Dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber and preparation method thereof

Abstract

The present invention discloses a dual-frequency / broadband switchable dynamically tuned metamaterial terahertz absorber, comprising M*N multilayer terahertz absorption units, each of which is distributed in an M*N two-dimensional pattern, where M and N are both positive integers. Each multilayer terahertz absorption unit comprises a metal substrate, a dielectric layer, and a resonant layer, arranged sequentially from bottom to top. The dielectric layer and the metal substrate are both square in shape with equal sides. The resonant layer comprises a single-layer graphene layer with a hollow cross, wherein a solid cross-shaped vanadium dioxide layer is embedded in the hollow portion of the single-layer graphene layer with the hollow cross. The single-layer graphene layer with the hollow cross has a cross-shaped shape. The absorber is dynamically tuned, has polarization insensitivity, and can maintain stable absorption within an incident angle range of 0-60°. A preparation method for the dual-frequency / broadband switchable dynamically tuned metamaterial terahertz absorber is also disclosed.

Description

Technical Field

[0001] The present invention relates to the field of terahertz wave technology, and in particular to a dual-frequency / broadband switchable dynamically tuned metamaterial terahertz absorber, and also to a method for preparing the dual-frequency / broadband switchable dynamically tuned metamaterial terahertz absorber. Background Art

[0002] Terahertz (THz) waves generally refer to electromagnetic waves with frequencies between 0.1 and 10 THz. Due to their low energy, strong penetration, and unique frequency and wavelength, the application of THz waves and related technologies has become a research hotspot in various fields. As fundamental functional devices for THz applications, THz absorbers are widely used in detectors, spectrum imaging, stealth, and other fields.

[0003] A terahertz absorber based on metamaterials is a device that can efficiently absorb incident terahertz waves. The main principle is to utilize different loss mechanisms to convert terahertz waves into heat or other forms of energy, ultimately achieving the effect of absorbing terahertz waves. Among various absorbers, absorbers based on metamaterial structures have received widespread attention from scholars at home and abroad in recent years. Compared with traditional absorbers, metamaterial absorbers have the characteristics of small size, high absorption rate and easy integration. Current absorbers use a stacked multi-layer structure or use multiple resonant structures of different sizes in the same plane to achieve multi-frequency absorption. The structure is complex and difficult to manufacture and process. Once the device is determined, its absorption function cannot be adjusted, which restricts the application of the absorber. Therefore, there is an urgent need to develop a terahertz dual-band / broadband switchable absorber with a simple structure, easy manufacture, and flexible tunability to meet the needs of practical terahertz applications. Summary of the Invention

[0004] The first purpose of the present invention is to propose a dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber, which can be dynamically tuned, has polarization insensitivity, can maintain stable absorption within the incident angle range of 0-60°, and has wide-angle absorption characteristics; the absorber has a simple structure and is easy to implement.

[0005] The second objective of the present invention is to propose a method for preparing a dual-frequency / broadband switchable dynamically tuned metamaterial terahertz absorber.

[0006] The first technical solution adopted by the present invention is a dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber, comprising M*N multilayer terahertz absorption units, wherein the M*N multilayer terahertz absorption units are distributed in an M*N two-dimensional manner, where M and N are both positive integers; each multilayer terahertz absorption unit comprises a metal substrate, a dielectric layer, and a resonant layer arranged in sequence from bottom to top; the dielectric layer and the metal substrate are both square in shape with equal side lengths;

[0007] The resonance layer includes a single-layer graphene layer with a hollow cross, wherein a solid cross-shaped vanadium dioxide layer is embedded in the hollow of the single-layer graphene layer with the hollow cross; the shape of the single-layer graphene layer with the hollow cross is a cross.

[0008] The present invention is also characterized in that:

[0009] The thickness t of a single graphene layer with a hollow cross g The length of the single-layer graphene layer with a hollow cross is equal to the length in the horizontal direction and the length in the vertical direction, and the width in the horizontal direction and the width in the vertical direction are equal; the length of the single-layer graphene layer with a hollow cross is equal to g 34µm-44µm, width w g 8µm-16µm; the thickness of the cross-shaped vanadium dioxide layer (VO2) is t v The length of the cross-shaped vanadium dioxide layer in the horizontal direction is equal to the length in the vertical direction, and the width in the horizontal direction is equal to the width in the vertical direction. The length of the cross-shaped vanadium dioxide layer (VO2) is l v 30µm-38µm, width w v The thickness of vanadium dioxide is 1µm-5µm; when the ambient temperature is lower than 340 K, vanadium dioxide is in the insulating phase, and the electrical conductivity at this time is 200S / m. When the ambient temperature is higher than 340 K, vanadium dioxide is in the metallic phase, and the electrical conductivity at this time is 200000S / m.

[0010] The material of the dielectric layer is Topas, and the relative dielectric constant is 2.35.

[0011] The side length p of the dielectric layer is 45µm-55µm, and the thickness h is 32µm-36µm.

[0012] The metal substrate is made of gold, with a conductivity of 4.56×10 7 S / m.

[0013] The side length of the metal substrate is equal to that of the dielectric layer, which is 45µm-55µm, and the thickness is t Au 0.2µm-0.8µm.

[0014] The second technical solution adopted by the present invention is a method for preparing a dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber, which specifically includes the following steps:

[0015] Step 1, preparation of metal substrate;

[0016] Step 2: Deposition of dielectric layer;

[0017] Step 3: Preparation of a cross-shaped vanadium dioxide layer;

[0018] Step 4: Transfer and patterning of the graphene layer with the hollow cross.

[0019] The present invention is also characterized in that:

[0020] Step 1 is as follows:

[0021] Step 1.1, substrate cleaning:

[0022] High-purity silicon was used as the substrate and ultrasonically cleaned with acetone, ethanol, and deionized water for 10-15 minutes to remove surface contaminants. After drying with nitrogen, the substrate was dried in an oven at 110-120°C for 30-40 minutes.

[0023] Step 1.2, metal film deposition:

[0024] Gold thin films were deposited using electron beam evaporation;

[0025] Step 1.3, annealing treatment:

[0026] Annealing at 300-350°C for 30-40 min to improve the crystallization quality and conductivity of the gold film;

[0027] Step 2 is as follows:

[0028] Step 2.1, Topas film preparation:

[0029] Topas thin films were deposited on metal substrates using chemical vapor deposition;

[0030] Step 2.2, curing treatment:

[0031] Curing at 150-160°C for 1-2 hours to ensure film density and stable dielectric properties;

[0032] Step 3 is as follows:

[0033] Step 3.1, VO2 thin film deposition:

[0034] Pulsed laser deposition is used to grow VO2 thin films on the dielectric layer.

[0035] Step 3.2, photolithography patterning:

[0036] The cross-shaped structure was defined using UV lithography.

[0037] Step 4 is as follows:

[0038] Step 4.1, graphene growth and transfer:

[0039] A single layer of graphene was grown on copper foil using chemical vapor deposition and then transferred to the surface of the dielectric layer using a wet method.

[0040] Step 4.2, graphene patterning:

[0041] The hollow cross structure was defined using electron beam lithography.

[0042] The beneficial effects of the present invention are:

[0043] (1) The dual-band / broadband switchable dynamically tuned metamaterial terahertz absorber of the present invention has an absorption peak of 99.4% at 0.807 THz and 98.6% at 2.166 THz when vanadium dioxide is in the insulating phase and the graphene chemical potential is 0.7 eV, exhibiting dual-band absorption. When vanadium dioxide is in the metallic phase and the graphene chemical potential is 0.4 eV, the absorber has an absorption rate exceeding 90% in the range of 0.993 THz-1.872 THz, exhibiting broadband absorption with a bandwidth of 0.879 THz, achieving switching between dual-band and broadband absorption modes.

[0044] (2) The dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber of the present invention can change the absorption spectrum of the absorber by adjusting the chemical potential of graphene, and has dynamic tuning capability.

[0045] (3) The dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber of the present invention is polarization-insensitive and can maintain stable absorption within the incident angle range of 0-60°, exhibiting wide-angle absorption characteristics. The absorber has a simple structure and is easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 Schematic diagram of the periodic structure of the dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber provided in Example 1 of the present invention;

[0047] Figure 2 Schematic diagram of the unit structure of the dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber provided in Example 1 of the present invention;

[0048] Figure 3 1 is a top view of the unit structure of the dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber provided in Example 1 of the present invention;

[0049] Figure 4 is an absorption spectrum diagram of the dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber provided in Example 1 of the present invention, wherein curve a represents dual-frequency absorption and curve b represents broadband absorption;

[0050] Figure 5is the normalized equivalent impedance of the dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber in dual-frequency mode provided by Example 1 of the present invention;

[0051] Figure 6 is the normalized equivalent impedance of the dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber in broadband mode provided by Example 1 of the present invention;

[0052] Figure 7 This is the electric field distribution diagram at 0.807 THz under dual-frequency mode TE polarization of the dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber provided in Example 1 of the present invention;

[0053] Figure 8 This is the electric field distribution diagram at 2.166 THz under dual-frequency mode TE polarization of the dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber provided in Example 1 of the present invention;

[0054] Figure 9 This is the electric field distribution diagram at 1.135 THz in the broadband mode TE polarization of the dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber provided in Example 1 of the present invention;

[0055] Figure 10 This is the electric field distribution diagram at 1.650 THz in the broadband mode TE polarization of the dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber provided in Example 1 of the present invention;

[0056] Figure 11 The effect of graphene chemical potential on the absorption spectrum in the dual-frequency mode of the dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber provided in Example 1 of the present invention;

[0057] Figure 12 The effect of graphene chemical potential on the absorption spectrum in broadband mode of the dual-band / broadband switchable dynamically tunable metamaterial terahertz absorber provided in Example 1 of the present invention;

[0058] Figure 13 The effect of polarization angle on the absorption spectrum of the dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber in dual-frequency mode provided by Example 1 of the present invention;

[0059] Figure 14 The effect of polarization angle on the absorption spectrum of the dual-band / broadband switchable dynamically tunable metamaterial terahertz absorber in broadband mode provided by Example 1 of the present invention;

[0060] Figure 15 The effect of the incident angle on the absorption spectrum of the dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber under dual-frequency mode TE polarization provided by Example 1 of the present invention;

[0061] Figure 16 The effect of the incident angle on the absorption spectrum of the dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber under dual-frequency mode TM polarization provided by Example 1 of the present invention;

[0062] Figure 17 The effect of the incident angle on the absorption spectrum of the dual-band / broadband switchable dynamically tunable metamaterial terahertz absorption broadband mode under TE polarization provided by Example 1 of the present invention;

[0063] Figure 18 This is the effect of the incident angle on the absorption spectrum of the dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber under broadband mode TM polarization provided by Example 1 of the present invention.

[0064] In the figure, 1. metal substrate, 2. dielectric layer, 3. resonant layer, 3-1. single-layer graphene layer with a hollow cross, 3-2. cross-shaped vanadium dioxide layer. DETAILED DESCRIPTION

[0065] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0066] The present invention provides a dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber, such as Figure 1-3 As shown, it includes M*N multilayer terahertz absorption units, and the M*N multilayer terahertz absorption units are distributed in M*N two dimensions, where M and N are both positive integers; each multilayer terahertz absorption unit includes a metal substrate 1, a dielectric layer 2, and a resonant layer 3 arranged in sequence from bottom to top; the dielectric layer 2 and the metal substrate 1 are both square in shape and have equal side lengths;

[0067] The resonance layer 3 includes a single-layer graphene layer 3-1 with a hollow cross, wherein a solid cross-shaped vanadium dioxide layer 3-2 is embedded in the hollow of the single-layer graphene layer 3-1; the single-layer graphene layer 3-1 with a hollow cross has a cross-shaped shape.

[0068] The thickness t of the single-layer graphene layer 3-1 with the hollow cross g The length of the single-layer graphene layer 3-1 with a hollow cross in the horizontal direction is equal to the length in the vertical direction, and the width in the horizontal direction is equal to the width in the vertical direction; the length l of the single-layer graphene layer 3-1 with a hollow cross is equal to g 34µm-44µm, width w g 8µm-16µm; the thickness of the cross-shaped vanadium dioxide layer 3-2 is t v The length of the cross-shaped vanadium dioxide layer 3-2 in the horizontal direction is equal to the length of the vertical direction, and the width of the horizontal direction is equal to the width of the vertical direction; the length of the cross-shaped vanadium dioxide layer 3-2 is lv 30µm-38µm, width w v The thickness of vanadium dioxide is 1µm-5µm; when the ambient temperature is lower than 340 K, vanadium dioxide is in the insulating phase, and the electrical conductivity at this time is 200S / m. When the ambient temperature is higher than 340 K, vanadium dioxide is in the metallic phase, and the electrical conductivity at this time is 200000S / m.

[0069] The dielectric layer 2 is made of Topas, and has a relative dielectric constant of 2.35.

[0070] The dielectric layer 2 has a side length p of 45µm-55µm and a thickness h of 32µm-36µm.

[0071] The material of the metal substrate 1 is gold, and the electrical conductivity is 4.56×10 7 S / m.

[0072] The side length of the metal substrate 1 is equal to the side length of the dielectric layer 2, which is 45µm-55µm, and the thickness is t Au 0.2µm-0.8µm.

[0073] The present invention also provides a method for preparing a dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber, which specifically comprises the following steps:

[0074] Step 1, preparation of a metal substrate 1;

[0075] Step 1 is as follows:

[0076] Step 1.1, substrate cleaning:

[0077] High-purity silicon was used as the substrate and ultrasonically cleaned with acetone, ethanol, and deionized water for 10-15 minutes to remove surface contaminants. After drying with nitrogen, the substrate was dried in an oven at 110-120°C for 30-40 minutes.

[0078] Step 1.2, metal film deposition:

[0079] Gold thin films were deposited using electron beam evaporation;

[0080] Step 1.3, annealing treatment:

[0081] Annealing at 300℃~350℃ for 30min-40min to improve the crystallization quality and conductivity of the gold film;

[0082] Step 2, deposition of dielectric layer 2;

[0083] Step 2 is as follows:

[0084] Step 2.1, Topas film preparation:

[0085] Topas thin films were deposited on metal substrates using chemical vapor deposition;

[0086] Step 2.2, curing treatment:

[0087] Curing at 150℃-160℃ for 1h-2h to ensure film density and stable dielectric properties;

[0088] Step 3, preparation of a cross-shaped vanadium dioxide 3-2 layer;

[0089] Step 3 is as follows:

[0090] Step 3.1, VO2 thin film deposition:

[0091] Pulsed laser deposition is used to grow VO2 thin films on the dielectric layer.

[0092] Step 3.2, photolithography patterning:

[0093] The cross-shaped structure was defined using UV lithography.

[0094] Step 4: Transferring and patterning the graphene layer 3-1 with the hollow cross.

[0095] Step 4 is as follows:

[0096] Step 4.1, graphene growth and transfer:

[0097] A single layer of graphene is grown on the copper foil by chemical vapor deposition and transferred to the surface of the dielectric layer 2 by a wet method;

[0098] Step 4.2, graphene patterning:

[0099] The hollow cross structure was defined using electron beam lithography.

[0100] Example 1:

[0101] like Figure 1-Figure 3 As shown, the dual-band / broadband switchable dynamically tunable metamaterial terahertz absorber includes 3*3 multilayer terahertz absorption units. The number of multilayer terahertz absorption units does not affect the overall absorption performance. Each multilayer terahertz absorption unit includes a metal substrate 1, a dielectric layer 2, and a resonant layer 3 arranged in sequence from bottom to top. The dielectric layer 2 and the metal substrate 1 are both square in shape with equal side lengths.

[0102] The resonance layer 3 includes a single-layer graphene layer 3-1 with a hollow cross, wherein a solid cross-shaped vanadium dioxide layer 3-2 is embedded in the hollow of the single-layer graphene layer 3-1; the single-layer graphene layer 3-1 with a hollow cross has a cross-shaped shape.

[0103] The thickness t of the single-layer graphene layer 3-1 with the hollow crossg is 0.34 nm; the length l of the single-layer graphene layer 3-1 with a hollow cross g is 40µm, width w g is 12µm; the thickness of the cross-shaped vanadium dioxide layer 3-2 is t v is 0.05µm; the length l of the cross-shaped vanadium dioxide layer 3-2 v 34µm, width w v When the ambient temperature is lower than 340 K, vanadium dioxide is in the insulating phase, and the electrical conductivity is 200 S / m. When the ambient temperature is higher than 340 K, vanadium dioxide is in the metallic phase, and the electrical conductivity is 200,000 S / m.

[0104] The dielectric layer 2 is made of Topas, and has a relative dielectric constant of 2.35.

[0105] The dielectric layer 2 has a side length p of 50 μm and a thickness h of 33 μm.

[0106] The material of the metal substrate 1 is gold, and the electrical conductivity is 4.56×10 7 S / m.

[0107] The side length of the metal substrate 1 is equal to the side length of the dielectric layer 2, which is p, 50µm, and the thickness is t Au It is 0.5µm, which is much larger than the skin depth of the incident electromagnetic wave, ensuring that the transmittance of the absorber is 0.

[0108] Figure 4 The absorption spectrum of the designed terahertz absorber is shown. When vanadium dioxide is in the insulating phase (conductivity of 200 S / m) and the graphene chemical potential is 0.7 eV, the absorption peaks are 99.4% at 0.807 THz and 98.6% at 2.166 THz, demonstrating dual-band absorption. When vanadium dioxide is in the metallic phase (conductivity of 200,000 S / m) and the graphene chemical potential is 0.4 eV, the absorber exhibits broadband absorption with an absorption rate exceeding 90% in the 0.993-1.872 THz range, with a bandwidth of 0.879 THz, achieving switching between dual-band and broadband absorption modes.

[0109] Figure 5 and Figure 6 The normalized equivalent impedance of the absorber is shown as a function of frequency, where the solid line is the real part of the impedance and the dashed line is the imaginary part of the impedance. Figure 5 In the dual-frequency mode, the real part of the impedance approaches 1 at 0.807 THz and 2.166 THz, and the imaginary part approaches 0; Figure 6In the example, when the absorber works in broadband mode, the real part of the absorber is close to 1 and the imaginary part is close to 0 in the range of 0.993-1.872 THz. The impedance matching in both working modes is consistent with Figure 4 The absorption spectra shown are consistent.

[0110] Figure 7-10 The electric field distribution of the absorber under TE polarization is given. Figure 7 and Figure 8 The electric field distribution diagrams for the absorber's dual-frequency mode at the center frequencies of the low-frequency absorption peak, 0.807 THz, and the high-frequency absorption peak, 2.166 THz, respectively. As can be seen, in dual-frequency mode, the electric field is distributed along the upper and lower outer edges of the hollow graphene cross and along the upper and lower inner edges of the crossbar. The electric field at the center frequency of the low-frequency absorption peak is primarily distributed along the upper and lower outer edges, while the electric field at the high-frequency absorption peak is primarily distributed along the upper and lower inner edges of the crossbar. Therefore, the low-frequency absorption peak primarily arises from electric dipole resonance. At the center frequency of the high-frequency absorption peak, however, the insulating vanadium dioxide acts as a dielectric, enabling electric field coupling between the upper and lower inner edges of the hollow graphene crossbar, thereby stimulating this absorption peak. Figure 9 and Figure 10 These are the electric field distribution diagrams at the two vertices of the absorption peak in the broadband mode of the absorber at 1.135 THz and 1.650 THz. At this time, vanadium dioxide is in the metallic phase, which is equivalent to a conductor, and there is no longer any electric field coupling between the internal edges of the graphene hollow cross. Moreover, the electric fields at both frequencies are distributed on both sides of the upper and lower outer edges of the graphene hollow cross, indicating that the entire broadband absorption comes from the electric dipole resonance. In summary, whether in dual-band mode or broadband mode, the absorber has electric dipole resonance, which indicates that graphene excites surface plasmons. When vanadium dioxide is in the insulating phase, the electric field is coupled, thereby introducing a new excitation mode and realizing dual-band absorption; when vanadium dioxide is in the metallic phase, this coupling disappears, so that the broadband absorption range is excited by the electric dipole resonance. This is the key to designing the switchable function of the absorber.

[0111] Figure 11 The dual-frequency mode absorption spectrum changes under different graphene chemical potentials. As the graphene chemical potential increases, the absorption of the low-frequency absorption peak first increases and then decreases, while the high-frequency absorption peak continues to decrease. The center frequencies of both absorption peaks also blue-shift. At a chemical potential of 0.7 eV, both absorption peaks have high absorptivity. Figure 12The changes in the absorption spectrum of the broadband mode under different graphene chemical potentials are demonstrated. As the graphene chemical potential increases, both the left and right vertices of the absorption band undergo a blue shift. The absorption at the left vertex first increases and then decreases, while the absorption rate at the right vertex continues to increase. When the chemical potential is 0.4 eV, the overall absorption rate and absorption bandwidth of the broadband absorption are optimal. In summary, the absorption rate in both modes is affected by the graphene chemical potential. This means that even after all the design parameters are finalized, the graphene chemical potential can still be changed to achieve the purpose of dynamically controlling the absorption performance of the absorber, which greatly increases the feasibility of the absorber in practical applications.

[0112] Figure 13 and Figure 14 The absorption spectra of the dual-band and broadband absorption modes are shown as a function of polarization angle. It is clear that both modes maintain stable absorption with varying polarization angles, demonstrating that the absorber's absorption performance is unaffected by the polarization angle and exhibits polarization-insensitive properties, a result of the centrosymmetric design.

[0113] Figure 15 and Figure 16 The effects of the incident angle of electromagnetic waves on the dual-frequency mode absorption spectrum under TE polarization and TM polarization are shown respectively. For both polarizations, the absorber can maintain stable absorption within the incident range of 0-60°. For TE polarization, after exceeding 60°, the absorption rate of the low-frequency absorption peak drops rapidly, and the high-frequency absorption peak undergoes a blue shift. After 70°, another absorption peak appears at 1.7 THz. For TM polarization, within the incident range of 0-60°, both absorption peaks maintain stable absorption, and the center frequencies of the two absorption peaks do not change. After 60°, the absorption rate begins to decrease.

[0114] Figure 17 and Figure 18 The influence of the incident angle of electromagnetic waves under TE polarization and TM polarization on the broadband mode absorption spectrum is demonstrated respectively. For TE polarization, in the range of 0-60°, the absorber maintains broadband absorption, and the bandwidth increases due to the blue shift of the second peak of the absorption band. After 60°, as the incident angle increases, the partial absorption rate between the two vertices decreases, gradually becoming dual-band absorption. For TM polarization, in the range of 0-40°, the absorption rate and bandwidth remain stable. After 40°, the right vertex undergoes a red shift, causing the absorption bandwidth to decrease. Up to 60°, the absorber still maintains broadband absorption. After 60°, the absorption rate decreases rapidly. In summary, by discussing the influence of the incident angle of electromagnetic waves under TE and TM polarization on the absorption spectra of the two modes, it can be concluded that both absorption modes of the absorber can maintain efficient and stable absorption in the electromagnetic wave incident angle range of 0-60°, and have the characteristics of wide-angle absorption.

[0115] Example 2

[0116] like Figure 1-Figure 3 As shown, the dual-band / broadband switchable dynamically tunable metamaterial terahertz absorber includes 3*3 multilayer terahertz absorption units. The number of multilayer terahertz absorption units does not affect the overall absorption performance. Each multilayer terahertz absorption unit includes a metal substrate 1, a dielectric layer 2, and a resonant layer 3 arranged in sequence from bottom to top. The dielectric layer 2 and the metal substrate 1 are both square in shape with equal side lengths.

[0117] The resonance layer 3 includes a single-layer graphene layer 3-1 with a hollow cross, wherein a solid cross-shaped vanadium dioxide layer 3-2 is embedded in the hollow of the single-layer graphene layer 3-1; the single-layer graphene layer 3-1 with a hollow cross has a cross-shaped shape.

[0118] The thickness t of the single-layer graphene layer 3-1 with the hollow cross g is 0.34 nm; the length l of the single-layer graphene layer 3-1 with a hollow cross g is 36µm, width w g is 8µm; the thickness of the cross-shaped vanadium dioxide layer 3-2 is t v is 0.06µm; the length l of the cross-shaped vanadium dioxide layer 3-2 v 30µm, width w v When the ambient temperature is lower than 340 K, vanadium dioxide is in the insulating phase, and the electrical conductivity is 200 S / m. When the ambient temperature is higher than 340 K, vanadium dioxide is in the metallic phase, and the electrical conductivity is 200,000 S / m.

[0119] The dielectric layer 2 is made of Topas, and has a relative dielectric constant of 2.35.

[0120] The dielectric layer 2 has a side length p of 45 μm and a thickness h of 32 μm.

[0121] The material of the metal substrate 1 is gold, and the electrical conductivity is 4.56×10 7 S / m.

[0122] The side length of the metal substrate 1 is equal to the side length of the dielectric layer 2, which is p, 45µm, and the thickness is t Au It is 0.2µm, which is much larger than the skin depth of the incident electromagnetic wave, ensuring that the transmittance of the absorber is 0.

[0123] Example 3

[0124] like Figure 1-Figure 3As shown, the dual-band / broadband switchable dynamically tunable metamaterial terahertz absorber includes 3*3 multilayer terahertz absorption units. The number of multilayer terahertz absorption units does not affect the overall absorption performance. Each multilayer terahertz absorption unit includes a metal substrate 1, a dielectric layer 2, and a resonant layer 3 arranged in sequence from bottom to top. The dielectric layer 2 and the metal substrate 1 are both square in shape with equal side lengths.

[0125] The resonance layer 3 includes a single-layer graphene layer 3-1 with a hollow cross, wherein a solid cross-shaped vanadium dioxide layer 3-2 is embedded in the hollow of the single-layer graphene layer 3-1; the single-layer graphene layer 3-1 with a hollow cross has a cross-shaped shape.

[0126] The thickness t of the single-layer graphene layer 3-1 with the hollow cross g is 0.34 nm; the length l of the single-layer graphene layer 3-1 with a hollow cross g 38µm, width w g is 10µm; the thickness of the cross-shaped vanadium dioxide layer 3-2 is t v is 0.07µm; the length l of the cross-shaped vanadium dioxide layer 3-2 v 32µm, width w v When the ambient temperature is lower than 340 K, vanadium dioxide is in the insulating phase, and the electrical conductivity is 200 S / m. When the ambient temperature is higher than 340 K, vanadium dioxide is in the metallic phase, and the electrical conductivity is 200,000 S / m.

[0127] The dielectric layer 2 is made of Topas, and has a relative dielectric constant of 2.35.

[0128] The side length p of the dielectric layer 2 is 47 μm, and the thickness h is 34 μm.

[0129] The material of the metal substrate 1 is gold, and the electrical conductivity is 4.56×10 7 S / m.

[0130] The side length of the metal substrate 1 is equal to the side length of the dielectric layer 2, which is p, 47µm, and the thickness is t Au It is 0.4µm, which is much larger than the skin depth of the incident electromagnetic wave, ensuring that the transmittance of the absorber is 0.

[0131] Example 4

[0132] like Figure 1-Figure 3As shown, the dual-band / broadband switchable dynamically tunable metamaterial terahertz absorber includes 3*3 multilayer terahertz absorption units. The number of multilayer terahertz absorption units does not affect the overall absorption performance. Each multilayer terahertz absorption unit includes a metal substrate 1, a dielectric layer 2, and a resonant layer 3 arranged in sequence from bottom to top. The dielectric layer 2 and the metal substrate 1 are both square in shape with equal side lengths.

[0133] The resonance layer 3 includes a single-layer graphene layer 3-1 with a hollow cross, wherein a solid cross-shaped vanadium dioxide layer 3-2 is embedded in the hollow of the single-layer graphene layer 3-1; the single-layer graphene layer 3-1 with a hollow cross has a cross-shaped shape.

[0134] The thickness t of the single-layer graphene layer 3-1 with the hollow cross g is 0.34 nm; the length l of the single-layer graphene layer 3-1 with a hollow cross g 42µm, width w g is 14µm; the thickness of the cross-shaped vanadium dioxide layer 3-2 is t v is 0.08µm; the length l of the cross-shaped vanadium dioxide layer 3-2 v is 36µm, width w v When the ambient temperature is lower than 340 K, vanadium dioxide is in the insulating phase, and the electrical conductivity is 200 S / m. When the ambient temperature is higher than 340 K, vanadium dioxide is in the metallic phase, and the electrical conductivity is 200,000 S / m.

[0135] The dielectric layer 2 is made of Topas, and has a relative dielectric constant of 2.35.

[0136] The side length p of the dielectric layer 2 is 52 μm, and the thickness h is 35 μm.

[0137] The material of the metal substrate 1 is gold, and the electrical conductivity is 4.56×10 7 S / m.

[0138] The side length of the metal substrate 1 is equal to the side length of the dielectric layer 2, which is p, 52µm, and the thickness is t Au It is 0.6µm, which is much larger than the skin depth of the incident electromagnetic wave, ensuring that the transmittance of the absorber is 0.

[0139] Example 5

[0140] like Figure 1-Figure 3As shown, the dual-band / broadband switchable dynamically tunable metamaterial terahertz absorber includes 3*3 multilayer terahertz absorption units. The number of multilayer terahertz absorption units does not affect the overall absorption performance. Each multilayer terahertz absorption unit includes a metal substrate 1, a dielectric layer 2, and a resonant layer 3 arranged in sequence from bottom to top. The dielectric layer 2 and the metal substrate 1 are both square in shape with equal side lengths.

[0141] The resonance layer 3 includes a single-layer graphene layer 3-1 with a hollow cross, wherein a solid cross-shaped vanadium dioxide layer 3-2 is embedded in the hollow of the single-layer graphene layer 3-1; the single-layer graphene layer 3-1 with a hollow cross has a cross-shaped shape.

[0142] The thickness t of the single-layer graphene layer 3-1 with the hollow cross g is 0.34 nm; the length l of the single-layer graphene layer 3-1 with a hollow cross g is 44µm, width w g is 16µm; the thickness of the cross-shaped vanadium dioxide layer 3-2 is t v is 0.05µm; the length l of the cross-shaped vanadium dioxide layer 3-2 v 38µm, width w v When the ambient temperature is lower than 340 K, vanadium dioxide is in the insulating phase, and the electrical conductivity is 200 S / m. When the ambient temperature is higher than 340 K, vanadium dioxide is in the metallic phase, and the electrical conductivity is 200,000 S / m.

[0143] The dielectric layer 2 is made of Topas, and has a relative dielectric constant of 2.35.

[0144] The side length p of the dielectric layer 2 is 55 μm, and the thickness h is 36 μm.

[0145] The material of the metal substrate 1 is gold, and the electrical conductivity is 4.56×10 7 S / m.

[0146] The side length of the metal substrate 1 is equal to the side length of the dielectric layer 2, which is p, 55µm, and the thickness is t Au It is 0.8µm, which is much larger than the skin depth of the incident electromagnetic wave, ensuring that the transmittance of the absorber is 0.

[0147] Example 6

[0148] A method for preparing a dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber specifically comprises the following steps:

[0149] Step 1, preparation of a metal substrate 1;

[0150] Step 1 is as follows:

[0151] Step 1.1, substrate cleaning:

[0152] High-purity silicon was used as the substrate and ultrasonically cleaned with acetone, ethanol, and deionized water for 10 minutes to remove surface contaminants. After drying with nitrogen, the substrate was dried in an oven at 110°C for 30 minutes.

[0153] Step 1.2, metal film deposition:

[0154] Gold thin films were deposited using electron beam evaporation;

[0155] Step 1.3, annealing treatment:

[0156] Annealing at 300 °C for 30 min to improve the crystallization quality and conductivity of the gold film;

[0157] Step 2, deposition of dielectric layer 2;

[0158] Step 2 is as follows:

[0159] Step 2.1, Topas film preparation:

[0160] Topas thin films were deposited on metal substrates using chemical vapor deposition;

[0161] Step 2.2, curing treatment:

[0162] Curing at 150°C for 1 hour to ensure film density and stable dielectric properties;

[0163] Step 3, preparation of a cross-shaped vanadium dioxide 3-2 layer;

[0164] Step 3 is as follows:

[0165] Step 3.1, VO2 thin film deposition:

[0166] Pulsed laser deposition is used to grow VO2 thin films on the dielectric layer.

[0167] Step 3.2, photolithography patterning:

[0168] The cross-shaped structure was defined using UV lithography.

[0169] Step 4: Transferring and patterning the graphene layer 3-1 with the hollow cross.

[0170] Step 4 is as follows:

[0171] Step 4.1, graphene growth and transfer:

[0172] A single layer of graphene is grown on the copper foil by chemical vapor deposition and transferred to the surface of the dielectric layer 2 by a wet method;

[0173] Step 4.2, graphene patterning:

[0174] The hollow cross structure was defined using electron beam lithography.

[0175] Example 7

[0176] A method for preparing a dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber specifically comprises the following steps:

[0177] Step 1, preparation of a metal substrate 1;

[0178] Step 1 is as follows:

[0179] Step 1.1, substrate cleaning:

[0180] High-purity silicon was used as the substrate and ultrasonically cleaned with acetone, ethanol, and deionized water for 15 minutes to remove surface contaminants. After drying with nitrogen, the substrate was dried in an oven at 120°C for 40 minutes.

[0181] Step 1.2, metal film deposition:

[0182] Gold thin films were deposited using electron beam evaporation;

[0183] Step 1.3, annealing treatment:

[0184] Annealing at 300°C~350°C for 40 min to improve the crystallization quality and conductivity of the gold film;

[0185] Step 2, deposition of dielectric layer 2;

[0186] Step 2 is as follows:

[0187] Step 2.1, Topas film preparation:

[0188] Topas thin films were deposited on metal substrates using chemical vapor deposition;

[0189] Step 2.2, curing treatment:

[0190] Curing at 160°C for 2h to ensure film density and stable dielectric properties;

[0191] Step 3, preparation of a cross-shaped vanadium dioxide 3-2 layer;

[0192] Step 3 is as follows:

[0193] Step 3.1, VO2 thin film deposition:

[0194] Pulsed laser deposition is used to grow VO2 thin films on the dielectric layer.

[0195] Step 3.2, photolithography patterning:

[0196] The cross-shaped structure was defined using UV lithography.

[0197] Step 4: Transferring and patterning the graphene layer 3-1 with the hollow cross.

[0198] Step 4 is as follows:

[0199] Step 4.1, graphene growth and transfer:

[0200] A single layer of graphene is grown on the copper foil by chemical vapor deposition and transferred to the surface of the dielectric layer 2 by a wet method;

[0201] Step 4.2, graphene patterning:

[0202] The hollow cross structure was defined using electron beam lithography.

[0203] Example 8

[0204] A method for preparing a dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber specifically comprises the following steps:

[0205] Step 1, preparation of a metal substrate 1;

[0206] Step 1 is as follows:

[0207] Step 1.1, substrate cleaning:

[0208] High-purity silicon was used as the substrate and ultrasonically cleaned with acetone, ethanol, and deionized water for 12 minutes to remove surface contaminants. After drying with nitrogen, the substrate was dried in an oven at 105°C for 35 minutes.

[0209] Step 1.2, metal film deposition:

[0210] Gold thin films were deposited using electron beam evaporation;

[0211] Step 1.3, annealing treatment:

[0212] Annealing at 300°C~350°C for 35 min to improve the crystallization quality and conductivity of the gold film;

[0213] Step 2, deposition of dielectric layer 2;

[0214] Step 2 is as follows:

[0215] Step 2.1, Topas film preparation:

[0216] Topas thin films were deposited on metal substrates using chemical vapor deposition;

[0217] Step 2.2, curing treatment:

[0218] Curing at 155°C for 1.5h to ensure film density and stable dielectric properties;

[0219] Step 3, preparation of a cross-shaped vanadium dioxide 3-2 layer;

[0220] Step 3 is as follows:

[0221] Step 3.1, VO2 thin film deposition:

[0222] Pulsed laser deposition is used to grow VO2 thin films on the dielectric layer.

[0223] Step 3.2, photolithography patterning:

[0224] The cross-shaped structure was defined using UV lithography.

[0225] Step 4: Transferring and patterning the graphene layer 3-1 with the hollow cross.

[0226] Step 4 is as follows:

[0227] Step 4.1, graphene growth and transfer:

[0228] A single layer of graphene is grown on the copper foil by chemical vapor deposition and transferred to the surface of the dielectric layer 2 by a wet method;

[0229] Step 4.2, graphene patterning:

[0230] The hollow cross structure was defined using electron beam lithography.

Claims

1. Dual-band / broadband switchable dynamically tunable metamaterial terahertz absorber, characterized by: The invention comprises M*N multilayer terahertz absorption units, wherein the M*N multilayer terahertz absorption units are distributed in an M*N two-dimensional manner, wherein M and N are both positive integers; each multilayer terahertz absorption unit comprises a metal substrate (1), a dielectric layer (2) and a resonant layer (3) arranged in sequence from bottom to top; the dielectric layer (2) and the metal substrate (1) are both square in shape and have equal side lengths; The resonance layer (3) comprises a single-layer graphene layer (3-1) with a hollow cross, wherein a solid cross-shaped vanadium dioxide layer (3-2) is embedded in the hollow of the single-layer graphene layer (3-1); the single-layer graphene layer (3-1) with a hollow cross has a cross-shaped outer shape.

2. The dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber according to claim 1, characterized in that: The thickness t of the single-layer graphene layer (3-1) with a hollow cross g The length of the single-layer graphene layer (3-1) with a hollow cross is equal to the length in the horizontal direction and the length in the vertical direction, and the width in the horizontal direction and the width in the vertical direction are equal; the length l of the single-layer graphene layer (3-1) with a hollow cross is equal to g 34µm-44µm, width w g 8µm-16µm; the thickness of the cross-shaped vanadium dioxide layer (3-2) is t v The cross-shaped vanadium dioxide layer (3-2) has the same length in the horizontal direction and the same length in the vertical direction, and the same width in the horizontal direction and the same width in the vertical direction. The length l of the cross-shaped vanadium dioxide layer (3-2) is v 30µm-38µm, width w v The thickness of vanadium dioxide is 1µm-5µm; when the ambient temperature is lower than 340 K, vanadium dioxide is in the insulating phase, and the electrical conductivity at this time is 200S / m. When the ambient temperature is higher than 340 K, vanadium dioxide is in the metallic phase, and the electrical conductivity at this time is 200000S / m.

3. The dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber according to claim 1, characterized in that: The material of the dielectric layer (2) is Topas, and the relative dielectric constant is 2.

35.

4. The dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber according to claim 3, characterized in that: The side length p of the dielectric layer (2) is 45µm-55µm, and the thickness h is 32µm-36µm.

5. The dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber according to claim 1, characterized in that: The metal substrate (1) is made of gold, and its electrical conductivity is 4.56×10 7 S / m.

6. The dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber according to claim 1, characterized in that: The side length of the metal substrate (1) is equal to the side length of the dielectric layer (2), which is 45µm-55µm, and the thickness is t Au 0.2µm-0.8µm.

7. A method for preparing a dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber, for preparing the dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber according to any one of claims 1 to 6, characterized in that: The specific steps include: Step 1, preparation of a metal substrate (1); Step 2, deposition of dielectric layer (2); Step 3, preparation of a cross-shaped vanadium dioxide layer (3-2); Step 4: Transfer and patterning of a single graphene layer (3-1) with a hollow cross.

8. The method for preparing the dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber according to claim 7, characterized in that: Step 1 is as follows: Step 1.1, substrate cleaning: High-purity silicon was used as the substrate and ultrasonically cleaned with acetone, ethanol, and deionized water for 10-15 minutes to remove surface contaminants. After drying with nitrogen, the substrate was dried in an oven at 110-120°C for 30-40 minutes. Step 1.2, metal film deposition: Gold thin films were deposited using electron beam evaporation; Step 1.3, annealing treatment: Anneal at 300℃~350℃ for 30min-40min; Step 2 is as follows: Step 2.1, Topas film preparation: Topas thin films were deposited on metal substrates using chemical vapor deposition; Step 2.2, curing treatment: Curing at 150℃-160℃ for 1h-2h.

9. The method for preparing the dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber according to claim 7, characterized in that: Step 3 is as follows: Step 3.1, VO2 thin film deposition: Pulsed laser deposition is used to grow VO2 thin films on the dielectric layer; Step 3.2, photolithography patterning: The cross-shaped structure was defined using UV lithography.

10. The method for preparing a dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber according to claim 7, characterized in that: Step 4 is as follows: Step 4.1, graphene growth and transfer: A single layer of graphene is grown on a copper foil by chemical vapor deposition and transferred to the surface of a dielectric layer (2) by a wet method; Step 4.2, graphene patterning: The hollow cross structure was defined using electron beam lithography.

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