Dual-frequency / broadband switchable dynamic tuning metamaterial terahertz absorber and preparation method thereof

Abstract

The invention discloses a dual-frequency / broadband switchable dynamic tuning metamaterial terahertz absorber which comprises M * N terahertz absorption units of a multi-layer structure, the M * N terahertz absorption units of the multi-layer structure are distributed in an M * N two-dimensional mode, and M and N are positive integers. Each terahertz absorption unit with the multi-layer structure comprises a metal substrate, a dielectric layer and a resonance layer which are sequentially arranged from bottom to top; the dielectric layer and the metal substrate are square and have the same side length; the resonance layer comprises a single-layer graphene layer with a hollow cross, and a solid cross-shaped vanadium dioxide layer is embedded in the hollow part of the single-layer graphene layer with the hollow cross; and the appearance of the single-layer graphene layer with the hollow cross is cross-shaped. The absorber can be dynamically tuned, has the characteristic of polarization insensitivity, and can keep stable absorption in an incidence angle range of 0-60 degrees. The invention further discloses a preparation method of the dual-frequency / broadband switchable dynamic tuning metamaterial terahertz absorber.

Description

Technical Field

[0001] The present invention relates to the technical field of terahertz waves, and in particular to a dual-frequency / broadband switchable dynamic tuning metamaterial terahertz absorber, and also to a preparation method of the dual-frequency / broadband switchable dynamic tuning metamaterial terahertz absorber. Background Art

[0002] Terahertz (THz) waves generally refer to electromagnetic waves with a frequency of 0.1 to 10 THz. Due to its 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 a basic functional device for THz applications, THz absorbers are widely used in detectors, spectrum imaging, stealth and other fields.

[0003] The terahertz absorber based on metamaterials is a device that can achieve efficient absorption of incident terahertz waves. The main principle is to use different loss mechanisms to convert terahertz waves into heat energy or other forms of energy, and finally achieve the effect of absorbing terahertz waves. Among various absorbers, absorbers based on metamaterial structures have received extensive 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. The current absorber adopts a stacked multi-layer structure or uses 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, it is urgent to develop a terahertz dual-frequency / broadband switchable absorber with simple structure, convenient manufacture, flexible and tunable 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 / wideband 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 tuned metamaterial terahertz absorber, comprising M*N multilayer terahertz absorption units, wherein the M*N multilayer terahertz absorption units are distributed in M*N two dimensions, wherein 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 and have equal side lengths;

[0007] The resonance layer comprises 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; and 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 of a single graphene layer with a hollow cross is t g 0.34nm; the length of the single-layer graphene layer 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 of the single-layer graphene layer with a hollow cross is l g 34μm-44μm, width w g 8μm-16μm; cross-shaped vanadium dioxide layer (VO 2 ) thickness t v The cross-shaped vanadium dioxide layer has an equal length in the horizontal direction and a same width in the vertical direction; the cross-shaped vanadium dioxide layer (VO 2 ) length l v 30μm-38μm, width w v It is 1μm-5μm; when the ambient temperature is lower than 340K, vanadium dioxide is in the insulating phase, and the electrical conductivity is 200S / m at this time. When the ambient temperature is higher than 340K, vanadium dioxide is in the metallic phase, and the electrical conductivity 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 45 μm-55 μm, and the thickness h is 32 μm-36 μm.

[0012] The material of the metal substrate is gold, and the conductivity is 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 tuned 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 a graphene layer with a hollow cross.

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

[0020] Step 1 is as follows:

[0021] Step 1.1, substrate cleaning:

[0022] Select high-purity silicon as the substrate, and use acetone, ethanol and deionized water for ultrasonic cleaning for 10-15 minutes in sequence to remove surface pollutants; after drying with nitrogen, dry it in an oven at 110-120 degrees Celsius for 30-40 minutes;

[0023] Step 1.2, metal film deposition:

[0024] The gold thin film was deposited by electron beam evaporation;

[0025] Step 1.3: Annealing treatment:

[0026] Annealing at 300℃~350℃ for 30min-40min to improve the crystal 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℃ for 1h-2h to ensure film density and stable dielectric properties;

[0032] Step 3 is as follows:

[0033] Step 3.1: VO 2 Thin film deposition:

[0034] Growth of VO on dielectric layer by pulsed laser deposition 2 film.

[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 is grown on a copper foil by chemical vapor deposition and then transferred to the surface of a dielectric layer by 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-frequency / broadband switchable dynamically tuned metamaterial terahertz absorber of the present invention has an absorption peak of 99.4% at 0.807THz and 98.6% at 2.166THz when vanadium dioxide is in the insulating phase and the chemical potential of graphene is 0.7eV, showing dual-frequency absorption. When vanadium dioxide is in the metallic phase and the chemical potential of graphene is 0.4eV, the absorber has an absorption rate of more than 90% in the range of 0.993THz-1.872THz, showing broadband absorption with a bandwidth of 0.879THz, realizing the switching between dual-frequency 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 tuned metamaterial terahertz absorber of the present invention 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a schematic diagram of the periodic structure of the dual-frequency / broadband switchable dynamically tuned metamaterial terahertz absorber provided in Example 1 of the present invention;

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

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

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

[0053] Figure 8 This is an 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] Fig. 9 This is the electric field distribution diagram at 1.135 THz under broadband mode TE polarization of the dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber provided in Example 1 of the present invention;

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

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

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

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

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

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

[0061] Fig.16The 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] Fig.17 The effect of the incident angle on the absorption spectrum of the dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorption broadband mode under TE polarization provided by Example 1 of the present invention;

[0063] Fig.18 This is the effect of the incident angle on the absorption spectrum under broadband mode TM polarization of the dual-frequency / broadband switchable dynamically tuned metamaterial terahertz absorber 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 is described in detail below with reference to the accompanying drawings and specific embodiments.

[0066] The present invention provides a dual-frequency / broadband switchable dynamically tuned 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, wherein 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, in which a solid cross-shaped vanadium dioxide layer 3-2 is embedded in the hollow part of the single-layer graphene layer 3-1 with a hollow cross; the single-layer graphene layer 3-1 with a hollow cross has a cross shape.

[0068] 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 in the horizontal direction and the vertical direction are equal, and the width in the horizontal direction and 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 8 μm-16 μm; the thickness t of the cross-shaped vanadium dioxide layer 3-2 v 0.05μm-0.08μm; the length of the cross-shaped vanadium dioxide layer 3-2 in the horizontal direction and the length in the vertical direction are equal, and the width in the horizontal direction and the width in the vertical direction are equal; the length l of the cross-shaped vanadium dioxide layer 3-2 v30μm-38μm, width w v It is 1μm-5μm; when the ambient temperature is lower than 340K, vanadium dioxide is in the insulating phase, and the electrical conductivity is 200S / m at this time. When the ambient temperature is higher than 340K, vanadium dioxide is in the metallic phase, and the electrical conductivity is 200000S / m.

[0069] The material of the dielectric layer 2 is Topas, and the relative dielectric constant is 2.35.

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

[0071] The material of the metal substrate 1 is gold, and the 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 45 μm-55 μm, 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 tuned metamaterial terahertz absorber, which specifically comprises the following steps:

[0074] Step 1, preparing a metal substrate 1;

[0075] Step 1 is as follows:

[0076] Step 1.1, substrate cleaning:

[0077] Select high-purity silicon as the substrate, and use acetone, ethanol and deionized water for ultrasonic cleaning for 10-15 minutes in sequence to remove surface pollutants; after drying with nitrogen, dry it in an oven at 110-120 degrees Celsius for 30-40 minutes;

[0078] Step 1.2, metal film deposition:

[0079] The gold thin film was deposited by electron beam evaporation;

[0080] Step 1.3: Annealing treatment:

[0081] Annealing at 300℃~350℃ for 30min-40min to improve the crystal 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: VO 2 Thin film deposition:

[0091] Growth of VO on dielectric layer by pulsed laser deposition 2 film.

[0092] Step 3.2, photolithography patterning:

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

[0094] Step 4: Transfer and patterning of 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 is 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] Embodiment 1:

[0101] like Figure 1-Figure 3 As shown, the dual-frequency / broadband switchable dynamically tuned metamaterial terahertz absorber includes 3*3 multi-layer terahertz absorption units. The number of multi-layer terahertz absorption units does not affect the overall absorption performance. Each multi-layer 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;

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

[0103] The thickness t of the single-layer graphene layer 3-1 with a hollow cross g 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 12 μm; the thickness of the cross-shaped vanadium dioxide layer 3-2 is t v is 0.05 μm; the length l of the cross-shaped vanadium dioxide layer 3-2 v 34μm, width w v 4μm; when the ambient temperature is lower than 340K, vanadium dioxide is in the insulating phase, and the electrical conductivity is 200S / m at this time. When the ambient temperature is higher than 340K, vanadium dioxide is in the metallic phase, and the electrical conductivity is 200000S / m.

[0104] The material of the dielectric layer 2 is Topas, and the relative dielectric constant is 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 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, 50 μm, 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 is 200S / m) and the chemical potential of graphene is 0.7eV, the absorption peak is 99.4% at 0.807THz and 98.6% at 2.166THz, showing dual-band absorption. When vanadium dioxide is in the metallic phase (conductivity is 200000S / m) and the chemical potential of graphene is 0.4eV, the absorber has an absorption rate of more than 90% in the range of 0.993-1.872THz, showing broadband absorption with a bandwidth of 0.879THz, realizing the 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 blue solid line is the real part of the impedance and the red dashed line is the imaginary part of the impedance. Figure 5 In the figure, when the absorber works in dual-frequency mode, the real part of the impedance approaches 1 at 0.807THz and 2.166THz, 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 similar to 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 These are the electric field distribution diagrams at the center frequency of the low-frequency absorption peak of 0.807THz and the center frequency of the high-frequency absorption peak of 2.166THz in the dual-frequency mode of the absorber. It can be seen that in the dual-frequency mode, the electric field is distributed on the upper and lower outer edges of the hollow graphene cross and on both sides of the upper and lower edges inside the cross arm. The electric field at the center frequency of the low-frequency absorption peak is mainly distributed on the upper and lower outer edges, while the electric field of the high-frequency absorption peak is mainly distributed on both sides of the upper and lower edges inside the cross arm. Therefore, the low-frequency absorption peak mainly comes from the electric dipole resonance. At the center frequency of the high-frequency absorption peak, vanadium dioxide in the insulating phase acts as a medium, causing electric field coupling between the upper and lower edges inside the graphene hollow cross cross arm, thereby exciting the absorption peak. Fig. 9 and Fig.10 These are the electric field distribution diagrams at the two vertices of the absorption peak in the broadband mode of the absorber at 1.135THz and 1.650THz. 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 inner edges of the hollow graphene cross. Moreover, the electric fields at the two frequencies are distributed on both sides of the upper and lower outer edges of the hollow graphene cross, indicating that the entire broadband absorption comes from the electric dipole resonance. In summary, whether it is a dual-frequency mode or a 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-frequency 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] Fig.11 The changes in the absorption spectrum of the dual-frequency mode under different graphene chemical potentials are shown. It can be seen that 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, and the center frequencies of the two absorption peaks are blue-shifted. When the chemical potential is 0.7 eV, both absorption peaks have a high absorption rate. Fig.12The changes in the absorption spectrum under different graphene chemical potentials in broadband mode are shown. When the graphene chemical potential increases, the left and right vertices of the absorption band are blue-shifted. The absorption of the left vertex first increases and then decreases, while the absorption rate of the right vertex continues to increase. When the chemical potential is 0.4eV, the overall absorption rate and absorption bandwidth of broadband absorption are ideal. In summary, the absorption rate in both modes is affected by the graphene chemical potential, which means that even after all the parameters of the design are finalized, the graphene chemical potential can still be changed to achieve the purpose of dynamically regulating the absorption performance of the absorber, which greatly increases the feasibility of the absorber in practical applications.

[0112] Fig.13 and Fig.14 The absorption spectra of the dual-band and broadband absorption modes are shown as a function of polarization angle. It is not difficult to see that both modes can maintain stable absorption as the polarization angle changes, indicating that the absorption performance of the absorber is not affected by the polarization angle and has polarization-insensitive characteristics, which is due to the central symmetric structure of the design.

[0113] Fig.15 and Fig.16 The influence of the incident angle of electromagnetic waves on the dual-frequency mode absorption spectrum under TE polarization and TM polarization is shown respectively. For both polarizations, the absorber can maintain stable absorption in 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 blue-shifts. After 70°, another absorption peak appears at 1.7THz. For TM polarization, in the incident range of 0-60°, both absorption peaks maintain stable absorption, and the center frequencies of the two absorption peaks do not change.

[0114] After 60°, the absorption rate begins to decrease.

[0115] Fig.17 and Fig.18 The influence of the incident angle of electromagnetic waves on the broadband mode absorption spectrum under TE polarization and TM polarization is shown 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 vertex of the absorption band. After 60°, as the incident angle increases, the partial absorption rate between the two vertices decreases and gradually becomes dual-band absorption. For TM polarization, in the range of 0-40°, the absorption rate and bandwidth remain stable. After 40°, the right vertex redshifts, causing the absorption bandwidth to decrease. Until 60°, the absorber still maintains broadband absorption. After 60°, the absorption rate decreases rapidly. In summary, through the discussion of the influence of the incident angle of electromagnetic waves on the absorption spectra of the two modes under TE and TM polarization, it can be concluded that the two absorption modes of the absorber can maintain efficient and stable absorption in the range of 0-60° electromagnetic wave incident angles, and have the characteristics of wide-angle absorption.

[0116] Example 2

[0117] like Figure 1-Figure 3 As shown, the dual-frequency / broadband switchable dynamically tuned metamaterial terahertz absorber includes 3*3 multi-layer terahertz absorption units. The number of multi-layer terahertz absorption units does not affect the overall absorption performance. Each multi-layer 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;

[0118] The resonance layer 3 includes a single-layer graphene layer 3-1 with a hollow cross, in which a solid cross-shaped vanadium dioxide layer 3-2 is embedded in the hollow part of the single-layer graphene layer 3-1 with a hollow cross; the single-layer graphene layer 3-1 with a hollow cross has a cross shape.

[0119] The thickness t of the single-layer graphene layer 3-1 with a hollow cross g is 0.34 nm; the length l of the single-layer graphene layer 3-1 with a hollow cross g 36μm, width w g The thickness of the cross-shaped vanadium dioxide layer 3-2 is t v is 0.06 μm; the length l of the cross-shaped vanadium dioxide layer 3-2 v 30μm, width w v 1μm; when the ambient temperature is lower than 340K, vanadium dioxide is in the insulating phase, and the electrical conductivity is 200S / m at this time. When the ambient temperature is higher than 340K, vanadium dioxide is in the metallic phase, and the electrical conductivity is 200000S / m.

[0120] The material of the dielectric layer 2 is Topas, and the relative dielectric constant is 2.35.

[0121] The side length p of the dielectric layer 2 is 45 μm, and the thickness h is 32 μm.

[0122] The material of the metal substrate 1 is gold, and the conductivity is 4.56×10 7 S / m.

[0123] The side length of the metal substrate 1 is equal to the side length of the dielectric layer 2, which is p, 45 μm, 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.

[0124] Example 3

[0125] like Figure 1-Figure 3As shown, the dual-frequency / broadband switchable dynamically tuned metamaterial terahertz absorber includes 3*3 multi-layer terahertz absorption units. The number of multi-layer terahertz absorption units does not affect the overall absorption performance. Each multi-layer 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;

[0126] The resonance layer 3 includes a single-layer graphene layer 3-1 with a hollow cross, in which a solid cross-shaped vanadium dioxide layer 3-2 is embedded in the hollow part of the single-layer graphene layer 3-1 with a hollow cross; the single-layer graphene layer 3-1 with a hollow cross has a cross shape.

[0127] The thickness t of the single-layer graphene layer 3-1 with a 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 10 μm; the thickness of the cross-shaped vanadium dioxide layer 3-2 is t v is 0.07 μm; the length l of the cross-shaped vanadium dioxide layer 3-2 v 32μm, width w v 2μm; when the ambient temperature is lower than 340K, vanadium dioxide is in the insulating phase, and the electrical conductivity is 200S / m at this time. When the ambient temperature is higher than 340K, vanadium dioxide is in the metallic phase, and the electrical conductivity is 200000S / m at this time.

[0128] The material of the dielectric layer 2 is Topas, and the relative dielectric constant is 2.35.

[0129] The side length p of the dielectric layer 2 is 47 μm, and the thickness h is 34 μm.

[0130] The material of the metal substrate 1 is gold, and the conductivity is 4.56×10 7 S / m.

[0131] The side length of the metal substrate 1 is equal to the side length of the dielectric layer 2, which is p, 47 μm, 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.

[0132] Example 4

[0133] like Figure 1-Figure 3As shown, the dual-frequency / broadband switchable dynamically tuned metamaterial terahertz absorber includes 3*3 multi-layer terahertz absorption units. The number of multi-layer terahertz absorption units does not affect the overall absorption performance. Each multi-layer 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;

[0134] The resonance layer 3 includes a single-layer graphene layer 3-1 with a hollow cross, in which a solid cross-shaped vanadium dioxide layer 3-2 is embedded in the hollow part of the single-layer graphene layer 3-1 with a hollow cross; the single-layer graphene layer 3-1 with a hollow cross has a cross shape.

[0135] The thickness t of the single-layer graphene layer 3-1 with a hollow cross g is 0.34 nm; the length l of the single-layer graphene layer 3-1 with a hollow cross g is 42μm, width w g is 14 μm; the thickness of the cross-shaped vanadium dioxide layer 3-2 is t v is 0.08 μm; the length l of the cross-shaped vanadium dioxide layer 3-2 v 36μm, width w v 3μm; when the ambient temperature is lower than 340K, vanadium dioxide is in the insulating phase, and the electrical conductivity is 200S / m at this time. When the ambient temperature is higher than 340K, vanadium dioxide is in the metallic phase, and the electrical conductivity is 200000S / m at this time.

[0136] The material of the dielectric layer 2 is Topas, and the relative dielectric constant is 2.35.

[0137] The side length p of the dielectric layer 2 is 52 μm, and the thickness h is 35 μm.

[0138] The material of the metal substrate 1 is gold, and the conductivity is 4.56×10 7 S / m.

[0139] The side length of the metal substrate 1 is equal to the side length of the dielectric layer 2, which is p, 52 μm, 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.

[0140] Example 5

[0141] like Figure 1-Figure 3As shown, the dual-frequency / broadband switchable dynamically tuned metamaterial terahertz absorber includes 3*3 multi-layer terahertz absorption units. The number of multi-layer terahertz absorption units does not affect the overall absorption performance. Each multi-layer 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;

[0142] The resonance layer 3 includes a single-layer graphene layer 3-1 with a hollow cross, in which a solid cross-shaped vanadium dioxide layer 3-2 is embedded in the hollow part of the single-layer graphene layer 3-1 with a hollow cross; the single-layer graphene layer 3-1 with a hollow cross has a cross shape.

[0143] The thickness t of the single-layer graphene layer 3-1 with a 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 16 μm; the thickness of the cross-shaped vanadium dioxide layer 3-2 is t v is 0.05 μm; the length l of the cross-shaped vanadium dioxide layer 3-2 v 38μm, width w v 5μm; when the ambient temperature is lower than 340K, vanadium dioxide is in the insulating phase, and the electrical conductivity is 200S / m at this time. When the ambient temperature is higher than 340K, vanadium dioxide is in the metallic phase, and the electrical conductivity is 200000S / m at this time.

[0144] The material of the dielectric layer 2 is Topas, and the relative dielectric constant is 2.35.

[0145] The side length p of the dielectric layer 2 is 55 μm, and the thickness h is 36 μm.

[0146] The material of the metal substrate 1 is gold, and the conductivity is 4.56×10 7 S / m.

[0147] The side length of the metal substrate 1 is equal to the side length of the dielectric layer 2, which is p, 55 μm, 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.

[0148] Example 6

[0149] The preparation method of the dual-frequency / broadband switchable dynamically tuned metamaterial terahertz absorber specifically comprises the following steps:

[0150] Step 1, preparing a metal substrate 1;

[0151] Step 1 is as follows:

[0152] Step 1.1, substrate cleaning:

[0153] High-purity silicon was selected as the substrate, and ultrasonic cleaning was performed with acetone, ethanol and deionized water for 10 minutes in sequence to remove surface pollutants; after drying with nitrogen, it was dried in an oven at 110°C for 30 minutes;

[0154] Step 1.2, metal film deposition:

[0155] The gold thin film was deposited by electron beam evaporation;

[0156] Step 1.3: Annealing treatment:

[0157] Annealing at 300 °C for 30 min to improve the crystal quality and conductivity of the gold film;

[0158] Step 2, deposition of dielectric layer 2;

[0159] Step 2 is as follows:

[0160] Step 2.1, Topas film preparation:

[0161] Topas thin films were deposited on metal substrates using chemical vapor deposition;

[0162] Step 2.2, curing treatment:

[0163] Curing at 150°C for 1h to ensure film density and stable dielectric properties;

[0164] Step 3, preparation of a cross-shaped vanadium dioxide 3-2 layer;

[0165] Step 3 is as follows:

[0166] Step 3.1: VO 2 Thin film deposition:

[0167] Growth of VO on dielectric layer by pulsed laser deposition 2 film.

[0168] Step 3.2, photolithography patterning:

[0169] The cross-shaped structure was defined using UV lithography.

[0170] Step 4: Transfer and patterning of the graphene layer 3 - 1 with the hollow cross.

[0171] Step 4 is as follows:

[0172] Step 4.1, graphene growth and transfer:

[0173] A single layer of graphene is grown on the copper foil by chemical vapor deposition, and is transferred to the surface of the dielectric layer 2 by a wet method;

[0174] Step 4.2, graphene patterning:

[0175] The hollow cross structure was defined using electron beam lithography.

[0176] Example 7

[0177] The preparation method of the dual-frequency / broadband switchable dynamically tuned metamaterial terahertz absorber specifically comprises the following steps:

[0178] Step 1, preparing a metal substrate 1;

[0179] Step 1 is as follows:

[0180] Step 1.1, substrate cleaning:

[0181] High-purity silicon was selected as the substrate, and ultrasonic cleaning was performed with acetone, ethanol and deionized water for 15 minutes in sequence to remove surface pollutants; after drying with nitrogen, it was dried in an oven at 120°C for 40 minutes;

[0182] Step 1.2, metal film deposition:

[0183] The gold thin film was deposited by electron beam evaporation;

[0184] Step 1.3: Annealing treatment:

[0185] Annealing at 300°C to 350°C for 40 min to improve the crystal quality and conductivity of the gold film;

[0186] Step 2, deposition of dielectric layer 2;

[0187] Step 2 is as follows:

[0188] Step 2.1, Topas film preparation:

[0189] Topas thin films were deposited on metal substrates using chemical vapor deposition;

[0190] Step 2.2, curing treatment:

[0191] Curing at 160°C for 2h ensures film density and stable dielectric properties;

[0192] Step 3, preparation of a cross-shaped vanadium dioxide 3-2 layer;

[0193] Step 3 is as follows:

[0194] Step 3.1: VO 2 Thin film deposition:

[0195] Growth of VO on dielectric layer by pulsed laser deposition 2 film.

[0196] Step 3.2, photolithography patterning:

[0197] The cross-shaped structure was defined using UV lithography.

[0198] Step 4: Transfer and patterning of the graphene layer 3 - 1 with the hollow cross.

[0199] Step 4 is as follows:

[0200] Step 4.1, graphene growth and transfer:

[0201] A single layer of graphene is grown on the copper foil by chemical vapor deposition, and is transferred to the surface of the dielectric layer 2 by a wet method;

[0202] Step 4.2, graphene patterning:

[0203] The hollow cross structure was defined using electron beam lithography.

[0204] Example 8

[0205] The preparation method of the dual-frequency / broadband switchable dynamically tuned metamaterial terahertz absorber specifically comprises the following steps:

[0206] Step 1, preparing a metal substrate 1;

[0207] Step 1 is as follows:

[0208] Step 1.1, substrate cleaning:

[0209] High-purity silicon was selected as the substrate, and ultrasonic cleaning was performed with acetone, ethanol and deionized water for 12 minutes in sequence to remove surface pollutants; after drying with nitrogen, it was dried in an oven at 105°C for 35 minutes;

[0210] Step 1.2, metal film deposition:

[0211] The gold thin film was deposited by electron beam evaporation;

[0212] Step 1.3: Annealing treatment:

[0213] Annealing at 300°C to 350°C for 35 min to improve the crystal quality and conductivity of the gold film;

[0214] Step 2, deposition of dielectric layer 2;

[0215] Step 2 is as follows:

[0216] Step 2.1, Topas film preparation:

[0217] Topas thin films were deposited on metal substrates using chemical vapor deposition;

[0218] Step 2.2, curing treatment:

[0219] Curing at 155°C for 1.5h ensures film density and stable dielectric properties;

[0220] Step 3, preparation of a cross-shaped vanadium dioxide 3-2 layer;

[0221] Step 3 is as follows:

[0222] Step 3.1: VO 2 Thin film deposition:

[0223] Growth of VO on dielectric layer by pulsed laser deposition 2 film.

[0224] Step 3.2, photolithography patterning:

[0225] The cross-shaped structure was defined using UV lithography.

[0226] Step 4: Transfer and patterning of the graphene layer 3 - 1 with the hollow cross.

[0227] Step 4 is as follows:

[0228] Step 4.1, graphene growth and transfer:

[0229] A single layer of graphene is grown on the copper foil by chemical vapor deposition, and is transferred to the surface of the dielectric layer 2 by a wet method;

[0230] Step 4.2, graphene patterning:

[0231] The hollow cross structure was defined using electron beam lithography.

Claims

1. Dual-frequency / broadband switchable dynamically tunable metamaterial terahertz absorber, characterized in that: The invention comprises M*N multilayer terahertz absorption units, wherein the M*N multilayer terahertz absorption units are distributed in M*N two dimensions, wherein M and N are both positive integers; each multilayer terahertz absorption unit comprises a metal substrate (1), a dielectric layer (2) and a resonance 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, and a solid cross-shaped vanadium dioxide layer (3-2) is embedded in the hollow of the single-layer graphene layer (3-1) with a hollow cross; The single-layer graphene layer (3-1) with a hollow cross has a cross shape.

2. The dual-frequency / broadband switchable dynamically tuned 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 is g The length of the single-layer graphene layer 3-1 with a hollow cross in the horizontal direction and the vertical direction are equal, and the width in the horizontal direction and the vertical direction are equal; the length of the single-layer graphene layer (3-1) with a hollow cross is l g 34μm-44μm, width w g 8 μm-16 μm; the thickness of the cross-shaped vanadium dioxide layer (3-2) is t v The cross-shaped vanadium dioxide layer (3-2) has an equal length in the horizontal direction and a equal length in the vertical direction, and an equal width in the horizontal direction and a equal width in the vertical direction; the length l of the cross-shaped vanadium dioxide layer (3-2) is v 30μm-38μm, width w v It is 1μm-5μm; when the ambient temperature is lower than 340K, vanadium dioxide is in the insulating phase, and the electrical conductivity is 200S / m at this time. When the ambient temperature is higher than 340K, vanadium dioxide is in the metallic phase, and the electrical conductivity 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 its 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 45 μm-55 μm, and the thickness h is 32 μm-36 μm.

5. The dual-frequency / broadband switchable dynamically tuned 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 45 μm-55 μm, and the thickness is t Au 0.2μm-0.8μm.

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

8. The method for preparing the dual-frequency / broadband switchable dynamically tuned metamaterial terahertz absorber according to claim 7, characterized in that: Step 1 is as follows: Step 1.1, substrate cleaning: Select high-purity silicon as the substrate, and use acetone, ethanol and deionized water for ultrasonic cleaning for 10-15 minutes in sequence to remove surface pollutants; after drying with nitrogen, dry it in an oven at 110-120 degrees Celsius 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°C-160°C for 1h-2h.

9. The method for preparing the dual-frequency / broadband switchable dynamically tuned 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 the dual-frequency / broadband switchable dynamically tuned 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 is 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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