Ultra-bandwidth terahertz absorption device based on vanadium dioxide

Abstract

The invention relates to the technical field of terahertz metamaterial devices, in particular to a terahertz absorption device based on vanadium dioxide ultra-bandwidth. The invention aims to overcome the common defects of function solidification, narrow absorption band and insufficient regulation and control flexibility of the conventional metamaterial wave absorber. The invention provides a wave absorber formed by stacking a vanadium dioxide resonance layer, a Topas dielectric layer and a metal reflecting layer from top to bottom. Effective regulation and control of the conductivity can be realized by utilizing the insulator-metal reversible phase change characteristic of vanadium dioxide under temperature regulation and control. A simulation result shows that when vanadium dioxide is in a metal state, the wave absorber realizes ultra-bandwidth strong absorption of 6.45 Thz in a frequency range of 4.17-10.62 Thz, and the average absorption rate reaches 97.2%; when vanadium dioxide is changed to an insulation state, the absorptivity is as low as 1.3%. The terahertz wave absorbing material is simple in structure and easy to prepare, has excellent terahertz wave absorbing performance, and can be widely applied to the fields of invisible devices, thermal radiation, thermal detection and the like.

Description

Technical Field

[0001] This invention relates to the field of terahertz wave technology, specifically to a terahertz absorption device based on vanadium dioxide ultrabandwidth. Background Technology

[0002] Terahertz waves are electromagnetic waves with frequencies ranging from 0.1 Thz to 10 Thz. This wave occupies a unique position between the microwave band and the infrared band, combining the advantages of both microwave and high-frequency electromagnetic wave components. Therefore, it has positive and important potential application value in fields such as electronic information, life science, communication, and sensing.

[0003] Terahertz absorbers are important terahertz functional devices. Based on their absorption characteristics, they can be broadly classified into narrowband absorbers, multiband absorbers, and broadband absorbers. Terahertz absorbers have broad application prospects in electromagnetic stealth, thermal radiation, thermal imaging, and other related fields.

[0004] Early terahertz metamaterial absorbers would generate strong electromagnetic resonance at a certain frequency, resulting in a narrow absorption bandwidth. Furthermore, once the structure of a metal absorber was fabricated, its absorption performance was often fixed, which greatly limited the development and application of absorbers.

[0005] Metamaterials are artificially designed periodic structural materials with unique physical properties not found in natural materials. They compensate for the lack of electromagnetic materials in the terahertz frequency band and can effectively generate unique electromagnetic responses to electromagnetic waves, enabling diverse control over the amplitude, transmission, and phase of terahertz waves. They are an effective way to realize terahertz control devices.

[0006] In view of the above-mentioned deficiencies in the prior art, the present invention proposes a terahertz absorption device based on vanadium dioxide ultrabandwidth, aiming to solve the problems existing in the prior art. Summary of the Invention

[0007] To achieve the above objectives, the present invention provides a terahertz absorption device based on vanadium dioxide ultrabandwidth, characterized in that: each structural unit of the device consists of a vanadium dioxide resonant layer, a Topas dielectric layer and a metal reflective layer from top to bottom, and the periodic side length of the structural unit is P=33um.

[0008] The absorber includes multiple structural units, which are distributed in an N×N pattern and arranged on a plane perpendicular to the incident direction of the terahertz wave, where N is a natural number.

[0009] The top layer is a patterned resonant layer made of vanadium dioxide. The pattern consists of four squares with circular cutouts and a central ring.

[0010] The four squares with circular cutouts are arranged in a cross shape with the central circular area as the center of symmetry. The side length is 11um, the distance from the central origin is r3=6um, the interval between two squares with circular cutouts is t=3um, and the thickness is h3=0.04um.

[0011] The central ring is located at the center of the unit structure, with an inner radius r1=3um, an outer radius r2=5um, and a thickness h3=0.04um.

[0012] The intermediate dielectric layer is made of Topas material, has a dielectric constant of 2.35, and a thickness of h2 = 6.4 μm.

[0013] The metal reflective layer is made of gold, which has an electrical conductivity of 4.56 × 10⁻⁶. 7 S / m, thickness h1=1um.

[0014] This invention aims to provide a terahertz absorption device based on vanadium dioxide ultrabandwidth. The absorber structure unit is composed of a vanadium dioxide resonant layer, a Topas dielectric layer, and a metal reflective layer stacked from top to bottom. Multiple absorber structure units are then arranged in an N×N periodic pattern to form a terahertz absorber. During use, the absorbance can be flexibly adjusted by changing the conductivity of the phase change material vanadium dioxide through temperature control, thus solving the technical problem that the absorption characteristics of traditional terahertz absorbers are fixed once manufactured. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0016] Figure 1 This is a three-dimensional diagram of a terahertz absorption device structure unit based on vanadium dioxide ultrabandwidth according to the present invention.

[0017] Figure 2 This is a front view of a terahertz absorption device structural unit based on vanadium dioxide ultrabandwidth according to the present invention.

[0018] Figure 3 This is a side view of a structural unit of a terahertz absorption device based on vanadium dioxide ultrabandwidth according to the present invention.

[0019] Figure 4 This is an absorption curve of a terahertz absorption device based on vanadium dioxide ultrabandwidth according to the present invention.

[0020] Figure 5 This is a schematic diagram of the equivalent impedance of a terahertz absorption device based on vanadium dioxide ultra-wideband in the metallic state, according to a simulation example of the present invention.

[0021] Figure 6 This is a simulation example of a terahertz absorption device based on vanadium dioxide ultra-wideband, showing the absorption spectra at different vanadium dioxide conductivity levels. Detailed Implementation

[0022] The specific embodiments of the present invention will be described in detail through the following examples. These examples are merely illustrative and are intended to help those skilled in the art to gain a deeper understanding of the present invention, rather than constituting a limitation thereof. For those skilled in the art, any non-substantial modifications and equivalent substitutions made based on an understanding of the core ideas of the present invention should be considered to fall within the protection scope of the claims of the present invention.

[0023] Please see Figures 1 to 3 This invention proposes a terahertz absorption device based on vanadium dioxide ultrabandwidth, comprising multiple structural units, which are distributed in an N×N pattern and arranged in a plane perpendicular to the incident direction of the terahertz wave, where N is a natural number.

[0024] Each of the structural units consists of a vanadium dioxide resonant layer, a Topas dielectric layer, and a metal reflective layer from top to bottom, making the terahertz metamaterial absorber formed by the invention a simple "sandwich" structure, thereby solving the problems of complex structure and difficult fabrication of terahertz absorbers.

[0025] The top layer uses patterned VO2 as the resonant layer. Four squares with circular cutouts are arranged symmetrically in a cross shape with the central circular area as the center of symmetry. The side length is w=11um, the distance from the central origin is r3=6um, and the interval between two squares with circular cutouts is t=3um. The inner radius of the central ring is r1=3um, and the outer radius is r2=5um. The thickness of VO2 is h3=0.04um.

[0026] The material of the absorbing medium layer is Topas, with a dielectric constant of 2.35 and a thickness of h2 = 6.4 μm.

[0027] The metal substrate is made of gold, which has an electrical conductivity of 4.56 × 10⁻⁶. 7 S / m, the thickness of the metal substrate h1=1um.

[0028] For further details, please refer to Figures 4 to 5To illustrate the performance characteristics of the vanadium dioxide-based ultrabandwidth terahertz absorber, this invention uses CST Microwave Studio 2022 for performance simulation. A frequency solver is used in the simulation, and a tetrahedral adaptive mesh is employed. Unit cell boundary conditions are used in the x and y directions, and open (add space) boundary conditions are used in the z direction. Linearly polarized electromagnetic waves are propagated along the -z axis via a Floquet port. Furthermore, the distance between the port location and the top-level structure is set to be greater than two wavelengths to simulate far-field detection in real-world scenarios.

[0029] In the terahertz band, the optical permittivity of vanadium dioxide can be described by the Drude model, while its relative permittivity can be represented by the Drude model. , Represented as:

[0030]

[0031] In the formula, the high-frequency dielectric constant =12, collision frequency =5.75×10 13 rad / s, plasma frequency With conductivity The relevant formula is:

[0032]

[0033] in S / m, rad / s. In the simulation, different conductivity values ​​were set. This was used to simulate the phase transition characteristics of vanadium dioxide. When VO2 is in the metallic state, its conductivity is 3 × 10⁻⁶. 5 S / m; when VO2 is in an insulating state, the conductivity is 300 S / m.

[0034] Absorption rate A is an important parameter reflecting the absorption performance of a device. Assuming that an electromagnetic wave is incident perpendicularly to the surface of the absorber structure along the -z axis, according to electromagnetic theory, the formula for calculating the absorption rate is:

[0035] Among them, S 11 and S 21 Let S and V represent the reflection coefficient and transmission coefficient, respectively, generated after the incident wave enters the device. Within the simulation frequency range, because the thickness of the metal substrate is much greater than its skin depth, the transmission coefficient S of the device is almost zero. Therefore, the formula for the absorptivity can be simplified to:

[0036]

[0037] Reference Figure 4 Vanadium dioxide is in a metallic state ( At a frequency of f = 8.78 THz, the absorber exhibits an average absorption rate greater than 97.2% in the frequency range of 4.17-10.62 THz (S / m), and achieves perfect absorption. Furthermore, according to the formula... The relative bandwidth of the absorber can be calculated to be approximately 87.2%, where f h =10.62Thz, f l =4.17Thz. The designed terahertz ultra-wideband absorber has great potential for application in broadband absorption.

[0038] The equivalent impedance of a metamaterial absorber is closely related to its equivalent permittivity and permeability, both of which can be tuned by changing the configuration parameters of the unit cell. Through appropriate dimensional design, the absorber can achieve impedance matching with free space over a wide frequency band, thereby extending its bandwidth for efficient absorption. Given the subwavelength characteristics of the metamaterial unit cell, its electromagnetic response can be macroscopically equivalent to a homogeneous dielectric plate.

[0039] Reference Figure 5 Within the absorption bandwidth, the real part of the relative impedance is close to 1 and the imaginary part is close to zero. At this time, the characteristic impedance of the absorber is basically the same as the impedance of free space, achieving impedance matching. This significantly reduces the reflection of incident electromagnetic waves on the absorber surface and maximizes the absorption effect of electromagnetic waves.

[0040] The modulation depth (MD) of a tunable metamaterial absorber can be calculated using a formula.

[0041]

[0042] in and These represent the absorption rates of VO2 in the metallic and dielectric states, respectively.

[0043] Typically, the conductivity of VO2 can be controlled by adjusting the temperature, thereby changing its dielectric constant and achieving continuous control over the absorber's absorption rate. For example... Figure 6 As shown, as the conductivity of VO2 gradually increases from 200 S / m to 3 × 10⁻⁶, 5 With an absorption ratio of S / m, the absorber's absorptivity and absorption bandwidth are significantly improved, with the absorptivity dynamically increasing from 1.3% to 97.2%. When the conductivity reaches 3×10... 5 At a frequency of S / m, the absorber exhibits a perfect absorption peak at f=8.78THz and demonstrates optimal absorption bandwidth. Based on this mechanism, we designed a metamaterial absorber with excellent modulation depth (98.6%).

[0044] By adjusting the conductivity of VO2, the absorption rate of this device can be controlled, thereby achieving the effects of absorption or reflection. Since VO2 is a phase change material, its conductivity can be modulated by electrical or thermal stimulation, thus enabling the device to switch between absorber and reflector functions.

[0045] In summary, a terahertz absorption device based on vanadium dioxide with ultra-widebandwidth was designed. This device consists of a VO2 resonant layer, a Topas dielectric layer, and a metal reflective layer. Simulation results show that when the conductivity of VO2 is between 300 S / m and 3 × 10⁻⁶ S / m… 5 When the S / m ratio is adjusted, the average absorptivity of the absorber can be dynamically adjusted from 1.3% to 97.2%. When VO2 is in an insulating state, the average absorptivity is 1.2%; when VO2 is in a metallic state, the absorber achieves an absorptivity exceeding 90% in the frequency range of 4.17-10.28 THz, with an absorption bandwidth of 6.45 THz. This design boasts advantages such as simple structure, wide adjustment range, high absorptivity, and ultra-wide absorption bandwidth, making it potentially valuable for applications in adjustable bandwidth absorbers, stealth devices, and thermal detection.

Claims

1. A terahertz absorption device based on vanadium dioxide ultrabandwidth, comprising multiple terahertz absorbing structural units arranged periodically, with no gaps between adjacent metamaterial terahertz absorbing structural units. Each terahertz absorbing structural unit consists of a vanadium dioxide resonant layer, a Topas dielectric layer, and a metal substrate layer from top to bottom. The periodic side length of the structural unit is p = 33 μm.

2. The terahertz absorption device based on vanadium dioxide ultrabandwidth as described in claim 1, characterized in that: The resonant layer material is vanadium dioxide, a phase change material, with an average absorption rate of up to 97.2%, an absorption bandwidth of 6.45 Thz, and a relative bandwidth of 98.6%.

3. The terahertz absorption device based on vanadium dioxide ultrabandwidth as described in claim 2, characterized in that: The top layer is a patterned vanadium dioxide resonant layer. The four squares with rounded corners have a side length of w=11um, the inner radius of the central ring is r1=3um, the outer radius is r2=5um, and the thickness of the vanadium dioxide is h3=0.04um.

4. The terahertz absorption device based on vanadium dioxide ultrabandwidth as described in claim 3, characterized in that: The dielectric layer is a Topas dielectric layer with a dielectric constant of 2.35 and a thickness of h2 = 6.5 μm.

5. A terahertz absorption device based on vanadium dioxide ultrabandwidth as described in claim 4, characterized in that: The metal base plate is made of gold, with an electrical conductivity of 4.56 × 10⁻⁶. 7 S / m, thickness h1=1um.

6. The terahertz absorption device based on vanadium dioxide ultrabandwidth as described in claim 5, characterized in that: The electrical conductivity of vanadium dioxide can be altered by external stimulation, enabling a reversible phase transition from a metallic state to an insulating state. External stimulation can include temperature, light, and voltage.

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