A terahertz-tunable broadband absorber based on vanadium dioxide

Abstract

The present invention relates to a terahertz controllable broadband absorber based on vanadium dioxide. The absorber unit cell structure is composed of a vanadium dioxide resonant pattern layer, a silicon dioxide dielectric layer and a gold film bottom plate layer from top to bottom. The vanadium dioxide resonant pattern layer is a composite structure consisting of an outer metal open resonant ring, an intermediate square ring and a Jerusalem cross structure inside the square ring. The Jerusalem cross structure consists of a cross, a rectangle at the end of the cross and a fan on the edge of the rectangle. The chord length of the fan is the same as the side length of the rectangle, and the central angle is θ. r . By regulating the external temperature, the conductivity of vanadium dioxide is changed, and its phase change characteristics from insulating state to metallic state are utilized to achieve dynamic regulation of the absorption rate from 3.3% to nearly 100%. The present invention has polarization insensitivity and wide incident angle stability, and achieves a broadband absorption effect of more than 90% in the range of 4.73-10.02THz, with an absorption bandwidth of 5.29THz and a relative bandwidth of 71.73%. It can be widely used in imaging, modulators, photoelectric switches and other fields.

Description

Technical Field

[0001] The invention belongs to the technical field of new materials and relates to a terahertz controllable broadband absorber which is polarization-insensitive, has a wide incident angle and a high wave absorption rate. Background Art

[0002] The terahertz band usually refers to a wavelength of about 0.01 to 3 mm, and the corresponding frequency is about 0.3 to 10 THz. Terahertz waves have the characteristics of both microwaves and infrared light waves, and contain many unique physical properties. They have important research value in the fields of imaging, communication, radar and spectroscopy, so it is of great significance to study terahertz functional devices. Metasurface is an artificially designed subwavelength structure with some special physical properties, such as abnormal reflection effect, negative refraction effect, inverse Doppler effect and perfect lens effect, which are not found in natural materials. By changing its structural size and arrangement, the polarization, phase, amplitude and resonance of electromagnetic waves can be effectively controlled. Metasurface absorber is one of the important applications of terahertz functional devices. It has the advantages of high absorption rate, thin thickness, small volume and weight, and flexible control of electromagnetic waves. It is widely used in terahertz imaging, communication sensing, switch modulation and other fields.

[0003] In recent years, research on terahertz metasurface absorbers has made significant breakthroughs. These designs can effectively absorb electromagnetic waves in a wide frequency band and solve the problem of narrow absorption bandwidth. However, once these designs are processed, they can only work in a certain frequency band and cannot realize the regulation function, or can only be passively regulated, and cannot be widely used in practical applications. By combining active materials such as graphene, black phosphorus and vanadium dioxide to design absorbers, the dynamic regulation of electromagnetic waves can be achieved through the adjustable properties of the materials themselves without changing the structure, thereby expanding the application potential of terahertz metasurface absorbers. At present, research on adjustable terahertz absorbers based on active materials has made significant progress, but there are currently two problems: (1) There are still disadvantages such as small adjustable range, narrow absorption bandwidth and complex structure, which limit the breadth and flexibility in practical applications; (2) The current calculation of absorbance adopts theoretical calculation method, but the actual absorbance on foggy and rainy days is lower than the theoretical calculation, resulting in the designed absorber absorption rate being lower than the theoretical absorbance. Summary of the invention

[0004] In view of the problems of currently designed adjustable terahertz absorbers, such as small adjustable amplitude, narrow absorption bandwidth, complex structure and inaccurate absorption rate in foggy and rainy days, the present invention provides a terahertz adjustable broadband absorber based on vanadium dioxide.

[0005] In order to achieve the above-mentioned invention object, the present invention adopts the following technical scheme:

[0006] The absorber consists of three layers, from top to bottom, vanadium dioxide resonant pattern layer, silicon dioxide dielectric layer and gold film bottom plate layer, and the three layers are tightly fitted. The vanadium dioxide resonant pattern layer is a composite structure consisting of an outer metal open resonant ring, a middle square ring and a Jerusalem cross structure inside the square ring. The Jerusalem cross structure consists of a cross, a rectangle at the end of the cross and a fan on the edge of the rectangle. The chord length of the fan is the same as the side length of the rectangle, and the central angle is θ r The unit cell structure is regularly arranged periodically in the x and y directions, and is distributed in M×N, where M represents the number of unit cells distributed in the x direction, and N represents the number of unit cells distributed in the y direction. In the present invention, M=N;

[0007] The method for designing a terahertz controllable broadband absorber according to the present invention is characterized in that the resonance pattern of the top layer of the designed metasurface structure is symmetrical about the diagonal line;

[0008] According to the terahertz controllable broadband absorber design method of the present invention, it is characterized in that the intermediate dielectric layer is made of silicon dioxide with a dielectric constant of 3.8;

[0009] The method for designing a terahertz controllable broadband absorber according to the present invention is characterized in that the designed intermediate dielectric layer and the metal base plate have the same size but different thicknesses;

[0010] According to the design method of a terahertz controllable broadband absorber of the present invention, the vanadium dioxide material can be described by the Drude model in the terahertz band, and its dielectric constant ε(ω) can be expressed as:

[0011]

[0012] In the formula, ε ∞ It is VO 2 High frequency dielectric constant of (vanadium dioxide), ε ∞ =12; collision frequency γ = 5.75×10 13 rad / s,ω p (σ) is the plasma frequency, ω p The relationship between (σ) and conductivity σ is as follows:

[0013]

[0014] Among them, σ 0 3×10 5 S / m,ω p (σ 0 ) is 1.4×10 15 rad / s.

[0015] According to the design method of a terahertz controllable broadband absorber of the present invention, the modulation depth Md of the absorber satisfies:

[0016]

[0017] Among them, A M (ω) is the absorption rate of vanadium dioxide in the metallic state, A D (ω) is the wave absorption rate of vanadium dioxide in the insulating state, ξ represents the relative error value of the modulation depth of the absorber;

[0018] According to the terahertz controllable broadband absorber design method of the present invention, the absorber absorption rate calculation value A(ω) satisfies:

[0019]

[0020] Among them, n-1 and n represent any two adjacent frequency points in the working frequency band, A n-1 (ω) and A n (ω) represents the absorption value obtained by simulation at the n-1th and nth frequency points, and ψ is the relative error value of the absorption value;

[0021] According to the terahertz controllable broadband absorber design method of the present invention, the absorber absorption rate A(ω) is calculated as follows:

[0022] A(ω)=1-R(ω)-T(ω)=1-|S 11 | 2 -|S 21 | 2

[0023] Where R(ω) is the reflectivity of the absorber, T(ω) is the transmittance of the absorber, and S 11 is the reflection coefficient of the absorber, S 21 is the transmission coefficient of the absorber. Since the thickness of the metal bottom plate is much greater than the skin depth of the electromagnetic wave in this working frequency band, the electromagnetic wave cannot be transmitted from the bottom plate, so T(ω) = 0. Therefore, the absorption rate A(ω) can be expressed as:

[0024]

[0025] Among them, Z in (ω) is the input impedance of the metasurface absorber, Z 0 is the wave impedance in free space, Z 0 =377Ω, μ and ε represent the magnetic permeability and dielectric constant of the metasurface absorber, μ 0 and ε 0 represents the magnetic permeability and dielectric constant of free space;

[0026] Then the wave absorption rate A(ω) of the metasurface absorber can be expressed by the wave absorption rate control function f(μ,ε):

[0027]

[0028] Ideal metasurface absorptivity control model F(A(ω)):

[0029]

[0030] Where q is the number of frequency sampling points of the absorber in the working bandwidth, g is 1 is the frequency starting value of the working bandwidth, g 2 is the final frequency value of the working bandwidth.

[0031] In fact, in fog and rain, the wave absorption rate is affected by the air humidity. The actual wave absorption rate control model FT(A(ω)) of the metasurface is expressed as:

[0032]

[0033] Where λ(R) is the humidity adjustment factor of the absorbance, R is the relative humidity value, and after calibration, λ(R) is expressed by the following function:

[0034]

[0035] The beneficial effects of the present invention are:

[0036] (1) The terahertz controllable broadband absorber based on vanadium dioxide proposed in the present invention can adjust the absorbing performance without changing the structural parameters through the phase change characteristics of vanadium dioxide, and has extremely strong practical value.

[0037] (2) The terahertz controllable broadband absorber based on vanadium dioxide proposed in the present invention has a conductivity of 2×10 5 S / m, the absorber can achieve an absorption rate of more than 90% in the range of 4.73-10.02THz, an absorption bandwidth of 5.29THz, a relative bandwidth of 71.73%, and an absorption rate of 99.63% at the resonant frequency of 7.35THz, achieving a nearly perfect absorption effect.

[0038] (3) The present invention proposes a terahertz controllable broadband absorber based on vanadium dioxide, which changes the conductivity of vanadium dioxide by adjusting the external temperature and utilizes its phase change characteristics from insulating state to metallic state, thereby achieving dynamic control of the absorption rate from 3.3% to nearly 100%.

[0039] (4) The vanadium dioxide-based terahertz controllable broadband absorber proposed in the present invention has a unit structure with a high degree of central symmetry, which makes the absorber polarization-insensitive.

[0040] (5) The vanadium dioxide-based terahertz controllable broadband absorber proposed in the present invention achieves an incident angle stability of 30° and 50° in TE and TM polarization modes, respectively.

[0041] (6) A humidity adjustment factor for absorbency was proposed to improve the design accuracy of absorber absorbency. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Schematic diagram of the top pattern of the designed terahertz tunable broadband absorber unit cell structure;

[0043] Figure 2 This is the side view of the designed terahertz controllable broadband absorber unit cell structure;

[0044] Figure 3 The conductivity of the designed terahertz tunable broadband absorber is 2×10 5 Absorption, reflectivity and transmittance curves at S / m;

[0045] Figure 4 The absorption rate curves of the top single structure and composite structure of the designed terahertz tunable broadband absorber;

[0046] Figure 5 This is the absorption rate curve of the designed terahertz controllable broadband absorber when the conductivity changes;

[0047] Figure 6 The absorption rate contour map of the designed terahertz tunable broadband absorber at different polarization angles;

[0048] Figure 7 The absorption rate contour map of the designed terahertz tunable broadband absorber at different incident angles in TE mode;

[0049] Figure 8 The absorption rate contour map of the designed terahertz tunable broadband absorber at different incident angles in TM mode;

[0050] Fig. 9 This is the normalized impedance curve of the designed terahertz tunable broadband absorber.

[0051] Fig.10 This is a comparison chart of the absorption rate of this design in the dry state in the laboratory and the absorption rate of this design in the dense fog state. DETAILED DESCRIPTION

[0052] In order to make the objectives, technical solutions and advantages of the embodiments of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0053] Combination Figure 1 to Figure 2As shown, the present invention provides a terahertz controllable broadband absorber based on vanadium dioxide, which consists of three layers, namely, a vanadium dioxide resonant pattern layer, a silicon dioxide dielectric layer, and a gold film bottom plate layer from top to bottom, and the three layers are tightly fitted. The vanadium dioxide resonant pattern layer is a composite structure consisting of an outer metal open resonant ring, an intermediate square ring, and a Jerusalem cross structure inside the square ring. The unit cell structure is regularly arranged periodically in the x and y directions, and is distributed in M×N, where M represents the number of unit cell distributions in the x direction, and N represents the number of unit cell distributions in the y direction. In the present invention, M=N;

[0054] The absorber is simulated using CST Microwave Studio, and the electromagnetic wave is vertically incident on the absorber structure along the -z axis direction. The structural unit adopts unit cell boundary conditions in the x and y directions and open addspace boundary conditions in the z direction.

[0055] The top resonance pattern is composed of an outer metal open resonant ring, a middle square ring and a Jerusalem cross structure inside the square ring. The outer ring length of the metal open resonant ring is l 1 =18μm, the inner ring length is l 2 =16μm, the opening spacing is l 3 =4μm; the outer ring length of the middle square ring is a=7μm, the inner ring length is b=5.5μm; the length of the Jerusalem cross structure in the square ring is l 4 =4μm, width is w 4 =0.3μm, the length of the dipole is l 5 =2μm, width is w 5 =0.6μm,θ r is 27 degrees; the thickness of the entire top resonant pattern is h 3 =0.25μm.

[0056] The intermediate dielectric layer is made of silicon dioxide with a dielectric constant of 3.8, a unit period of p=19 μm, and a thickness of h 2 =5μm.

[0057] The material of the metal bottom plate is gold film, and the conductivity is 4.09×10 7 S / m, unit period is p=19μm, thickness is h 1 =0.2μm, which is much larger than the skin depth of electromagnetic waves in this frequency band.

[0058] Furthermore, the conductivity of vanadium dioxide in the insulating state and the metallic state is set to 200 S / m and 2×10 5 S / m, setting the conductivity of vanadium dioxide between the metallic state and the dielectric state to be: 2×10 3 S / m, 2×10 4S / m, 1×10 5 S / m.

[0059] Furthermore, according to the design method of the terahertz controllable broadband absorber of the present invention, the modulation depth Md of the absorber satisfies:

[0060]

[0061] Among them, A M (ω) is the absorption rate of vanadium dioxide in the metallic state, A D (ω) is the absorption rate of vanadium dioxide in the insulating state, ξ represents the relative error value of the modulation depth of the absorber;

[0062] Furthermore, the absorber absorbency calculation value A(ω) satisfies:

[0063]

[0064] Among them, n-1 and n represent any two adjacent frequency points in the working frequency band, A n-1 (ω) and A n (ω) represents the absorbance value obtained by simulation at the n-1th and nth frequency points, and ψ represents the relative error value of the absorber absorbance;

[0065] Furthermore, the absorber absorption rate A(ω) is calculated as follows:

[0066] A(ω)=1-R(ω)-T(ω)=1-|S 11 | 2 -|S 21 | 2

[0067] Where R(ω) is the reflectivity of the absorber, T(ω) is the transmittance of the absorber, and S 11 is the reflection coefficient of the absorber, S 21 is the transmission coefficient of the absorber. Since the thickness of the metal bottom plate is much greater than the skin depth of the electromagnetic wave in this working frequency band, the electromagnetic wave cannot be transmitted from the bottom plate, so T(ω) = 0. Therefore, the absorption rate A(ω) can be expressed as:

[0068]

[0069] Among them, Z in (ω) is the input impedance of the metasurface absorber, Z 0 is the wave impedance in free space, Z 0 =377Ω, μ and ε represent the magnetic permeability and dielectric constant of the metasurface absorber, μ 0 and ε 0 represents the magnetic permeability and dielectric constant of free space;

[0070] Furthermore, the wave absorption rate A(ω) of the metasurface absorber can be expressed by the wave absorption rate control function f(μ,ε):

[0071]

[0072] Finally, the metasurface absorption rate control model F(A(ω)) is obtained:

[0073]

[0074] Where q is the number of frequency sampling points of the absorber in the working bandwidth, g is 1 is the frequency starting value of the working bandwidth, g 2 is the final frequency value of the working bandwidth;

[0075] In fact, in fog and rain, the wave absorption rate is affected by the air humidity. The actual wave absorption rate control model FT(A(ω)) of the metasurface is expressed as:

[0076]

[0077] Where λ(R) is the humidity adjustment factor of the absorbance, R is the relative humidity value, and after calibration, λ(R) is expressed by the following function:

[0078]

[0079] Specific embodiments: 1) designing a metasurface absorber unit;

[0080] 2) The top layer is designed to be a composite pattern structure consisting of an outer metal open resonant ring, a middle square ring, and a Jerusalem cross structure inside the square ring. The material of the entire composite structure is vanadium dioxide, and the conductivity in the insulating state and the metallic state are 200S / m and 2×10 5 S / m. The outer ring length of the metal split resonant ring is l 1 =18μm, the inner ring length is l 2 =16μm, the opening spacing is l 3 =4μm; the outer ring length of the middle square ring is a=7μm, the inner ring length is b=5.5μm; the length of the Jerusalem cross structure in the square ring is l 4 =4μm, width is w 4 =0.3μm, the length of the dipole is l 5 =2μm, width is w 5 =0.6μm; the thickness of the entire top resonant pattern is h 3 =0.25μm, such as Figure 1 shown.

[0081] 3) Design the intermediate dielectric layer: Use silicon dioxide material with a dielectric constant of 3.8, establish a unit period of p = 19 μm, thickness h 2 =5μm dielectric layer, such as Figure 2 shown.

[0082] 4) Design of metal base plate: The conductivity is 4.09×10 7 S / m gold film material, establish a unit period of p = 19μm, thickness h 1 = 0.2μm gold film base, such as Figure 2 shown.

[0083] 5) Set the simulation frequency range: 3–12THz.

[0084] 6) The electromagnetic simulation software CST Microwave Studio was used to construct the absorber model. Unit cell boundary conditions were used in the x and y directions, open add space boundary conditions were used in the z direction, and Floquet port was used for excitation. The incident electromagnetic wave was a plane electromagnetic wave, incident vertically along the -z direction.

[0085] 7) When the conductivity of vanadium dioxide is 2×10 5 When S / m (metallic state), the wave absorption rate curve of the terahertz adjustable broadband absorber of the present invention is as follows: Figure 3 As shown. The expected value of the absorber's absorption rate is set to 97%, and the relative error of the absorption rate ψ is 3%. After simulation, the average absorption rate in the range of 4.73-10.02THz is 97.5%, the absorption bandwidth is 5.29THz, the relative bandwidth is 71.73%, and the absorption rate at the resonant frequency of 7.35THz is 99.63%. The relative error is less than the maximum allowable error of 3%, which shows that the absorber proposed in the present invention can achieve a nearly perfect absorption effect.

[0086] 8) Figure 4 The absorption rate curves of the single structure and the composite structure. It can be seen from the figure that the absorber based on each individual structure has low absorption rate and narrow absorption bandwidth. When the three individual structures are combined together, the structure can achieve wide-band perfect absorption through the coupling effect between the structures.

[0087] 9) Figure 5 The conductivity of vanadium dioxide changes from 200 S / m to 2×10 5 Absorption rate curve at S / m. With the change of vanadium dioxide conductivity, the absorption rate can be dynamically adjusted from 3.3% to nearly 100%, and the modulation depth of the absorber can reach 0.97, which shows that the designed absorber has potential application prospects in modulators, photoelectric switches and other fields.

[0088] 10) When the electromagnetic wave is incident vertically, the absorption rate contour diagram at different polarization angles is as follows: Figure 6 As shown in the figure, as the polarization angle changes in the range of 0-90°, the resonant frequency and absorption intensity of the absorber do not change significantly, indicating that the absorber has good polarization insensitivity. This is mainly due to the high central symmetry of the designed absorber unit, which can generate strong resonance when electromagnetic waves with different polarization angles are vertically incident on the absorber.

[0089] 11) Figure 7 and Figure 8 The following are the absorption contours for the incident angle θ from 0 to 60° in TE and TM modes. In TE mode, as the incident angle increases, the absorption gradually decreases, the relative bandwidth narrows and blue shifts, but the broadband absorption effect of 30° (absorption>90%) can still be maintained overall; in TM mode, as the incident angle increases from 0° to 50°, the relative bandwidth and absorption change little, and when the incident angle is greater than 50°, the absorption bandwidth and absorption drop rapidly. Generally speaking, within the range of θ<50°, a wide operating frequency band and excellent absorption performance can be achieved.

[0090] 12) Fig. 9 The normalized impedance value curve of the designed terahertz adjustable broadband absorber is shown in the figure. As can be seen from the figure, in the range of 4.73-10.02THz, the real part of the absorber's equivalent impedance is close to 1, and the imaginary part is close to 0. This shows that the equivalent impedance of the absorber and the impedance of free space are nearly perfectly matched in the range of 4.73-10.02THz, thus producing a broadband near-perfect absorbing effect.

[0091] 13) Fig.10 This is a comparison chart of the absorbance of this design in the laboratory dry state and the absorbance of this design in the dense fog state. It can be seen from the figure that the measurement results of the existing design method in the dense fog state deviate greatly from the actual results. In order to illustrate the correctness of the present invention, the measurement results in the dense fog state are deduced from the results in the ideal state by the present invention, and it is found that it almost coincides with the theoretical calculation, thereby illustrating the correctness of the present invention.

[0092] The above contents are the technical principles and specific implementation methods of the present invention. Without departing from the spirit and principles of the embodiments of the present invention, the exemplary embodiments may be improved, or some features of the embodiments may be arranged and replaced in other ways, which does not affect the essential content of the present invention.

Claims

1. A terahertz controllable broadband absorber based on vanadium dioxide, the main features of which are: The absorber is composed of three layers, which are a vanadium dioxide resonant pattern layer, a silicon dioxide dielectric layer and a gold film bottom plate layer from top to bottom, and the three layers are tightly fitted; the vanadium dioxide resonant pattern layer is a composite structure consisting of an outer metal open resonant ring, an intermediate square ring and a Jerusalem cross structure inside the square ring, wherein the outer ring length of the outer metal open resonant ring is l1=18μm, the inner ring length is l2=16μm, and the opening spacing is l3=4μm; the outer ring length of the intermediate square ring is a=7μm, and the inner ring length is b=5.5μm; the Jerusalem cross structure inside the square ring is composed of a cross, a rectangle at the end of the cross and a fan on the edge of the rectangle, the chord length of the fan is the same as the side length of the rectangle, and the central angle is θ r The length of the cross structure is l4=4μm, the width is w4=0.3μm, the length of the dipole is l5=2μm, the width is w5=0.6μm; the unit cell structure is regularly arranged periodically in the x and y directions, with an M×N distribution, where M represents the number of unit cells in the x direction, and N represents the number of unit cells in the y direction, M=N, the x direction is the horizontal direction, and the y direction is the direction perpendicular to the x direction in the horizontal plane.

2. The terahertz controllable broadband absorber based on vanadium dioxide designed according to claim 1 is characterized in that: The resonant pattern of the top layer of the designed metasurface structure is symmetrical about the diagonal line.

3. The vanadium dioxide-based terahertz controllable broadband absorber designed according to claim 2 is characterized in that: The silicon dioxide dielectric layer is made of silicon dioxide with a dielectric constant of 3.

8.

4. The vanadium dioxide-based terahertz controllable broadband absorber designed according to claim 3 is characterized in that: The designed intermediate dielectric layer and the metal base plate have the same size but different thicknesses.

5. The vanadium dioxide-based terahertz controllable broadband absorber designed according to claim 4, characterized in that: The vanadium dioxide material can be described by the Drude model in the terahertz band, and the dielectric constant ε(ω) of the vanadium dioxide material is expressed as: Among them, ε ∞ is the high frequency dielectric constant of vanadium dioxide, ε ∞ =12; collision frequency γ = 5.75×10 13 rad / s,ω p (σ) is the plasma frequency, ω p The relationship between (σ) and conductivity σ is as follows: Among them, σ0 is 3×10 5 S / m,ω p (σ0) is 1.4×10 15 rad / s.

6. The vanadium dioxide-based terahertz controllable broadband absorber according to claim 5, characterized in that: The modulation depth Md of the absorber satisfies: Among them, A M (ω) is the absorption rate of vanadium dioxide in the metallic state, A D (ω) is the absorption rate of vanadium dioxide in the insulating state, and ξ represents the relative error value of the modulation depth of the absorber.

7. The vanadium dioxide-based terahertz controllable broadband absorber according to claim 6, characterized in that: The absorber absorbency calculation value A(ω) satisfies: Among them, n-1 and n represent any two adjacent frequency points in the working frequency band, A n-1 (ω) and A n (ω) represents the absorption value obtained by simulation at the n-1th and nth frequency points, and ψ is the relative error value of the absorption value.

8. The vanadium dioxide-based terahertz controllable broadband absorber according to claim 7, characterized in that: The absorber absorption rate A(ω) is calculated as follows: A(ω)=1-R(ω)-T(ω)=1-|S 11 | 2 -|S 21 | 2 Where R(ω) is the reflectivity of the absorber, T(ω) is the transmittance of the absorber, and S 11 is the reflection coefficient of the absorber, S 21 is the transmission coefficient of the absorber. Since the thickness of the metal bottom plate is much greater than the skin depth of the electromagnetic wave in this working frequency band, the electromagnetic wave cannot be transmitted from the bottom plate, so T(ω) = 0. Therefore, the absorption rate A(ω) can be expressed as: Among them, Z in (ω) is the input impedance of the metasurface absorber, Z0 is the wave impedance in free space, Z0=377Ω, μ and ε represent the magnetic permeability and dielectric constant of the metasurface absorber, μ0 and ε0 represent the magnetic permeability and dielectric constant of free space; Then the wave absorption rate A(ω) of the metasurface absorber can be expressed by the wave absorption rate control function f(μ,ε): Ideal metasurface absorptivity control model F(A(ω)): Where q is the number of frequency sampling points of the absorber in the working bandwidth, g1 is the starting value of the frequency of the working bandwidth, and g2 is the final value of the frequency of the working bandwidth.

9. The vanadium dioxide-based terahertz controllable broadband absorber according to claim 8, characterized in that The actual metasurface absorption control model FT(A(ω)) in fog and rain is expressed as: Where λ(R) is the humidity adjustment factor of the absorbance, R is the relative humidity value, and after calibration, λ(R) is expressed by the following function:

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