Switching type electromagnetic induction transparent metasurface with continuously adjustable transmissivity

Abstract

The invention relates to a switch type electromagnetic induction transparent metasurface with continuously adjustable transmissivity, and belongs to the technical field of electromagnetic wave metamaterials. The structure of each unit cell unit sequentially comprises a dielectric layer and a metal patch layer from bottom to top; the metal patch layer comprises a resonant ring and a three-rod resonator; the three-rod resonator is composed of three metal rods extending outwards from the center of the three-rod resonator every 120 degrees, and the center of the three-rod resonator coincides with the circle center of the resonant ring. The technical problems that when an existing EIT metasurface serves as an optical switch, the transmissivity is low, continuous regulation and control are difficult, an active regulation and control mechanism is complex, cost is high and the like are solved, and continuous regulation and control of the microwave optical switch are achieved.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave metamaterials technology. Specifically, this invention relates to a switch-type electromagnetic induction transparent metasurface with continuously adjustable transmittance. Background Technology

[0002] Electromagnetically Induced Transparency (EIT) is a technique that utilizes laser-induced atomic coherence to eliminate the absorption of electromagnetic waves of specific frequencies by a medium. Its principle involves the coherent superposition of quantum energy states, causing destructive interference between the quantum amplitudes of two transition paths. This results in the arrangement number of excited states becoming zero, thereby eliminating absorption and creating a narrow-band transparent window in the originally strongly absorbed spectrum.

[0003] EIT metasurfaces introduce the EIT concept from atomic physics into the field of subwavelength artificial composite materials. By simulating the quantum EIT effect, they overcome the limitations of atomic systems requiring harsh conditions such as low temperatures and vacuum, reproducing a highly transparent transmission window. Their working principle is as follows: there are two transmission modes: a "bright mode" and a "dark mode." The "bright mode" is strongly coupled to the propagating electromagnetic wave and possesses broadband resonance characteristics with a low quality factor (Q factor); the "dark mode" is a subradiative mode with narrow resonance and a high Q factor, which cannot be directly excited by the propagating wave but is excited by the "bright mode." These two modes couple with each other at the transparency frequency through destructive interference, similar to destructive interference in quantum systems, thus inducing transparency.

[0004] However, existing EIT metasurfaces suffer from the following technical problems: First, low transmittance. Due to the high dispersivity of the simulated atomic medium, the extremely wideband resonance generated by the plasmonic metasurface results in a very low quality factor for the transparent window, and consequently, very low transmittance (manifesting as high insertion loss in microwaves). Second, sensitivity to changes in structural parameters. Generally, EIT surfaces are achieved by simultaneously coupling low-Q dipole resonances and high-Q guided-mode resonances within the transparent window. This relies heavily on multiple interacting structures within the unit cell, such as orthogonal silicon rods and silicon-based rod-ring resonators. When multiple structural parameters vary over a large range, the resonant frequency of the bright mode becomes difficult to synchronize with the dark mode, leading to significant detuning between the two coupled modes. Third, in most current literature, the active control mechanism used as an optical switch is complex. For example, phase change materials can be used to achieve a transition from an amorphous to a crystalline state through electrothermal pulses, thereby changing the refractive index and losses to control the on / off state of the EIT (Electro-Induced Transmission). Similarly, methods such as liquid crystal electro-control and graphene electro-control to adjust material properties can shift the EIT resonant frequency or achieve binary switching, but these switching methods require external excitation triggering, which is costly. To achieve continuous control, the requirements for the material's operating environment are even more stringent. Summary of the Invention

[0005] To address the shortcomings of existing EIT metasurfaces as optical switches, such as low transmittance, difficulty in continuous control, and complex and costly active control mechanisms, this invention proposes a switch-type electromagnetic induction transparent metasurface with continuously adjustable transmittance to solve the aforementioned technical problems.

[0006] A switchable electromagnetic induction transparent metasurface with continuously adjustable transmittance, comprising:

[0007] The metasurface comprises a plurality of unit cells; the side length of the unit cell is a;

[0008] The structure of the unit cell, from bottom to top, includes: a dielectric layer and a metal patch layer;

[0009] The metal patch layer includes: a resonant ring and a three-bar resonator;

[0010] The resonant ring has a radius of R and a width of W.

[0011] The three-bar resonator is composed of three metal bars extending outward from the center of the three-bar resonator at intervals of 120°.

[0012] The distance from the end of the metal rod to the center of the three-bar resonator is L; the width of the metal rod is V;

[0013] The center of the three-bar resonator coincides with the center of the resonant ring;

[0014] The units for a, R, L, W, and V are mm, and a / 2 > R > L > 0.

[0015] Furthermore, the metal patch layer is located at the center of the unit cell.

[0016] Furthermore, the metal patch layer is made of metal and has a gold-plated surface;

[0017] The metallic material includes copper or silver, and has a thickness of 0.035 mm.

[0018] Furthermore, the dielectric layer is made of a low-loss tangent material with a thickness ranging from 0.2 mm to 2 mm;

[0019] The low-loss tangential materials include: Taconic RF-35, PTFE, and Rogers series sheets.

[0020] Furthermore, the thickness h of the dielectric layer is 0.625 mm.

[0021] Furthermore, the dielectric layer has a relative permittivity εr = 3.35 and a loss tangent tanδ = 0.0027.

[0022] Furthermore, N1×N2 unit cells are arranged in a matrix along the x and y directions to form an N1×N2 unit cell array, thus forming a metasurface;

[0023] N1 and N2 are positive integers, where N1≥8 and N2≥8;

[0024] The metasurface is used to adjust the transmittance of linearly polarized waves in the x and y directions.

[0025] Furthermore, the metasurface includes unit cells with a rotation angle of Φ;

[0026] The unit cell with a rotation angle of Φ refers to the metal patch layer of the unit cell with a rotation angle of Φ.

[0027] The rotation angle of the metal patch layer is Φ, which refers to the angle between the direction of a certain metal rod in the three-bar resonator of the metal patch layer and the counterclockwise direction of the -x direction.

[0028] The unit cell with a rotation angle of Φ is used to adjust the transmittance of linearly polarized waves in the x and y directions.

[0029] Furthermore, when the metasurface is composed of unit cells with a rotation angle of Φ, the xy plane of the metasurface is rotated counterclockwise by an angle θ(t) with the z-axis as the axis to form a metasurface with a rotation angle of θ(t);

[0030] The metasurface with a rotation angle of θ(t) is used to: adjust the transmittance of linearly polarized waves in the x-direction and the y-direction at a rate of Δθ.

[0031] Where Φ∈[0°,30°], θ(t)=θ(t-1)+△θ; θ(t)∈[-Φ,30°-Φ], t is the time series, and △θ is the angular velocity of the xy plane rotation of the metasurface.

[0032] Furthermore, N1 = N2 = 12, 15, or 20;

[0033] Φ = 0° or 10° or 20° or 30°.

[0034] The advantages of this invention compared to the prior art are:

[0035] (1) Simple and easy-to-process unit cell structure: The required size of the unit cell is in the traditional millimeter range, and the entire plane is formed by the repeated extension of the unit in two dimensions. It can be made by using printed circuit board materials and etching metal patterns. The processing technology is simple and easy to implement, similar to a single-layer PCB board structure. The material can be a low-loss tangential board for radio frequency, and the metal layer is obtained by etching a conventional copper thin film. No special materials or special processes are required within the microwave frequency operating range.

[0036] (2) Simple active control method: Unlike the existing active control methods that use additional excitation control such as electrothermal and rely on special materials (such as liquid crystal, graphene, etc.) and are costly, the present invention only needs to rotate a two-dimensional plane to realize the opening and closing of the transparent window. Only additional mechanical control is required, which greatly simplifies the active control process and reduces costs.

[0037] (3) Continuous controllability: Existing technologies utilize additional excitations such as electrothermal control, and the material properties are sensitive to changes in the intermediate process, generally only showing two states: on and off. However, this invention can not only show the on and off states, but also display the switching process by rotating the angle. If the mechanical rotation is continuous, the corresponding performance also changes continuously, similar to an adjustable attenuation device in a circuit, except that it is applied to space electromagnetic waves rather than circuit guided waves, realizing continuous control of microwave optical switches.

[0038] (4) Excellent transparent window performance: Considering the conductor conductivity and dielectric loss tangent, the peak transmittance of the transparent window is close to 99%, and the transmittance is around 10% when the transparent window is closed. The modulation depth (converted to dB) is 17dB, which has good transparent window performance. Moreover, the modulation depth and the peak value of the transparent window have good performance in the microwave band.

[0039] (5) Good overall performance: The present invention utilizes EIT to realize the design structure of adjustable attenuation plane, which can simultaneously meet the advantages of superior transparent window performance, continuous control as microwave optical switch, simple active control method and easy realization by mature processing technology on the market, and has significant positive effects. Attached Figure Description

[0040] Figure 1 This is a three-dimensional structural diagram of a unit cell provided in an embodiment of the present invention.

[0041] Figure 2 This is a top view of a unit cell with a rotation angle of 0°, provided as an embodiment of the present invention.

[0042] Figure 3 This is a top view of a unit cell with a rotation angle of 30°, provided as an embodiment of the present invention.

[0043] Figure 4 This is a schematic diagram of a hyperplane provided in an embodiment of the present invention.

[0044] Figure 5 The present invention provides a transmission frequency response curve for linearly polarized waves in the x-direction when the rotation angle is 0° and 30°.

[0045] Figure 6 The present invention provides a transmission frequency response curve for linearly polarized waves in the y-direction when the rotation angle is 0° and 30°.

[0046] Figure 7 The transmission frequency response contour diagram of a linearly polarized wave in the x-direction when the rotation angle changes continuously from 0° to 30° is provided as an embodiment of the present invention.

[0047] Figure 8 The transmission frequency response contour diagram of a linearly polarized wave in the y-direction when the rotation angle changes continuously from 0° to 30° is provided as an embodiment of the present invention.

[0048] Figure 9 This invention provides transmittance curves for a 5.52 GHz linearly polarized wave in the x and y directions as the rotation angle changes continuously from 0 to 30°.

[0049] Reference numerals: 1, metal patch layer; 2, dielectric layer; 3, resonant ring; 4, three-bar resonator. Detailed Implementation

[0050] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0051] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0052] Example

[0053] This invention proposes a switch-type electromagnetic induction transparent metasurface with continuously adjustable transmittance, which solves the technical problems of low transmittance, difficulty in continuous control, and complex and costly active control mechanism when existing EIT metasurfaces are used as optical switches.

[0054] This invention provides a switchable electromagnetic induction transparent metasurface with continuously adjustable transmittance, the metasurface comprising a plurality of unit cells; the side length of the unit cell is a.

[0055] like Figure 1 , Figure 2 As shown, the structure of the unit cell, from bottom to top, includes: a dielectric layer 2 and a metal patch layer 1;

[0056] The metal patch layer 1 includes: a resonant ring 3 and a three-bar resonator 4;

[0057] Resonant ring 3 has a radius of R and a ring width of W.

[0058] The three-bar resonator 4 is composed of three metal bars extending outward from the center of the three-bar resonator at intervals of 120°; the length of the end of the metal bar from the center of the three-bar resonator is L; the width of the metal bar is V; the center of the three-bar resonator coincides with the center of the resonant ring.

[0059] The units for a, R, L, W, and V are mm, and a / 2 > R > L > 0.

[0060] This invention can be applied to radio frequency microwave to terahertz to optical bands, and the corresponding values ​​of a, R, L, W, and V are determined experimentally according to specific application scenarios.

[0061] For example, in a 5.5GHz application scenario, a=40mm, R=14mm, L=12mm, W=2.5mm, V=2.5mm. If applied to a 50GHz application scenario, the dimensions involved can be reduced proportionally to 15%.

[0062] The metal patch layer 1 and the dielectric layer 2 are tightly adhered to the upper and lower surfaces.

[0063] The metal patch layer 1 is located at the center of the unit cell.

[0064] The metal patch layer 1 is made of metal and has a gold-plated surface.

[0065] The metal material includes materials with good electrical conductivity such as copper or silver. The thickness of the PCB board is generally 0.035mm, and the impact of conductive loss and processing thickness on performance can be ignored.

[0066] The dielectric layer 2 is made of a low-loss tangent material, and its thickness h ranges from 0.2 mm to 2 mm, with the specific thickness selectable according to performance requirements. For example, the thickness h of the dielectric layer 2 is 0.625 mm.

[0067] The low-loss tangential material includes: Taconic RF-35, PTFE, Rogers series and other sheet materials.

[0068] For example, the dielectric layer 2 uses a Rogers RO4003 substrate with a relative permittivity εr=3.35 and a loss tangent tanδ=0.0027.

[0069] This invention can be made using printed circuit board materials and etched with metal patterns. The processing technology is simple and easy to implement, similar to a single-layer PCB board structure. The material can be a low-loss tangential material for radio frequency, and the metal layer is obtained by etching a conventional copper thin film. No special materials or special processes are required within the microwave frequency operating range.

[0070] like Figure 4 As shown, N1×N2 unit cells are arranged in a matrix along the x and y directions to form an N1×N2 unit cell array, thus forming a metasurface; N1 and N2 are positive integers. The metasurface is used to adjust the transmittance of linearly polarized waves in the x and y directions. Figure 4 In the middle, the direction above the metasurface towards -z is the incident direction of the linearly polarized wave, and the direction below the metasurface towards -z is the direction of the transmitted wave after the metasurface modulation effect.

[0071] Specifically, when N1=N2=1, the metasurface is formed by a single unit cell. However, in practical applications, N1=N2=1 is unusable because the metasurface size is much smaller than the wavelength, so a single unit cell is ineffective. Therefore, only structures with N1=N2≥8 exhibit subwavelength effects. Thus, generally, the values ​​of N1 and N2 should be greater than or equal to 8, i.e., N1≥8 and N2≥8.

[0072] Preferably, N1=N2=12, 15, or 20; that is, the entire plane extends along the x and y directions with 12×12, 15×15, or 20×20 unit cells. When the number of unit cells is large enough, the effect of edge diffraction can be ignored, reducing the error between the simulation and the actual sample. It is worth noting that these geometric parameters are only examples. Relevant designers can refer to similar structures to implement transparent windows in any frequency band, but the invention should be protected when using similar structures.

[0073] like Figure 2 , Figure 3 As shown, the metasurface of the present invention includes unit cells with a rotation angle of Φ;

[0074] The unit cell with a rotation angle of Φ refers to the metal patch layer of the unit cell with a rotation angle of Φ.

[0075] The rotation angle of the metal patch layer is Φ, which refers to the angle between the direction of a certain metal rod in the three-bar resonator of the metal patch layer and the counterclockwise direction of the -x direction.

[0076] The unit cell with a rotation angle of Φ is used to adjust the transmittance of linearly polarized waves in the x and y directions.

[0077] For example, Figure 2 For unit cells with a rotation angle Φ = 0°, Figure 2 It is a unit cell with a rotation angle Φ = 30°.

[0078] For a unit cell, the frequency response of the transmitted wave is affected by the rotation angle Φ of the unit cell. Therefore, by setting the rotation angle Φ of the unit cell, the transmittance of the linearly polarized waves in the x and y directions can be adjusted.

[0079] Furthermore, when the metasurface is composed of unit cells with a rotation angle of Φ, the xy plane of the metasurface is rotated counterclockwise by an angle θ(t) with the z-axis as the axis to form a metasurface with a rotation angle of θ(t);

[0080] The metasurface with a rotation angle of θ(t) is used to: adjust the transmittance of linearly polarized waves in the x-direction and linearly polarized waves in the y-direction;

[0081] Where Φ∈[0°,30°], θ(t)=θ(t-1)+△θ; θ(t)∈[-Φ,30°-Φ], t is the time series, and △θ is the angular velocity of the xy plane rotation of the metasurface.

[0082] It can be seen that when Φ=∈[0°,30°], θ(t) changes continuously from -Φ to 30°-Φ when the metasurface is in use.

[0083] For example, Φ = 0° or 10° or 20° or 30°.

[0084] For example, when Φ=0°, the metasurface is used and θ(t) varies continuously from 0° to 30°.

[0085] For example, when Φ=10°, the metasurface is used and θ(t) varies continuously from -10° to 20°.

[0086] For example, when Φ=20°, the metasurface is used and θ(t) varies continuously from -20° to 10°.

[0087] For example, when Φ=30°, θ(t) varies continuously from -30° to 0° when the metasurface is used.

[0088] When the rotation angle of the metasurface is θ(t), the actual rotation angle of the unit cell is Φ+θ(t). Since the rotation angle of the unit cell is what actually modulates the linearly polarized wave, the technical effect of the metasurface at this time is equivalent to the technical effect of a metasurface composed of unit cells with a rotation angle of Φ+θ(t). Therefore, for a metasurface, the frequency response of the transmitted wave is affected by the combined influence of the unit cell rotation angle Φ and the metasurface rotation angle θ(t), which is equivalent to the influence of the unit cell with a rotation angle of Φ+θ(t). Therefore, in practical applications, given that the unit cell rotation angle Φ is already fixed, the transmittance of linearly polarized waves in the x and y directions can be adjusted by changing the size of Φ+(t) by adjusting the size of the metasurface rotation angle θ(t). When analyzing the frequency response of the transmitted wave, the rotational change of the metasurface can be equivalent to the change of the rotation angle Φ of the metal patch layer in the unit cell of the metasurface with a fixed position, and the frequency response of the transmitted wave can be analyzed accordingly.

[0089] The following irradiation experiment was conducted using linearly polarized waves with a frequency range of 4.4 GHz to 6.0 GHz as incident waves to analyze how the change in the rotation angle Φ of the metal patch layer produces the technical effect of adjusting the transmittance of the linearly polarized waves in the x and y directions.

[0090] Figure 5 The transmission frequency response curves of linearly polarized waves in the x-direction are shown when the rotation angles of the metal patch layer are 0° and 30°, respectively.

[0091] Figure 6 The transmission frequency response curves of linearly polarized waves in the y-direction are shown when the rotation angles of the metal patch layer are 0° and 30°, respectively.

[0092] Figure 5 and Figure 6 In the diagram, the horizontal axis represents the frequency of the transmitted wave in GHz, and the vertical axis represents the transmittance (range 0~1). The transmittance is taken as dB20 and is called the insertion loss.

[0093] exist Figure 5 In the meantime, when Φ=30°, a transmission window for linearly polarized waves in the x-direction appears around 5.5GHz-5.55GHz, with a transmittance close to 80% or higher, and a peak transmittance close to 100% at 5.52GHz;

[0094] When Φ=0°, the transmission window for linearly polarized waves in the x-direction is closed.

[0095] And in Figure 6 In the meantime, when Φ=0°, a transmission window for linearly polarized waves in the y-direction appears around 5.5GHz-5.55GHz, with a transmittance close to 80% or higher, and a peak transmittance close to 100% at 5.52GHz;

[0096] When Φ = 30°, the transmission window for linearly polarized waves in the y-direction is closed.

[0097] It is evident that the frequency response of this metal patch layer is completely opposite to that of linearly polarized waves in the x and y directions, proving that the metasurface provided by this invention is sensitive to the polarization direction of the incident wave. Moreover, for incident linearly polarized waves of specific frequencies (such as 5.5GHz-5.55GHz), changing the Φ value can achieve the technical effect of increasing the transmittance of linearly polarized waves in one direction and decreasing the transmittance of linearly polarized waves in the other direction.

[0098] Figure 7 The contour plot shows the transmission frequency response of linearly polarized waves in the x-direction when the rotation angle of the metal patch layer changes continuously from 0° to 30°.

[0099] Figure 8 The contour plot shows the transmission frequency response of linearly polarized waves in the y-direction when the rotation angle of the metal patch layer changes continuously from 0° to 30°.

[0100] Figure 7 and Figure 8 In the graph, the horizontal axis represents the frequency of the transmitted wave in GHz; the vertical axis represents the rotation angle Φ in degrees (deg); and the color represents the transmittance, which is a function f(x,y) related to x and y, with blue indicating low transmittance and red indicating high transmittance.

[0101] exist Figure 7In the process, as the rotation angle Φ gradually increases from 0 to 30°, the transmittance of the linearly polarized wave in the x-direction gradually increases, especially at 5.52 GHz, where the transmittance increases from close to 10% to a peak value close to 100%.

[0102] and Figure 8 In the meantime, as the rotation angle Φ gradually increases from 0 to 30°, the transmittance of the linearly polarized wave in the y direction gradually decreases, especially at 5.52 GHz, where the transmittance drops from nearly 100% at its peak to nearly 10%.

[0103] Figure 9 Table 1 shows the transmittance curves of a linearly polarized wave with a frequency of 5.52 GHz in the x and y directions as the rotation angle Φ continuously varies from 0 to 30°. Figure 9 The corresponding data table. Table 1 illustrates the transmittance and insertion loss (dB) of linearly polarized waves in the x and y directions for every 1° change in rotation angle from 0 to 30°.

[0104] Table 1. Transmittance and insertion loss data of linearly polarized waves at 5.52 GHz as a function of rotation angle Φ.

[0105] Rotation angle Φ x-direction linear polarized wave transmittance y-direction linear polarization wave transmittance x-direction linearly polarized wave insertion loss Y-direction linearly polarized wave insertion loss 0° 14.01% 99.88% -17.07 -0.01 1° 13.97% 98.04% -17.09 -0.17 2° 14.17% 98.81% -16.97 -0.10 3° 14.72% 97.10% -16.64 -0.26 4° 15.09% 95.46% -16.43 -0.40 5° 16.32% 93.64% -15.75 -0.57 6° 16.93% 91.59% -15.43 -0.76 7° 20.36% 86.80% -13.82 -1.23 8° 23.30% 82.34% -12.65 -1.69 9° 25.68% 79.83% -11.81 -1.96 10° 29.07% 75.33% -10.73 -2.46 11° 32.69% 71.43% -9.71 -2.92 12° 36.64% 66.84% -8.72 -3.50 13° 42.77% 61.15% -7.38 -4.27 14° 45.20% 58.21% -6.90 -4.70 15° 51.40% 52.31% -5.78 -5.63 16° 56.28% 46.73% -4.99 -6.61 17° 62.16% 40.95% -4.13 -7.76 18° 64.87% 38.46% -3.76 -8.30 19° 70.36% 32.97% -3.05 -9.64 20° 74.81% 29.23% -2.52 -10.68 21° 78.77% 25.16% -2.07 -11.99 22° 82.46% 22.42% -1.68 -12.99 23° 84.83% 19.45% -1.43 -14.22 24° 90.26% 16.19% -0.89 -15.82 25° 88.88% 16.54% -1.02 -15.63 26° 90.33% 15.66% -0.88 -16.11 27° 95.20% 14.08% -0.43 -17.03 28° 97.53% 13.57% -0.22 -17.35 29° 96.98% 14.18% -0.27 -16.97 30° 97.47% 14.44% -0.22 -16.81

[0106] Insertion loss (IL) refers to the signal power attenuation caused by inserting components (such as cables, connectors, filters, antennas, etc.) into a transmission link, and is expressed in decibels (dB).

[0107] A metasurface can be imagined as a two-port device, with the incident port for input and the transmission port for output. Transmittance refers to the proportion of transmitted wave energy in the incident wave energy.

[0108] Insertion loss is taken as dB20 based on transmittance T: Insertion loss IL = −20log 10 |Transmittance T|. Because communication systems are cascaded structures, the operations are transformed from multiplication to logarithmic relationships, which are then addition and subtraction relationships, thus simplifying the calculations.

[0109] In engineering in this field, the following classic values ​​are of greater interest:

[0110] 0dB: Ideal lossless state (does not actually exist);

[0111] -3 dB: Output power is half of input power (half-power point).

[0112] -10 dB: The output power is only 1 / 10 of the input power (90% attenuation).

[0113] from Figure 9As can be seen from Table 1, when the rotation angle Φ changes continuously from 0 to 30°, the transmittance of linearly polarized waves in the x and y directions is sensitive to the rotation angle, and the linearly polarized waves in the x and y directions have opposite transmittance trends and transmission effects at the same rotation angle.

[0114] Considering conductor conductivity and dielectric loss tangent, the peak transmittance of the transparent window is close to 99%, and the transmittance is around 10% when the transparent window is closed. The transmittance is continuously adjustable within the range of 10% to 100%, with a modulation depth of 17 dB, exhibiting excellent transparent window performance. Furthermore, it demonstrates good performance in both modulation depth and peak transmittance within the microwave band, demonstrating superior transparent window performance and enabling the function of a microwave optical switch. Moreover, this invention not only enables the on and off functions of a microwave optical switch but also allows for switching process control through changes in the rotation angle. If the mechanical rotation is continuous, the corresponding transmittance performance also changes continuously, similar to an adjustable attenuation device in a circuit, except that it is applied to space electromagnetic waves rather than circuit-guided waves, thus achieving continuous control of the microwave optical switch.

[0115] When the rotation angle of the metasurface is θ(t), the actual rotation angle of the unit cell is Φ+θ(t). Since the rotation angle of the unit cell is what actually regulates the linearly polarized wave, the technical effect of the metasurface at this time is equivalent to that of a metasurface composed of unit cells with a rotation angle of Φ+θ(t). In practical applications, given that the rotation angle Φ of the unit cell is already fixed, the transmittance of linearly polarized waves in the x and y directions can be adjusted by changing the magnitude of the metasurface rotation angle θ(t), thus achieving continuous control of the microwave optical switch.

[0116] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A switch-type electromagnetic induction transparent metasurface with continuously adjustable transmittance, characterized in that: The metasurface comprises a plurality of unit cells; the side length of the unit cell is a; The structure of the unit cell, from bottom to top, includes: a dielectric layer and a metal patch layer; The metal patch layer includes: a resonant ring and a three-bar resonator; The resonant ring has a radius of R and a width of W. The three-bar resonator is composed of three metal bars extending outward from the center of the three-bar resonator at intervals of 120°. The distance from the end of the metal rod to the center of the three-bar resonator is L; the width of the metal rod is V; The center of the three-bar resonator coincides with the center of the resonant ring; The units for a, R, L, W, and V are mm, and a / 2 > R > L > 0.

2. The continuously adjustable transmittance switchable electromagnetic induction transparent metasurface according to claim 1, characterized in that: The metal patch layer is located at the center of the unit cell.

3. The continuously adjustable transmittance switchable electromagnetic induction transparent metasurface according to claim 1, characterized in that: The metal patch layer is made of metal material and has a gold-plated surface. The metallic material includes copper or silver, and has a thickness of 0.035 mm.

4. The continuously adjustable transmittance switchable electromagnetic induction transparent metasurface according to claim 1, characterized in that: The dielectric layer is made of a low-loss tangential material with a thickness ranging from 0.2 mm to 2 mm. The low-loss tangential materials include: Taconic RF-35, PTFE, and Rogers series sheets.

5. The continuously adjustable transmittance switchable electromagnetic induction transparent metasurface according to claim 1, characterized in that: The thickness h of the dielectric layer is 0.625 mm.

6. The continuously adjustable transmittance switchable electromagnetic induction transparent metasurface according to claim 1, characterized in that: The dielectric layer has a relative permittivity εr = 3.35 and a loss tangent tanδ = 0.0027.

7. The continuously adjustable transmittance switchable electromagnetic induction transparent metasurface according to claim 1, characterized in that: N1×N2 unit cells are arranged in a matrix along the x and y directions to form an N1×N2 unit cell array, thus forming a metasurface; N1 and N2 are positive integers, where N1≥8 and N2≥8; The metasurface is used to adjust the transmittance of linearly polarized waves in the x and y directions.

8. The continuously adjustable transmittance switchable electromagnetic induction transparent metasurface according to claim 7, characterized in that: The metasurface comprises a unit cell with a rotation angle of Φ; The unit cell with a rotation angle of Φ refers to the metal patch layer of the unit cell with a rotation angle of Φ. The rotation angle of the metal patch layer is Φ, which refers to the angle between the direction of a certain metal rod in the three-bar resonator of the metal patch layer and the counterclockwise direction of the -x direction. The unit cell with a rotation angle of Φ is used to adjust the transmittance of linearly polarized waves in the x and y directions.

9. A continuously adjustable transmittance switchable electromagnetic induction transparent metasurface according to claim 8, characterized in that: When the metasurface is composed of unit cells with a rotation angle of Φ, the xy plane of the metasurface is rotated counterclockwise by an angle θ(t) with the z-axis as the axis to form a metasurface with a rotation angle of θ(t). The metasurface with a rotation angle of θ(t) is used to: adjust the transmittance of linearly polarized waves in the x-direction and the y-direction at a rate of Δθ. Where Φ∈[0°,30°], θ(t)=θ(t-1)+△θ; θ(t)∈[-Φ,30°-Φ], t is the time series, and △θ is the angular velocity of the xy plane rotation of the metasurface.

10. A continuously adjustable transmittance switchable electromagnetic induction transparent metasurface according to claim 9, characterized in that: N1=N2=12 or 15 or 20; Φ = 0° or 10° or 20° or 30°.

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