero or more additional elements or steps. Individual embodiments are described as though they were the only possible embodiments. Numerous and various embodiments can be made by those skilled in the art based on the teachings of the present specification without departing from the scope of the disclosure. Individual embodiments are described as though only one of each embodiment is needed. Multiple instances of individual embodiments are also possible. The illustrations presented are not necessarily drawn to scale and certain features can be exaggerated or minimized.

[0041] It should be noted that the steps of the methods in other embodiments are not necessarily performed in the order shown and described in this specification. In some other embodiments, the steps of the methods can be more or fewer than those described in this specification. Furthermore, individual steps described in this specification can be broken down into multiple steps in other embodiments; and multiple steps described in this specification can be combined into a single step in other embodiments.

[0042] Embodiment One

[0043] The present application aims to propose a graphene three-bit multifunctional encoding metasurface based on geometric phase. The core of the present application is a metasurface unit array composed of a plurality of periodically arranged metasurface units, wherein the structure of a single metasurface unit is the basis for realizing 3-bit phase encoding and dynamic mode switching, and its specific structure is as shown in Figure 1 Figure 1 (a) is a schematic diagram of 8 different rotation angles of the unit, Figure 1 (b) is a top view of a single unit.

[0044] Specifically, the single metasurface unit is sequentially composed of a top functional composite layer, a middle medium layer and a bottom ground metal layer from top to bottom, and the materials, parameters and functions of each layer are as follows:

[0045] The top functional composite layer (array layer) is composed of a fixed connection of an "I" type metal arm and a graphene patch, and is the core functional layer for realizing phase control and mode switching. The material of the "I" type metal arm is gold, and the thickness is 0.5 μm (0.3~0.7 μm is the preferred value), and the structural parameters are specifically: the width w=7.2 μm (7.0~7.5 μm is the preferred value), the outer circle metal circle radius R1=40 μm (38~42 μm is the preferred value), and the inner circle metal circle radius R2=24.2 μm (23~25 μm is the preferred value); the connection width d=10 μm (9~11 μm is the preferred value) between the graphene patch and the "I" type metal arm, and the Fermi energy level of the graphene can be adjusted in the range of 0~1.0 eV by external bias voltage to realize mode switching.

[0046] ​The intermediate dielectric layer (dielectric layer) is made of polyimide (excellent in insulation and dielectric stability, suitable for terahertz band), has a dielectric coefficient ε=3.5 (an optimal value in the range of 3.0-4.0), and a thickness of 17 μm (an optimal value in the range of 15-19 μm), and mainly functions to support the top functional composite layer and the bottom grounding metal layer and to regulate the propagation path of terahertz waves in the unit, thereby ensuring the stability of the phase response.

[0047] The bottom grounding metal layer (metal grounding layer) is also made of gold and has a thickness of 0.5 μm (consistent with the thickness of the top metal arm to avoid electromagnetic impedance mismatch caused by thickness difference), and functions to block the penetration of terahertz waves to the bottom of the metasurface, thereby ensuring the energy concentration in the reflection direction in the reflection mode and providing a grounding loop for the bias regulation of graphene.

[0048] In the embodiment, the period P (i.e., the distance between the centers of two adjacent units) of the metasurface unit is 100 μm (an optimal value in the range of 95-105 μm), which meets the subwavelength requirement (the unit period is much smaller than the working wavelength to avoid grating lobes) of the terahertz band (1.35-1.42 THz). In actual applications, the size of the metasurface unit array can be adjusted as required (for example, 3x3 units are used to form a super unit and 24x24 units are used to form a vortex wave array), and the units are arranged according to the periodic rule to ensure the consistency of the overall electromagnetic response.

[0049] The present application realizes 3-bit phase encoding by rotating the angle of the top "I"-shaped metal arm in combination with the geometric phase theory, and the core is to cover the 360° phase range by 8 preset discrete rotation angles, and the specific implementation process is as follows:

[0050] 1. Determination of rotation angle

[0051] To realize 3-bit encoding (corresponding to 2 3 =8 phase states), the rotation angle α of the "I"-shaped metal arm needs to cover 360°, and the phase difference between adjacent angles is uniform (to reduce quantization error). In the present embodiment, the 8 preset discrete rotation angles are 0°, 22.5°, 45°, 67.5°, 90°, 112.5°, 135°, and 157.5°, and the difference between any adjacent angles is 22.5°, and the corresponding phase difference is 45° (the relationship between geometric phase and rotation angle is "phase difference=2x rotation angle difference", 2x22.5°=45°).

[0052] 2. Phase coverage and stability verification

[0053] For example, Figure 3As shown (phase distribution when graphene Fermi level is 0eV), in the 1.0~1.8THz wide frequency range, the 8 different rotation angle units all maintain smooth 45° phase difference, and the phase response is not abrupt, proving that the design can stably cover the 360° phase range. This uniform phase difference is the key to realizing high-precision beam control - for example, in multi-beam splitting, beam overlap can be avoided; in abnormal deflection, the deflection angle can be accurately controlled.

[0054] 3. Implementation of dual-polarization independent coding

[0055] As shown in (a)-(d) of Figure 2 (a)-(d) of , when the graphene Fermi level is fixed at 0eV, whether left circularly polarized light (LCP) or right circularly polarized light (RCP) is incident, the reflection phase of the 8 units covers 360°, and the reflection amplitude is higher than 80%, and the reflection response of LCP and RCP is completely consistent. This shows that the present application can realize dual-polarization independent 3-bit phase coding, which is twice the information capacity of traditional single-polarization coding metasurfaces, and can adapt to multi-polarization terahertz communication scenarios.

[0056] Figure 2 And Figure 2 (c) and (d) of show the simulation results of the reflection phase and amplitude under LCP and RCP incidence after adjusting the graphene Fermi level to 1.0eV. Due to the good metallic properties of graphene at high Fermi level, the graphene and the "I" type metal surface become a whole, and through the simulation data it can be seen that at this time the phase of the 8 different super units under LCP or RCP incidence does not change significantly, but the reflection amplitude is significantly lower than that when the graphene Fermi level is at 0eV, only 30% reflectivity, that is, by adjusting the Fermi level the amplitude reflectivity of the unit can be changed significantly, which provides a basis for switching the reflection mode. And from

[0057] (a) and (c) or (b) and (d) it can be seen that the reflection response of LCP and RCP incidence under the same graphene Fermi level is consistent.

[0058] In this embodiment, the present application realizes mode switching by using the electrically tunable characteristics of the graphene Fermi level, changes the Fermi level (Ef) of the graphene by adjusting the external bias voltage, and then changes its conductivity, so that the metasurface switches between reflection mode and absorption mode. The specific implementation process and performance are as follows:

[0059] When the graphene Fermi level is adjusted to 0eV, the graphene shows semiconductor characteristics, its conductivity is low, it is "isolated" from the top "class I" metal arm, and the metasurface is mainly reflective. Figure 2 As shown in (a) and (c) of the drawings, the reflection amplitude of the 8 units is higher than 80% at a frequency of 1.35 THz, the energy loss is small, and the energy demand of terahertz beam control (splitting, deflection, and vortex wave generation) can be met.

[0060] 2. Absorption mode (Ef=1.0eV)

[0061] When the graphene Fermi level is raised to 1.0eV, the conductivity of the graphene is significantly improved, showing metallic characteristics, and is "integrated as a whole" with the top "class I" metal arm, forming an equivalent resistance load to absorb the incident terahertz wave energy. As shown in (a) and (c) of the drawings, the absorption rate reaches 98.9% at a frequency of 1.42 THz; in a wide frequency range of 0.6~1.8 THz, by adjusting Ef (0~1.0eV), the absorption rate can be dynamically controlled from 20% to 98.9%, which is suitable for terahertz stealth (high absorption rate) and energy collection (moderate absorption rate) scenarios. Figure 8

[0062] 3. Convenience of mode switching

[0063] Mode switching only needs to adjust the Fermi level of the graphene through an external bias circuit, without changing the physical structure of the metasurface, and has a fast response speed (depending on the carrier mobility of the graphene), which can realize real-time dynamic switching and solve the defect of "single working mode" of the prior art.

[0064] Embodiment Two

[0065] Based on Embodiment One, this embodiment verifies the high-precision beam control capability of the application, and the following provides three specific examples (multi-beam splitting, abnormal deflection, and vortex wave generation), which are simulated and verified at a frequency of 1.35 THz and a graphene Ef=0eV (reflection mode).

[0066] Example 1: Multi-beam splitting (two-beam splitting)

[0067] Coding sequence and array design: 3×3 metasurface units are used to form a super unit, the "0" (α=0°) and "1" (α=45°) coding units with a phase difference of π (corresponding to a rotation angle difference of 45°) are selected as the coding units, and are periodically arranged along the x-axis direction in the form of "01010101…", and the coding period Γ=600μm (an optimal value in the range of 550~650μm).

[0068] Simulation results: as shown in (a) and (c) of the drawings, Figure 4 ​As shown in (a) (three-dimensional far-field reflection image) and (b) (normalized reflection amplitude curve), the incident plane wave is split into two symmetrical reflected waves with azimuth angles φ of 0° and 180° respectively and elevation angle θ = 22°. The energy distribution of the two beams is uniform and there is no obvious interference, proving that the present invention can achieve high-precision multi-beam splitting and is suitable for multi-user access scenarios in terahertz communication.

[0069] Example 2: Two-bit anomalous beam deflection

[0070] Encoding sequence and array design: The encoding units are selected with phases of 0, π / 2, π, and 3π / 2, namely “0” (α=0°), “1” (α=22.5°), “2” (α=45°), and “3” (α=67.5°), and are arranged periodically along the x-axis in the pattern “01230123…”. The encoding period Γ=1200μm (preferred value in the range of 1100~1300μm).

[0071] Simulation results: such as Figure 5 As shown in (a) and (b), the elevation angle θ = 10° and the azimuth angle φ = 0° of the reflected beam are almost consistent with the theoretical calculation value (θ = 10.67°), proving that the design can achieve high-precision abnormal deflection and is suitable for radar beam scanning scenarios.

[0072] Example 3: Three-bit anomalous beam deflection and vortex wave generation

[0073] Encoding sequence and array design: Eight phase states of “0~7” encoding units (corresponding to α=0°~157.5°) are used, arranged periodically along the x-axis in the pattern “01234567…”, with an encoding period Γ=2400μm (preferred value in the range of 2200~2600μm).

[0074] Simulation results: such as Figure 6 As shown in (a) and (b), the elevation angle θ = 6° and the azimuth angle φ = 0° of the reflected beam are negligible compared with the theoretical calculation value (θ = 5.71°). The accuracy is significantly improved compared with the two-bit deflection, which verifies the advantages of 3-bit coding in high-precision beam control.

[0075] In this embodiment, vortex wave generation and multi-channel expansion are as follows:

[0076] Single vortex wave generation: Encoding units with a phase difference of π / 2, namely "0" (α=0°), "1" (α=22.5°), "2" (α=45°), and "3" (α=67.5°), are selected and arranged in a counter-clockwise spiral array of 24×24 units to generate a vortex wave with a topological charge l=1. For example... Figure 7 As shown in (a), the vortex wave exhibits a conical beam with zero central amplitude, which conforms to the typical characteristics of a vortex wave.

[0077] Multi-channel vortex wave generation: combined with the Fourier convolution theorem, convolution operation is performed on the encoding sequence (such as Figure 7 the phase distribution calculation process shown in (c) of the application), the unit arrangement mode is optimized. As shown in (b) of the application, Figure 7 finally, three independent vortex beams are realized: the two side beams are deflected by 20° (5°-25° range), the center beam remains vertical, and the sidelobe energy is lower than the main lobe, solving the limitation of the traditional vortex wave "single path", which can improve the terahertz communication capacity and radar multi-target detection capability.

[0078] The specific embodiments of the application realize high-precision beam control and dynamic mode switching in the terahertz band by the technical scheme of "three-layer composite unit structure+3-bit phase encoding+fermi level regulation". Among them:

[0079] 1. The parameter design of the unit structure (such as metal thickness, dielectric constant of dielectric layer, unit period) ensures the stability of the phase response and the reliability of the mode switching;

[0080] 2. The design of eight discrete rotation angles realizes 360° phase coverage, and the consistency of dual-polarization response improves the information capacity;

[0081] 3. The adjustment of the graphene fermi level realizes the dynamic switching of the reflection / absorption mode, which adapts to the needs of multiple scenes;

[0082] 4. Multiple beam control embodiments (splitting, deflection, vortex wave) verify the high precision and practicality of the technical scheme.

[0083] The skilled in the art can adjust the unit size, encoding sequence or array size within the parameter range defined by the claims according to the actual needs, which can realize the core function of the application, so this embodiment is not the only limitation of the application. Any equivalent modification based on the inventive concept falls within the scope of the application.

[0084] The above embodiments only express several embodiments of the application, which are described in detail and specifically, but cannot be understood as a limitation on the scope of the application. It should be pointed out that for ordinary skilled in the art, without departing from the inventive concept, a number of modifications and improvements can be made, which all belong to the protection scope of the application. Therefore, the protection scope of the application should be subject to the appended claims.

Claims

1. A graphene three-bit multifunctional coding metasurface based on geometric phase, characterized in that, include: Metal grounding layer; A dielectric layer disposed on the metal grounding layer; and an array layer composed of multiple unit structures, the array layer being disposed on the dielectric layer; Each of the aforementioned unit structures includes a metal resonant patch and a graphene layer; the metal resonant patch is an anisotropic structure with an "I"-shaped structure. The multiple unit structures are selected and arranged from at least two basic units. The basic units have the same geometric structure, but their respective metal resonant patches have a preset, different rotation angle relative to a reference axis, so as to generate different phase responses to the incident circularly polarized electromagnetic waves based on the geometric phase principle. The Fermi level of the graphene layer can be electrically modulated by an externally applied bias voltage, allowing the metasurface to switch between at least two operating modes: Reflection mode: At the first Fermi level, the metasurface exhibits high reflectivity. The arrangement of the unit structures in the array layer generates a preset phase gradient distribution for the incident electromagnetic wave, so as to control the reflected beam. Absorption mode: At the second Fermi level, the metasurface exhibits high absorption characteristics, and the reflection of incident electromagnetic waves is significantly suppressed. The first Fermi level is 0 eV, and in the reflection mode, the reflection amplitude of the metasurface is higher than 80%; the second Fermi level is 1.0 eV, and in the absorption mode, the electromagnetic wave absorption rate of the metasurface at a specific frequency point is higher than 95%.

2. The graphene three-bit multifunctional coding metasurface as described in claim 1, characterized in that, The basic unit includes eight types, each with a metal resonant patch whose rotation angle is stepped at 22.5°, together forming a 3-bit encoding unit to achieve phase coverage of the reflected electromagnetic wave within the range of 0 to 360°.

3. The graphene three-bit multifunctional coding metasurface as described in claim 1, characterized in that, The metasurface operates in the terahertz frequency band.

4. The graphene three-bit multifunctional coding metasurface as described in claim 1, characterized in that, In the reflection mode, the metasurface can achieve independent phase coding control for both left and right circularly polarized waves.

5. The graphene three-bit multifunctional coding metasurface as described in claim 1, characterized in that, In the reflection mode, by arranging unit structures with different phase responses in a specific coding sequence, the metasurface is used to achieve at least one of the following functions: beam splitting, anomalous beam deflection, or vortex beam generation.

6. The graphene three-bit multifunctional coding metasurface as described in claim 5, characterized in that, The metasurface is used to generate vortex beams, and its unit structure is arranged as follows: At least four basic units with a 90° phase difference are arranged in a spiral spatial arrangement to generate a vortex beam carrying orbital angular momentum.

7. The graphene three-bit multifunctional coded metasurface as described in claim 6, characterized in that, The metasurface is used to simultaneously generate multiple vortex beams propagating in different directions by superimposing the phase distribution used to generate the vortex beams with a gradient phase sequence via Fourier convolution.

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