Terahertz ultrawideband absorption and polarization conversion bifunctional electromagnetic metamaterials and their applications

Abstract

This invention relates to the field of electromagnetic metamaterials technology, specifically disclosing a terahertz ultra-wideband absorption and polarization conversion dual-functional electromagnetic metamaterial and its applications. This metamaterial is composed of multiple unit structures arranged periodically. Each unit structure, from bottom to top, comprises a metal backplate layer, a first dielectric layer, a polarization converter layer, a VO2 film layer, a second dielectric layer, a VO2 resonant ring layer, a third dielectric layer, and a VO2 absorbing layer. The metamaterial provided by this invention overcomes the problems of single function and narrow operating bandwidth in the terahertz field. Compared to general metamaterials, this metamaterial can switch between different functions by adjusting the conductivity of VO2, achieving ultra-wideband absorption and polarization conversion. It has potential value in fields such as terahertz stealth, radar imaging, and wireless communication.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic metamaterials technology, specifically to a terahertz ultrawideband absorption and polarization conversion dual-function electromagnetic metamaterial and its applications. Background Technology

[0002] Absorption and polarization conversion are two important functions in the field of electromagnetic materials. Absorption is commonly used for energy capture, conversion, and sensor development, while polarization conversion is widely used in polarization control and optical modulation. Absorption refers to a material converting light energy into other forms of energy, while polarization conversion changes the polarization state of light through specific methods, thereby improving the performance and efficiency of optical systems.

[0003] In terms of absorption, technology has evolved from early single-frequency absorbers to multi-frequency, broadband, and ultra-wideband absorbers, gradually exploring the broad application prospects of electromagnetic metamaterials. Compared with traditional absorbers, electromagnetic metamaterial absorbers possess a simple design, excellent absorption performance, lightweight structure, and thinner thickness. Furthermore, they offer design flexibility, tunable absorption bands, and customizable electromagnetic properties, greatly expanding their applicability in various applications. Regarding polarization conversion, in optical communication equipment, incident light signals must undergo polarization processing to be effectively received and decoded. Metamaterial polarizers can not only efficiently adjust the polarization state of light but also play a crucial role in optical communication signal processing, significantly improving the stability and efficiency of optical transmission. Due to their high precision, low loss, and good repeatability, these polarizers can be integrated into antennas and RF front-end devices, thereby enhancing the power output and signal sensitivity of the equipment, and are widely used in Wi-Fi, cellular communication, and satellite communication. Compared with traditional polarizers, metamaterial polarizers have higher polarization control precision, a wider operating bandwidth, and more flexible adjustability, which has profound significance for research and application in information technology, optical communication, and electronics.

[0004] CN115020987A discloses a method for realizing a terahertz broadband absorption and polarization conversion dual-function metamaterial. A substrate reflector is fixedly mounted on the bottom inner side of the metamaterial unit, upon which a polyethylene cyclic olefin copolymer (ToPaS) dielectric layer, a rectangular strip, a vanadium dioxide thin film layer, another polyethylene cyclic olefin copolymer dielectric layer, and a concentric vanadium dioxide ring patch are sequentially arranged. By changing external conditions, the vanadium dioxide is transformed between an insulating state and a metallic state, achieving dual-function switching of the metamaterial device. While the dual-function metamaterial design disclosed in CN115020987A can achieve broadband operation within a certain frequency band, it has limitations in bandwidth expansion, failing to meet the application requirements of ultra-wideband applications. The aforementioned metamaterial structure is relatively large, which not only makes its promotion and integration in practical applications more difficult but also negatively impacts the performance and stability of the device. Especially under the requirement of wider bandwidth, the larger size of the metamaterial often makes it difficult to further extend the spectral response. To overcome these limitations, this invention proposes a dual-functional metamaterial design with a small size. By optimizing the material structure and design parameters, it solves the problems of limited bandwidth and excessive size in the prior art, thereby enabling wider applications and superior performance. Summary of the Invention

[0005] This invention provides a dual-functional electromagnetic metamaterial for terahertz ultra-wideband absorption and polarization conversion, and its applications. It can simultaneously achieve both ultra-wideband absorption and polarization conversion at the terahertz frequency, and the metamaterial is small in size. Furthermore, it optimizes the matching degree between electromagnetic waves and the metamaterial structure, extending the metamaterial's operating frequency band from wideband to ultra-wideband. This invention significantly improves the metamaterial's response capability across a wider frequency range by precisely adjusting the metamaterial unit structure and material properties.

[0006] The technical solution of this invention is to provide a terahertz ultra-wideband absorption and polarization conversion dual-function electromagnetic metamaterial, which is composed of multiple unit structures arranged periodically. Each unit structure, from bottom to top, consists of a metal backplate layer, a first dielectric layer, a polarization converter layer, a VO2 film layer, a second dielectric layer, a VO2 resonant ring layer, a third dielectric layer, and a VO2 absorbing layer. The polarization converter is an asymmetric king-shaped structure made of metal. The VO2 resonant ring layer is a VO2 ring structure with nine arrayed rings. The VO2 absorbing layer is formed by rotating an ellipse with its center point as the center, rotating it 45° each time, and rotating it 3 times to form a shape consisting of four intersecting ellipses. A regular octagon is removed from the center of this shape, and eight sectors and 16 irregular quadrilaterals are removed from the ellipse outside the regular octagon. The remaining structure is symmetrical along the major axis, minor axis, and center of the ellipse.

[0007] Optionally, the metal backing layer is made of gold material and has a thickness of 0.05~0.15μm.

[0008] Optionally, the first dielectric layer, the second dielectric layer, and the third dielectric layer are all PI material layers with a dielectric constant of 1.9 to 2.1.

[0009] Optionally, the thicknesses of the first dielectric layer, the second dielectric layer, and the third dielectric layer are 2.1~2.2μm, 2.55~2.65μm, and 2.55~2.65μm, respectively.

[0010] Optionally, the polarization converter is made of gold and its asymmetrical king-shaped structure includes three horizontal bars and vertical bars connecting the three horizontal bars. The upper and lower horizontal bars have different lengths, namely 3.65~3.75μm and 3.45~3.55μm, respectively, and both have a width of 1.65~1.75μm. The middle horizontal bar has a length of 2.95~3.05μm and a width of 0.55~0.65μm. The width of the vertical bar connecting the three horizontal bars is 0.95~1.05μm. A disk with a radius of 0.95~1.05μm is also provided in the middle of the vertical bar. The total distance between the upper and lower horizontal bars is 7.35~7.45μm.

[0011] Optionally, the thickness of the VO2 membrane is 0.05~0.15μm.

[0012] Optionally, the outer radius and inner radius of the VO2 rings in the VO2 resonant ring layer are 1.15~1.25μm and 0.95~1.05μm, respectively, and the distance between the centers of two adjacent VO2 rings is 2.45~2.55μm.

[0013] Optionally, the semi-major axis and semi-minor axis of the VO2 absorbing layer are 3.45~3.55μm and 0.95~1.05μm, respectively; the circumradius of the regular octagon is 0.95~1.05μm; the central angle of the sector is 97°~107° and the radius of the sector is 0.44~0.54μm; a pair of interior opposite angles of the irregular quadrilateral are 134°~144° and 67°~77°, respectively, and the lengths of its long side and short side are 0.27~0.37μm and 0.15~0.25μm, respectively.

[0014] Optionally, the length and width of the unit structure are both 7.7~8.3μm, and the height is 7.2~7.6μm; the asymmetric king-shaped structure in the polarization converter layer is set obliquely.

[0015] The present invention also relates to the application of the metamaterial in the fields of terahertz stealth, radar imaging, and wireless communication.

[0016] The present invention has the following beneficial effects:

[0017] The device prepared with the metamaterial provided by the present invention can achieve ultra-wideband absorption and line-to-line polarization conversion in the terahertz range. In the metallic state of VO2, the metamaterial exhibits ultra-wideband absorption, with the absorption rate exceeding 90% in the frequency range of 5.8 - 17.5 THz, and the relative bandwidth being 100.4%. Its ultra-wideband absorption is mainly achieved by the resonance of NVRR and VFPA. The applications of absorption cover multiple fields such as communication, radar, stealth technology, and electromagnetic wave absorption materials. These applications play an important role in realizing efficient communication, accurate target detection, and protecting electronic devices from electromagnetic interference. In the non-metallic state of VO2, the function of polarization conversion is achieved. The polarization conversion function is mainly completed by an asymmetric king-shaped polarization converter. In the terahertz frequency band of 6.1 - 20.9 THz, the reflection of polarized waves is the line-to-line polarization conversion of polarized waves, and the polarization conversion rate is greater than 90%, with a relative bandwidth of 109.4%. In this frequency band, the applications of polarization conversion cover multiple fields such as antenna systems, wireless communication, and radar systems. Through polarization conversion technology, polarization adaptation of signals, improvement of communication quality, and extraction of target characteristics can be achieved, thereby meeting the requirements of different applications.

[0018] The present invention reduces the overall unit structure size to less than 10 μm, and the relative bandwidth of both working states is greater than 100%, achieving ultra-wideband absorption characteristics. In terms of the absorption structure, the present invention adopts a more complex five-layer structure, which is successively a VO2 film layer, a dielectric layer, a VO2 resonant ring layer, a dielectric layer, and a VO2 wave-absorbing layer. The resonance effects of the upper and lower layers significantly expand the absorption bandwidth. To enhance the polarization conversion performance, the present invention adopts a more complex "king" - shaped geometric pattern than the original rectangular metal patch, and introduces a bilateral asymmetry design of the "king" shape and an internal embedded disk structure. These designs optimize the polarization conversion ability of the metamaterial, providing a wider working frequency band and more excellent polarization conversion effect compared with the prior art. Description of the Drawings

[0019] Figure 1 In (a), (b), (c), (d), and (e), there are schematic diagrams of the unit structure and details of some layers of the terahertz ultra-wideband absorption and polarization conversion dual-functional electromagnetic metamaterial of Example 1.

[0020] Figure 2 are the absorption and reflection curves of the terahertz ultra-wideband absorption and polarization conversion dual-functional electromagnetic metamaterial of Example 2.

[0021] Figure 3 are the effects of three different structures of VFPA, NVRR, and DLS of the terahertz ultra-wideband absorption and polarization conversion dual-functional electromagnetic metamaterial of Example 3 on the absorption rate.

[0022] Figure 4 It is a graph showing the variation of the absorption rate with the conductivity of VO2 in the terahertz ultra-wideband absorption and polarization conversion dual-functional electromagnetic metamaterial of Example 4.

[0023] Figure 5 In (a) and (b), they are the curves of the absorption rate varying with the unit structure in the terahertz ultra-wideband absorption and polarization conversion dual-functional electromagnetic metamaterial of Example 5 when the conductivity of VO2 is = 2×10 5 S / m. Among them, in (a), the semi-minor axis of the elliptical disk (b) The difference between the inner and outer radii of the NVRR .

[0024] Figure 6 In (a) and (b), they are respectively the curves of the absorption rate varying with the incident angle and polarization angle in the terahertz ultra-wideband absorption and polarization conversion dual-functional electromagnetic metamaterial of Example 6.

[0025] Figure 7 In (a) and (b), they are respectively the co-polarization coefficient and cross-polarization coefficient curves and the polarization conversion curve of the y-polarized wave in the terahertz ultra-wideband absorption and polarization conversion dual-functional electromagnetic metamaterial of Example 8.

[0026] Figure 8 In (a)-(c), they are the curves of the polarization conversion rate varying with the unit structure parameters in the terahertz ultra-wideband absorption and polarization conversion dual-functional electromagnetic metamaterial of Example 9 when the conductivity is = 20 S / m. Among them, (a) the radius of the metal disk of the king-shaped polarization converter ; (b) the length of the middle rectangle of the king shape ; (c) the semi-minor axis of the elliptical disk . Detailed implementation manners

[0027] In the following examples, the experimental methods are all conventional methods unless otherwise specified. The materials used in the following examples are all commercially available products unless otherwise specified.

[0028] The following will describe the implementation schemes of the present invention in detail in combination with examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.

[0029] Example 1:

[0030] The terahertz ultra-wideband absorption and polarization conversion dual-functional electromagnetic metamaterial provided in this embodiment is composed of multiple unit structures arranged periodically. Each unit structure contains eight layers, from bottom to top: a metal backplate, a PI dielectric layer, an asymmetric zigzag polarization converter, a patternless VO2 layer, a PI dielectric layer, nine VO2 resonant rings (NVRR), a PI dielectric layer, and a VO2 flower-shaped absorbing layer (VFPA). Figure 1 As shown in (a), the unit structure periodicity The thicknesses of the dielectric substrates are respectively , , The thickness of the remaining structures is The thickness of the entire structure .

[0031] Figure 1 (b) shows the specific parameters of the W-shaped polarization converter, including its length. The king-shaped arms are designed with asymmetrical lengths, with their lengths being respectively... , Their widths are all Length of the middle structure ,width Disk radius The width of the metal strip connecting these three parts is... . Figure 1 (c) is a schematic diagram of 9 VO2 resonant rings. The unit structure of the NVRR is a VO2 ring, and its outer diameter is... ,inner diameter The distance between the two centers . Figure 1 (d) is a schematic diagram of the VO2 flower-shaped absorbing layer. The VFPA consists of four identical elliptical disks, where the major semi-axis of the ellipse is... short half-shaft The radius of the circumscribed circle of the regular octagon is removed from the middle. . Figure 1 (e) is a magnified view of the details of the removed sector and irregular quadrilateral in VFPA, where the angle of the removed sector is... The radius of the sector is The angle of the irregular quadrilateral is and The lengths of its long side and short side are respectively and .

[0032] Example 2:

[0033] Simulation tests were conducted using CST simulation software. The metamaterial was simulated within a frequency range of 0.1–19 THz, and its reflectivity and absorptivity to electromagnetic waves within this frequency range were calculated. Figure 2 As shown, in the 5.8–17.5 THz band, the metamaterial's absorptivity is greater than 90%, with an absorption bandwidth of 11.7 THz. The relative bandwidth is 100.4%. Based on the trend of the curves in the figure, the absorptivity experienced a process of first increasing, then decreasing, then increasing again and decreasing again within the 5.8–17.5 THz frequency range. The maximum absorptivity was achieved at 7.1 THz and 15.3 THz, approaching 100%, indicating perfect absorption at these two frequencies.

[0034] Example 3:

[0035] The influence of different components of the metamaterial surface structure on the absorption rate was analyzed, and the components of the structure of this invention were analyzed. When VO2 is in the metallic state, the unpatterned VO2 layer acts as a metallic backplate, which can totally reflect incident electromagnetic waves. Therefore, this example focuses on analyzing the structure of each layer of VO2. The absorption structure of VO2 is divided into three parts: retaining only VFPA, retaining only NVRR, and the overall structure (DLS). Figure 3 As shown, retaining only the VFPA achieves ultra-wideband absorption in the 6.3-15.7 THz frequency range, with a bandwidth of 9.4 THz and a relative bandwidth of 85.5%. However, retaining only the NVRR results in an overall absorption rate below 80%. Compared to the structure containing only the VFPA, the effective absorption bandwidth of the dual-layer structure increases by 2.3 THz, and the relative bandwidth increases by 14.9%. Based on the trends in absorption rate and absorption band exhibited by the different structures, it can be inferred that the NVRR only functions when resonating with the VFPA, achieving a wider absorption band.

[0036] The bifunctional metamaterial proposed in CN115020987A employs a three-layer composite structure in its absorption section, consisting of a VO2 film, a polyethylene cyclic olefin copolymer (ToPaS) dielectric layer, and a VO2 concentric ring. While this structure achieves broadband absorption in the terahertz band, it fails to meet the current demand for even wider bandwidth absorption. To address this shortcoming, this invention proposes a more complex structure employing a VO2 film layer, a dielectric layer, a VO2 resonant ring layer (NVRR), another dielectric layer, and a VO2 absorbing layer (VFPA). Through the resonance effect of the upper and lower layers, the absorption bandwidth is significantly extended, successfully achieving ultra-wideband absorption. Compared to the design in CN115020987A, this invention not only achieves better bandwidth extension but also further reduces the thickness of the absorption structure, providing more possibilities for the future application of metamaterials in integrated systems.

[0037] Example 4:

[0038] To analyze the influence of VO2 conductivity on absorption performance in metamaterials, the absorption rates of VO2 under several different conductivity states were calculated, and their changing trends were analyzed. For example... Figure 4 As shown, as the conductivity of VO2 gradually decreases, the absorption rate of the metamaterial for incident electromagnetic waves also gradually decreases. The conductivity is... At a conductivity of S / m, the metamaterial achieved ultrawideband absorption with a relative bandwidth of 100.4%. However, when the conductivity decreased to... At a conductivity of 20 S / m, the effective absorption bandwidth decreases. The effective absorption frequency band decreases to 7.8-13.2 THz, and the relative bandwidth decreases to 54.2%. As the conductivity continues to decrease, the metamaterial's ability to absorb electromagnetic waves gradually decreases. When the conductivity drops to 20 S / m, the absorption rate drops below 30%. Based on the above trends, it can be concluded that metamaterials can only efficiently absorb incident electromagnetic waves when VO₂ is in a metallic state.

[0039] Example 5:

[0040] Simulation tests were conducted using CST simulation software. The metamaterial's properties can be optimized by adjusting parameters. The minor semi-axis of the ellipse in the VFPA composition structure was selected. The difference between the inner and outer diameters of the annulus in the NVRR unit structure Two parameters that significantly affect the absorption rate were analyzed using a controlled variable method to explore their optimal values. For example... Figure 5 As shown in (a), when As the frequency increases, the right endpoint of the absorption frequency shifts from 16 THz to 18 THz, and the absorption bandwidth shows an increasing trend. However, when... At that time, the absorption rate in the 9.7-13 THz range dropped below 90%, causing the ultrawideband absorption to change into a dual-wideband absorption. With With further increases in bandwidth, the bandwidth of dual-band absorption decreases. Taking into account both absorption performance and bandwidth, a value of [value missing] for the minor semi-axis of the ellipse was ultimately chosen. .like Figure 5 As shown in (b), with the thickness difference between the inner and outer diameters of the ring... As the frequency increases, the right endpoint of the effective absorption frequency shifts to the right, increasing from 16.7 THz to over 22 THz. The overall trend is similar to... Figure 5 The similarity observed in (a). When At that time, the absorption rate in the frequency band centered at 11THz dropped below 90%, resulting in dual-band absorption. With... As the frequency increases, the bandwidth of dual-band absorption also decreases. Ultimately, the optimal value for best absorption performance is selected. .

[0041] Example 6:

[0042] Considering that electromagnetic waves typically incident on metamaterials at different incident and polarization angles in practical applications, the effects of varying the incident and polarization angles within a certain range on the absorptivity were investigated. Incident angles ranging from 0° to 60° and polarization angles ranging from 0° to 45° were selected. Figure 6 As shown in (a), the operating frequency band exhibits a blue shift with increasing incident angle. Within the range of 0° to 30°, the absorption band remains almost constant. When the incident angle exceeds 30°, the absorption efficiency decreases, and the absorption transitions from ultra-wideband to dual-frequency absorption. With further increases in the incident angle, the metamaterial's absorption rate of electromagnetic waves further decreases. Figure 6 As shown in (b), the absorptivity curves at four different polarization angles almost overlap, indicating that the metamaterial's absorptivity remains almost constant across the range of polarization angles. This demonstrates the metamaterial's polarization insensitivity, which is closely related to the symmetry of the metamaterial's absorbing structure. Based on the above trend, it can be concluded that this metamaterial can achieve ultra-wideband absorption of electromagnetic waves at small incident angles and is insensitive to the polarization of electromagnetic waves.

[0043] Example 7:

[0044] When the conductivity of VO2 is 20 S / m, VO2 is in a non-metallic state. The unpatterned layer of VO2 loses its function of reflecting electromagnetic waves and allows electromagnetic waves to pass through completely. The polarization converter plays a role, and at this time, the metamaterial produces a polarization conversion effect on the incident electromagnetic waves. Figure 7 (a) Curves for the two polarization coefficients, where This is called the cross-polarization coefficient. This is called the common polarization coefficient. When... The curve in the figure is greater than The curve indicates that the electromagnetic wave has undergone a polarization transition. At a frequency of 5.4 THz, and They begin to intersect. When the frequency exceeds 6.9 THz, It dropped below 0.1, while This increases to above 0.9, resulting in excellent line-to-line polarization conversion. When the frequency exceeds 20 THz, It started to descend. It begins to rise. When the two intersect, the polarization conversion effect disappears. Figure 7(b) shows the polarization conversion rate curve for the y-polarized wave. It can be observed that the polarization converter achieves an ultra-wideband polarization conversion rate exceeding 90% in the frequency range of 6.1–20.9 THz, with a bandwidth of 14.8 THz and a relative bandwidth of 109.4. In the 7–10 THz band, the polarization conversion rate approaches 100%, achieving complete conversion of the incident y-polarized wave into an x-polarized wave.

[0045] Example 8:

[0046] The scanning parameters were investigated using the controlled variable method to explore the influence of the king-shaped polarization converter and the upper absorption structure on polarization conversion.

[0047] Figure 8 (a) shows the effect of changes in the radius of the central disk of the king-shaped polarization converter on PCR. As the disk radius... As the concentration increases, the PCR frequency range gradually decreases. When... PCR efficiency dropped below 90% in the frequency range of 16.6 THz to 19.3 THz. With With the increase of [value], the range of this frequency band has expanded. When As the frequency range increases to 15.6 THz-20.3 THz, the polarization conversion efficiency further decreases, and the minimum PCR value drops to 70%. Considering the partial overlap between the metal disk and the cross-linking structure, when Less than When the disk coincides with the king-shaped structure, the effect of the ring on polarization conversion is not significant. Taking all the above factors into consideration, the radius was ultimately chosen. for . Figure 8 (b) shows the length The effect of changes on PCR. It can be seen that the changes... This also affects the polarization conversion rate in the high-frequency range. When PCR decreased to below 90% in the frequency range of 16.6 THz to 18.6 THz, leading to a shift from ultrawideband polarization conversion to dual-band polarization conversion. When Increase At that time, the frequency range extended to 15.6 THz to 18.9 THz. Furthermore, in the frequency range of 10.7 THz to 14.1 THz, as... As the polarization rate increases, the PCR gradually rises, eventually approaching a perfect polarization transition. Considering the continuity of polarization transition frequencies, the final result will be... Length optimized to . Figure 8 (c) demonstrates the modification of the absorption structure. The effect on PCR was observed to remain almost unchanged, indicating that VO2 can completely transmit electromagnetic waves without affecting polarization conversion. Based on the above method, the parameters of the zigzag polarization converter were optimized through parameter scanning to improve the efficiency of polarization conversion.

[0048] In summary, this invention proposes a dual-functional electromagnetic metamaterial for terahertz ultra-wideband absorption and polarization conversion. This device can switch the metamaterial's function by adjusting the conductivity of VO2, thus achieving both broadband absorption and polarization conversion.

[0049] The above embodiments describe preferred embodiments of the present invention, but the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other way. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A terahertz ultrawideband absorption and polarization conversion dual-functional electromagnetic metamaterial, characterized in that: It consists of multiple unit structures arranged periodically. Each unit structure, from bottom to top, consists of a metal backplate layer, a first dielectric layer, a polarization converter layer, a VO2 film layer, a second dielectric layer, a VO2 resonant ring layer, a third dielectric layer, and a VO2 absorbing layer. The polarization converter is an asymmetrical king-shaped structure made of metal. The VO2 resonant ring layer is a VO2 ring structure with nine arrays distributed. The VO2 absorbing layer is formed by rotating an ellipse with its center point as the center, rotating it 45° each time, and rotating it 3 times to form a shape with four intersecting ellipses. A regular octagon is removed from the center of this shape, and eight sectors and 16 irregular quadrilaterals are removed from the ellipse outside the regular octagon. The remaining structure is symmetrical along the major axis, minor axis, and center of the ellipse.

2. The metamaterial according to claim 1, characterized in that: The metal backing layer is made of gold material and has a thickness of 0.05~0.15μm.

3. The metamaterial according to claim 1, characterized in that: The first dielectric layer, the second dielectric layer, and the third dielectric layer are all PI material layers with a dielectric constant of 1.9~2.

1.

4. The metamaterial according to claim 3, characterized in that: The thicknesses of the first dielectric layer, the second dielectric layer, and the third dielectric layer are 2.1~2.2μm, 2.55~2.65μm, and 2.55~2.65μm, respectively.

5. The metamaterial according to claim 1, characterized in that: The polarization converter is made of gold and has an asymmetrical king-shaped structure consisting of three horizontal bars and vertical bars connecting them. The upper and lower horizontal bars have different lengths, 3.65~3.75μm and 3.45~3.55μm respectively, and both have a width of 1.65~1.75μm. The middle horizontal bar has a length of 2.95~3.05μm and a width of 0.55~0.65μm. The vertical bars connecting the three horizontal bars have a width of 0.95~1.05μm. A disk with a radius of 0.95~1.05μm is also provided in the middle of the vertical bars. The total distance between the upper and lower horizontal bars is 7.35~7.45μm.

6. The metamaterial according to claim 1, characterized in that: The thickness of the VO2 membrane is 0.05~0.15μm.

7. The metamaterial according to claim 1, characterized in that: The outer and inner radii of the VO2 rings in the VO2 resonant ring layer are 1.15~1.25μm and 0.95~1.05μm, respectively, and the distance between the centers of two adjacent VO2 rings is 2.45~2.55μm.

8. The metamaterial according to claim 1, characterized in that: The semi-major axis and semi-minor axis of the VO2 absorbing layer are 3.45~3.55μm and 0.95~1.05μm, respectively; the circumradius of the regular octagon is 0.95~1.05μm; the central angle of the sector is 97°~107° and the radius of the sector is 0.44~0.54μm; a pair of interior opposite angles of the irregular quadrilateral are 134°~144° and 67°~77°, respectively, and the lengths of its long side and short side are 0.27~0.37μm and 0.15~0.25μm, respectively.

9. The metamaterial according to any one of claims 1 to 8, characterized in that: The unit structure has a length and width of 7.7~8.3μm and a height of 7.2~7.6μm; the asymmetric king-shaped structure in the polarization converter layer is set obliquely.

10. The application of the metamaterial according to any one of claims 1 to 9 in the field of terahertz stealth.

11. The application of the metamaterial according to any one of claims 1 to 9 in the field of radar imaging.

12. The application of the metamaterial according to any one of claims 1 to 9 in the field of wireless communication.

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