Dynamically adjustable multi-band terahertz transmission-type modulator based on graphene metasurface

Abstract

The invention belongs to the field of wireless communication, relates to a terahertz modulator in a terahertz communication system, and particularly provides a dynamically adjustable multi-band terahertz transmission-type modulator based on a graphene metasurface, which is used for solving the problems of single working band, low spectrum utilization rate, poor modulation capability, insufficient modulation depth and the like in the prior art. The terahertz transmission-type modulator is composed of a plurality of modulation units arranged in a periodic array mode, each modulation unit is composed of a substrate layer and a graphene metasurface layer arranged on the upper surface of the substrate layer, and each graphene metasurface layer is of an axial symmetry structure and is composed of a double-opening circular ring, a long rectangular branch knot and two short rectangular branch knots. In conclusion, the terahertz transmission-type modulator is obtained through the structural design of the graphene metasurface layer and the substrate layer, dynamic adjustable multi-working-frequency-band modulation is achieved within the terahertz frequency band range, and the terahertz transmission-type modulator has the excellent characteristics of being simple in structure, wide in working range, large in modulation depth, high in sensitivity and the like.

Description

Technical Field

[0001] The present invention belongs to the field of wireless communications and relates to a terahertz modulator in a terahertz communication system. Specifically, a multi-band terahertz transmission modulator based on a dynamically adjustable graphene metasurface is provided. Background Art

[0002] Terahertz waves are electromagnetic waves with frequencies between 100 GHz and 10 THz and wavelengths between 0.03 mm and 3 mm, combining the advantages of long-wave submillimeter waves and short-wave infrared waves. Due to their superior transmission capabilities, terahertz waves are expected to become a key communications frequency band after microwave and optical communications, playing a key role in military equipment, national security, and civilian communications. Using terahertz waves for communication is an effective solution to alleviate the increasingly limited spectrum resources and wireless system capacity constraints. Terahertz modulators, as one of the most critical devices in terahertz communication systems, have become a hot topic in terahertz science and technology research.

[0003] Metamaterials are synthetic materials composed of periodically arranged subwavelength units that exhibit extraordinary electromagnetic properties not found in natural materials. These unique properties include artificial magnetization, negative refractive index, and electromagnetically induced transparency. Therefore, researchers have proposed a variety of metamaterials that can be configured into tunable designs, ranging from two-dimensional (2D) to three-dimensional (3D) structures. For example, in patent publication number CN117950211A, She Rongbin et al. disclosed an all-dielectric metasurface composite structure terahertz modulator, its preparation method, and application, achieving single-peak transmission modulation in the terahertz band. In patent publication number CN118625545A, Zhang Jing et al. disclosed a lattice-enhanced multifunctional terahertz optical modulator that achieved dual-peak modulation in the terahertz band by varying the lattice period. Furthermore, in patent publication number CN119511564A, Shu Fangzhou et al. disclosed a terahertz modulator based on an aluminum and germanium antimony telluride composite dumbbell hole array that achieved single-peak transmittance modulation in the terahertz band by utilizing the germanium antimony telluride phase transition. However, conventional metamaterial modulators cannot be actively adjusted; once their structure is fabricated, their electromagnetic properties cannot be altered, making them difficult to meet the requirements of complex and changing electromagnetic environments.

[0004] It is worth noting that graphene, as a two-dimensional honeycomb lattice structure composed of closely packed carbon atoms, has excellent tunable conductivity and carrier mobility, which can reach 15,000 cm at room temperature. 2 / (Vs); Furthermore, graphene's surface conductivity can be easily tuned by an external voltage without changing structural parameters. Compared to noble metals, graphene offers several advantages in surface plasmon research. For example, by designing graphene patterns, surface plasmon polaritons (SPPs) can be generated in transverse magnetic modes upon excitation by an external light field. These are collective oscillations of free electrons on the surface. Incident electromagnetic waves of a specific frequency are confined within the patterned region of the surface, thereby achieving an actively tunable plasmon-induced transparency (PIT) effect. This enables a range of applications, including electro-optic modulators and optical switching devices. Furthermore, another key application of the PIT effect generated by graphene metasurfaces is sensing, as the resonant peak frequency within the PIT window is highly sensitive to changes in the refractive index of the surrounding medium. For metallic metasurfaces, the PIT effect can be achieved to some extent through specific nanostructure design. However, achieving actively controllable terahertz modulation remains difficult due to inherent challenges such as high losses, limited frequency tunability, weak plasmon intensity, and inefficient coupling. Therefore, it is of practical significance to study terahertz modulators based on graphene metasurfaces. Summary of the Invention

[0005] The present invention aims to provide a dynamically adjustable multi-band terahertz transmission modulator based on a graphene metasurface, addressing the problems of existing terahertz modulators, such as a single operating frequency band, low spectrum utilization, poor modulation capability, and insufficient modulation depth. This invention creatively proposes a dynamically adjustable multi-band terahertz transmission modulator based on a graphene metasurface, achieving dynamically adjustable multi-band modulation within the terahertz frequency band. The modulator exhibits excellent characteristics, including a simple structure, a wide operating range, a large modulation depth, and high sensitivity.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A dynamically adjustable multi-band terahertz transmission modulator based on a graphene metasurface is composed of a plurality of modulation units arranged in a periodic array, wherein the modulation units are composed of a substrate layer and a graphene metasurface layer provided on its upper surface; the graphene metasurface layer adopts an axisymmetric structure, consisting of a double-opening circular ring, a long rectangular branch and two short rectangular branches; the center of the double-opening circular ring coincides with the center of the upper surface of the substrate layer, and the opening direction forms an angle θ with the midline of the upper surface of the substrate layer; the long rectangular branch is arranged along the opening of the double-opening circular ring, and the two midlines of the long rectangular branch coincide with the two symmetry axes of the graphene metasurface layer; the two short rectangular branches are arranged in the double-opening circular ring and are both perpendicular to the long rectangular branch.

[0008] Furthermore, the angle θ=15°~45°.

[0009] Furthermore, the modulation unit adopts a square structure, and the unit period P=102μm~106μm.

[0010] Furthermore, the base layer is made of silicon or silicon dioxide, and has a thickness of H=100 μm to 150 μm.

[0011] Furthermore, the thickness of the graphene supersurface layer is 0.334 nm.

[0012] Furthermore, the outer diameter R2 of the double-opening circular ring is 48 μm to 52 μm, the inner diameter R1 is 35 μm to 45 μm, and the opening width W3 is 5 μm to 15 μm.

[0013] Furthermore, the length of the long rectangular branch is L2 = 95μm ~ 105μm, and the width is W2 = 0.5μm ~ 0.6μm; the length of the short rectangular branch is L1 = 25μm ~ 35μm, and the width is W1 = 0.5μm ~ 0.6μm, and the spacing between two short rectangular branches is a = 10μm ~ 30μm.

[0014] Based on the above technical solution, the beneficial effect of the present invention is to provide a dynamically adjustable multi-band terahertz transmission modulator based on a graphene metasurface, which has the characteristics of simple structure, multi-band, dynamic adjustment, high resonance intensity, and high sensing sensitivity. The specific advantages are as follows:

[0015] (1) Compared with the prior art, the present invention achieves excellent characteristics such as multiple resonance frequency bands, high resonance intensity and large modulation range, and its minimum full width at half maximum (FWHM) is only 6.3 GHz;

[0016] (2) The device unit proposed in the present invention has a simple structure, excellent performance, and has excellent resonance frequency band and transmission performance that can be dynamically modulated, which greatly expands the application range of terahertz modulators;

[0017] (3) The present invention has good polarization switching performance, can modulate the terahertz transmission efficiency by changing the polarization angle, and has switchable multi-resonance frequency bands;

[0018] (4) The present invention has excellent sensing performance. As the ambient refractive index n increases, the resonance frequency band gradually moves to a lower frequency, and the transmission efficiency remains almost unchanged. The maximum sensitivity S and quality factor FOM reach 510GHz / RIU and 46.43RIU respectively. -1 . BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the structure of the dynamically adjustable multi-band terahertz transmission modulator based on the graphene metasurface in the present invention.

[0020] Figure 2Schematic diagram of the unit structure of the dynamically adjustable multi-band terahertz transmission modulator based on the graphene metasurface in the present invention.

[0021] Figure 3 This is a transmission efficiency curve of the dynamically adjustable multi-band terahertz transmission modulator based on the graphene metasurface in the present invention in the TE mode (φ=0°).

[0022] Figure 4 The transmission efficiency of the multi-band terahertz transmission modulator based on the graphene metasurface dynamically adjustable in the range of 100 to 800 GHz varies with the chemical potential V of the graphene metasurface. f (0.4eV increasing to 0.8eV) change curve.

[0023] Figure 5 This is a curve diagram of the transmission efficiency of the dynamically adjustable multi-band terahertz transmission modulator based on the graphene metasurface in the range of 100 to 800 GHz as the relaxation time τ of the graphene metasurface increases from 0.2Ps to 0.8Ps.

[0024] Figure 6 The transmission efficiency of the multi-band terahertz transmission modulator based on the graphene metasurface dynamically adjustable in the range of 100 to 800 GHz varies with the incident polarization angle. (From 0° to 90°) change curve.

[0025] Figure 7 This is a curve diagram of the transmission efficiency of the dynamically adjustable multi-band terahertz transmission modulator based on the graphene metasurface in the present invention in the range of 100 to 800 GHz as the substrate thickness H increases from 100 μm to 150 μm.

[0026] Figure 8 This is a curve diagram of the transmission efficiency of the dynamically adjustable multi-band terahertz transmission modulator based on the graphene metasurface in the present invention in the range of 100 to 800 GHz as the ambient refractive index n increases from 1.00 to 1.04. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and beneficial effects of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0028] This embodiment provides a multi-band terahertz transmission modulator based on a dynamically adjustable graphene metasurface. Figure 1As shown, it is composed of a number of modulation units arranged in a periodic array, and any two adjacent modulation units are spliced without spacing; the modulation unit is composed of a base layer 2 and a graphene super surface layer 1 provided on its upper surface, the modulation unit adopts a square structure, and the unit period P = 102μm ~ 106μm; the base layer 2 is made of silicon or silicon dioxide, with a refractive index ε = 1.53 ~ 1.96 and a thickness H = 100μm ~ 150μm; the thickness of the graphene super surface layer 1 is 0.334nm, and the band gap of the intrinsic graphene is zero, so that the intrinsic graphene exhibits metallic properties, and its conductivity can be expressed as σ g =σ intra +σ inter , where σ intra and σ inter They represent the intra-band conductance and inter-band conductance, respectively, and can be expressed as the following formula:

[0029]

[0030] Where, j represents an imaginary number (j×j=-1), and e=1.6×10 -19 C represents the charge of the electron, K B =1.38×10 -23 J / K represents the Boltzmann constant, h = 1.05 × 10 -34 J·s represents the reduced Planck constant, T = 300K represents the ambient temperature, w = 2πf represents the angular frequency of the incident electromagnetic wave (f = 100 to 800 GHz is the frequency of the incident electromagnetic wave), V f and τ represent the chemical potential and relaxation time of graphene, respectively;

[0031] At room temperature (hω<<2|V f |), the interband conductance σ of graphene inter can be ignored; therefore, the surface conductivity mainly depends on the intra-band contribution; according to the Pauli exclusion principle, the conductivity of graphene can be simplified to the Drude model:

[0032]

[0033] According to formula (3), the conductivity of the graphene supersurface can be changed by changing the chemical potential V f or relaxation time τ to achieve dynamic adjustment without changing its geometric structure; accordingly, the dielectric constant ε of the graphene metamaterial g (ω) can be calculated from the conductivity σ(ω):

[0034]

[0035] Where, Δ = 0.334 nm represents the thickness of the graphene metasurface, ε0 = 8.85 × 10-12 F / m represents the dielectric constant of vacuum;

[0036] It can be seen that by controlling the chemical potential V of graphene metamaterials f The dielectric constant of graphene metamaterials can be dynamically adjusted by adjusting the relaxation time τ. A dielectric constant model of graphene metamaterials can be established to simulate and analyze its dynamic modulation properties in terahertz modulation devices. Based on this, the present invention uses Matlab software to calculate the dielectric constant of different chemical potentials V f The graphene material with a relaxation time τ was imported into the finite time-domain difference software (FDTD Solutions) for the construction and simulation analysis of the terahertz transmission modulator. Its chemical potential V f The modulation range of is 0.40eV~0.80eV, and the modulation range of relaxation time τ is 0.20Ps~0.80Ps.

[0037] Graphene supersurface layer such as Figure 2 As shown, its pattern structure can be realized by picosecond laser processing or photolithography; the unit pattern structure of the graphene super surface layer, such as Figure 2 As shown, the graphene super surface layer adopts an axisymmetric structure, consisting of a double-mouthed circular ring, a long rectangular branch and two short rectangular branches; the center of the double-mouthed circular ring coincides with the center of the upper surface of the substrate layer, and the opening direction forms an angle θ with the midline of the upper surface of the substrate layer; the long rectangular branch is arranged along the opening of the double-mouthed circular ring, and the two midlines of the long rectangular branch coincide with the two symmetry axes of the graphene super surface layer; the two short rectangular branches are arranged in the double-mouthed circular ring, and are both perpendicular to the long rectangular branches. In addition, it should be noted that the double-mouthed circular ring is formed by the circular ring opening along any diameter, and the opening edge is parallel to the diameter. The direction of the diameter is defined as the opening direction of the double-mouthed circular ring. Furthermore, the geometric size parameters of the graphene supersurface layer are set as: R1=35~45μm, R2=48~52μm, W1=W2=0.5μm, W3=5~15μm, L1=25~35μm, L2=95~105μm, a=10~30μm, θ=15°~45°.

[0038] The beneficial effects of the present invention are described in detail below in conjunction with simulation tests.

[0039] During the simulation test, the incident electromagnetic wave range is set to 100GHz~800GHz, and the transmission direction of the incident light wave is perpendicular to the XOY plane and incident downward; when the electric field (E) propagates along the X-axis and Y-axis, the polarization angle The angles are 0° and 90°, representing the transverse electric (TE) mode and transverse magnetic (TM) mode, respectively. The transmission characteristics of the terahertz modulator were simulated using Lumerical finite-difference time-domain (FDTD) solving software. During the simulation, the grid size was 2nm×2nm×2nm to ensure the reliability of the model. Periodic boundary conditions were selected in the X and Y directions, and a perfectly matched layer (PML) boundary condition was added in the Z-axis direction.

[0040] like Figure 3 The figure shows the transmission efficiency curve of the multi-band terahertz transmission modulator based on the graphene metasurface in the TE mode (φ=0°). It can be seen from the figure that in the TE mode When the frequency of the incident electromagnetic wave is between 100 and 800 GHz, the terahertz transmission modulator produces four resonance peaks, located at 293.9 GHz (ω1), 318.4 GHz (ω2), 557.8 GHz (ω3) and 664.9 GHz (ω4), with corresponding full width at half maximum (FWHM) values of 29.4 GHz, 25.2 GHz, 6.3 GHz and 12.6 GHz, respectively. The terahertz transmission efficiency at the four resonant frequency points is 7.2%, 5.5%, 5.7% and 2.4%, respectively. At the same time, the maximum transmission efficiency in the non-resonant frequency band can reach 98.5%.

[0041] like Figure 4 The figure shows the transmission efficiency of the above-mentioned multi-band terahertz transmission modulator based on the dynamic adjustable graphene metasurface in the range of 100 to 800 GHz as the graphene metasurface chemical potential V f (0.4eV increases to 0.8eV) change curve, by applying the gate voltage V g The chemical potential V of the graphene supersurface can be effectively controlled f , the formula is as follows:

[0042]

[0043] Where V is the Fermi velocity (V F =c / 300, c=3×10 8 m / s represents the speed of light in vacuum), V g is the external gate voltage value, ε0=8.85×10 12 F / m represents the dielectric constant of vacuum, ε g represents the relative dielectric constant of graphene metamaterial, e=1.6×10 -19 C represents the charge of the electron, and H represents the thickness of the substrate layer;

[0044] Based on the dynamic tunability of graphene chemical potential, Figure 5It can be seen that as the chemical potential of graphene increases from 0.4eV to 0.8eV, the resonance intensity of the terahertz transmission modulator changes little, and the four resonance frequencies all move toward high frequencies; the modulation ranges of the four resonance frequencies are 284.8~303.2GHz, 309.3~328.2GHz, 548.7~572.5GHz and 649.5~688.4GHz respectively; and the modulation trend of the resonance frequency satisfies a certain linear relationship with the chemical potential of graphene, which means that by adjusting the chemical potential of graphene, the multiple resonance frequencies of the terahertz transmission modulator can be dynamically controlled in the range of 100~800GHz, thereby improving the spectrum utilization of the terahertz modulation device and increasing the practical application efficiency.

[0045] like Figure 5 The figure shows the variation of the transmission efficiency of the above-mentioned dynamically adjustable multi-band terahertz transmission modulator based on the graphene metasurface in the range of 100 to 800 GHz as the graphene metasurface relaxation time τ increases from 0.2Ps to 0.8Ps. The electron relaxation time τ of graphene can be adjusted by the following formula:

[0046]

[0047] Among them, V f and v represent the chemical potential and carrier mobility of graphene, respectively, e = 1.6 × 10 -19 C represents the charge of the electron, v F =10 6 m / s represents the Fermi velocity; in practical applications, by adding or subtracting organic molecules from the surface of the graphene metasurface layer, the carrier mobility v can be significantly changed, thereby changing the relaxation time τ;

[0048] Dynamic tunability based on relaxation time, by Figure 5As can be seen, as the relaxation time τ increases, the transmission efficiency at the four resonant frequencies can be effectively modulated while the resonant frequency remains unchanged. The modulation ranges of the terahertz transmission efficiency at the four resonant frequencies are 7.2% to 75.3%, 5.5% to 77.2%, 5.7% to 53.8%, and 2.4% to 60.1%, respectively, with modulation depths corresponding to 68.1%, 71.7%, 48.1%, and 57.7%, respectively. This unique modulation characteristic stems from changes in the carrier scattering mechanism of graphene. Changing the relaxation time τ effectively reduces the electron-phonon scattering probability and increases the real part of the graphene surface conductivity, thereby significantly enhancing the local field confinement capability. Therefore, compared with traditional noble metal metasurface control methods that rely on geometric reconstruction, the designed dynamically tunable multi-band terahertz transmission modulator based on the graphene metasurface can effectively modulate the transmission spectrum by modulating the chemical potential and relaxation time of the graphene layer without changing the geometry, and can be widely used in controllable optical switching and detection.

[0049] like Figure 6 The figure shows the transmission efficiency of the above-mentioned multi-band terahertz transmission modulator based on the dynamically adjustable graphene metasurface in the range of 100 to 800 GHz as a function of the incident polarization angle. The change curve of (increasing from 0° to 90°) shows that the terahertz modulator proposed in the present invention has an asymmetric structure and thus exhibits polarization-dependent characteristics. Based on this, the comparison of polarization is and The transmission curve in mode is given by Figure 6 It can be seen that the resonance position at ω1 remains basically unchanged; on the contrary, the resonance positions at ω2, ω3 and ω4 move toward high frequency, and the modulation ranges are 318.4~345.2GHz, 557.8~583.3GHz and 664.9~717.4GHz respectively; at the same time, in the TM mode, the resonance intensity of the terahertz modulator at ω1 and ω2 decreases; the modulation ranges of the transmission efficiency are 7.2%~41.9% and 5.5%~32.7% respectively, and the modulation depths correspond to 34.7% and 27.2%. It is worth noting that when the polarization angle of the incident polarized light is When the terahertz modulator is switched to 0.5V, the resonant frequencies at ω1 and ω2 merge to 305.2GHz, and the resonant intensity remains essentially unchanged. Meanwhile, the resonant intensities at ω3 and ω4 decrease, with the transmission efficiency modulation ranges of 5.7% to 49.8% and 2.4% to 45.3%, respectively, and the modulation depths corresponding to 44.1% and 42.9%. Therefore, the terahertz transmission device can be modulated by changing the polarization angle of the incident electromagnetic wave. It exhibits excellent polarization switching performance and exhibits switchable multi-resonance and polarization-dependent characteristics, making it suitable for optical logic operation applications.

[0050] like Figure 7 The figure shows the variation curve of the transmission efficiency of the above-mentioned multi-band terahertz transmission modulator based on the dynamic adjustable graphene metasurface in the range of 100 to 800 GHz with the substrate thickness H (increasing from 100 μm to 150 μm). It can be seen from the figure that with the increase of the substrate thickness H, the various resonance frequencies of the terahertz transmission modulator move to low frequencies; in particular, the modulation range of the resonance frequency at ω4 can be reduced from 676.2 GHz to 655.1 GHz, and the resonance intensity remains basically unchanged. This is because the path phase of the terahertz wave when it is transmitted in the substrate layer It can be expressed as the following formula:

[0051]

[0052] Where H and ε are the thickness and dielectric constant of the substrate layer, respectively, and f is the frequency of the interfering electromagnetic wave. When the electromagnetic wave is incident vertically, the path phase and the incident angle θ can be regarded as fixed values. Therefore, when the thickness H of the substrate layer increases, the frequency f of the interfering electromagnetic wave will decrease, which will cause the resonant frequency of the device to move to a low frequency. It can be seen that the dynamically adjustable multi-band terahertz transmission modulator based on the graphene metasurface proposed in the present invention has excellent operating frequency modulation characteristics.

[0053] like Figure 8 The figure shows the variation curve of the transmission efficiency of the above-mentioned dynamically adjustable multi-band terahertz transmission modulator based on the graphene metasurface in the range of 100 to 800 GHz with the environmental refractive index n (increasing from 1.00 to 1.04). The sensing characteristics of the terahertz transmission modulator applied to the sensing field are studied. By covering different substances to be tested on the graphene metasurface layer, the refractive index parameters of the surrounding environment will change, thereby changing the transmission characteristics of the modulator. Therefore, by monitoring the offset of the resonant frequency of the terahertz transmission modulator, the refractive index of the substance to be tested can be sensed. Figure 8It can be seen that with the increase of the ambient refractive index n, the four resonant frequencies gradually move to lower frequencies, and the transmission efficiency remains almost unchanged; the modulation ranges of the four resonant frequencies are 286.9~293.9GHz, 312.8~318.4GHz, 546.1~557.8GHz and 644.5~664.9GHz respectively; and then according to the calculation formula of sensitivity S: S=Δf / Δn, Δf and Δn represent the changes in resonant frequency and ambient refractive index respectively, it is calculated that the sensitivity of the terahertz transmission modulator at the four operating frequencies reaches 175GHz / RIU, 140GHz / RIU, 292.5GHz / RIU and 510GHz / RIU respectively; in addition, according to the calculation formula of quality factor FOM: FOM=S / FWHM, FWHM is the full width at half maximum at the resonant frequency, the FOM at the four resonant frequencies is calculated to reach 5.95RIU respectively. -1 , 5.56RIU -1 , 46.43RIU -1 and 40.48RIU -1 ; The results show that the above-mentioned terahertz transmission modulator has excellent sensing sensitivity and detection accuracy, and can be widely used in the field of terahertz sensing and detection.

[0054] In summary, the present invention obtains a terahertz transmission modulator based on the structural design of the graphene metasurface layer and the substrate layer, which produces four resonance peaks in the range of 100-800 GHz, located at 293.9 GHz (ω1), 318.4 GHz (ω2), 557.8 GHz (ω3) and 664.9 GHz (ω4), and the minimum full width at half maximum (FWHM) is only 6.3 GHz; firstly, by changing the chemical potential and relaxation time of the graphene metasurface, the dynamic regulation of the resonance frequency band and transmission efficiency of the terahertz transmission modulator is realized, and the maximum transmission efficiency modulation depth can be adjusted. Reaching 71.7%; secondly, the resonant frequency of the terahertz transmission modulator proposed in the present invention can also be controlled by changing the thickness of the substrate layer; thirdly, the present invention can realize the modulation of the terahertz transmission device by changing the polarization angle of the incident electromagnetic wave, has good polarization light switching performance, and exhibits switchable multi-resonance and polarization dependence characteristics; fourthly, the present invention studies the sensing characteristics of the terahertz transmission modulator by changing the ambient refractive index, and calculates that the maximum sensitivity S of the four resonant frequency bands reaches 510GHz / RIU, and the maximum quality factor FOM reaches 46.43RIU -1 .

[0055] The above description is only a specific embodiment of the present invention. Any feature disclosed in this specification, unless otherwise stated, can be replaced by other equivalent or alternative features with similar purposes; all disclosed features, or all steps in the methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A dynamically adjustable multi-band terahertz transmission modulator based on a graphene metasurface, comprising a plurality of modulation units arranged in a periodic array, wherein the modulation units are composed of a substrate layer and a graphene metasurface layer disposed on its upper surface; characterized in that: The graphene super surface layer adopts an axisymmetric structure, consisting of a double-opening circular ring, a long rectangular branch and two short rectangular branches; the center of the double-opening circular ring coincides with the center of the upper surface of the base layer, and the opening direction forms an angle θ with the midline of the upper surface of the base layer; the long rectangular branch is arranged along the opening of the double-opening circular ring, and the two midlines of the long rectangular branch coincide with the two symmetry axes of the graphene super surface layer; the two short rectangular branches are arranged in the double-opening circular ring and are both perpendicular to the long rectangular branch.

2. The multi-band terahertz transmission modulator based on a dynamically adjustable graphene metasurface according to claim 1, characterized in that: Angle θ = 15° ~ 45°.

3. The dynamically adjustable multi-band terahertz transmission modulator based on graphene metasurface according to claim 1, characterized in that: The modulation unit adopts a square structure, and the unit period P = 102μm ~ 106μm.

4. The dynamically adjustable multi-band terahertz transmission modulator based on graphene metasurface according to claim 1, characterized in that: The base layer is made of silicon or silicon dioxide, and has a thickness of H=100 μm to 150 μm.

5. The dynamically adjustable multi-band terahertz transmission modulator based on graphene metasurface according to claim 1, characterized in that: The thickness of the graphene supersurface layer is 0.334 nm.

6. The dynamically adjustable multi-band terahertz transmission modulator based on graphene metasurface according to claim 1, characterized in that: The outer diameter R2 of the double-opening circular ring is 48 μm to 52 μm, the inner diameter R1 is 35 μm to 45 μm, and the opening width W3 is 5 μm to 15 μm.

7. The dynamically adjustable multi-band terahertz transmission modulator based on graphene metasurface according to claim 1, characterized in that: The length of the long rectangular branch is L2 = 95μm ~ 105μm, and the width is W2 = 0.5μm ~ 0.6μm; the length of the short rectangular branch is L1 = 25μm ~ 35μm, and the width is W1 = 0.5μm ~ 0.6μm, and the distance a between two short rectangular branches is 10μm ~ 30μm.

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