CN112490681A - Three-dimensional paper-cut metamaterial adjustable wave absorber and design method thereof - Google Patents

Abstract

The invention belongs to the technical field of metamaterial electromagnetic regulation, in particular to a three-dimensional kirigami metamaterial adjustable wave absorber and a design method thereof. The kirigami metamaterial adjustable wave absorber of the present invention is composed of M*N metamaterial units with periodic extension; the metamaterial unit is a tetrahedron formed by folding and splicing two strips, and the four faces are the same, and each face can pass through The folding angle β is regulated; each surface is composed of a three-layer structure, of which the middle layer is PET, the upper and lower sides of the PET are ITO, and the ITO layer is a completely symmetrical double-opening resonant ring. The kirigami metamaterial adjustable wave absorber of the present invention can realize the mechanical regulation of the electromagnetic wave reflection amplitude (absorption amplitude) under TE polarization and the mechanical regulation of the reflected electromagnetic wave resonance frequency (absorption frequency band) under TM polarization by changing the folding angle β , when β =45°, the excellent function of fully polarized large-angle wide-band wave absorption can be realized; the invention has the advantages of high flexibility and high efficiency.

Description

Three-dimensional kirigami metamaterial tunable absorber and its design method

technical field

The invention belongs to the technical field of electromagnetic regulation of metamaterials, and in particular relates to an adjustable metamaterial wave absorber and a design method thereof.

Background technique

Metamaterials refer to the idea of simulating natural atoms and molecules to constitute matter, and adopting subwavelength units according to the electromagnetic theory to form periodic or quasi-periodic structures in a certain arrangement. Because metamaterials have some physical properties that natural materials do not have, they have been one of the hotspots of research by scientists at home and abroad in recent years. The emergence of metamaterials has turned people's dream of radar stealth into reality, and the development of perfect metamaterial absorbers is also very rapid, with bright application prospects. Nonetheless, for the two major problems of full-polarization wide-angle broadband absorption and tunability in existing reports, they cannot be well solved, which greatly hinders practical applications. Full-polarization large-angle broadband absorption is very challenging. The main reason is that when the oblique incident angle of electromagnetic waves is particularly large, the structure of metamaterials is equivalent to asymmetrical, which cannot guarantee full-polarization absorption. Guaranteed good absorption in one polarization. The second problem of regulation is also very difficult. The tunable metamaterials reported so far are basically based on electronic components. This method is troublesome to manufacture and is very difficult for the process; 3D printing technology, by printing different molds, has a high cost and is not adjustable in nature. Therefore, how to solve the problem of fully polarized large-angle broadband absorption and tunability is the key to the designed metamaterial tunable absorber.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a metamaterial wave absorber and a design method thereof which can realize full polarization, wide angle, wide frequency, adjustable amplitude and resonance frequency under the excitation of linear polarized wave.

The kirigami metamaterial adjustable wave absorber provided by the present invention is based on the multi-dipole coupling theory and the kirigami folding structure, and is specifically composed of M*N metamaterial units with the same structural parameters that are periodically extended at equal intervals in space The metamaterial unit is a three-dimensional structure, and is mainly a tetrahedron formed by folding and splicing two strips cut from a two-dimensional metasurface, and the four faces of the tetrahedron are identical; wherein, each face (two-dimensional metasurface) ) is a three-layer structure, and the middle layer is polyethylene terephthalate (PET); attached to the upper and lower sides of PET is a completely symmetrical rectangular double-opening resonator ring structure, and its material is ITO; mark two strips The folding angle is β, the structural parameters of the double-slit resonator ring structure are: the length and width of the outer split ring are m and n respectively, the slit width of the two split rings is w ₁ , the width of the split ring is w ₂ , and the width of the opening is w 1 . is g.

The metamaterial unit is a three-dimensional structure, and its period in the horizontal plane is p=2*m*sinβ;

Among them, the metamaterial unit is divided into three modes (that is, the splicing mode of two folded strips), as follows:

Mode 1: It is a "well"-shaped structure formed by oppositely splicing two folded strips; the period in the x-axis direction is 2*m*cosβ, and the period in the y-axis direction is 2*m*sinβ.

Mode 2: Compared with Mode 1, the two opposite strips are separated by a certain distance; the period in the x-axis direction is 2*m*cosβ, and the period in the y-axis direction is 2*m*sinβ+k (k= 2).

Mode 3: It is equivalent to folding the strip structure of Mode 1 by 90 degrees, the adjacent cells are connected by the midpoint of the boundary edge, and the two adjacent strip structures are placed opposite each other with a difference of half a period; the period in the x-axis direction is 2 *n, the period in the y-axis direction is 2*m*cosβ.

The kirigami metamaterial adjustable wave absorber provided by the present invention, wherein the three different structural modes of the metamaterial unit can realize three functions of modulating electromagnetic waves under the excitation of linear polarized waves and different folding angles β:

Function 1: When the folding angle β is changed, the electromagnetic wave reflection amplitude can be mechanically controlled (f ₁ ) under TE polarization (the electric field is along the y-axis direction);

Function 2: When the folding angle β is changed, the mechanical regulation of the resonant frequency of the reflected electromagnetic wave (f ₂ , f ₃ ) can be realized under TM polarization (the electric field is along the x-axis direction);

The third function, when the folding angle β=45°, can be used as a broadband tunable absorber (f ₀ ).

f ₀ is the working frequency band of the broadband absorber, f ₁ is the working frequency band of the reflection amplitude regulation, f ₂ and f ₃ . The working frequency band of resonance frequency regulation.

Among them, the folding angle β is mainly regulated by the action of external mechanical force, thereby modulating the electromagnetic wave.

As shown in Figure 2, each face (two-dimensional metasurface) of the metamaterial unit is a three-layer structure, which is composed of three layers of media ITO, PET, and ITO, such as mode 1, its four faces are exactly the same, each Each surface is composed of three layers of dielectric ITO, PET, and ITO, wherein, the ITO layer is a double split resonant ring structure.

As shown in Fig. 3, when excited in mode 1 (β=45°), it can be seen that at F=4.75 GHz, the four surface currents respectively form a circular current, each forming a magnetic dipole, and the two opposite surfaces The magnetic dipole on can be understood as longitudinal coupling in the same direction, which can be approximately understood as the proximity of N and S poles, which can make the system more stable, so that the resonance frequency is at a low frequency. When F=13.57GHz, the current flow direction of the four surfaces can be seen, each forms an electric dipole, and the electric dipoles on the two opposite surfaces are laterally coupled in the same direction, which can be approximately understood as two in the same direction The placed current lines will repel each other, causing the system to require more restoring force, so the resonant frequency is at high frequencies. By changing the folding angle β, the distance between the two dipoles can be changed, and the reflection amplitude and resonance frequency of the electromagnetic wave can be adjusted. The principle of Mode 2 is similar to Mode 1. Mode 3, as shown in Fig. 4, the surface current distribution at the next resonance point of TM polarization can be seen, one magnetic dipole is formed on each surface, and the z-axis component p of the magnetic dipole on the two surfaces _z = pcosβ is equal in magnitude and opposite in direction, which can be approximated as reverse lateral coupling; its component along the _y -axis, py = psinβ, can be approximated as longitudinal coupling in the same direction; when the folding angle β increases, the center point of the two faces The distance between l=mcosβ will decrease, so the interaction between the two dipoles will increase, and then the resonance frequency of the electromagnetic wave can be regulated. Due to the change of the period length, the reflection amplitude can then be regulated.

According to the requirements of the three-function integrated metamaterial tunable absorber, the present invention optimizes the design of the metamaterial unit structure, and the specific steps are as follows:

The first step is to construct the unit structure according to the basic theory of multi-dipole coupling

Both electric and magnetic polypoles can radiate energy outward. In general, the interaction between two spatially placed dipoles can be divided into lateral coupling and longitudinal coupling, as shown in Figure 8. When two dipoles are laterally coupled in the same direction, the restoring force of the system increases and the resonant frequency is high; when two dipoles are laterally coupled in opposite directions, the system is relatively stable and the resonance frequency is low. However, when the two dipoles are longitudinally coupled, the situation is exactly the opposite. When longitudinally coupled in the same direction, the system becomes more stable and the resonant frequency is lower; when the reverse longitudinal coupling is performed, the restoring force increases and the resonance frequency is relatively high. According to this principle, the three-dimensional kirigami metamaterial unit structure is designed. By changing the folding angle β, the interaction between the dipoles can be changed, so as to achieve the purpose of regulation.

In mode 1, to design the unit structure, first design an outer ring structure, as shown in Figure 5(a), the -10dB bandwidth is very narrow, and the effect is not very good; then design a double ring structure, as shown in Figure 5(b) ), the -10dB bandwidth is significantly improved, but it is still not ideal at low frequencies; then a double split resonator structure is designed, and the simulation results are shown in Figure 5(c). -10dB or less. Then the structural parameters are optimized, as shown in Figure 6, the simulation results under each parameter can be obtained through simulation, and after the parameters are finally optimized, m=16mm, n=12mm, w ₂ =2.3mm, w ₁ =g =0.3mm; wherein, the thickness of PET is 0.1mm, and the resistance value of ITO is 100Ω/sq.

The second step is to construct three paper-cut patterns

According to the first step, three paper-cut modes are designed as shown in Figure 7: Mode 1: Two folded strips are spliced to form a "well"-shaped structure; Mode 2 (similar to Mode 1): Two folded Good strip structures are placed opposite each other (there is a certain distance between the two strip structures); Mode 3: It is equivalent to turning the strip structure of Mode 1 90 degrees, and adjacent units are connected by the midpoint of the boundary edge, that is, adjacent The two stripe structures are staggered with a difference of half a period.

According to the constructed three models, the multi-dipole coupling theory is applied to analyze the regulation mechanism as follows:

As shown in Figure 8, two spatially placed dipoles (electric dipoles or magnetic dipoles, electric dipoles are shown in the figure) interact, and the interaction energy between them is:

是p₁指向p₂的单位矢量，当两个偶极子为单纯的纵向耦合或者横向耦合时，可以简化为：in,

is the unit vector of p ₁ pointing to p _2. When the two dipoles are purely longitudinally or laterally coupled, they can be simplified as:

Among them, γ=+1, is the interaction coefficient, when two dipoles are coupled laterally, γ=-2, when two dipoles are coupled longitudinally, γ=+1, p ₁ and p ₂ are two dipoles The magnitude of the moment. For example, when two electric dipoles interact, the two oppositely placed dipoles will attract each other under lateral coupling, which will reduce the restoring force of the system, making the system stable and the resonant frequency relatively low; the opposite Yes, two dipoles placed in the same direction will repel each other, so that the restoring force of the system increases and the resonant frequency is relatively high. The situation of longitudinal coupling and lateral coupling is just the opposite. Two electric dipoles placed in the same direction, the positive and negative charges at the two ends close to each other attract each other, which will reduce the restoring force of the system, making the system stable and the resonant frequency is low; When two dipoles are placed in opposite directions, the charges at the two ends that are close to each other will repel each other, which will improve the restoring force of the system and make the resonance frequency higher.

Accordingly, the three modes are designed as follows:

Mode 1, as shown in Figure 9, is a schematic diagram of the functions under two polarizations. In order to better understand the regulation mechanism, the distance between the two opposite surfaces is obtained by the geometric relationship as l ₁ =msin2β(2β≤90°) (when β>45°, it is equivalent to the designed metamaterial rotating 90 degrees , so no analysis is performed), the length of the period is a ₁ =2mcosβ (β≤45°), and the width is b ₁ =2msinβ (β≤45°). When the folded angle β is changed by external mechanical force, β increases and the period along the y direction increases, that is, the effective ITO absorption area along the y direction becomes larger, resulting in better TE polarized wave absorption and better reflection. The amplitude is reduced, that is, function 1: the mechanical regulation of the electromagnetic wave reflection amplitude can be achieved under TE polarization; according to the dipole theory mentioned above and the current distribution diagram in Figure 3, it can be obtained that two adjacent surfaces will also interact with each other. They will form two components, namely |M _x |=|M|·sinβ, |M _y |=|M|·cosβ, the components along the y-axis can be approximately longitudinally coupled in the same direction, and the components along the x-axis The opposite components can be considered as reverse longitudinal coupling, and the two opposite surfaces can be considered as same-direction longitudinal coupling. When β increases, the distance _l1 between the two opposing dipoles will increase, and the interaction force will decrease, which is considered to be resonance. The frequency will move to the high frequency, that is, the second function: the mechanical regulation of the resonance frequency of the reflected electromagnetic wave can be realized under the TM polarization. As shown in Figure 10, when β=45°, it can be used as a broadband absorber in this state. The main mechanism is that the period b ₁ along the y-axis (TE polarization) reaches a maximum value, and the absorption effect is the best , the distance l ₁ between the dipoles on the two opposite surfaces under TM polarization is the largest, and the longitudinal coupling effect of the two magnetic dipoles in the same direction is the smallest (the low frequency resonance frequency moves to the high frequency), and the electric dipole The lateral co-coupling effect is the smallest (the high frequency resonant frequency moves to the low frequency), as shown in Figure 15, when β=30°, the middle frequency band of the two resonant frequencies will reach -10dB or more (the broadband absorbing wave is split into two narrow bands Therefore, only when β=45° reaches the extreme value, the two resonant frequency points are close, so that the intermediate frequency band is below -10dB, and finally the two narrow-band absorbing waves are seamlessly connected into a broadband absorbing wave, reaching the maximum absorbing wave. bandwidth. In the range of 3.46GHz to 15.61GHz, the absorption rate of electromagnetic waves under vertical incidence can reach more than 90%, the absolute bandwidth can reach 12.15GHz, and the relative bandwidth can reach 127.43%; within the incident angle of 60°, the TE polarized wave absorption rate can reach 74% Above, the absorption rate of TM polarized wave can reach more than 90%, but there will be drift at high frequency, that is, function three: fully polarized large-angle broadband absorber.

Mode 2, as shown in Figure 11, has a similar regulatory mechanism to Mode 1. Both function one and function two are similar to mode 1, but the operating frequency band is different. When the folding angle β=45°, as shown in Figure 12, it can also be used as a broadband absorber in this state. The absorption rate can reach more than 80% under the vertical incidence of electromagnetic waves in the range of 6GHz to 16GHz, and the absolute bandwidth reaches 10GHz, the relative bandwidth reaches 90.91%; within 60° of oblique incidence angle, the absorption rate of TE polarized wave below 14.5GHz can reach more than 80%, and the absorption rate of TM polarized wave can reach more than 90%, in the range of 14.5GHz-16 GHz The internal absorption rate can also reach more than 74%, that is, the third function: fully polarized large-angle broadband absorber.

Mode 3, as shown in Figure 13, according to the geometric relationship, the distance between the center points of two adjacent surfaces is l=mcosβ. As shown in Fig. 4, the surface current distribution at the next resonance point under TM polarization can be seen, one magnetic dipole is formed on each surface, and the z-axis component p _z of the magnetic dipole on two adjacent surfaces is = pcosβ is equal in size and opposite in direction, which can be approximated as reverse lateral coupling; its component along the _y -axis py = psinβ can be approximated as longitudinal coupling in the same direction; when the folding angle β increases, the two dipoles The effect of TM will increase, making the system stable, reducing the restoring force of the system, and then adjusting the resonant frequency of the electromagnetic wave to move to a low frequency, that is, the second function: the mechanical regulation of the resonant frequency of the reflected electromagnetic wave can be realized under the TM polarization. As the folding angle β increases, the period length l=2mcosβ decreases, the resonance generated by the excited metamaterial becomes stronger, and the reflection amplitude decreases, that is, function 1: the electromagnetic wave reflection amplitude can be realized under TE polarization. Mechanical regulation. When the folding angle β=45°, as shown in Fig. 14, it can also be used as a broadband absorber in this state, mainly because the period length l=2mcosβ and the height of the metamaterial h=msinβ reach the extreme value. At this time, the area where ITO acts is the largest, so the absorption effect is the best. In the range of 4GHz to 15.5GHz, the absorption rate of TE polarized wave can reach more than 90%, the absorption rate of TM polarized wave can reach more than 82%, the absolute bandwidth can reach 11.55GHz, and the relative bandwidth can reach 90%; Within the angle of 60°, the absorption rate of TE polarized wave can reach more than 70%, and the absorption rate of TM polarized wave can reach more than 72%, that is, function three: fully polarized large-angle broadband absorber.

Step 3: Change the folding angle β of the three kirigami modes to evaluate the regulation range of electromagnetic wave absorption

With the theoretical support of the first step and the three kirigami modes of the second step, the different electromagnetic wave absorption regulation ranges of the three modes at different folding angles β (β≤45°) can be analyzed.

Mode 1: The experimental results are shown in Figure 9. When the folding angle β changes from 10° to 30°, the reflected amplitude of the electromagnetic wave changes from 0.55 to 0.1 under TE polarization, and the resonant frequency of the reflected electromagnetic wave changes from 2.0 GHz to 3.9 GHz under TM polarization. (The relative bandwidth control range can reach 38.7%); the simulation results are shown in Figure 18. When the folding angle β changes from 1.5° to 30°, the reflection coefficient of electromagnetic waves under TE polarization (the smaller the reflection coefficient, the better the absorption effect of electromagnetic waves). ) changes from -23dB to -3dB, and the resonance frequency of the reflected electromagnetic wave under TM polarization is from 0.7GHz to 3.9GHz (the relative bandwidth regulation range can reach 139.1%).

Mode 2: The experimental results are shown in Figure 11. When the folding angle β changes from 20° to 45°, the reflected amplitude of the electromagnetic wave changes from 0.5 to 0.1 under TE polarization, and the resonant frequency of the reflected electromagnetic wave changes from 3.2 GHz to 4.9 GHz under TM polarization. (The relative bandwidth control range can reach 41.9%); the simulation results are shown in Figure 19. When the folding angle β changes from 3° to 45°, the electromagnetic wave reflection coefficient changes from -19dB to -3dB under TE polarization, and under TM polarization The resonant frequency of the reflected electromagnetic wave is from 1.7GHz to 4.7GHz (the relative bandwidth control range can reach 93.7%).

Mode 3: The experimental results are shown in Figure 13. When the folding angle β changes from 20° to 45°, the reflected amplitude of the electromagnetic wave changes from 0.48 to 0.05 under TE polarization, and the resonant frequency of the reflected electromagnetic wave changes from 13.3 GHz to 6.6 GHz under TM polarization. (The relative bandwidth control range can reach 67.3%); the simulation results are shown in Figure 20. When the folding angle β changes from 10° to 45°, the electromagnetic wave reflection coefficient changes from -5dB to -32dB under TE polarization, and under TM polarization The resonant frequency of the reflected electromagnetic wave is from 15.5GHz to 5.4GHz (the relative bandwidth control range can reach 96.7%).

Step 4: Determine three functions according to the three paper-cut modes and the different folding angles β

First, under the action of external mechanical force, by changing the angle β of the kirigami, the mechanical regulation of the electromagnetic wave reflection amplitude under TE polarization can be achieved in all three modes (that is, working in the frequency band f ₁ function 1); The mechanical regulation of the resonant frequency of the reflected electromagnetic wave can be achieved under the fold (that is, the function 2 of the frequency band f ₂ and f ₃ ); when the folding angle β=45°, all three modes can be used as a fully polarized large-angle broadband absorber ( That is, function 3) that works in the frequency band f ₀ .

Calculate Poisson's ratio and relative density in three modes:

Poisson's ratio mainly refers to the negative value of the ratio of the transverse normal strain to the axial normal strain when the material is in unidirectional tension or compression. The calculation formula is:

where v is the Poisson's ratio, l is the length of the metamaterial unit, and w is the width of the metamaterial unit. So the Poisson's ratio of mode 1 can be obtained as:

Wherein, l ₁ =2m·cosβ, and w ₃ =2m·sinβ.

The Poisson's ratio for Mode 2 is:

Wherein, l ₂ =2m·cosβ, and w ₄ =2m·sinβ+k.

In mode 3, since the transverse normal strain is 0, the Poisson's ratio can be obtained as 0 according to the calculation formula. The calculation results of Poisson’s ratio under the three modes are shown in Figure 21(a). It can be seen that as the folding angle β (β≤45°) increases, the Poisson’s ratio increases, and mode 2 is more efficient than mode 2. The Poisson's ratio of 1 is large.

The relative density mainly refers to the ratio of the volume of the metamaterial to the space occupied by the cube. For example, the relative density of mode 1 is:

The relative density of Mode 2 is:

The relative density of mode 3 is

The calculated results of the relative densities in the three modes are shown in Fig. 21(b). It can be seen that with the increase of the folding angle β (β≤45°), the relative density will decrease, the change trend of mode 1 and mode 3 is the same, and the relative density of mode 2 is smaller than that of mode 1.

The three-dimensional kirigami metamaterial tunable absorber and its design method provided by the present invention can realize the mechanical regulation of the electromagnetic wave reflection amplitude (absorption amplitude) under TE polarization and the reflected electromagnetic wave resonance frequency under TM polarization by changing the folding angle β ( The mechanical regulation of the absorbing frequency band), in which, when β=45°, the excellent function of fully polarized large-angle broadband absorbing can be realized. The invention has the advantages of high integration, flexibility and change.

Description of drawings

Figure 1 is a functional schematic diagram of an integrated metamaterial with the functions of fully polarized large-angle broadband absorption, amplitude modulation, and resonance frequency modulation.

Figure 2 is a schematic diagram of the metamaterial unit structure.

Figure 3 shows the current distribution of the metamaterial unit at two resonance points of mode 1 (β=45°) at 4.75 and 13.57 GHz.

Figure 4 shows the current distribution of the metamaterial unit at the resonant frequency of 5.4 GHz under the mode 3TM polarization.

Figure 5 is a schematic diagram of the unit design flow.

Figure 6 is a schematic diagram of the optimal design of structural parameters.

Figure 7 is a schematic diagram of three different modes.

Figure 8 is a schematic diagram of the interaction of two dipoles.

FIG. 9 is a schematic diagram of the functions at two polarizations when β changes in mode 1 (experimental results).

FIG. 10 is a schematic diagram of the simulation results of large-angle broadband absorption under two polarizations when β=45° in mode 1.

Figure 11 is a schematic diagram of the functions at two polarizations when β changes in mode 2 (experimental results).

FIG. 12 is a schematic diagram of the simulation results of large-angle broadband absorption under two polarizations when β=45° in mode 2.

Figure 13 is a schematic diagram of the functions at two polarizations when β changes in mode 3 (experimental results).

FIG. 14 is a schematic diagram of the simulation results of large-angle broadband absorption under two polarizations when β=45° in mode 2.

FIG. 15 is a schematic diagram of the simulation results when β changes under two polarizations in mode 1.

Figure 16 is a flow chart of the fabrication of the designed metamaterial tunable absorber.

Figure 17 is a schematic diagram of the experimental test.

FIG. 18 is a schematic diagram of the simulation result of Mode 1.

FIG. 19 is a schematic diagram of the simulation result of Mode 2.

FIG. 20 is a schematic diagram of the simulation results of Mode 3.

Figure 21 shows Poisson's ratio and relative density for the three modes.

Detailed ways

The specific implementation of the metamaterial tunable wave absorber will be described in detail below with examples. Firstly, three modes are constructed according to the theory of multi-dipole coupling. By changing the folding angle β, the mechanical regulation of the electromagnetic wave reflection amplitude under TE polarization and the mechanical regulation of the reflected electromagnetic wave resonance frequency under TM polarization can be realized. When =45°, the excellent function of fully polarized large-angle broadband absorption can be realized. The specific regulation mechanism is shown above. For verification, the production process and the testing process are described in detail below.

1. Cut the processed ITO plane structure into the required strip structure: the actual production is a plane structure (the designed ITO structure is attached to the PET board), which requires post-processing, as shown in Figure 16, the main Cut (or cut with scissors) a cutting knife along the cutting line in the x-axis direction into a desired strip-shaped structure, and then fold the cut strip-shaped structure according to the folding line.

2. Etch the grooved structure on the foam board: In order to ensure the accuracy of the folding angle β, the grooved structure is etched on the foam board, and then the folded strip structure is fixed in the groove. In order to ensure the accuracy of etching, as shown in Figure 16, white paper with etching lines is pasted on the foam board, and etching is performed along the lines on the white paper. Under different modes and different folding angles β, only Different groove structures need to be etched. Then insert the folded strip structure into the slot, and the production is completed. For different folding angles β in different modes, it is only necessary to insert foam boards with different groove-like structures, and the fabrication is completed. Figure 16 shows the schematic diagrams of the fabricated metamaterial tunable absorbers in three modes.

3. Experimental verification: The test was carried out in a microwave anechoic chamber. After verification, the test results were basically consistent with the simulation results. Figure 18, Figure 19, and Figure 20 are schematic diagrams of the simulation results of the three modes. Figure 9, Figure 11, and Figure 13 are the simulation results. Schematic diagram of the experimental test results of the three modes. The three functions of the designed metamaterial tunable absorber are verified: by changing the folding angle β, the mechanical regulation of the electromagnetic wave reflection amplitude under TE polarization and the mechanical regulation of the reflected electromagnetic wave resonance frequency under TM polarization can be achieved. When β=45°, the excellent function of fully polarized large-angle broadband absorption can be realized.

4. The specific results are as follows:

Mode 1: As shown in Figure 9, when the folding angle β changes from 10° to 30°, the electromagnetic wave reflection amplitude under TE polarization changes from 0.55 to 0.1, that is, function 1: Mechanical regulation of electromagnetic wave reflection amplitude can be realized under TE polarization The resonant frequency of the reflected electromagnetic wave under TM polarization is from 2.0GHz to 3.9GHz (the relative bandwidth control range can reach 38.7%), that is, the second function: the mechanical adjustment of the reflected electromagnetic wave resonance frequency can be realized under the TM polarization; as shown in Figure 10 , when β=45°, it can be used as a broadband absorber in this state, the absorption rate can reach more than 90% under vertical incidence of electromagnetic waves in the range of 3.46GHz to 15.61GHz, the absolute bandwidth reaches 12.15GHz, and the relative bandwidth reaches 127.43%, within the incident angle of 60°, the absorption rate of TE polarized wave can reach more than 74%, and the absorption rate of TM polarized wave can reach more than 90%, but there will be drift at high frequency, that is, function three: large full polarization Angle Broadband Absorber.

Mode 2: As shown in Figure 11, when the folding angle β changes from 20° to 45°, the electromagnetic wave reflection amplitude changes from 0.5 to 0.1 under TE polarization, that is, function 1: Mechanical regulation of electromagnetic wave reflection amplitude can be realized under TE polarization ; The resonant frequency of the reflected electromagnetic wave under TM polarization is from 3.2GHz to 4.9GHz (the relative bandwidth control range can reach 41.9%), that is, the second function: the mechanical adjustment of the reflected electromagnetic wave resonance frequency can be realized under the TM polarization; when the folding angle β= At 45°, as shown in Figure 12, in this state, it can also be used as a broadband absorber. In the range of 6GHz to 16GHz, the absorption rate can reach more than 80% under vertical incidence of electromagnetic waves, the absolute bandwidth reaches 10GHz, and the relative bandwidth reaches 90.91%, within 60° of the oblique incident angle, the absorption rate of TE polarized wave below 14.5GHz can reach more than 80%, and the absorption rate of TM polarized wave can reach more than 90% at 14.5GHz. Can reach more than 74%, that is, function three: fully polarized large-angle broadband absorber.

Mode 3: As shown in Figure 13, when the folding angle β changes from 20° to 45°, the electromagnetic wave reflection amplitude changes from 0.48 to 0.05 under TE polarization, that is, function 1: Mechanical regulation of electromagnetic wave reflection amplitude can be realized under TE polarization ; The resonant frequency of the reflected electromagnetic wave under TM polarization is from 13.3GHz to 6.6GHz (the relative bandwidth control range can reach 67.3%), that is, the second function: the mechanical adjustment of the reflected electromagnetic wave resonance frequency can be realized under the TM polarization; when the folding angle β= At 45°, as shown in Figure 14, in this state, it can also be used as a broadband absorber. Under normal incidence in the range of 4GHz to 15.5GHz, the TE polarized wave absorption rate can reach more than 90%, and the TM polarized wave absorbs The absorption rate can reach more than 82%, the absolute bandwidth can reach 11.55GHz, the relative bandwidth can reach 90%, and the absorption rate of TE polarized wave can reach more than 70% and the TM polarized wave absorption rate can reach 72% within the oblique incidence angle of 60°. The above is the third function: fully polarized large-angle broadband absorber.

Claims (4)

1. a three-dimensional kirigami metamaterial tunable absorber, based on multi-dipole coupling theory and kirigami folding structure, is characterized in that, specifically by M*N metamaterial units with the same structural parameters in space etc. The metamaterial unit is a three-dimensional structure, which is a tetrahedron formed by folding and splicing two strips cut from a two-dimensional metasurface, and the four faces of the tetrahedron are the same; wherein, each face is Three-layer structure, the middle layer is PET; the one attached to the upper and lower sides of PET is ITO; the ITO layer is a completely symmetrical rectangular double-slit resonator ring structure; note the folding angle of the two strips as β , the structural parameters of the double-slit resonator ring structure are: the length and width of the outer split ring are m and n respectively, the slit width of the two split rings is w ₁ , the width of the split ring is w ₂ , and the width of the opening is g ; The metamaterial unit is a three-dimensional structure, and its period in the horizontal plane is p =2* m *sin β ; Among them, the metamaterial unit is divided into three modes, as follows: Mode 1: It is a "well"-shaped structure formed by oppositely splicing two folded strips; the period in the x-axis direction is 2 *m* cos β , and the period in the y-axis direction is 2* m *sin β ; Mode 2: Compared with mode 1, the two opposite strips are separated by a certain distance; the period in the x-axis direction is 2 *m* cos β , and the period in the y-axis direction is 2* m *sin β+k , k=2; Mode 3: It is equivalent to folding the strip structure of Mode 1 by 90 degrees, the adjacent cells are connected by the midpoint of the boundary edge, and the two adjacent strip structures are placed opposite each other with a difference of half a period; the period in the x-axis direction is 2 * n , the period in the y-axis direction is 2 *m* cos β ; The above three different structural modes of the metamaterial unit can realize three functions of modulating electromagnetic waves at different folding angles β under the excitation of linearly polarized waves: Function 1: When the folding angle β is changed, the mechanical regulation of electromagnetic wave reflection amplitude is realized under TE polarization ( f ₁ ); Function 2: When the folding angle β is changed, the mechanical regulation of the resonance frequency of the reflected electromagnetic wave is realized under the TM polarization ( f ₂ , f ₃ ); Function three, when the folding angle β = 45°, it acts as a broadband tunable absorber ( f ₀ ); f ₀ is the working frequency band of the broadband absorber, f ₁ is the working frequency band controlled by the reflection amplitude, and f ₂ and f ₃ are the working frequency bands controlled by the resonant frequency. 2. The three-dimensional kirigami metamaterial tunable absorber according to claim 1, wherein the structural parameters of the double-slit resonator ring structure in the metamaterial unit are as follows: m =16 mm, n =12 mm, w ₂ = 2.3 mm, w ₁ = g = 0.3 mm, where the thickness of PET is 0.1 mm, and the resistance of ITO is 100 Ω/sq. 3. a design method of three-dimensional kirigami metamaterial adjustable absorber as claimed in claim 1, is characterized in that, concrete steps are as follows: Step 1: According to the multi-dipole coupling theory, construct the unit structure Electric/magnetic multipoles can radiate energy outwards; the interaction between two dipoles placed in space is divided into lateral coupling and longitudinal coupling; when two dipoles are laterally coupled in the same direction, the restoring force of the system increases , the resonant frequency is higher; when the two dipoles are coupled in the opposite lateral direction, the system is relatively stable and the resonance frequency is lower; when the two dipoles are longitudinally coupled in the same direction, the system becomes more stable and the resonance frequency is lower; When the two dipoles are longitudinally coupled in reverse, the restoring force increases and the resonant frequency is relatively high. According to this principle, the three-dimensional kirigami metamaterial unit structure is designed, and the electromagnetic interaction between the dipoles is changed by changing the folding angle β . So as to achieve the purpose of regulating the frequency of electromagnetic absorption; Step 2: Build Three Cutout Patterns Mode 1: It is a "well"-shaped structure formed by opposing splicing of two folded strips; Mode 2: The two opposite strips are separated by a certain distance compared to Mode 1; Mode 3: It is equivalent to folding the strip structure of Mode 1 by 90 degrees, the adjacent cells are connected by the midpoint of the boundary edge, and the two adjacent strip structures are placed opposite each other with a difference of half a cycle; Step 3: Change the folding angle β of the three kirigami patterns, and evaluate the regulation range of electromagnetic wave absorption The different electromagnetic absorption regulation ranges of the three modes at different folding angles β are analyzed: Mode 1: When the folding angle β changes from 10° to 30°, the reflected amplitude of the electromagnetic wave changes from 0.55 to 0.1 under the TE polarization, and the resonant frequency of the reflected electromagnetic wave under the TM polarization changes from 2.0 GHz to 3.9 GHz; Mode 2: When the folding angle β changes from 20° to 45°, the reflected amplitude of the electromagnetic wave changes from 0.5 to 0.1 under the TE polarization, and the resonant frequency of the reflected electromagnetic wave changes from 3.2 GHz to 4.9 GHz under the TM polarization; Mode 3: When the folding angle β changes from 20° to 45°, the reflected amplitude of the electromagnetic wave changes from 0.48 to 0.05 in the TE polarization, and the resonant frequency of the reflected electromagnetic wave in the TM polarization changes from 13.3 GHz to 6.6 GHz; Step 4: Determine three functions according to the three paper-cut modes and the different folding angles β First, under the action of external mechanical force, by changing the angle β of the paper-cut, the mechanical regulation of the electromagnetic wave reflection amplitude under TE polarization is realized in the three modes, that is, the function one works in the frequency band f ₁ ; the reflected electromagnetic wave is realized under TM polarization. Mechanical regulation of the resonance frequency, that is, the second function of working in the frequency bands f ₂ and f ₃ ; when the folding angle β = 45°, all three modes can be used as a fully polarized large-angle broadband absorber, that is, working in the frequency band f ₀ function three. 4. the design method of three-dimensional kirigami metamaterial adjustable wave absorber according to claim 3, it is characterized in that, determine the final structural parameter of double-opening resonant ring structure in metamaterial unit, be specific as follows: m =16 mm, n =12 mm, w ₂ =2.3 mm, g = w ₁ =0.3 mm; the thickness of PET is 0.1 mm, the dielectric constant is 3.0, the tangent loss is 0.003; the resistance value of ITO is 100 Ω/sq.

Images