Ultra-broadband and multi-frequency switchable terahertz absorber based on vanadium dioxide

Abstract

The present invention discloses an ultra-wideband, multi-frequency switchable terahertz absorber based on vanadium dioxide, belonging to the field of terahertz wave technology. The absorber comprises: an ultra-wideband, multi-frequency switchable terahertz absorber unit having a multi-layer structure, wherein, from top to bottom, a mutually bonded upper patterned VO2 layer, an upper SiO2 dielectric layer, a lower VO2 layer, an intermediate patterned gold layer, a lower SiO2 dielectric layer, and a bottom gold layer are sequentially arranged; the upper patterned VO2 layer is disc-shaped, with a square annular slit disposed within the disc; the intermediate patterned gold layer comprises an inner ring, an outer ring, and an open square ring, spaced from the inside out, with the opening of the open square ring disposed in the middle of each edge. The present invention is based on an ultra-wideband, multi-frequency switchable terahertz absorber based on vanadium dioxide. The designed absorber can achieve switching from ultra-wideband absorption to multi-frequency absorption by adjusting the conductivity of the vanadium dioxide through temperature control.

Description

Technical Field

[0001] The present invention relates to the technical field of terahertz waves, and in particular to an ultra-wideband and multi-frequency switchable terahertz absorber based on vanadium dioxide. Background Art

[0002] Terahertz (THz) waves lie between microwaves and infrared. With the rapid development of THz detection technology, the exploration and application of THz-related fields has become a hot topic. Due to its unique wavelength range, THz waves possess strong penetration, low radiation intensity, and abundant spectrum resources. However, due to the lack of natural materials with electromagnetic compatibility, THz research has been stagnant. However, the emergence of metamaterials has effectively addressed this issue. Therefore, the combination of metamaterials and THz waves holds great promise for applications in wireless communications, sensing, medical imaging, and other fields.

[0003] Since Landy first proposed a perfect absorber based on electromagnetic metamaterials in 2008, a growing number of researchers have proposed different types of metamaterial-based terahertz absorbers. These absorbers range in bandwidth from narrowband, broadband, to ultra-broadband, with peaks ranging from single-frequency, dual-frequency, to multi-frequency, and with functions ranging from single absorption, adjustable absorption amplitude, to adjustable operating frequency. A wide variety of terahertz absorbers have been designed to meet diverse requirements. Currently, most terahertz absorbers are difficult to modify in size and performance after fabrication. Therefore, the introduction of active materials into absorber designs enhances tunability and versatility, expanding their application range. Ultimately, the challenge of designing terahertz absorbers with wider operating bandwidths and the ability to achieve secondary functions using simple switching methods remains a challenge in designing multifunctional terahertz absorbers.

[0004] Therefore, it is necessary to provide an ultra-wideband-multi-frequency switchable terahertz absorber based on vanadium dioxide. Summary of the Invention

[0005] The purpose of the present invention is to provide an ultra-wideband-multi-frequency switchable terahertz absorber based on vanadium dioxide, so as to solve the problem of achieving the second function of the absorber by a simple switching method.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A vanadium dioxide-based ultra-wideband and multi-frequency switchable terahertz absorber, wherein the ultra-wideband and multi-frequency switchable terahertz absorption unit is a multi-layer structure, which is sequentially provided with an upper patterned VO2 layer, an upper SiO2 dielectric layer, a lower VO2 layer, an intermediate patterned gold layer, a lower SiO2 dielectric layer and a bottom gold layer.

[0008] The upper patterned VO2 layer is in the shape of a disk, a square annular slit is provided inside the disk, and the four corners of the square annular slit intersect with the disk and are provided with notches;

[0009] The middle patterned gold layer comprises an inner circular ring, an outer circular ring and an open square ring which are sequentially arranged from the inside to the outside, and the opening of the open square ring is arranged in the middle position of each side;

[0010] The side lengths of the upper SiO2 dielectric layer, the lower VO2 layer, the lower SiO2 dielectric layer and the bottom gold layer are equal to the period length of the ultra-wideband-multi-frequency switchable terahertz absorption unit, and the side lengths of the upper patterned VO2 layer and the middle patterned gold layer are both smaller than the period length of the ultra-wideband-multi-frequency switchable terahertz absorption unit.

[0011] Furthermore, the radius of the upper patterned VO2 layer is 12 μm-16 μm, the width of the square ring slit is 0.5 μm-2.5 μm, and the side length is 22 μm; the thickness of the upper patterned VO2 layer is 0.02 μm-0.2 μm.

[0012] Furthermore, the side length of the open square ring is 32μm, the width of the square ring is 0.5μm-2μm, and the opening width of the open square ring is 1μm-3μm; the outer diameter of the outer ring is 10μm-12μm, and the inner diameter is 9μm; the outer diameter of the inner ring is 5μm-7μm, and the inner diameter is 4μm; the thickness of the patterned gold layer in the middle layer is 1μm-3μm.

[0013] Furthermore, the thickness of the upper SiO2 dielectric layer is 4μm-8μm, the thickness of the lower VO2 layer is 0.5μm, the thickness of the lower SiO2 dielectric layer is 4μm-8μm, and the thickness of the bottom gold layer is 0.2μm; the side lengths of the upper SiO2 dielectric layer, the lower VO2 layer, the lower SiO2 dielectric layer and the bottom gold layer are all 33μm.

[0014] Furthermore, the electrical conductivity of the upper patterned VO2 layer and the lower VO2 layer in the insulating phase is 20 S / m, and the electrical conductivity in the metallic phase is 200,000 S / m.

[0015] Furthermore, the relative dielectric constant of the upper SiO2 dielectric layer and the lower SiO2 dielectric layer is 2.13.

[0016] Furthermore, the bottom gold layer is made of gold with an electrical conductivity of 4.56×10 7 S / m.

[0017] Furthermore, the ultra-wideband-multi-frequency switchable terahertz absorber includes M*N multi-layer structures of the ultra-wideband-multi-frequency switchable terahertz absorption units, and the M*N multi-layer structures of the ultra-wideband-multi-frequency switchable terahertz absorption units are distributed in M*N two dimensions, where M and N are both positive integers.

[0018] The present invention has the following beneficial effects:

[0019] 1. The present invention is based on an ultra-wideband to multi-frequency switchable terahertz absorber based on vanadium dioxide. The designed absorber can switch from ultra-wideband absorption to multi-frequency absorption by adjusting the conductivity of vanadium dioxide through temperature control. When the conductivity of vanadium dioxide is 200,000 S / m, the absorber has an absorption bandwidth of 5.4 THz with a 90% absorption rate within the range of 3.9-9.3 THz. When the conductivity of vanadium dioxide is 20 S / m, the absorber exhibits multi-frequency absorption, with four absorption peaks with an absorption rate above 90%, located at 3.94 THz, 7.06 THz, 7.7 THz, and 9.16 THz, with an absorption rate of 82% at 9.9 THz.

[0020] 2. The ultra-wideband-multi-frequency switchable terahertz absorber based on vanadium dioxide of the present invention is polarization-insensitive and maintains excellent absorption performance under different polarization angles and a wide incident angle of 0°-80°.

[0021] 3. The ultra-wideband-multi-frequency switchable terahertz absorber based on vanadium dioxide of the present invention can tune the position and absorption intensity of the absorption peak in the multi-frequency absorption mode to a certain extent by changing the structural parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The periodic structure of the ultra-wideband and multi-frequency switchable terahertz absorption unit based on vanadium dioxide provided in Example 1 of the present invention;

[0023] Figure 2 A schematic diagram of the unit structure of the ultra-wideband and multi-frequency switchable terahertz absorber based on vanadium dioxide provided in Example 1 of the present invention;

[0024] Figure 3 A front view of the structure of an ultra-wideband, multi-frequency switchable terahertz absorption unit based on vanadium dioxide provided in Example 1 of the present invention;

[0025] Figure 4 A top view of the upper patterned VO2 layer of the ultra-wideband-multi-frequency switchable terahertz absorption unit based on vanadium dioxide provided in Example 1 of the present invention;

[0026] Figure 5A top view of the patterned gold layer in the middle layer of the ultra-wideband and multi-frequency switchable terahertz absorption unit based on vanadium dioxide provided in Example 1 of the present invention;

[0027] Figure 6 The absorption spectrum of the ultra-wideband-multi-frequency switchable terahertz absorber of vanadium dioxide in the metallic phase provided in Example 1 of the present invention;

[0028] Figure 7 Absorption spectrum of the ultra-wideband-multi-frequency switchable terahertz absorber of vanadium dioxide in the insulating phase provided in Example 1 of the present invention;

[0029] Figure 8 The real and imaginary parts of the relative impedance of the ultra-wideband-multi-frequency switchable terahertz absorber of vanadium dioxide in the metallic phase provided in Example 1 of the present invention;

[0030] Figure 9 The real and imaginary parts of the relative impedance of the ultra-wideband and multi-frequency switchable terahertz absorber of vanadium dioxide in the insulating phase provided in Example 1 of the present invention;

[0031] Figure 10 Absorption spectra of the ultra-wideband-multi-frequency switchable terahertz absorber with conductivity of vanadium dioxide at 20, 200, 2000, 20,000, and 200,000 S / m provided in Example 1 of the present invention;

[0032] Figure 11 The electric field distribution of the ultra-wideband-multi-frequency switchable terahertz absorber provided in Example 1 of the present invention at a frequency of 8 THz and a vanadium dioxide conductivity of 200,000 S / m;

[0033] Figure 12 The electric field distribution of the ultra-wideband-multi-frequency switchable terahertz absorber provided in Example 1 of the present invention at a frequency of 3.94 THz and a vanadium dioxide conductivity of 20 S / m;

[0034] Figure 13 The electric field distribution of the ultra-wideband-multi-frequency switchable terahertz absorber provided in Example 1 of the present invention at a frequency of 7.7 THz and a vanadium dioxide conductivity of 20 S / m;

[0035] Figure 14 Absorption spectra of the ultra-wideband, multi-frequency switchable terahertz absorber with a vanadium dioxide conductivity of 200,000 S / m provided in Example 1 of the present invention under different incident angles of TE waves;

[0036] Figure 15 This is the absorption spectrum of the ultra-wideband-multi-frequency switchable terahertz absorber with a vanadium dioxide conductivity of 20 S / m provided in Example 1 of the present invention under different incident angles of TE waves.

[0037] Among them: 1. upper patterned VO2 layer; 2. upper SiO2 dielectric layer; 3. lower VO2 layer; 4. middle patterned gold layer; 5. lower SiO2 dielectric layer; 6. bottom gold layer. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0039] The present invention provides an ultra-wideband-multi-frequency switchable terahertz absorber based on vanadium dioxide, such as Figure 1 As shown, it includes M*N multi-layer structures of ultra-wideband-multi-frequency switchable terahertz absorption units, and the M*N multi-layer structures of ultra-wideband-multi-frequency switchable terahertz absorption units are distributed in M*N two dimensions, where M and N are both positive integers.

[0040] Each multi-layer ultra-wideband-multi-frequency switchable terahertz absorption unit includes an upper patterned VO2 layer 1, an upper SiO2 dielectric layer 2, a lower VO2 layer 3, an intermediate patterned gold layer 4, a lower SiO2 dielectric layer 5 and a bottom gold layer 6, which are arranged in sequence from top to bottom. The six layers of materials are bonded to each other.

[0041] The side lengths of the upper SiO2 dielectric layer 2, the lower VO2 layer 3, the lower SiO2 dielectric layer 5 and the bottom gold layer 6 are equal and are the period length of the absorption unit, and the side lengths of the upper patterned VO2 layer 1 and the middle patterned gold layer 4 are slightly smaller than the period length.

[0042] The upper patterned VO2 layer 1 is disc-shaped with a square annular slit inside. The disc radius R is 12μm-16μm, the slit width d is 0.5μm-2.5μm, the slit side length c is fixed at 22μm, and the thickness t6 of the upper patterned VO2 layer 1 is 0.02μm-0.2μm.

[0043] The middle patterned gold layer 4 consists of an open square ring, an outer circular ring, and an inner circular ring. The side length a of the open square ring is fixed at 32 μm, the square ring width b is 0.5 μm-2 μm, and the opening width w is 1 μm-3 μm. The outer diameter r1 of the outer circular ring is 10 μm-12 μm, the inner diameter r2 is fixed at 9 μm, the outer diameter r3 of the inner circular ring is 5 μm-7 μm, and the inner diameter r4 is fixed at 4 μm. The thickness t3 of the middle patterned gold layer 4 is 1 μm-3 μm.

[0044] The thickness t5 of the upper SiO2 dielectric layer 2 is 4 μm to 8 μm, the thickness t4 of the lower VO2 layer 3 is 0.5 μm, the thickness t2 of the lower SiO2 dielectric layer 5 is 4 μm to 8 μm, and the thickness t1 of the bottom gold layer 6 is 0.2 μm. The side length P of the upper SiO2 dielectric layer 2, the lower VO2 layer 3, the lower SiO2 dielectric layer 5, and the bottom gold layer 6 is 33 μm.

[0045] The conductivity of the upper patterned VO2 layer 1 and the lower VO2 layer 3 in the insulating phase is 20 S / m, and the conductivity in the metallic phase is 200,000 S / m. The relative dielectric constant of the upper SiO2 dielectric layer 2 and the lower SiO2 dielectric layer 5 is 2.13. The material of the bottom gold layer 6 is gold, and the conductivity is 4.56×10 7 S / m.

[0046] The present invention is based on an ultra-wideband to multi-frequency switchable terahertz absorber based on vanadium dioxide. The designed absorber can switch from ultra-wideband absorption to multi-frequency absorption by adjusting the conductivity of vanadium dioxide through temperature control. When the conductivity of vanadium dioxide is 200,000 S / m, the absorber has an absorption bandwidth of 5.4 THz with a 90% absorption rate within the range of 3.9-9.3 THz. When the conductivity of vanadium dioxide is 20 S / m, the absorber exhibits multi-frequency absorption, with four absorption peaks with an absorption rate above 90% at 3.94 THz, 7.06 THz, 7.7 THz, and 9.16 THz, with an absorption rate of 82% at 9.9 THz.

[0047] The ultra-wideband-multi-frequency switchable terahertz absorber based on vanadium dioxide of the present invention is polarization-insensitive and maintains excellent absorption performance under different polarization angles and a wide incident angle of 0°-80°.

[0048] Example 1

[0049] like Figure 1 As shown, the ultra-wideband-multi-frequency switchable terahertz absorber based on vanadium dioxide in this embodiment includes 3*3 multi-layered ultra-wideband-multi-frequency switchable terahertz units. The number of multi-layered ultra-wideband-multi-frequency switchable terahertz units does not affect the overall absorption performance. Each multi-layered ultra-wideband-multi-frequency switchable terahertz device unit includes an upper patterned VO2 layer 1, an upper SiO2 dielectric layer 2, a lower VO2 layer 3, an intermediate patterned gold layer 4, a lower SiO2 dielectric layer 5 and a bottom gold layer 6, which are arranged in sequence from top to bottom.

[0050] In this embodiment, the side lengths of the upper SiO2 dielectric layer 2, the lower VO2 layer 3, the lower SiO2 dielectric layer 5 and the bottom gold layer 6 are equal and are the period length of the absorption unit, and the side lengths of the upper patterned VO2 layer 1 and the middle patterned gold layer 4 are slightly smaller than the period length. The specific parameters are as follows.

[0051] In this embodiment, the disk radius R of the upper patterned VO2 layer is 15 μm, the slit width d is 1 μm, the slit side length c is 22 μm, and the thickness t6 is 0.05 μm.

[0052] The patterned gold layer 4 in the middle layer consists of an open square ring, an outer circular ring, and an inner circular ring. The side length a of the open square ring is 32 μm, the width b of the square ring is 1 μm, and the opening width w is 2 μm. The outer diameter r1 of the outer circular ring is 10 μm, the inner diameter r2 of the outer circular ring is 9 μm, the outer diameter r3 of the inner circular ring is 5 μm, and the inner diameter r4 of the inner circular ring is 4 μm. The thickness t3 of the patterned gold layer 4 in the middle layer is 2 μm.

[0053] The relative dielectric constant of the upper SiO2 dielectric layer 2 and the lower SiO2 dielectric layer 5 is 2.13, and their thicknesses t5 and t2 are 6 μm and 5 μm respectively. The bottom gold layer 6 is made of gold with a conductivity of 4.56×10 7 S / m, the thickness t1 is 0.2μm, and the side lengths P of the dielectric layer and the reflective layer are both 33μm.

[0054] In its metallic phase, VO2 has a conductivity of 200,000 S / m, exhibiting absorption in the 3.9-9.3 THz range, with a 90% absorption bandwidth of 5.4 THz. In its insulating phase, VO2 has a conductivity of 20 S / m and exhibits multi-frequency absorption, with four absorption peaks exceeding 90% at 3.94 THz, 7.06 THz, 7.7 THz, and 9.16 THz.

[0055] The periodic structure of the absorber in this embodiment is as follows Figure 1 As shown, the unit structure diagram is as follows Figure 2 As shown, it contains six layers, from top to bottom, namely, upper patterned VO2 layer 1, upper SiO2 dielectric layer 2, lower VO2 layer 3, middle patterned gold layer 4, lower SiO2 dielectric layer 5 and bottom gold layer 6. The main view of the unit structure is shown in Figure 3 As shown, the thickness t6 of the upper patterned VO2 layer 1 is 0.05 μm, the thickness t5 of the upper SiO2 dielectric layer 2 is 6 μm, the thickness t4 of the lower VO2 layer 3 is 0.5 μm, the thickness t3 of the middle patterned gold layer 4 is 2 μm, the thickness t2 of the lower SiO2 dielectric layer 5 is 5 μm, and the thickness t1 of the bottom gold layer 6 is 0.2 μm.

[0056] The top view of the upper patterned VO2 layer 1 and the middle patterned gold layer 4 is shown in FIG. Figure 4 and Figure 5As shown, the disk radius R of the patterned VO2 layer is 15μm, the slit width d is 1μm, and the slit side length c is 22μm. The patterned gold layer consists of an open square ring, an outer ring, and an inner ring. The open square ring has a side length a of 32μm, a square ring width b of 1μm, and an opening width w of 2μm. The outer ring has an outer diameter r1 of 10μm, an inner diameter r2 of 9μm, an inner diameter r3 of 5μm, and an inner diameter r4 of 4μm.

[0057] The absorption spectra of vanadium dioxide absorbers in metallic and insulating phases are as follows: Figure 6 and Figure 7 As shown. When VO2 is in the metallic phase (conductivity is 200,000 S / m), the structure exhibits ultra-wideband absorption, with an absorption rate of more than 90% in the range of 3.9-9.3 THz and an absorption bandwidth of 5.4 THz. When VO2 is in the insulating phase (conductivity is 20 S / m), the structure exhibits multi-frequency absorption, with five absorption peaks observed in the entire terahertz range. There are four absorption peaks with an absorption rate of more than 90%, namely 3.94 THz (98%), 7.06 THz (96%), 7.7 THz (98%) and 9.16 THz (94%). The absorption rate at 9.9 THz is 82%.

[0058] The real and imaginary parts of the absorber's relative impedance in the metallic and insulating phases of vanadium dioxide are as follows: Figure 8 and Figure 9 As shown. When the VO2 conductivity is 200000 S / m, it can be seen that within the corresponding high absorption rate frequency range, the solid line indicates that the real part of the impedance Re(z) approaches 1, and the dotted line indicates that the imaginary part of the impedance Im(z) approaches 0. At this time, the equivalent impedance of the absorber is approximately equal to the equivalent impedance of free space. When the VO2 conductivity is 20 S / m, the real part Re(z) of the equivalent impedance at the frequency corresponding to the absorption peak is close to 1, and the imaginary part Im(z) is close to 0. The absorber achieves impedance matching at 3.94 THz, 7.06 THz, 7.7 THz and 9.16 THz, thereby achieving a multi-frequency high absorption effect with an absorption rate of more than 90%.

[0059] The absorption spectra of VO2 absorber at different conductivities are as follows Figure 10 As shown in Figure 2, the conductivity of VO2 can be controlled by temperature, thereby regulating the absorber's absorptivity. When VO2 is in the metallic phase, which has high conductivity, the designed absorber exhibits ultra-broadband absorption. When VO2 is in the insulating phase, the absorber achieves high multi-band absorption in the terahertz band.

[0060] The electric field distribution of the absorber at a frequency of 8 THz and a vanadium dioxide conductivity of 200,000 S / m is as follows: Figure 11As shown, the electric field distribution of the absorber at frequencies of 3.94 THz and 7.7 THz and a vanadium dioxide conductivity of 20 S / m is shown as follows: Figure 12 and Figure 13 As shown. Figure 11 It can be seen that the electric field energy is mainly concentrated between the edge of the upper VO2 disk and the slits of the inner square pattern. There is almost no energy distribution in the square ring and circular ring gold layers in the middle layer. The energy is mainly distributed in the upper three layers. Therefore, ultra-wideband absorption is mainly achieved by the upper three layers. The lower VO2 layer prevents most of the terahertz waves from entering the lower three layers, so there is almost no energy distribution in the lower three layers. Figure 12 It can be seen that the electric field energy of the absorption peak at 3.94 THz is mainly concentrated at the upper and lower edges of the outer ring and the opening of the square ring, and the energy is mainly distributed near the patterned gold layer in the middle layer. Figure 13 It can be seen that the electric field energy of the absorption peak at 7.7 THz is mainly concentrated at the upper and lower edges and the opening of the square ring. Therefore, different parts of the patterned gold layer absorb terahertz energy at different frequencies, thus forming multi-frequency absorption.

[0061] When the VO2 conductivity is 200000S / m and 20S / m respectively, the effect of the incident angle on the absorptivity is as follows: Figure 14 and Figure 15 As shown in the figure, when the incident angle is within a wide range of 0°-80°, the absorber can maintain a high absorption rate within the corresponding frequency range and at the corresponding frequency point. The designed terahertz absorber has excellent wide-angle absorption characteristics.

[0062] Example 2

[0063] The ultra-wideband-multi-frequency switchable terahertz absorber based on vanadium dioxide in this embodiment includes 3*3 multi-layer ultra-wideband-multi-frequency switchable terahertz units, and each multi-layer ultra-wideband-multi-frequency switchable terahertz unit includes an upper patterned VO2 layer 1, an upper SiO2 dielectric layer 2, a lower VO2 layer 3, an intermediate patterned gold layer 4, a lower SiO2 dielectric layer 5 and a bottom gold layer 6 arranged in sequence from top to bottom.

[0064] In this embodiment, the side lengths of the upper SiO2 dielectric layer 2, the lower VO2 layer 3, the lower SiO2 dielectric layer 5 and the bottom gold layer 6 are equal and are the period length of the absorption unit, and the side lengths of the upper patterned VO2 layer 1 and the middle patterned gold layer 4 are slightly smaller than the period length.

[0065] In this embodiment, the upper patterned VO2 layer 1 is disc-shaped with a square ring-shaped slit inside. The disc radius R is 16 μm, the slit width d is 1.5 μm, the slit side length c is 22 μm, and the thickness t6 of the upper patterned VO2 layer 1 is 0.08 μm.

[0066] The middle patterned gold layer 4 consists of an open square ring, an outer circular ring, and an inner circular ring. The side length a of the open square ring is 32 μm, the square ring width b is 0.5 μm, and the opening width w is 1.5 μm. The outer diameter r1 of the outer circular ring is 10.5 μm, and the inner diameter r2 is fixed at 9 μm. The outer diameter r3 of the inner circular ring is 5.5 μm, and the inner diameter r4 is fixed at 4 μm. The thickness t3 of the middle patterned gold layer 4 is 1.5 μm.

[0067] The thickness t5 of the upper SiO2 dielectric layer 2 is 5 μm, the thickness t4 of the lower VO2 layer 3 is 0.5 μm, the thickness t2 of the lower SiO2 dielectric layer 5 is 6 μm, and the thickness t1 of the bottom gold layer 6 is 0.2 μm. The side length P is 33 μm.

[0068] The conductivity of the upper patterned VO2 layer 1 and the lower VO2 layer 3 in the insulating phase is 20 S / m, and the conductivity in the metallic phase is 200,000 S / m. The relative dielectric constant of the upper SiO2 dielectric layer 2 and the lower SiO2 dielectric layer 5 is 2.13. The material of the bottom gold layer 6 is gold, and the conductivity is 4.56×10 7 S / m.

[0069] Example 3

[0070] The vanadium dioxide-based ultra-wideband, multi-frequency switchable terahertz absorber of this embodiment includes 3*3 multi-layer ultra-wideband, multi-frequency switchable terahertz units. Each multi-layer ultra-wideband, multi-frequency switchable terahertz unit includes, arranged from top to bottom, an upper patterned VO2 layer 1, an upper SiO2 dielectric layer 2, a lower VO2 layer 3, an intermediate patterned gold layer 4, a lower SiO2 dielectric layer 5, and a bottom gold layer 6. The side lengths of the upper SiO2 dielectric layer 2, the lower VO2 layer 3, the lower SiO2 dielectric layer 5, and the bottom gold layer 6 are all equal and are the period length of the absorber unit. The side lengths of the upper patterned VO2 layer 1 and the intermediate patterned gold layer 4 are slightly smaller than the period length.

[0071] In this embodiment, the upper patterned VO2 layer 1 is disc-shaped with a square ring-shaped slit inside. The disc radius R is 14 μm, the slit width d is 2 μm, the slit side length c is 22 μm, and the thickness t6 of the upper patterned VO2 layer 1 is 0.02 μm.

[0072] In this embodiment, the middle patterned gold layer 4 consists of an open square ring, an outer circular ring, and an inner circular ring. The side length a of the open square ring is 32 μm, the square ring width b is 1.5 μm, and the opening width w is 1 μm. The outer diameter r1 of the outer circular ring is 11 μm, and the inner diameter r2 is fixed at 9 μm. The outer diameter r3 of the inner circular ring is 6 μm, and the inner diameter r4 is fixed at 4 μm. The thickness t3 of the middle patterned gold layer 4 is 1 μm.

[0073] The thickness t5 of the upper SiO2 dielectric layer 2 is 4 μm, the thickness t4 of the lower VO2 layer 3 is 0.5 μm, the thickness t2 of the lower SiO2 dielectric layer 5 is 7 μm, and the thickness t1 of the bottom gold layer 6 is 0.2 μm. The side length P is 33 μm.

[0074] The conductivity of the upper patterned VO2 layer 1 and the lower VO2 layer 3 in the insulating phase is 20 S / m, and the conductivity in the metallic phase is 200,000 S / m. The relative dielectric constant of the upper SiO2 dielectric layer 2 and the lower SiO2 dielectric layer 5 is 2.13. The material of the bottom gold layer 6 is gold, and the conductivity is 4.56×10 7 S / m.

[0075] Example 4

[0076] The ultra-wideband-multi-frequency switchable terahertz absorber based on vanadium dioxide in this embodiment includes 3*3 multi-layer ultra-wideband-multi-frequency switchable terahertz units, and each multi-layer ultra-wideband-multi-frequency switchable terahertz unit includes an upper patterned VO2 layer 1, an upper SiO2 dielectric layer 2, a lower VO2 layer 3, an intermediate patterned gold layer 4, a lower SiO2 dielectric layer 5 and a bottom gold layer 6 arranged in sequence from top to bottom.

[0077] Among them, the side lengths of the upper SiO2 dielectric layer 2, the lower VO2 layer 3, the lower SiO2 dielectric layer 5 and the bottom gold layer 6 are equal and are the period length of the absorption unit, and the side lengths of the upper patterned VO2 layer 1 and the middle patterned gold layer 4 are slightly smaller than the period length.

[0078] In this embodiment, the upper patterned VO2 layer 1 is disc-shaped with a square annular slit inside. The disc radius R is 13 μm, the slit width d is 2.5 μm, the slit side length c is 22 μm, and the thickness t6 of the upper patterned VO2 layer 1 is 0.02 μm.

[0079] In this embodiment, the middle patterned gold layer 4 consists of an open square ring, an outer circular ring, and an inner circular ring. The side length a of the open square ring is 32 μm, the square ring width b is 2 μm, and the opening width w is 2.5 μm. The outer circular ring has an outer diameter r1 of 11.5 μm and a fixed inner diameter r2 of 9 μm. The inner circular ring has an outer diameter r3 of 6.5 μm and a fixed inner diameter r4 of 4 μm. The thickness t3 of the middle patterned gold layer 4 is 2.5 μm.

[0080] The thickness t5 of the upper SiO2 dielectric layer 2 is 4 μm, the thickness t4 of the lower VO2 layer 3 is 0.5 μm, the thickness t2 of the lower SiO2 dielectric layer 5 is 8 μm, and the thickness t1 of the bottom gold layer 6 is 0.2 μm. The side length P is 33 μm.

[0081] The conductivity of the upper patterned VO2 layer 1 and the lower VO2 layer 3 in the insulating phase is 20 S / m, and the conductivity in the metallic phase is 200,000 S / m. The relative dielectric constant of the upper SiO2 dielectric layer 2 and the lower SiO2 dielectric layer 5 is 2.13. The material of the bottom gold layer 6 is gold, and the conductivity is 4.56×10 7 S / m.

[0082] Example 5

[0083] The ultra-wideband-multi-frequency switchable terahertz absorber based on vanadium dioxide in this embodiment includes 3*3 multi-layer ultra-wideband-multi-frequency switchable terahertz units, and each multi-layer ultra-wideband-multi-frequency switchable terahertz unit includes an upper patterned VO2 layer 1, an upper SiO2 dielectric layer 2, a lower VO2 layer 3, an intermediate patterned gold layer 4, a lower SiO2 dielectric layer 5 and a bottom gold layer 6 arranged in sequence from top to bottom.

[0084] Among them, the side lengths of the upper SiO2 dielectric layer 2, the lower VO2 layer 3, the lower SiO2 dielectric layer 5 and the bottom gold layer 6 are equal and are the period length of the absorption unit, and the side lengths of the upper patterned VO2 layer 1 and the middle patterned gold layer 4 are slightly smaller than the period length.

[0085] In this embodiment, the upper patterned VO2 layer 1 is disc-shaped with a square ring-shaped slit inside. The disc radius R is 12 μm, the slit width d is 2.5 μm, the slit side length c is 22 μm, and the thickness t6 of the upper patterned VO2 layer 1 is 0.02 μm.

[0086] In this embodiment, the middle patterned gold layer 4 consists of an open square ring, an outer circular ring, and an inner circular ring. The side length a of the open square ring is 32 μm, the square ring width b is 1 μm, and the opening width w is 3 μm. The outer circular ring has an outer diameter r1 of 12 μm and a fixed inner diameter r2 of 9 μm. The inner circular ring has an outer diameter r3 of 7 μm and a fixed inner diameter r4 of 4 μm. The thickness t3 of the middle patterned gold layer 4 is 3 μm.

[0087] The thickness t5 of the upper SiO2 dielectric layer 2 is 6 μm, the thickness t4 of the lower VO2 layer 3 is 0.5 μm, the thickness t2 of the lower SiO2 dielectric layer 5 is 5 μm, and the thickness t1 of the bottom gold layer 6 is 0.2 μm. The side length P is 33 μm.

[0088] The conductivity of the upper patterned VO2 layer 1 and the lower VO2 layer 3 in the insulating phase is 20 S / m, and the conductivity in the metallic phase is 200,000 S / m. The relative dielectric constant of the upper SiO2 dielectric layer 2 and the lower SiO2 dielectric layer 5 is 2.13. The material of the bottom gold layer 6 is gold, and the conductivity is 4.56×10 7 S / m.

[0089] The present invention's ultra-wideband, multi-frequency switchable terahertz absorber based on vanadium dioxide utilizes the insulating-to-metallic phase transition characteristics of VO2. By controlling the temperature, the electrical conductivity of VO2 can be controlled, thereby regulating the absorber's absorptivity, enabling switchable absorption from ultra-wideband to multi-frequency. The present invention's ultra-wideband, multi-frequency switchable terahertz absorber possesses switchable functionality and excellent absorption performance, demonstrating potential application value.

[0090] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. An ultra-wideband, multi-frequency switchable terahertz absorber based on vanadium dioxide, characterized in that: The ultra-wideband-multi-frequency switchable terahertz absorber comprises M*N multi-layer ultra-wideband-multi-frequency switchable terahertz absorption units, wherein the M*N multi-layer ultra-wideband-multi-frequency switchable terahertz absorption units are distributed in an M*N two-dimensional manner, wherein M and N are both positive integers; the ultra-wideband-multi-frequency switchable terahertz absorption units are sequentially provided with an upper patterned VO2 layer, an upper SiO2 dielectric layer, a lower VO2 layer, an intermediate patterned gold layer, a lower SiO2 dielectric layer and a bottom gold layer, which are bonded to each other from top to bottom; The upper patterned VO2 layer is in the shape of a disk, a square annular slit is provided inside the disk, and the four corners of the square annular slit intersect with the disk and are provided with notches; The middle patterned gold layer comprises an inner circular ring, an outer circular ring and an open square ring which are sequentially spaced from the inside to the outside, and the opening of the open square ring is arranged in the middle position of each side; The side lengths of the upper SiO2 dielectric layer, the lower VO2 layer, the lower SiO2 dielectric layer and the bottom gold layer are equal to the period length of the ultra-wideband-multi-frequency switchable terahertz absorption unit, and the side lengths of the upper patterned VO2 layer and the middle patterned gold layer are both smaller than the period length of the ultra-wideband-multi-frequency switchable terahertz absorption unit.

2. The vanadium dioxide-based ultra-wideband multi-frequency switchable terahertz absorber according to claim 1, characterized in that: The radius of the upper patterned VO2 layer is 12µm-16µm, the width of the square ring slit is 0.5µm-2.5µm, and the side length is 22µm; the thickness of the upper patterned VO2 layer is 0.02µm-0.2µm.

3. The ultra-wideband multi-frequency switchable terahertz absorber based on vanadium dioxide according to claim 1, characterized in that: The side length of the open square ring is 32µm, the width of the square ring is 0.5µm-2µm, and the opening width of the open square ring is 1µm-3µm; the outer diameter of the outer ring is 10µm-12µm, and the inner diameter is 9µm; the outer diameter of the inner ring is 5µm-7µm, and the inner diameter is 4µm; the thickness of the patterned gold layer in the middle layer is 1µm-3µm.

4. The vanadium dioxide-based ultra-wideband multi-frequency switchable terahertz absorber according to claim 1, characterized in that: The thickness of the upper SiO2 dielectric layer is 4µm-8µm, the thickness of the lower VO2 layer is 0.5µm, the thickness of the lower SiO2 dielectric layer is 4µm-8µm, and the thickness of the bottom gold layer is 0.2µm; the side lengths of the upper SiO2 dielectric layer, the lower VO2 layer, the lower SiO2 dielectric layer and the bottom gold layer are all 33µm.

5. The vanadium dioxide-based ultra-wideband multi-frequency switchable terahertz absorber according to claim 1, characterized in that: The electrical conductivity of the upper patterned VO2 layer and the lower VO2 layer in the insulating phase is 20 S / m, and the electrical conductivity in the metallic phase is 200,000 S / m.

6. The ultra-wideband and multi-frequency switchable terahertz absorber based on vanadium dioxide according to claim 1, characterized in that: The relative dielectric constant of the upper SiO2 dielectric layer and the lower SiO2 dielectric layer is 2.

13.

7. The ultra-wideband multi-frequency switchable terahertz absorber based on vanadium dioxide according to claim 1, characterized in that: The bottom gold layer is made of gold, and its conductivity is 4.56×10 7 S / m.

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