Terahertz ultra-wideband absorption and polarization conversion dual-function electromagnetic metamaterial and application thereof

Abstract

The invention relates to the technical field of electromagnetic metamaterials, and particularly discloses a terahertz ultra-wideband absorption and polarization conversion dual-function electromagnetic metamaterial and application thereof. The metamaterial is formed by periodically arranging a plurality of unit structures; each unit structure is sequentially provided with a metal backboard 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 wave absorbing layer from bottom to top. The metamaterial provided by the invention can overcome the problems of single function, narrow working band and the like of the metamaterial in the terahertz field. Compared with a common metamaterial, the metamaterial can switch different functions by adjusting the conductivity of VO2, and ultra-wideband absorption and polarization conversion are achieved. The method has potential value in application in the fields of terahertz stealth, radar imaging, wireless communication and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic metamaterials, and in particular to a terahertz ultra-wideband absorption and polarization conversion dual-function electromagnetic metamaterial and its application. Background Art

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

[0003] In terms of absorption, the technology has evolved from early single-frequency absorbers to multi-frequency, broadband and ultra-broadband absorbers, gradually exploring the broad application prospects of electromagnetic metamaterials. Compared with traditional absorbers, electromagnetic metamaterial absorbers have simple design, excellent absorption performance, lightweight structure and thin thickness. In addition, they have design flexibility, adjustable absorption band, and their electromagnetic properties can be customized according to needs, which greatly expands their applicability in various applications. In terms of polarization conversion, in optical communication equipment, the incident light signal must be polarized before it can be effectively received and decoded. Metamaterial polarizers can not only efficiently adjust the polarization state of light, but also play an important role in optical communication signal processing, greatly improving the stability and efficiency of optical transmission. Due to their high precision, low loss, and good repeatability, this type of polarizer can be integrated into antennas and RF front-end equipment to enhance the power output and signal sensitivity of the equipment, and is widely used in Wi-Fi, cellular communications, satellite communications and other fields. Compared with traditional polarizers, metamaterial polarizers have higher polarization control accuracy, wider operating frequency band and more flexible adjustability. Their research and application in information technology, optical communications and electronics have far-reaching significance.

[0004] CN115020987A discloses a method for realizing a dual-function metamaterial of terahertz broadband absorption and polarization conversion, wherein a substrate reflector is fixedly installed at the bottom of the inner side of the metamaterial unit, on which a polyethylene cycloolefin copolymer ToPaS dielectric layer, a rectangular strip, a vanadium dioxide film layer, a polyethylene cycloolefin copolymer dielectric layer and a vanadium dioxide concentric ring patch are arranged in sequence. By changing the external conditions, the vanadium dioxide is transformed between the insulating state and the metallic state, thereby realizing the dual-function switching of the metamaterial device. The dual-function metamaterial design disclosed in CN115020987A, although it can achieve a broadband working state within a certain frequency band, has certain limitations in bandwidth expansion and fails to meet the application requirements of ultra-wideband. The metamaterial structure mentioned is relatively large in size, which not only makes its promotion and integration in practical applications more difficult, but also has a certain negative impact on the performance and stability of the equipment. Especially under the requirement of a wider frequency band, larger-sized metamaterials often make it difficult to further expand the spectrum response. In order to overcome these limitations, the present invention proposes a dual-function metamaterial design with small size, which solves the problems of limited bandwidth and excessive size in the prior art by optimizing the material structure and design parameters, thereby achieving wider applications and better performance. Summary of the invention

[0005] The present invention provides a terahertz ultra-wideband absorption and polarization conversion dual-function electromagnetic metamaterial and its application, which can realize ultra-wideband absorption and polarization conversion at the same time in terahertz, and the metamaterial is small in size, and the matching degree between electromagnetic waves and metamaterial structure is optimized, so that the working frequency band of the metamaterial is extended from broadband to ultra-wideband. The present invention significantly improves the response ability of the metamaterial in a wider frequency band by accurately adjusting the metamaterial unit structure and material properties.

[0006] The technical solution of the present invention is to provide a terahertz ultra-wideband absorption and polarization conversion dual-function electromagnetic metamaterial, which is composed of a plurality of unit structures arranged periodically; each unit structure is provided with a metal backplane layer, a first dielectric layer, a polarization converter layer, a VO 2 Film layer, second dielectric layer, VO 2 Resonant ring layer, third dielectric layer and VO 2 Wave absorbing layer; the polarization converter is a metal asymmetric W-shaped structure; VO 2 The resonant ring layer is composed of 9 VO 2 Ring structure; VO 2The wave absorbing layer is an ellipse that is rotated with its center point as the center of the circle, each rotation angle is 45 degrees, and it is rotated three times to form a figure formed by the intersection of four ellipses. A regular octagon is cut out from the center of the figure, and eight sectors and 16 irregular quadrilaterals are cut out from the ellipse outside the regular octagon. The remaining structure is a symmetrical structure along the major axis, minor axis and center of the ellipse.

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

[0008] Optionally, the first dielectric layer, the second dielectric layer and the third dielectric layer are all PI material layers, and the dielectric constant is 1.9-2.1.

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

[0010] Optionally, the polarization converter is made of gold material, and its asymmetric W-shaped structure includes three horizontal bars and vertical bars connecting the three horizontal bars. The lengths of the upper horizontal bar and the lower horizontal bar are different, which are 3.65-3.75μm and 3.45-3.55μm respectively, and the widths are both 1.65-1.75μm. The length of the middle horizontal bar is 2.95-3.05μm, and the width is 0.55-0.65μm. The width of the vertical bar connecting the three horizontal bars is 0.95-1.05μm; a disk is also provided in the middle of the vertical bar, and the radius of the disk is 0.95-1.05μm; the total distance between the upper horizontal bar and the lower horizontal bar is 7.35-7.45μm.

[0011] Optionally, VO 2 The thickness of the film layer is 0.05 to 0.15 μm.

[0012] Optionally, VO 2 VO in the resonant ring layer 2 The outer and inner radii of the ring are 1.15-1.25 μm and 0.95-1.05 μm respectively. 2 The distance between the centers of the circles is 2.45 to 2.55 μm.

[0013] Optionally, VO 2 The major and minor semi-axes of the ellipse of the absorbing layer are 3.45-3.55 μm and 0.95-1.05 μm respectively; the radius of the circumscribed circle of the regular octagon is 0.95-1.05 μm; the central angle of the sector is 97°-107°, and the radius of the sector is 0.44-0.54 μm; a set of inner angles of the irregular trapezoid are 134°-144° and 67°-77° respectively, and the lengths of its long and short sides are 0.27-0.37 μm and 0.15-0.25 μm respectively.

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

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

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

[0017] The device prepared by using the metamaterial provided by the present invention can achieve ultra-wideband absorption and line-line polarization conversion in the terahertz range. In the metallic state of VO 2 , the metamaterial exhibits ultra-wideband absorption, and the absorption rate exceeds 90% in the frequency range of 5.8 - 17.5 THz, and the relative bandwidth is 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 achieving efficient communication, accurate target detection, and protecting electronic devices from electromagnetic interference. In the non-metallic state of VO 2 , the function of polarization conversion is realized. The polarization conversion function is mainly completed by the asymmetric king-shaped polarization converter. In the terahertz frequency band of 6.1 - 20.9 THz, the line-line polarization conversion of y-polarized wave reflected into x-polarized wave is realized, and the polarization conversion rate is greater than 90%, and the relative bandwidth is 109.4%. In this frequency band, the applications of polarization conversion cover multiple fields such as antenna systems, wireless communication, and radar systems. Through the polarization conversion technology, the polarization adaptation of signals, the improvement of communication quality, and the extraction of target characteristics can be realized, thereby meeting the requirements of different applications.

[0018] The present invention reduces the overall unit structure size to within 10 μm, and the relative bandwidth of both working states is greater than 100%, realizing the ultra-wideband absorption characteristic. In terms of the absorption structure, the present invention adopts a more complex five-layer structure, which is a VO2 film layer, a dielectric layer, a VO2 resonant ring layer, a dielectric layer, and a VO2 wave-absorbing layer in sequence. The resonance effects of the upper and lower layers significantly expand the absorption bandwidth. In order 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 inlaid disc structure. These designs optimize the polarization conversion ability of the metamaterial, providing a wider working frequency band and a more excellent polarization conversion effect compared with the prior art. Description of the Drawings

[0019] Figure 1(a), (b), (c), (d) and (e) 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 These 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 This is the effect of three different structures of the terahertz ultra-wideband absorption and polarization conversion dual-functional electromagnetic metamaterial VFPA, NVRR and DLS on the absorption rate of Example 3.

[0022] Figure 4 The absorption rate of the terahertz ultra-wideband absorption and polarization conversion dual-function electromagnetic metamaterial of Example 4 varies with VO 2 Conductivity change curve.

[0023] Figure 5 (a) and (b) are the terahertz ultra-wideband absorption and polarization conversion dual-functional electromagnetic metamaterial of Example 5 in VO 2 The conductivity is σ=2×10 5 The curve of the absorption rate changing with the unit structure at S / m. (a) The semi-minor axis r of the elliptical disk b (b) NVRR inner and outer radius difference Δr.

[0024] Figure 6 (a) and (b) are respectively curves showing the variation of the absorptivity of the terahertz ultra-wideband absorption and polarization conversion dual-functional electromagnetic metamaterial of Example 6 with the incident angle and polarization angle.

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

[0026] Figure 8 (a)-(c) are graphs showing the polarization conversion rate of the medium-terahertz ultra-wideband absorption and polarization conversion dual-function electromagnetic metamaterial of Example 9 when the conductivity is σ=20S / m as a function of the unit structure parameters. (a) The radius r of the metal disk of the W-shaped polarization converter 1 ; (b) The length of the middle rectangle of the W-shaped 4 ; (c) semi-minor axis r of the elliptical disk b . DETAILED DESCRIPTION

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

[0028] The embodiments of the present invention will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention.

[0029] Embodiment 1:

[0030] The terahertz ultra-wideband absorption and polarization conversion dual-function electromagnetic metamaterial provided in this embodiment is composed of multiple unit structures arranged periodically; the unit structure contains eight layers, from the bottom to the top, a metal backplane, a PI dielectric layer, an asymmetric W-shaped polarization converter, and a patternless VO 2 layer, PI dielectric layer, 9 VO 2 Resonant ring (NVRR), PI dielectric layer, VO 2 Flower-shaped absorber (VFPA). Figure 1 As shown in (a), the unit structure period p = 8μm. The thickness of the dielectric substrate is h 2 =2.6μm,h 5 =2.15μm,h 7 =2.15μm, the thickness of other structures is h m =0.1μm, the thickness of the entire structure is H=7.4μm.

[0031] Figure 1 (b) shows the specific parameters of the W-shaped polarization converter. The length of the W-shaped polarization converter is l 1 =7.4μm, the double arms of the W-shaped are designed with asymmetric lengths, and their lengths are l 2 =3.7μm,l 3 =3.5μm. Its width is t 2 =1.7μm. Middle structure length l 4 =3.0μm, width t 1 =0.6μm, disk radius r 1 =1.0μm. The width of the metal strip connecting these three parts is l 5 =1.0μm. Figure 1 (c) is 9 VO 2 Schematic diagram of the resonant ring. The unit structure of the NVRR is VO 2 The ring, with an outer diameter r 3 =1.2μm, inner diameter r 2 =1.0μm, the distance between the two centers of the circle is d=2.5μm. Figure 1 (d) is VO 2 Schematic diagram of the flower-shaped absorber. The VFPA consists of four identical elliptical disks, where the major semi-axis r a =3.5μm, short semi-axis r b=1.0μm, the radius of the circumscribed circle of the regular octagon dug out in the middle is r 4 =0.75μm. Figure 1 (e) is a magnified schematic diagram of the local details of the sector and irregular trapezoid dug out in the VFPA, where the angle of the dug out sector is α 1 =102°, the radius of the sector is r 5 =0.49μm, the angle of the trapezoid is α 2 =139° and α 3 =72°, and the lengths of its long and short sides are m=0.32μm and n=0.2μm respectively.

[0032] Embodiment 2:

[0033] The CST simulation software was used to perform simulation tests. The metamaterial was simulated and tested in the frequency range of 0.1 to 19 THz, and the reflectivity and absorptivity of the metamaterial to electromagnetic waves in this frequency range were calculated. Figure 2 As shown in the figure, in the 5.8-17.5THz band, the absorptivity of the metamaterial is greater than 90%, and the absorption bandwidth is 11.7THz. The relative bandwidth is 100.4%. According to the changing trend of the curve in the figure, the absorptivity experienced a process of first rising and then falling, then rising and then falling in the frequency range of 5.8-17.5THz. The maximum absorptivity was obtained at the 7.1THz and 15.3THz frequencies, and the absorptivity was close to 100%, indicating that perfect absorption occurred at these two frequency points.

[0034] Embodiment 3:

[0035] The influence of different components of the metamaterial surface structure on the absorption rate is analyzed, and the various components of the structure of the present invention are analyzed. 2 In the metallic state, there is no pattern VO 2 The layer is equivalent to a metal backplane, which can fully reflect the incident electromagnetic waves. Therefore, in this case, the VO 2 The structure of each layer. 2 The absorption structure of is divided into three parts, namely, only retaining VFPA, only retaining NVRR and the overall structure (DLS). Figure 3 As shown in the figure, when only VFPA is retained, ultra-wideband absorption is achieved in the frequency range of 6.3-15.7THz, with a bandwidth of 9.4THz and a relative bandwidth of 85.5%. When only NVRR is retained, the overall absorption rate is less than 80%. Compared with the structure containing only VFPA, the effective absorption bandwidth of the double-layer structure increases by 2.3THz and the relative bandwidth increases by 14.9%. According to the trends of the absorption rate and absorption band under the above different structures, it can be inferred that NVRR can only play a role when it resonates with VFPA to achieve a wider absorption band.

[0036] The dual-function metamaterial proposed in CN115020987A uses VO in the absorption part. 2 film, polyethylene cycloolefin copolymer ToPaS dielectric layer and VO 2 The three-layer composite structure composed of concentric rings can achieve broadband absorption in the terahertz band, but it fails to meet the current demand for wider bandwidth absorption. To address this shortcoming, the present invention proposes a more complex structure using VO 2 Film layer, dielectric layer, VO 2 Resonant ring layer (NVRR), dielectric layer and VO 2 Wave absorbing layer (VFPA). Through the resonance of the upper and lower layers, the absorption bandwidth is significantly expanded, and the ultra-wideband absorption effect is successfully achieved. Compared with the design in CN115020987A, the present invention not only achieves better results in bandwidth expansion, but also further reduces the thickness of the absorption structure, providing more possibilities for the promotion of metamaterials in integrated applications in the future.

[0037] Embodiment 4:

[0038] To analyze the VO in metamaterial components 2 The effect of conductivity on the absorption performance was calculated for VO 2 The absorption rates under several different conductivity states are analyzed and their changing trends are shown. Figure 4 As shown in VO 2 As the conductivity gradually decreases, the metamaterial's absorption rate of incident electromagnetic waves also gradually decreases. The conductivity is σ = 2×10 5 S / m, the metamaterial achieves ultra-broadband absorption with a relative bandwidth of 100.4%. 4 S / m, the effective absorption bandwidth decreases. The effective absorption frequency band is reduced to 7.8-13.2THz, and the relative bandwidth is reduced to 54.2%. As the conductivity continues to decrease, the metamaterial's ability to absorb electromagnetic waves gradually decreases. When the conductivity drops to 20S / m, the absorption rate drops below 30%. Based on the above trend, it can be concluded that metamaterials can only absorb electromagnetic waves when the VO 2 Only when it is in a metallic state can it efficiently absorb incident electromagnetic waves.

[0039] Embodiment 5:

[0040] The simulation test was carried out by CST simulation software. By adjusting the parameters, the performance of the metamaterial can be optimized. The short semi-axis r of the ellipse in the VFPA structure was selected. b The two parameters that have a significant impact on the absorption rate are the inner and outer diameter difference Δr of the ring of the NVRR unit structure. The optimal values ​​of these two parameters are explored by scanning the parameters using the control variable method. Figure 5As shown in (a), when r b As r increases, the right end point of the absorption frequency moves from 16 THz to 18 THz, and the absorption bandwidth shows an increasing trend. b =1.1μm, the absorption rate in the range of 9.7-13THz drops below 90%, resulting in ultra-wideband absorption becoming dual-wideband absorption. b The further increase of , the bandwidth of dual-band absorption decreases. Considering the absorption performance and bandwidth comprehensively, the ellipse minor semi-axis value was finally selected as r b =1.0μm. Figure 5 As shown in (b), as the thickness difference Δr between the inner and outer diameters of the ring increases, the right end point of the effective absorption frequency moves to the right, increasing from 16.7 THz to more than 22 THz. Figure 5 (a) is similar to that observed in Figure 2. When Δr = 0.3 μm, the absorption rate in the frequency band centered at 11 THz drops below 90%, resulting in dual-band absorption. As Δr increases, the bandwidth of the dual-band absorption also decreases, and the optimal value for the best absorption performance is finally selected as Δr = 0.2 μm.

[0041] Embodiment 6:

[0042] Considering that in practical applications, electromagnetic waves usually enter metamaterials at different incident angles and polarization angles, the effect of changing the incident angle and polarization angle on the absorption rate within a certain range was explored. The incident angles of 0° to 60° and the polarization angles of 0° to 45° were selected. Figure 6 As shown in (a), as the incident angle increases, the working frequency band shows a blue shift. In the range of 0° to 30°, the absorption band remains almost unchanged. When the incident angle exceeds 30°, the absorption efficiency decreases, and the absorption changes from ultra-wideband to dual-band absorption. As the incident angle further increases, the absorption rate of the metamaterial to electromagnetic waves further decreases. Figure 6 As shown in (b), the absorption rate curves at four different polarization angles almost overlap, indicating that the absorption rate of the metamaterial remains almost unchanged within the range of polarization angle. This shows the polarization insensitivity of the metamaterial, which is closely related to the symmetry of the structure of the absorption part of the metamaterial. According to 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] Embodiment 7:

[0044] When VO 2 When the conductivity is 20S / m, VO 2 In the non-metallic state, VO 2 The unpatterned layer loses its reflection function for electromagnetic waves and completely transmits the electromagnetic waves, and the polarization converter comes into play. At this time, the metamaterial produces a polarization conversion effect on the incident electromagnetic waves. Figure 7(a) Curves of two polarization coefficients, where r xy It is called the cross-polarization coefficient, r yy It is called the co-polarization coefficient. xy The curve in the figure is greater than r yy The curve shows that the electromagnetic wave undergoes polarization conversion. At the 5.4THz frequency point, r xy and r yy When the frequency exceeds 6.9THz, r yy drops below 0.1, while r xy When the frequency exceeds 20THz, r xy Start to decline, r yy When the two intersect, the polarization conversion effect disappears. Figure 7 (b) shows the curve of the polarization conversion rate of the y-polarized wave. It can be observed that the polarization converter achieves ultra-wideband polarization conversion with a polarization conversion rate of more than 90% in the frequency range of 6.1-20.9THz, with a bandwidth of 14.8THz and a relative bandwidth of 109.4. In the 7-10THz frequency band, the polarization conversion rate is close to 100%, achieving the conversion of all incident y-polarized waves into x-polarized waves.

[0045] Embodiment 8:

[0046] The scanning parameters were explored by controlling the variable method, and the influence of the W-shaped polarization converter and the upper absorption structure on the polarization conversion was explored.

[0047] Figure 8 (a) shows the effect of the radius change of the central disk of the W-shaped polarization converter on PCR. 1 As r increases, PCR in the high frequency range gradually decreases. 1 = 1.3 μm, PCR drops below 90% in the frequency range of 16.6 THz to 19.3 THz. 1 As the frequency increases, the range of the frequency band expands. 1 =1.6μm, the frequency range increases to 15.6THz-20.3THz, the polarization conversion efficiency further decreases, and the minimum value of PCR drops to 70%. Considering that the metal disk partially overlaps with the cross structure, when r 1 When the radius is less than 1.0 μm, the disk and the W-shaped structure overlap, and the effect of the ring on polarization conversion is not obvious. Considering the above factors, the radius r is finally selected. 1 is 1.0μm. Figure 8 (b) shows the length l 4 The effect of changes on PCR. 4It also affects the polarization conversion rate of the high frequency part. 4 = 3.9 μm, PCR drops below 90% in the frequency range of 16.6 THz to 18.6 THz, resulting in the transformation of ultra-wideband polarization conversion to dual-band polarization conversion. 4 When the frequency increases by 4.8 μm, the frequency range expands to 15.6 THz to 18.9 THz. In addition, in the frequency range of 10.7 THz to 14.1 THz, as l 4 As the polarization frequency increases, PCR gradually increases and eventually approaches perfect polarization conversion. Considering the continuity of polarization conversion frequency, the final value of l 4 The length was optimized to 3.0 μm. Figure 8 (c) shows the change of r in the absorption structure. b It can be observed that PCR remains almost unchanged, indicating that VO 2 The electromagnetic wave can be completely transmitted without affecting the polarization conversion. According to the above method, the parameters of the W-shaped polarization converter are optimized by parameter scanning to improve the efficiency of polarization conversion.

[0048] In summary, the present invention proposes a dual-functional electromagnetic metamaterial with terahertz ultra-wideband absorption and polarization conversion. The device can be used to adjust VO 2 The conductivity of the metamaterial is used to switch the function of the metamaterial, realizing the functions of broadband absorption and polarization conversion.

[0049] The above embodiments describe the preferred implementation of the present invention, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A terahertz ultra-wideband absorption and polarization conversion dual-function electromagnetic metamaterial, characterized by: It is composed of a plurality of unit structures arranged periodically; each unit structure is provided with a metal backplane 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 in sequence from bottom to top; the polarization converter is an asymmetric W-shaped structure made of metal material; the VO2 resonant ring layer is a VO2 circular ring structure distributed in 9 rows; the VO2 absorbing layer adopts an ellipse that rotates with its center point as the center of the circle, each rotation angle is 45°, and it rotates 3 times to form a figure formed by the intersection of 4 ellipses, a regular octagon is cut out from the center of the figure, and the remaining structure is formed after eight sectors and 16 irregular quadrilaterals are cut out from the ellipse outside the regular octagon; the structure is a symmetrical structure along the major axis, minor axis and center of the ellipse.

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

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, and the dielectric constant is 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 2.1-2.2 μm, 2.55-2.65 μm and 2.55-2.65 μm respectively.

5. The metamaterial according to claim 1, characterized in that: The polarization converter is made of gold material, and its asymmetric Chinese-W-shaped structure includes three horizontal bars and vertical bars connecting the three horizontal bars. The lengths of the upper horizontal bar and the lower horizontal bar are different, which are 3.65-3.75 μm and 3.45-3.55 μm respectively, and the widths are both 1.65-1.75 μm. The length of the middle horizontal bar is 2.95-3.05 μm, and the width is 0.55-0.65 μm. The width of the vertical bar connecting the three horizontal bars is 0.95-1.05 μm; a disk is also provided in the middle of the vertical bar, and the radius of the disk is 0.95-1.05 μm; the total distance between the upper horizontal bar and the lower horizontal bar is 7.35-7.45 μm.

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

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

8. The metamaterial according to claim 1, characterized in that: The major and minor semi-axes of the ellipse of the VO2 absorbing layer are 3.45~3.55μm and 0.95~1.05μm respectively; the radius of the circumscribed circle 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 set of internal angles of the irregular trapezoid are 134°~144° and 67°~77°, and the lengths of its long and short sides 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 length and width of the unit structure are both 7.7-8.3 μm, and the height is 7.2-7.6 μm; the asymmetric W-shaped structure in the polarization converter layer is arranged obliquely.

10. Application of the metamaterial according to any one of claims 1 to 9 in the fields of terahertz stealth, radar imaging, and wireless communication.

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