A two-mode multi-peak tunable absorber based on vanadium dioxide

Abstract

A two-dimensional metasurface composed of periodic array distributed basic structure units, each basic structure unit comprising three layers of structures, from top to bottom: a center-symmetric nested VO2-metal composite superstructure layer, comprising a center-symmetrically distributed outer ring of vanadium dioxide, a vanadium dioxide connecting block, and a plurality of nested metal frames, each metal frame being nested layer by layer in size from large to small, and being symmetrically distributed with the center of the outer ring of vanadium dioxide as the center of symmetry, the outer ring of vanadium dioxide being physically connected with the outermost metal frame, and the vanadium dioxide connecting block being distributed on the inner side of the metal frame and connecting each metal frame and being symmetrically distributed with the center of the outer ring of vanadium dioxide as the center of symmetry; an FR-4 dielectric layer and a metal reflection layer. The application switches vanadium dioxide between the metal state and the insulating state by regulating the ambient temperature, and realizes dynamic reversible tuning of the absorption mode through temperature control.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of metamaterial absorbers, and particularly relates to a dual-mode multi-peak tunable absorber based on vanadium dioxide. BACKGROUND

[0002] Terahertz (THz) waves have important applications in high-speed communication, biomedical imaging, non-destructive testing and stealth technology, but the development of efficient control devices such as absorbers and filters still faces challenges. Traditional absorbers are mostly based on metal-dielectric periodic structures, and high absorption at specific frequencies is achieved through geometric resonance, but their fixed frequency bands and narrow bandwidths such as single or double peaks make it difficult to adapt to dynamic electromagnetic environment requirements.

[0003] Metamaterials can break through the limitations of natural materials by adjusting the effective electromagnetic parameters through sub-wavelength artificial periodic structures, and achieve super-normal absorption characteristics. Although traditional metamaterial absorbers have good absorption performance, they still have problems such as fixed structure, complex multi-peak design and single tuning scheme. Therefore, researchers introduce functional materials such as graphene, liquid crystals and phase change materials to couple with metamaterial structures to achieve active control of the absorber. Vanadium dioxide has an insulating state-metallic state superfast phase transition characteristic, and when the temperature reaches about 340K, the electrical conductivity changes by several orders of magnitude, with a response time of picoseconds, making it an ideal candidate for dynamic metamaterials.

[0004] According to the reported literature, most of the metamaterial absorbers based on vanadium dioxide are single-frequency tunable, and high-quality multi-peak absorption tunable with multiple functions is still a challenge.

[0005] Therefore, how to solve the problems of single-frequency limitation, single function and poor consistency of multi-peak absorption tuning in the dynamic tuning of metamaterial absorbers based on vanadium dioxide, and provide a kind of dual-mode multi-peak tunable absorber based on vanadium dioxide which realizes multi-peak and dynamic tuning in the terahertz wave band with high efficiency and multi-function integration is a technical problem that needs to be solved by those skilled in the art. SUMMARY

[0006] The purpose of the present application is to provide a dual-mode multi-peak tunable absorber based on vanadium dioxide to solve the problems in the prior art.

[0007] To this end, the above-mentioned purpose of the present application is achieved by the following technical solutions:

[0008] A dual-mode multi-peak tunable absorber based on vanadium dioxide, characterized by a two-dimensional metasurface composed of periodically arrayed basic structural units, each basic structural unit including a three-layer structure from top to bottom:

[0009] The center-symmetric nested VO2-metal composite superstructure layer comprises a center-symmetrically distributed outer VO2 ring, a VO2 connecting square and a plurality of nested metal frames, each metal frame is nested layer by layer from large to small in size, and is symmetrically distributed with the center of the outer VO2 ring as the center, the outer VO2 ring is physically connected with the outermost metal frame, and the VO2 connecting square is distributed on the inner side of the metal frame and connects each metal frame and is symmetrically distributed with the center of the outer VO2 ring as the center.

[0010] The FR-4 dielectric layer isolates the center-symmetric nested VO2-metal composite superstructure layer and the metal reflection layer, and assists in dissipating energy through dielectric loss.

[0011] The metal reflection layer forms a Fabry-Perot resonant cavity with the center-symmetric nested VO2-metal composite superstructure layer, and enhances the local field.

[0012] The VO2 is switched between the metal state and the insulating state by adjusting the environmental temperature, and the absorption mode is dynamically and reversibly tuned by temperature control.

[0013] When the VO2 is in the insulating state, the wave absorber forms a five-peak absorption mode, and the peak frequencies are 0.53 THz, 0.76 THz, 1.09 THz, 1.50 THz and 2.17 THz.

[0014] When the VO2 is in the metal state, the wave absorber switches to a two-peak absorption mode.

[0015] While the above technical solutions are adopted, the application can also adopt or combine the following technical solutions:

[0016] As a preferred technical solution of the application, in the center-symmetric nested VO2-metal composite superstructure layer, the metal frame is an aluminum frame, which is a square frame, and there are five nested square frames, each VO2 connecting square is arranged in the middle of the frame of each metal frame, and bridges the adjacent metal frames.

[0017] As a preferred technical solution of the application, the side length of each metal frame is l1=85μm, l2=65μm, l3=46μm, l4=32μm and l5=21μm, and the width of the metal frame is b=4.5μm.

[0018] The outer radius of the outer VO2 ring is 64μm, and the width is 3μm.

[0019] As a preferred technical solution of the application, the width of the VO2 connecting square is w=11.5μm, the thickness is h1=0.5μm, and each VO2 connecting square forms a cross-shaped distribution in the nested metal frame.

[0020] As a preferred technical scheme of the present application: the FR-4 medium layer has a dielectric constant epsilon = 4.1 and a loss tangent angle tan delta = 0.03.

[0021] The FR-4 medium layer has a thickness h2 = 19.5 microns.

[0022] As a preferred technical scheme of the present application: the metal reflection layer is a continuous thin film structure, the selected material is aluminum, the thickness h3 = 1.2~1.5 microns, and the conductivity is 3.56*10 7 S / m.

[0023] As a preferred technical scheme of the present application: the basic structure unit period length is 128 microns.

[0024] Compared with the prior art, the present application has the following beneficial effects: the present application adopts a composite resonance design of a nested aluminum frame connected with a vanadium dioxide (VO2) connection structure, combines the insulating state-metal state phase transition characteristics of VO2, and successfully solves the three technical problems existing in traditional metamaterial absorbers:

[0025] The present application solves the problems of fixed frequency and low tuning freedom caused by the dependence of traditional absorbers on single resonance structure and the realization of active switching (0.4~2.4THz) of five-peak / two-peak absorption modes by the nested arrangement of aluminum frames with decreasing size from large to small and the dynamic conductivity regulation of VO2 connection blocks, significantly expands the tunable range, and realizes dynamic multi-frequency compatibility by temperature regulation <340K insulating state→five-peak, ≥340K metal state→two-peak, adaptive communication frequency selection, multi-modal imaging and other different terahertz application scenarios:

[0026] The present application uses the outer ring of vanadium dioxide as a shared resonance unit, and through multi-mode coupling, the absorption bandwidth is improved to 1.64THz of five-peak coverage, and the absorption rate is all above 95%, among which the two-peak mode is 100%, solving the problems of single absorption peak and low absorption rate caused by single resonance mode, and the refractive index sensitivity of the five-peak mode reaches 0.1~0.576THz / RIU, realizing high sensitivity sensing for detecting the refractive index changes before and after cell canceration.

[0027] The center-symmetric design and subwavelength periodic arrangement of the present application ensure stable performance under 0°~60° incident angle and any polarization (TE / TM), solving the problems of polarization direction and incident angle sensitivity and poor environmental adaptability of traditional structures.

[0028] The application discloses a kind of based on vanadium dioxide dual-mode multi-peak tunable wave absorber, solves the problem of frequency fixed, low tuning degree of freedom of traditional metamaterial wave absorber, with high absorption rate, multi-mode switching and sensing function, realizes the synergistic optimization of multi-peak dynamic tunable and multifunctional integration, and has great application prospect in terahertz intelligent device field. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is a structure schematic diagram of a kind of based on vanadium dioxide dual-mode multi-peak tunable wave absorber of the application;

[0030] Figure 2 It is the side view of single structural unit in the application;

[0031] Figure 3 It is the plan view of single structural unit in the application;

[0032] Figure 4 It is the absorption curve diagram of a kind of based on vanadium dioxide dual-mode multi-peak tunable wave absorber when vanadium dioxide is in insulating state, in the figure, realize TE indicates the absorption spectrum under transverse electric wave, dotted line TM indicates the absorption spectrum under transverse magnetic wave, and two lines coincide;

[0033] Figure 5 It is the absorption curve diagram of a kind of based on vanadium dioxide dual-mode multi-peak tunable wave absorber when vanadium dioxide is in metal state, in the figure, realize TE indicates the absorption spectrum under transverse electric wave, dotted line TM indicates the absorption spectrum under transverse magnetic wave, and two lines coincide;

[0034] Figure 6 It is the absorption curve diagram of a kind of based on vanadium dioxide dual-mode multi-peak tunable wave absorber when the metal frame and metal reflection layer of center-symmetrical nested VO2-metal composite superstructure layer are replaced by gold, vanadium dioxide is in dielectric state and metal state respectively;

[0035] Figure 7 It is the absorption curve diagram of a kind of based on vanadium dioxide dual-mode multi-peak tunable wave absorber when FR-4 dielectric layer material is replaced by G-10, vanadium dioxide is in dielectric state and metal state respectively;

[0036] Figure 8 It is the equivalent impedance schematic diagram of a kind of based on vanadium dioxide dual-mode multi-peak tunable wave absorber when vanadium dioxide is in insulating state;

[0037] Figure 9 It is the equivalent impedance schematic diagram of a kind of based on vanadium dioxide dual-mode multi-peak tunable wave absorber when vanadium dioxide is in metal state;

[0038] Figure 10 It is the absorption spectrum diagram of a kind of based on vanadium dioxide dual-mode multi-peak tunable wave absorber under different polarization angles.

[0039] Figure 11 is a dual-mode multi-peak tunable absorber based on vanadium dioxide at different incident angles, the absorption spectrum of the absorber;

[0040] Figure 12 is a dual-mode multi-peak tunable absorber based on vanadium dioxide, the absorption characteristic curve of different refractive index of the measured object;

[0041] Figure 13 is a dual-mode multi-peak tunable absorber based on vanadium dioxide, the sensitivity curve when used as a sensor;

[0042] In the drawings: basic structural unit 100; center-symmetric nested VO2-metal composite superstructure layer 10; vanadium dioxide outer ring 101; vanadium dioxide connecting block 102; metal frame 103; FR-4 dielectric layer 20; metal reflection layer 30. DETAILED DESCRIPTION

[0043] The application will be further described in detail with reference to the drawings and specific examples.

[0044] A dual-mode multi-peak tunable absorber based on vanadium dioxide is a dual-mode multi-peak dynamic tunable metamaterial absorber of vanadium dioxide, which realizes dynamic tuning of five peaks and two peaks through composite resonant structure and phase change control, and solves the problems of poor multi-frequency compatibility and low tuning freedom in the prior art.

[0045] A dual-mode multi-peak tunable absorber based on vanadium dioxide is a two-dimensional super surface composed of periodically arrayed basic structural units, each basic structural unit including three layers of structures, from top to bottom:

[0046] The center-symmetric nested VO2-metal composite superstructure layer includes a center-symmetrically distributed vanadium dioxide outer ring, a vanadium dioxide connecting block, and a plurality of nested metal frames, each metal frame is nested layer by layer in size from large to small, and is centered on the center of the vanadium dioxide outer ring, the vanadium dioxide outer ring is physically connected to the four corners of the outermost metal frame, and the vanadium dioxide connecting block is distributed on the inner side of the metal frame and connects each metal frame, and is centered on the center of the vanadium dioxide outer ring;

[0047] The FR-4 dielectric layer isolates the center-symmetric nested VO2-metal composite superstructure layer and the metal reflection layer, and assists in dissipating energy through dielectric loss;

[0048] The metal reflection layer forms a Fabry-Perot resonant cavity with the center-symmetric nested VO2-metal composite superstructure layer, and enhances the local field.

[0049] The phase transition temperature threshold of the vanadium dioxide film is 340K±5K, the vanadium dioxide is switched between the metal state and the insulating state by regulating the ambient temperature, and the absorption mode is dynamically and reversibly tuned by temperature control:

[0050] When the temperature is < 340K, the vanadium dioxide is in the insulating state, a five-peak absorption mode is formed, the peak frequencies are 0.53THz, 0.76THz, 1.09THz, 1.50THz and 2.17THz, and the absorption rate is greater than or equal to 95%;

[0051] When the temperature is greater than or equal to 340K, the vanadium dioxide is switched to the metal state, and a two-peak absorption mode is formed, and the absorption rate is 100%.

[0052] The wave absorber comprises a plurality of basic structural units arranged in a periodic array along a horizontal plane, each basic structural unit is composed of three layers from top to bottom, a center-symmetric nested VO2-metal composite superstructure layer, an FR-4 dielectric layer and a bottom metal reflective aluminum layer. The center-symmetric nested VO2-metal composite superstructure layer is composed of a vanadium dioxide outer ring and a small block and five aluminum frames, and the metal reflective layer is a continuous metal film.

[0053] The metal frame of the center-symmetric nested VO2-metal composite superstructure layer is an aluminum frame, the number of aluminum frames is 5, the sizes of the metal frames are nested and distributed, the vanadium dioxide outer ring is at the outermost side, the vanadium dioxide block connects the five aluminum frames, the connection is the center of the aluminum frame edge, and the overall pattern is symmetrically distributed. The outer ring radius of the vanadium dioxide outer ring is 64μm, the outer ring width is 3μm, the side length l1 of the first aluminum frame is 85μm, the side length l2 of the second aluminum frame is 65μm, the side length l3 of the third aluminum frame is 46μm, the side length l4 of the fourth aluminum frame is 32μm, the side length l5 of the fifth aluminum frame is 21μm, the width b of all aluminum frames is 4.5μm, and the width w of the vanadium dioxide connecting block is 11.5μm. The conductivity of the vanadium dioxide of the center-symmetric nested VO2-metal composite superstructure layer is 5×10 5 S / m in the metal state, and the conductivity is 20S / m in the insulating state. The thickness h1 of the center-symmetric nested VO2-metal composite superstructure layer is 0.5μm.

[0054] The dielectric layer material is FR-4, the dielectric constant ε is 4.1, the loss tangent angle The thickness h2 of the dielectric layer is 19.5μm.

[0055] The VO2 in the application is vanadium dioxide.

[0056] The FR-4 in the application specifically refers to a flame-retardant glass fiber reinforced epoxy resin laminated board, which belongs to an electronic grade composite material.

[0057] The metal reflection layer selection material is aluminum, and the electrical conductivity is 3.56*10 7 S / m, and the thickness range h3 of the metal reflection layer is 1.2-1.5 μm.

[0058] In the application, the nested aluminum frame and vanadium dioxide connection structure, the top patterned layer is composed of five aluminum frames of different sizes, which are connected by vanadium dioxide blocks to form multiple coupled resonance units, and the vanadium dioxide outer ring is used as a shared resonance unit to expand the absorption bandwidth and enhance the mode coupling, realizing the design of a multi-resonant structure.

[0059] The plurality of basic structure units are periodically arranged, and each period has a length of 128 μm.

[0060] The electrical conductivity of the vanadium dioxide in the vanadium dioxide and aluminum layer can be described by the Drude model as:

[0061]

[0062] In the above formula, is the high-frequency dielectric constant, and the value is , is the collision frequency, and the value is , is the plasma frequency related to the electrical conductivity of vanadium dioxide, which can be expressed as the electrical conductivity of vanadium dioxide:

[0063]

[0064] In the above formula, is the initial value for calculating the plasma frequency, is the initial value of the plasma frequency.

[0065] When the vanadium dioxide is in an insulating state, ; when the vanadium dioxide is in a metallic state, .

[0066] By changing the environmental temperature of the wave absorber, the electrical conductivity of the vanadium dioxide material is adjusted, so that the vanadium dioxide realizes reversible regulation between the metallic state and the insulating state, and the absorber can be switched between the five-peak absorption mode and the two-peak absorption mode.

[0067] ​The application has the advantages that the two-mode multi-peak tunable wave absorber based on vanadium dioxide has more absorption frequencies and higher absorption rate compared with traditional absorbers.

[0068] The wave absorber has the advantages of incident angle stability, polarization insensitivity and polarization insensitivity, and has potential application value in the fields of optical invisibility, electromagnetic shielding and sensors.

[0069] The wave absorber can also be used as a sensor, and the five absorption peaks can correspond to five modes, with sensitivities of 0.1 THz / RIU, 0.157 THz / RIU, 0.226 THz / RIU, 0.314 THz / RIU and 0.576 THz / RIU, respectively, having very high sensitivity.

[0070] The application of the two-mode multi-peak tunable wave absorber based on vanadium dioxide can be applied to detect the change of refractive index before and after cell carcinogenesis, and the dynamic switching between insulating state (five peaks) and metallic state (two peaks) is realized by temperature control, and the precise detection is realized by using the refractive index RI change of cancerous cells to cause the terahertz resonance peak frequency shift of the wave absorber.

[0071] Embodiment 1

[0072] In order to realize efficient multi-peak absorption and dynamic tuning in the terahertz wave band, the application provides a two-mode multi-peak tunable wave absorber based on vanadium dioxide, which comprises a plurality of periodically arranged structure units, as shown in Figure 1 In this embodiment, each structure unit is composed of a center-symmetric nested VO2-metal composite superstructure layer, an FR-4 dielectric layer and a metal reflection layer, as shown in Figure 2 And Figure 3 The number of metal frame-aluminum frame in the center-symmetric nested VO2-metal composite superstructure layer is 5, and the large frame is nested and distributed, the outer circle of vanadium dioxide is on the outermost side, the vanadium dioxide block connects the five aluminum frames, the connection is the center of the aluminum frame edge, and the overall pattern is symmetrically distributed, as shown in Figure 3 The metal reflection layer material is aluminum.

[0073] As Figure 2 , a single structural unit of a vanadium dioxide-based dual-mode multi-peak tunable absorber is a square, with the length of each structural unit being p, the dielectric layer material being FR-4, the dielectric constant being ε = 4.1, the loss tangent angle being tan δ = 0.02, and the thickness being h2. The schematic diagram of the center-symmetric nested VO2-metal composite superstructure layer is shown in Figure 3 , the number of aluminum frames is 5, the large frames are nested and distributed, the vanadium dioxide circles are on the outermost side, the vanadium dioxide squares connect the 5 aluminum frames, the connection is the center of the aluminum frame edge, and the overall pattern is symmetrically distributed. The outer circle radius of the outer circle of the vanadium dioxide is 64 μm, the outer circle width is 3 μm, the length of the first aluminum frame is l1 = 85 μm, the length of the second aluminum frame is l2 = 65 μm, the length of the third aluminum frame is l3 = 46 μm, the length of the fourth aluminum frame is l4 = 32 μm, the length of the fifth aluminum frame is l5 = 21 μm, the width of all aluminum frames is b = 4.5 μm, and the width of the vanadium dioxide connecting square is w2 = 11.5 μm. The conductivity of the vanadium dioxide in the vanadium dioxide and aluminum layers is 2 × 10 5 S / m in the metallic state and 20 S / m in the insulating state. The thickness of the center-symmetric nested VO2-metal composite superstructure layer is h1, and the thickness of the vanadium dioxide film layer is h2. The material of the metal reflection layer is selected to be aluminum, the conductivity is 3.56 × 10 7 S / m, and the thickness is h3. As shown in Figure 4 , the phase state of the vanadium dioxide is controlled by the environment temperature, when the vanadium dioxide is in the insulating state, the absorber is in the five-peak absorption mode, the absorption peak frequencies are 0.53 THz, 0.76 THz, 1.09 THz, 1.50 THz, and 2.17 THz, respectively, and the absorption rates are 95.1%, 96.7%, 97%, 99.2%, and 100%, respectively, when the electromagnetic waves are incident as TE and TM waves, the absorption performance of the absorber is unchanged; when the vanadium dioxide is in the metallic state, the absorber is in the two-peak absorption mode, the absorption rates both reach 100%, when the electromagnetic waves are incident as TE and TM waves, the absorption performance of the absorber is unchanged, as shown in Figure 5 .

[0074] The metal layer and the metal frame of the absorber can also be replaced by other metal materials besides aluminum. As shown in Figure 6 , the metal material in the absorber is replaced by gold, the conductivity is 4.56 × 10 7 S / m, and the absorption rate of the absorber is basically consistent with the absorption rate when the metal material of the absorber is aluminum. At the same time, the dielectric layer of the absorber can also be replaced by a material with a similar dielectric constant to FR-4. As shown in Figure 7 ​As shown, the dielectric layer of the wave absorber is replaced by G-10, which has a dielectric constant ε = 4.8 and a loss tangent tan δ = 0.025. The absorption rate of the wave absorber is basically the same as that when the dielectric layer of the wave absorber is FR-4.

[0075] The mechanism of the one based on vanadium dioxide dual-mode multi-peak tunable wave absorber in this embodiment mainly utilizes electromagnetic resonance and impedance matching theory. The main role of the center-symmetric nested VO2-metal composite superstructure layer is to make the vanadium dioxide and aluminum in the structural unit produce strong electromagnetic resonance with the incident electromagnetic wave of a specific frequency through pattern design, and the electromagnetic wave energy is concentrated in the local structure, thereby enhancing the interaction between the electromagnetic wave and the material. By adjusting the electrical properties of vanadium dioxide to a specific state, impedance matching between the target frequency band incident electromagnetic wave and the absorber interface can be achieved, reducing the reflection of electromagnetic waves and enhancing absorption. Among them, when the vanadium dioxide is in the dielectric state, five aluminum frames cause one absorption peak respectively; when the vanadium dioxide is in the metallic state, the absorption peaks are fused into two.

[0076] The principle of the wave absorber is further explained by the impedance matching theory. When the electromagnetic wave irradiates the surface of the wave absorber, the reflection of the electromagnetic wave is reduced as much as possible, so that it enters the wave absorbing material, which can enhance the absorption rate of the wave absorber. The relative impedance of the wave absorber can be obtained by the following formula: , wherein μ is the magnetic permeability and ε is the dielectric constant.

[0077] When the equivalent magnetic permeability and the equivalent dielectric constant of the wave absorber match the free space, the reflection coefficient of the structure will be reduced to 0. Figure 8 and Figure 9 The real part and the imaginary part of the relative impedance of the wave absorber calculated according to the S parameter are shown. As can be seen from the figure, when the vanadium dioxide is in the metallic phase and the insulating phase, the real part of the relative impedance is close to 1 and the imaginary part is close to 0, indicating that the designed wave absorber and the free space have achieved impedance matching at this time, so that the incident electromagnetic wave enters the internal structure to the greatest extent and is consumed.

[0078] As Figure 10 , the absorption rate of the absorber remains unchanged when the polarization angle of the terahertz wave changes from 0° to 90°, indicating that the wave absorber of this example has polarization insensitive characteristics. As Figure 11 , the first absorption peak remains unchanged when the incident angle of the absorber changes, has the strongest stability and angle adaptability. The second and third absorption peaks remain unchanged before the incident angle is 30°, and decrease at 60°. The fourth and fifth absorption peaks will split to produce new resonance peaks as the angle increases. The production of new resonance peaks may be due to the new local electromagnetic field generated by the field of different angles and the structure of the absorber. In summary, we can conclude that the wave absorber has certain absorption angle stability, and the first absorption peak has the strongest adaptability, meeting the wide-angle incidence requirement in different electromagnetic field environments and having a wide range of applications.

[0079] The narrow-band wave absorber can be applied to the sensing field as a sensor. The sensitivity (S) of the sensor is an important index for evaluating the sensor, and is defined as: S = Δf / Δn , wherein Δf represents the change in frequency, and Δn represents the change in refractive index. Figure 12 When the refractive index of the measured object changes from 1.0 to 1.8, the absorption resonance peak of the wave absorber produces a red shift, as shown in FIG. 6. Figure 13 The sensitivities of the five absorption peak modes of the wave absorber are 0.1 THz / RIU, 0.157 THz / RIU, 0.226 THz / RIU, 0.314 THz / RIU and 0.576 THz / RIU, respectively.

[0080] The present application designs a novel dual-mode multi-peak dynamically controllable absorber by combining the unique electromagnetic properties of vanadium dioxide, which can achieve efficient absorption in five peaks and two peaks, and has the ability to flexibly control the absorption intensity, is not sensitive to the absorption angle and polarization, and can adapt to the application requirements under complex incident conditions. In addition, the absorber can also be used as a sensor with high sensitivity and can be applied to multiple fields.

[0081] The application discloses a kind of based on vanadium dioxide dual-mode multi-peak tunable wave absorber, and it is related to electromagnetic super material technical field.The wave absorber includes several periodic array arrangement basic structure unit, each structure unit has multilayer structure, from top to bottom is top center symmetry nested VO2-metal composite superstructure layer, FR-4 dielectric layer and metal reflection layer respectively.Utilize the thermal induced phase transition characteristics of vanadium dioxide, when vanadium dioxide is in dielectric state, wave absorber can realize high-quality five-peak absorption;When vanadium dioxide is in metal state, absorber can realize two-peak absorption.Wave absorber has angle stability, polarization insensitivity and polarization insensitivity characteristics, has strong application flexibility, simultaneously, wave absorber can also be used for sensor, compared with same terahertz narrow-band sensor, the sensor of the present application has great advantage in high refractive index sensitivity, can be applied to disease detection, drug analysis and environmental monitoring etc.Field.

[0082] The above specific embodiments are used to explain and illustrate the present application, and are only preferred embodiments of the present application, but not limit the present application, any modification, equivalent replacement, improvement, etc. made to the present application falls within the protection scope of the present application.

Claims

1. A two-mode multi-peak tunable absorber based on vanadium dioxide, characterized in that, The two-dimensional metasurface is composed of periodic array distributed basic structure units, each basic structure unit includes three layers of structures, from top to bottom are respectively: The center-symmetric nested VO2-metal composite superstructure layer includes a center-symmetric distributed vanadium dioxide outer ring, a vanadium dioxide connecting square and a plurality of nested metal frames, each metal frame is nested layer by layer from large to small in size, and is distributed in a center-symmetric manner with the center of the vanadium dioxide outer ring as the center, the vanadium dioxide outer ring is physically connected with the outermost metal frame, and the vanadium dioxide connecting square is distributed on the inner side of the metal frame and connects each metal frame, and is distributed in a center-symmetric manner with the center of the vanadium dioxide outer ring as the center; The FR-4 dielectric layer isolates the center-symmetric nested VO2-metal composite superstructure layer and the metal reflection layer, and assists in dissipating energy through dielectric loss; The metal reflection layer forms a Fabry-Perot resonant cavity with the center-symmetric nested VO2-metal composite superstructure layer, and enhances the local field, By adjusting the environmental temperature to switch the vanadium dioxide between the metal state and the insulating state, the absorption mode is dynamically and reversibly tuned by temperature control: When the vanadium dioxide is in the insulating state, the wave absorber forms a five-peak absorption mode, the peak frequencies are 0.53 THz, 0.76 THz, 1.09 THz, 1.50 THz and 2.17 THz, and the peak absorption rate is above 95%; When the vanadium dioxide is in the metal state, the wave absorber switches to a two-peak absorption mode, and the absorption rate is 100%.

2. The dual-mode multi-peak tunable absorber based on vanadium dioxide according to claim 1, characterized in that: In the center-symmetric nested VO2-metal composite superstructure layer, the metal frame is selected as an aluminum frame, which is a square frame, and there are five nested distribution, and each vanadium dioxide connecting square is arranged in the middle of the frame of each metal frame, and bridges the adjacent metal frames.

3. The dual-mode multi-peak tunable absorber based on vanadium dioxide according to claim 2, characterized in that: The side length of each metal frame is l1=85μm, l2=65μm, l3=46μm, l4=32μm and l5=21μm, and the width of the metal frame is b=4.5μm.

4. The dual-mode multi-peak tunable absorber based on vanadium dioxide according to claim 3, characterized in that: The width of the vanadium dioxide connecting square is w=11.5μm, and the thickness is h1=0.5μm, and each vanadium dioxide connecting square forms a cross-shaped distribution in the nested metal frame.

5. The dual-mode multi-peak tunable absorber based on vanadium dioxide of claim 1, wherein: The dielectric constant of the FR-4 dielectric layer is ε=4.1, and the loss tangent angle is tanδ=0.03; The thickness of the FR-4 dielectric layer is h2=19.5μm.

6. The dual-mode multi-peak tunable absorber based on vanadium dioxide of claim 1, wherein: The metal reflection layer is a continuous film structure, the material is selected as aluminum, the thickness h3=1.2~1.5μm, and the conductivity is 3.56×10 7 S / m.

7. The vanadium dioxide-based dual-mode multi-peak tunable absorber according to claim 1, characterized in that: The period length of the basic structure unit is 128μm.

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