A multifunctional metasurface based on amplitude-phase decoupling modulation

Abstract

The present invention discloses a multifunctional metasurface based on amplitude-phase decoupling modulation, which relates to the field of antenna technology. The multifunctional metasurface includes: l × l A metasurface unit including an upper part, a metal gap layer and a lower part, l =2,3,4...; In the upper portion, a rotatable metal ring is attached to the top surface of the first dielectric substrate; four rectangular regions of equal length are circumferentially spaced evenly around the metal ring, with a rectangular metal patch at the center; a rectangular metal patch is placed between the first and second dielectric substrates; a metal slot layer is located beneath the second dielectric substrate, with a rectangular slot at the center; in the lower portion, a third dielectric substrate, a rectangular metal patch, and a fourth dielectric substrate are arranged symmetrically from top to bottom; the lengths of the rectangular metal patch and the rectangular slot are perpendicular to each other. This multifunctional metasurface supports multiple radiation modes and polarization patterns, achieving a high level of integration.

Description

Technical Field

[0001] The present invention relates to the field of antenna technology, and in particular to a multifunctional metasurface based on amplitude-phase decoupling modulation. Background Art

[0002] With the deepening of metasurface theoretical research and the demand for miniaturization, integration, and high-speed devices in modern communication systems, electromagnetic devices with wider ranges and the ability to simultaneously integrate multiple functions have emerged. Multifunctional metasurface technology can greatly improve the transmission efficiency and capacity of communication channels, providing more degrees of freedom for communication systems. Therefore, research in this field has become a hot topic among researchers. Although multifunctional metasurface design based on phase modulation has achieved fruitful results, amplitude, as a key degree of freedom, still holds great potential in metasurface design. To achieve more complex functions and better results, it is often necessary to independently control the amplitude and phase of the metasurface unit structure. For some complex or high-quality wavefront control tasks, such as the manipulation of diffracted beams, the generation of high-quality holograms, and the synthesis of complex beams, the amplitude and phase (AP) responses always need to be obtained independently and simultaneously. This amplitude-phase decoupling feature can be flexibly applied in multiple fields.

[0003] In 2020, a related journal introduced a method of using multi-layer metal cross patches and slots to form a metasurface unit. By separately adjusting the length of the patches and the corresponding slots, the co-polarization response of the x and y polarizations can be independently controlled simultaneously. This proves that the unit has complete control over the incident and transmission responses of linearly polarized waves. However, the system can only achieve independent amplitude-phase decoupling control of linearly polarized incident waves in half-space, and the effect is poor in terms of integration. In 2021, some scholars proposed to achieve amplitude-phase decoupling modulation of circularly polarized incident waves by adjusting the two orientation angles of meta-atoms. This design achieves better results through polarization multiplexing and amplitude-phase decoupling, and has a dual-focus metalens with transverse and axial focuses. That is, the unit can achieve complete control over the incident and transmission responses of circularly polarized waves. However, the system can only achieve amplitude-phase decoupling control of circularly polarized incident waves in half-space, and the effect is poor in terms of integration. In 2023, a related journal proposed a three-frequency, multi-channel metasurface that uses frequency multiplexing to achieve on-demand independent amplitude-phase decoupled modulation of two transmissions and one reflection for circularly polarized incident waves at three different frequencies. This design achieves full-space radiation, but only for circularly polarized waves. The unit structure is relatively complex, making simulation and design difficult.

[0004] It can be seen that most of the current research on multifunctional amplitude-phase decoupling metasurfaces is concentrated on a single polarization mode or a single radiation direction. There are technical problems such as a single radiation mode and polarization mode, and low integration, which has certain limitations. Summary of the Invention

[0005] In order to solve the above-mentioned technical problems existing in the prior art, the present invention provides a multifunctional metasurface based on amplitude-phase decoupling modulation.

[0006] The specific technical solutions for the above-mentioned multifunctional metasurface are as follows:

[0007] include l × l metasurface units, l =2,3,4...;

[0008] The metasurface unit includes:

[0009] A first metal ring is attached to the upper surface of the first dielectric substrate;

[0010] Four rectangular areas of equal length are provided at equal intervals in the circumferential direction on the first metal ring, and non-adjacent rectangular areas have equal widths, forming a first rectangular pair and a second rectangular pair;

[0011] A first rectangular metal patch is also provided at the center of the first metal ring;

[0012] A second rectangular metal patch is provided between the first dielectric substrate and the second dielectric substrate;

[0013] The metal gap layer is provided between the second dielectric substrate and the third dielectric substrate, and a rectangular gap is provided in the center; the long side of the rectangular gap is perpendicular to the long side of the first rectangular metal patch;

[0014] A third rectangular metal patch is provided between the third dielectric substrate and the fourth dielectric substrate;

[0015] A second metal ring having the same width as the first metal ring is attached to the lower surface of the fourth dielectric substrate;

[0016] Four rectangular areas of equal length are provided at equal intervals in the circumferential direction on the second metal ring, and non-adjacent rectangular areas have equal widths, forming a third rectangular pair and a fourth rectangular pair;

[0017] A fourth rectangular metal patch is also provided at the center of the second metal ring;

[0018] In different metasurface units:

[0019] The angle between the long side of the first rectangular metal patch and the diameter of the first rectangular pair is different; the angle between the long side of the first rectangular metal patch and the diameter of the third rectangular pair is different;

[0020] The widths of the rectangular areas in the first rectangular pair and the third rectangular pair are both equal to the width of the first metal ring;

[0021] The width of the second rectangle is not equal to the width of the rectangular area in the center, and is greater than or equal to the width of the first metal ring;

[0022] The widths of the rectangular areas in the fourth rectangle are not equal and are greater than or equal to the width of the first metal ring.

[0023] In the technical solution provided by the present invention, by adjusting the rotation angles of the first and second metal rings and the widths of the rectangular areas in the second and fourth rectangular pairs in different metasurface units, full-phase and full-amplitude reflection responses to forward right-handed circularly polarized incident waves and backward right-handed circularly polarized incident waves can be achieved, such as reflection reconstruction of a preset pattern. Furthermore, by adjusting the lengths of the rectangular metal patches and metal gap layers in different metasurface units, full-phase and full-amplitude transmission responses to x-polarized incident waves can be achieved, and the function of a lateral dual-focus metal lens can be further realized. In addition, the use of a stacked structure and a slotted middle layer can ensure that low-frequency circularly polarized waves are directly reflected, while high-frequency linearly polarized waves pass through the gaps. Both linearly polarized waves and circularly polarized waves can achieve amplitude-phase decoupled modulation, and reduce the mutual influence between linearly polarized and circularly polarized incident waves, transmission and reflection functions, significantly improving the integration of the metasurface.

[0024] In short, the technical solution provided by the present invention overcomes the technical problems of the prior art, such as single radiation mode, single polarization mode, and low integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the structure of a metasurface unit in one embodiment of the present invention.

[0026] Figure 2 Schematic diagram of the arrangement of metal rings and rectangular metal patches on the upper surface of the top dielectric substrate of a metasurface unit in one embodiment of the present invention.

[0027] Figure 3 Schematic diagram of the structure of the metal gap layer of the super surface unit in one embodiment of the present invention.

[0028] Figure 4 Schematic diagram of the arrangement of the top dielectric substrate when the metasurface units form an array in one embodiment of the present invention.

[0029] Figure 5 Schematic diagram of the arrangement of the second layer of dielectric substrate when the metasurface units form an array in one embodiment of the present invention.

[0030] Figure 6 Schematic diagram of the arrangement of the metal gap layer when the metasurface units form an array in one embodiment of the present invention.

[0031] Figure 7 The transmission response relationship diagram of the metasurface unit to the x-polarized incident wave in one embodiment of the present invention is shown in FIG. 1 , wherein (a) is the amplitude of the incident wave. a 、 Ls (b) is the phase relationship diagram with a 、 Ls Change relationship diagram.

[0032] Figure 8 The amplitude of the reflection response of the metasurface unit to the right-hand circularly polarized incident wave in one embodiment of the present invention varies with the rx 、 β Change relationship diagram.

[0033] Figure 9 is the phase of the metasurface unit's reflection response to the right-handed circularly polarized incident wave in one embodiment of the present invention. rx 、 β Change relationship diagram.

[0034] Figure 10 The amplitude and phase distribution of each metasurface unit in the array according to an embodiment of the present invention, where (a) is the amplitude distribution and (b) is the phase distribution.

[0035] Figure 11 is the different parameters in one embodiment of the present invention. x Polarization electric field intensity image, where (a) is the xy Plane, focal length z =-150mm, frequency f =14GHz x Polarization electric field intensity image, (b) is xz flat, y Directional metasurface y Axis center point ( y =-5.4mm), frequency f =14GHz x Polarization electric field intensity image.

[0036] Figure 12 In one embodiment of the present invention xy On the plane, take y =0 (the vertical coordinates of the two foci), do x 1D graph showing the relationship between axis and electric field strength.

[0037] Figure 13 This is an experimental image of the letter "B" with 36×36 pixels in one embodiment of the present invention, where (a) is a grayscale image, (b) is a schematic diagram of the amplitude distribution of each metasurface unit obtained by theoretical calculation, and (c) is a schematic diagram of the phase distribution of each metasurface unit obtained by theoretical calculation.

[0038] Figure 14 Schematic diagram of the full-wave simulation results of the letter "B" corresponding to the metasurface with 36×36 pixels for the backward incident RCP plane wave in one embodiment of the present invention; wherein, (a) is xy noodle z= -140mm RCP wave electric field intensity, (b) is xy noodle z = -150mm RCP (Right-hand Circularly Polarized) wave electric field intensity, (c) is xy noodle z =-160mm RCP wave electric field intensity.

[0039] Figure 15 This is an experimental image of the letter "F" with 36×36 pixels in one embodiment of the present invention, where (a) is a grayscale image, (b) is a schematic diagram of the amplitude distribution of each metasurface unit obtained by theoretical calculation, and (c) is a schematic diagram of the phase distribution of each metasurface unit obtained by theoretical calculation.

[0040] Figure 16 Schematic diagram of the full-wave simulation results of the letter "F" corresponding to the metasurface with 36×36 pixels for the forward incident RCP plane wave in one embodiment of the present invention; wherein, (a) is xy noodle z = -140mm RCP wave electric field intensity, (b) is xy noodle z = -150mm RCP wave electric field intensity, (c) is xy noodle z =-160mm RCP wave electric field intensity.

[0041] The reference numerals in the figure are as follows: first metal ring - 1; first dielectric substrate - 2; second dielectric substrate - 3; metal gap layer - 4; third dielectric substrate - 5; fourth dielectric substrate - 6; second metal ring - 7; rectangular metal patch - 8;

[0042] The first rectangular metal patch is 81 ; the second rectangular metal patch is 82 ; the third rectangular metal patch is 83 ; and the fourth rectangular metal patch is 84 . DETAILED DESCRIPTION

[0043] Hereinafter, the technical solution provided by the present invention will be further elaborated in combination with embodiments and drawings.

[0044] Example 1:

[0045] This embodiment involves the following terms:

[0046] (1) Amplitude: Amplitude indicates the size or strength of a signal and is usually expressed in decibels (dB) or linear values (absolute values). The amplitude of the reflection coefficient S11 represents the voltage reflection coefficient of the port. If the amplitude is -20 dB, it corresponds to a linear value of 0.1, and the power reflection ratio is 0.01. The smaller the amplitude and the closer it is to negative infinity dB, the weaker the reflection. The amplitude of the transmission coefficient S21 represents the transmission efficiency of the signal from port 1 to port 2. The larger the amplitude and the closer it is to 0 dB, the higher the transmission efficiency.

[0047] (2) Phase: Phase represents the relative delay of a signal in time or space, measured in degrees (°) or radians (rad). Phase differences reflect differences in signal propagation paths or nonlinear phase responses of devices. The phase of the reflection coefficient S11 represents the phase shift of the reflected signal. The phase of the transmission coefficient S21 represents the phase delay of the transmitted signal. Amplitude and phase together constitute the complex S parameter.

[0048] (3) Amplitude-phase decoupling: Amplitude-phase decoupling is a key technology in metasurface design. It refers to the ability to independently control the amplitude and phase of electromagnetic waves by adjusting the geometric parameters or material properties of the metasurface units when designing the metasurface units. This independent control capability greatly improves the design flexibility and functional diversity of metasurfaces, making them perform better in applications such as wavefront control, metalenses, and holographic imaging.

[0049] (4) Multifunctional metasurface: This refers to a metasurface material that can simultaneously control multiple electromagnetic wave properties (such as reflection, transmission, polarization, phase, amplitude, etc.). It achieves multiple controls on electromagnetic waves through carefully designed subwavelength structural units, and has high flexibility and diverse functions. Compared with traditional single-function metasurfaces, multifunctional electromagnetic metasurfaces can achieve different types of electromagnetic wave control on the same platform, thereby meeting more complex application requirements.

[0050] (5) Linearly polarized wave: Linearly polarized wave refers to an electromagnetic wave whose electric field vector remains unchanged along a certain direction during propagation, presenting a linear polarization state. x Polarized waves and y Polarized waves. y Polarized waves in this invention refer to the electric field angle and y An incident plane wave with an axis angle of 0°. x Polarized waves in this invention refer to the electric field angle and y An incident plane wave with an axis angle of 90°.

[0051] (6) Circularly polarized waves: Circularly polarized waves are a special polarization form of electromagnetic waves in which the electric field vector rotates along a spiral path at a constant speed over time. Circularly polarized waves are divided into left-hand circularly polarized waves and right-hand circularly polarized waves. The difference between them lies in the direction of rotation of the electric field vector. Along the propagation direction of the wave, the electric field vector of the left-hand circularly polarized wave rotates counterclockwise, while the electric field vector of the right-hand circularly polarized wave rotates clockwise.

[0052] (7) Holographic imaging: The basic principle of metasurface holographic imaging is to arrange units with amplitude and phase control capabilities in a specific way, so that the metasurface can form a three-dimensional reconstruction of the target object in space for incident waves of different polarizations and frequencies, and reconstruct the preset holographic image. Metasurface holographic imaging can be used in fields such as three-dimensional display, optical stealth, and micro-optical equipment.

[0053] (8) Multi-focusing lens: The basic principle of the metasurface multi-focusing lens is to arrange units with amplitude and phase control capabilities in a specific way so that the metasurface can generate multiple focal points simultaneously on the same plane for a specific incident wave. Each unit can adjust the amplitude and phase of the electromagnetic wave according to the design requirements and change the propagation direction of the electromagnetic wave. Through the precise design of these units, the metasurface can generate multiple focal points simultaneously. The metasurface multi-focusing lens can be applied to multi-focus imaging systems, optical microscopes, optical communications and other fields.

[0054] Specifically, this embodiment designs a method that works at two frequencies and simultaneously regulates x Multifunctional amplitude-phase decoupling metasurface unit for polarized and circularly polarized incident waves. Through theoretical calculations, different AP combinations are assigned to each unit and arrayed to design a 36×36 array. Full-wave simulation of the array is performed to obtain a three-functional metasurface covering the entire space. x The polarized incident wave will form a double focal point in the transmission direction, and the circularly polarized waves incident from the forward and reverse directions will be reflected from the front and back surfaces respectively to reconstruct the preset image. By changing the physical structure of the top and bottom rings of the metasurface unit, the forward incident and reverse incident circularly polarized waves are regulated to form holographic images in the reflection direction respectively. By changing the length of the four-layer patch and the corresponding slit respectively, the forward incident circularly polarized waves are regulated. x Polarized waves form double focal points in the transmission direction.

[0055] This multifunctional metasurface unit, which uses amplitude-phase decoupling, utilizes a multi-layer dielectric stack structure consisting of four dielectric substrates, four patch layers, and a metal gap layer. Each metal layer sandwiches a dielectric substrate layer, and the gap layer in between reflects circularly polarized incident waves while simultaneously regulating linearly polarized incident waves, achieving full spatial amplitude-phase decoupling and independent control of the two polarization modes.

[0056] Specifically, the structure of the amplitude-phase decoupling multifunctional metasurface unit is as follows: Figure 1 As shown in the exploded view of the metasurface unit, it comprises, from top to bottom, four dielectric substrates: a first dielectric substrate 2, a second dielectric substrate 3, a third dielectric substrate 5, and a fourth dielectric substrate 6; four layers of rectangular metal patches 8, a metal slot layer 4, a first metal ring 1 on the top layer, and a second metal ring 7 on the bottom layer. The first dielectric substrate 2 is located at the top layer, with the first rectangular metal patch 81 and the first metal ring 1 above it. The second dielectric substrate 3 is located below the first dielectric substrate 2, with the second rectangular metal patch 82 placed above it, and the metal slot layer 4 below it. The third dielectric substrate 5 is located below the metal slot layer 4, with the third rectangular metal patch 83 below it. The fourth dielectric substrate 6 is located below the third rectangular metal patch 83, with the second metal ring 7 and the fourth rectangular metal patch 84 placed below it (on the bottom surface of the unit structure). The entire metasurface unit is made of F4B sheet material with a dielectric constant of 3.5. The metasurface period p = 10.8 mm, and the dielectric substrate thickness h is 1.5 mm.

[0057] The specific structure of the metasurface unit is as follows Figure 2 、 Figure 3 As shown. The metasurface unit consists of four layers of metal patches 8, a first metal ring 1 on the top layer, a second metal ring 7 on the bottom layer, and a metal gap layer 4. a The length of the metal gap layer 4 Ls length, together to complete the transmission x Polarized wave amplitude and phase decoupling modulation. Among them, the four layers of rectangular metal patches 8 change synchronously, and the width of the rectangular metal patches 8 b =3mm, length a The gap width of the metal gap layer 4 varies from 2mm to 5.8mm. ws =0.5mm, length Ls The range is from 0.5mm to 6mm. By independently setting the rotation angle of the first metal ring 1 and the second metal ring 7 and their respective rx The width of the metal ring 1 and the metal layer of the metal gap layer 4 form a reflection, and together complete the amplitude and phase decoupling modulation of the reflected right-hand circularly polarized wave. Among them, the rotation angle of the first metal ring 1 and the second metal ring 7 is β 1 and β 2 can be set independently and any value between 0-180° can be selected. rw =0.2mm, the inner radius of the ring is r =4.3mm, rectangular outside the ring y The shaft width is ry =0.2mm, width w The first metal ring 1 and the second metal ring 7 are both 1.6mm.x Shaft length rx 1 and rx 2 can be set independently, the range of change is 0.2mm-1.1mm. Fixed ry And change rx The amplitude of the incident right-hand circularly polarized wave can be adjusted to vary from 0 to 1; and the phase of the incident right-hand circularly polarized wave can be adjusted by changing the rotation angle of the first metal ring 1 and the second metal ring 7 to cover a range of 0-360°.

[0058] The AP combination required for each unit is calculated based on the principles of different applications, thereby determining the 36×36 metasurface array combination. The schematic diagram of the arrangement of the top dielectric substrate when the metasurface units form an array is shown in the following figure: Figure 4 As shown, the bottom layer 5 is the same as the first layer except for the ring structure, and is not shown separately. The arrangement diagram of the second layer of dielectric substrate 3 when the metasurface unit forms an array is shown in FIG. Figure 5 As shown, the arrangement diagram of the metal gap layer 4 when the metasurface units form an array is as shown in FIG. Figure 6 shown.

[0059] 1. Working principle of amplitude-phase decoupling metasurface unit:

[0060] The main method used is to combine geometric phase and propagation phase to achieve amplitude-phase decoupled modulation of circularly polarized incident waves. The geometric phase and propagation phase control the phase response and amplitude response of the circularly polarized incident wave, respectively. The amplitude and phase of the co-polarization reflection coefficient and cross-polarization reflection coefficient of the circularly polarized wave can be written as:

[0061] ;

[0062] ;

[0063] ;

[0064] ;

[0065] Wherein, the subscripts + and - represent right-hand circularly polarized waves (RHCP) and left-hand circularly polarized waves (LHCP), respectively. r ++ is the magnitude of the co-polarization reflection coefficient for right-hand circularly polarized wave incidence, for x Direction Phase and y Directional phase Φ y The phase difference, represents the phase of the co-polarization and cross-polarization reflection coefficients, r -+ is the magnitude of the cross-polarization reflection coefficient for right-hand circularly polarized wave incidence.

[0066] It can be seen that the magnitudes of the co-polarization and cross-polarization reflection coefficients are determined only by and Φ y Phase difference The phase of the co-polarization reflection coefficient depends on the geometric phase (2 β ) and propagation phase ( and Φ y ), the phase of the cross-polarization reflection coefficient is determined only by the propagation phase. This embodiment uses right-hand circularly polarized wave incident, so the phase of the right-hand circularly polarized wave reflection coefficient can be changed by adjusting the rotation angle of the first metal ring 1 and the second metal ring 7; y Width of the directional rectangular patch ry ,Adjustment x Width of the directional rectangular patch ( rx ), the phase difference can be changed and , thereby regulating the amplitude of the right-hand circularly polarized wave reflection coefficient.

[0067] In this embodiment, four layers of synchronously changing metal rectangular patches and the rectangular slots in the middle layer are used to realize the x Amplitude-phase decoupled modulation of polarized incident waves. x The phase and amplitude distributions of the polarization transmission response are respectively determined by the length of the rectangular patch a Perpendicular to the length a Length of the rectangular slot in the direction Ls Control. Although this structure x The amplitude-phase decoupling modulation relationship of the polarization transmission response is complex and nonlinear, but by properly choosing a In principle, any AP combination with an amplitude ranging from 0-1 and a phase ranging from 0-360° can be achieved by adjusting the length of Ls.

[0068] 2. Arrangement principle of metasurface array:

[0069] (1) Multi-focusing lenses are of vital importance for energy harvesting and efficient wireless power transmission. x Polarized incident waves have the ability to decouple amplitude and phase, and are designed to z =-150mm, xy Planar lateral bifocal metalens. The complex amplitude distribution required for the metasurface array can be expressed as:

[0070] ;

[0071] Where, x 、 y 、 z Represent the three axes of the three-dimensional coordinate system, A 1.A 2 are focal lengths f 1. f 2The amplitude of the two foci, ( x 1, y 1) and ( x 2, y 2) The transverse coordinates of the two foci, λ 0 is the wavelength of the working frequency in free space. The amplitudes of the dual focal points are both set to 1, and the focal coordinates are set to ( x 1, y 1)=(-75mm,0mm),( x 2, y 2)=(75mm,0mm). Therefore, according to the specific focal amplitude, focal length and coordinates set, the amplitude and phase distribution of the corresponding position on the metasurface unit can be calculated to form the required metasurface array.

[0072] (2) Holographic imaging also shows great application prospects in the fields of information coding, near-field communication, data storage and security. In order to prove that the designed metasurface unit has the ability to decouple the amplitude and phase of the forward RCP and backward RCP incident waves, the design can be respectively z =±150mm, xy Planar reflection reconstructs a metasurface array of preset letters. Rayleigh-Sommerfeld diffraction theory is used to analyze the AP combination of metasurface units required to reconstruct the target image. The AP distribution of the metasurface units can be expressed as the following formula:

[0073] ;

[0074] ;

[0075] ;

[0076] Where, represents the coordinates of the hologram plane, represents the coordinates of the imaging plane, and are the electric field distributions on the hologram plane and the imaging plane, respectively. λ and k are the operating wavelength and wave number in free space, n is the serial number of the metasurface unit in the imaging plane, r 1 is a point on the hologram plane and the point on the imaging plane The distance between S 0 is the imaging area; F is the focal length, i.e. z Axis direction, the distance between the imaging plane and the hologram plane, in this embodimentF =±150mm; Hologram plane The corresponding metasurface unit y The AP distribution of the metasurface units on the imaging plane is calculated to form the required metasurface array.

[0077] 3. Simulation results and explanation:

[0078] Metasurface unit pairs x The amplitude of the transmission response of the polarized incident wave varies with a 、 Ls The relationship between changes such as Figure 7 As shown in (a), the metasurface unit pair x The phase of the transmission response of the polarized incident wave varies with a 、 Ls The relationship between changes such as Figure 7 As shown in (b). It can be seen that when the length of the rectangular metal patch 8 a The length of the gap in the metal gap layer 4 remains unchanged. Ls When the length changes from 0.5mm to 5.5mm, the amplitude can change from 0 to 1; Ls Unchanged, long a When changing from 2mm to 5.5mm, the phase covers the range of -180° to 180°.

[0079] The amplitude of the metasurface unit's reflection response to the right-handed circularly polarized incident wave varies with rx 、 β The relationship between changes such as Figure 8 As shown in the figure, the phase of the metasurface unit's reflection response to the right-hand circularly polarized incident wave varies with rx 、 β The relationship between changes such as Figure 9 As shown. It can be seen that when β constant, rx When the amplitude changes from 0.2mm to 0.9mm, the amplitude can change from 0 to 1, while the phase change is small, and the phase change is within 60 degrees. This phase change can be adjusted by fine-tuning the rotation angle. β To achieve compensation. Figure 10 It can be seen that when rx constant, β When changing from 0-180°, the amplitude remains almost unchanged, while the phase can cover the range of 0-360°. β Including the rotation angle of the first metal ring 1 β 1 and the rotation angle of the second metal ring 7 β 2. It can respond to right-hand circularly polarized waves incident from the top or bottom surface.

[0080] for xThe dual-focus function of the polarized incident wave transmission response is used to calculate and sample the complex amplitude distribution of the metasurface array, thereby extracting the amplitude and phase of each unit. The AP distribution of each metasurface unit in the 36×36 array obtained by theoretical calculation is as follows: Figure 10 As shown in (a) and (b).

[0081] The metasurface array composed of metasurface units is x Full-wave simulation results in the transmission direction when a polarized wave is incident. Figure 11 (a) is in xy Plane, focal length z =-150mm, frequency f =14GHz x Polarization electric field intensity image. Figure 11 (b) is in xz flat, y Directional metasurface y Axis center point ( y =-5.4mm), frequency f =14GHz x Polarization electric field intensity image. Among them, Ex is x Polarization xy The electric field strength on a plane, V / m (volts per meter) is the unit of electric field strength. Figure 11 In (a) and (b), clear double focal points can be clearly observed. Figure 12 For Figure 11 (a) xy On the plane, take y =0 (the vertical coordinates of the two foci), do x A 1D graph showing the relationship between the axis and the electric field strength. Figure 12 It can be seen that the amplitudes of the two foci are close to 1, and the focal coordinates are ( x 1, y 1)=(-70mm,0mm),( x 2, y 2)=(81mm,0mm), which is quite close to the initial focal coordinates. The full-wave simulation results of the bifocal metalens are consistent with the theoretical results.

[0082] For the holographic imaging function of the forward and backward incident RCP wave reflection response, the complex amplitude distribution of the metasurface imaging plane is calculated and sampled, thereby extracting the specific amplitude and phase distribution of each unit in the array. Figure 13 (a) is a grayscale image of the letter "B" with a pixel size of 36×36. When the backward RCP wave is incident, the AP distribution of the metasurface unit is manipulated to be at a lower frequency. f =6GHz, xy noodle,z =-150mm, reflection Figure 13 The letter "B" shown in (a). Figure 13 (b) and (c) show the AP distribution of each metasurface unit in the 36×36 array obtained through theoretical calculation.

[0083] Figure 14 (a), (b), and (c) are the full-wave simulation results of the metasurface array for the backward incident RCP plane wave. Specifically, they are xy Plane, z=-140mm, z =-150mm, z =-160mm RCP wave electric field intensity image. Among them, ELCP is left-hand circularly polarized wave. xy The electric field intensity of the plane. It can be seen that in the holographic imaging plane z =-150mm and ±10mm positions have obvious letter "B" displayed, and the imaging effect is better.

[0084] Figure 15 (a) is a grayscale image of the letter "F" with a pixel size of 36×36. Under the condition of forward RCP wave incidence, the AP distribution of the metasurface unit is manipulated to be at a lower frequency. f =6GHz, xy flat, z =150mm, reflection Figure 15 The letter "F" shown in (a). Figure 15 (b) and (c) show the amplitude and phase distribution of each metasurface unit in the array obtained through theoretical calculations.

[0085] Figure 16 (a), (b), and (c) are the full-wave simulation results of the metasurface array for the forward incident RCP plane wave. Specifically, they are xy Plane, z=140mm, z =150mm, z =160mm RCP wave electric field intensity image. It can be seen that at the holographic imaging plane z =150mm and the ±10mm positions have obvious letter "F" displayed, and the imaging effect is better.

[0086] This example constructs a 36×36 metasurface array to achieve optimal focusing and imaging. The low-cost F4B substrate is used, and the multi-layer dielectric substrates are secured using a PCB manufacturing process with insulated nylon screws. This makes it easy to manufacture and install, while maintaining a low cost. It should be noted that while the metasurface provided in this example is a 36×36 array, the array size can be adjusted to meet specific needs in practical applications.

[0087] Combined with the above embodiments, it can be seen that the technical solution provided by the present invention solves the problem that traditional multifunctional metasurfaces can only work in half space. It adopts a stacked structure and a slot design in the middle layer to ensure that low-frequency circularly polarized waves are directly reflected and high-frequency linearly polarized waves pass through the slots. Both linearly polarized waves and circularly polarized waves can achieve amplitude-phase decoupling modulation. In addition, optimization has been made in terms of integration. Through structural innovation and changes in the variable range, the mutual influence between linearly polarized and circularly polarized incident waves, transmission and reflection functions is reduced, thereby improving the integration of the metasurface. Furthermore, a full-process methodology has been developed that uses amplitude-phase decoupling metasurface units, starting from actual functions, writes code for different functions to perform AP calculations, and then converts them into the physical length of the unit. Finally, Matlab-Cst joint automatic modeling is used to transform the unit into a complex array, and full-wave simulation analysis of the array is performed.

[0088] In summary, the present invention designs a metasurface unit with amplitude-phase decoupling, which can greatly improve the design flexibility and functional diversity of the metasurface. Existing metasurface electromagnetic wave modulation methods are mostly phase-only modulation PO (Phase-Only Modulation) method, amplitude-only modulation AO (Amplitude-Only Modulation) method, etc. Due to the omission of important information such as amplitude or phase, the PO and AO methods have large noise and low precision. Metasurfaces with amplitude-phase decoupling modulation can significantly improve the efficiency of beam control, making it perform better in applications such as wavefront control, superlens, and holographic imaging. At the same time, on the basis of amplitude-phase decoupling modulation of the metasurface unit, a variety of combination integrations are provided in terms of polarization mode, radiation direction, frequency band, etc., with higher integration.

[0089] It should be noted that the above embodiment proposes a specific implementation technology of an amplitude-phase decoupled multifunctional metasurface, but the actual technical solution is not limited to this. For unit design, independent and non-interfering decoupling control of the polarized waves of the transmitted line can be achieved by introducing mutually orthogonal rectangular patches and mutually orthogonal rectangular slits. At the same time, by using the PG (Propagation phase) phase combined with the PB (Pancharatnam-Berry, geometric phase) phase method, an axially symmetric structure can be set to achieve amplitude-phase decoupling control of the circularly polarized incident wave. It is also possible to change the resonance point, bandwidth and other indicators of the metasurface operation by changing the size variation range of structures such as patches, rings, and slits and the number of stacking layers.

[0090] It can be seen from the above embodiments and the accompanying drawings that in the technical solution provided by the present invention, by adjusting the rotation angles of the first metal ring and the second metal ring and the widths of the rectangular areas in the second rectangular pair and the fourth rectangular pair in different metasurface units, it is possible to achieve full-phase and full-amplitude reflection responses to forward right-handed circularly polarized incident waves and backward right-handed circularly polarized incident waves, such as the reflection reconstruction of a preset pattern; further, by adjusting the lengths of the rectangular metal patches and the metal gap layers ... x The full-phase and full-amplitude transmission response of the polarized incident wave can further realize the function of a lateral dual-focus metalens. In addition, the use of a stacked structure and a slotted middle layer can ensure that low-frequency circularly polarized waves are directly reflected, while high-frequency linearly polarized waves pass through the gaps. Both linearly polarized waves and circularly polarized waves can be modulated with amplitude and phase decoupling, and the mutual influence between linearly polarized and circularly polarized incident waves, transmission and reflection functions is reduced, significantly improving the integration of the metasurface.

[0091] In short, the technical solution provided by the present invention overcomes the technical problems of the prior art, such as single radiation mode, single polarization mode, and low integration.

Claims

1. A multifunctional metasurface based on amplitude-phase decoupling modulation, characterized in that: include l × l metasurface units arranged in an array, l ≥2; The metasurface unit includes: A first metal ring (1) is attached to the upper surface of the first dielectric substrate (2); Four rectangular areas of equal length are provided at equal intervals in the circumferential direction of the first metal ring (1), and the non-adjacent rectangular areas have equal widths, forming a first rectangular pair and a second rectangular pair; A first rectangular metal patch (81) is also provided at the center of the first metal ring (1); A second rectangular metal patch (82) is provided between the first dielectric substrate (2) and the second dielectric substrate (3); The metal gap layer (4) is provided between the second dielectric substrate (3) and the third dielectric substrate (5), and a rectangular gap is provided at the center; the long side of the rectangular gap is perpendicular to the long side of the first rectangular metal patch (81); A third rectangular metal patch (83) is provided between the third dielectric substrate (5) and the fourth dielectric substrate (6); A second metal ring (7) having the same width as the first metal ring (1) is attached to the lower surface of the fourth dielectric substrate (6); Four rectangular areas of equal length are provided at equal intervals in the circumferential direction on the second metal ring (7), and the non-adjacent rectangular areas have equal widths, forming a third rectangular pair and a fourth rectangular pair; A fourth rectangular metal patch (84) is also provided at the center of the second metal ring (7); In different metasurface units: The long side of the first rectangular metal patch (81) has a different angle with the diameter of the first rectangular pair; the long side of the first rectangular metal patch (81) has a different angle with the diameter of the third rectangular pair; The widths of the rectangular areas in the first rectangular pair and the third rectangular pair are both equal to the width of the first metal ring (1); The widths of the rectangular areas in the center of the second rectangle are not equal and are greater than or equal to the width of the first metal ring (1); The widths of the rectangular areas in the fourth rectangle are not equal and are greater than or equal to the width of the first metal ring (1).

2. The multifunctional metasurface based on amplitude-phase decoupling modulation according to claim 1, characterized in that: In different metasurface units, the lengths of the rectangular metal patches (8) are not equal, and the lengths of the metal gap layers (4) are not equal.

3. The multifunctional metasurface based on amplitude-phase decoupling modulation according to claim 1, characterized in that: Also includes: The plane where the array is located is xy Flat, with z Towards, xy The AP distribution of the hypersurface unit in the hypersurface of the preset pattern reconstructed by plane reflection is as follows: ； ； ； Where, represents the coordinates of the hologram plane, represents the coordinates of the imaging plane, and are the electric field distributions on the hologram plane and the imaging plane, respectively. i is the imaginary unit, r is the inner radius of the first metal ring, λ and k are the operating wavelength and wave number in free space, n is the serial number of the metasurface unit in the imaging plane, r 1 is a point on the hologram plane Points on the imaging plane The distance between S 0 is the imaging area, F is the distance between the imaging plane and the hologram plane, is the corresponding metasurface unit in the hologram plane y coordinate.

4. The multifunctional metasurface based on amplitude-phase decoupling modulation according to claim 2, characterized in that: Also includes: The plane where the array is located is xy Flat, with z Towards, xy Complex amplitude distribution in the metasurface of a planar lateral bifocal metalens , the formula is as follows: ； in, x 、 y 、 z Represent the three axes of the three-dimensional coordinate system, A 1. A 2 are focal lengths f 1. f 2The amplitude of the two foci, ( x 1, y 1) and ( x 2, y 2) The transverse coordinates of the two foci, λ 0 is the wavelength of the operating frequency in free space.

5. The multifunctional metasurface based on amplitude-phase decoupling modulation according to claim 4, characterized in that: described z Towards, xy The planar lateral bifocal metalens is specifically z =-150mm, xy lateral bifocal metalens, ( x 1, y 1)=(-75mm,0mm),( x 2, y 2)=(75mm,0mm), the amplitude of both focal points is 1.

6. A multifunctional metasurface based on amplitude-phase decoupling modulation according to any one of claims 1 to 5, characterized in that: In each metasurface unit, All dielectric substrates are square, with a side length of 10.8 mm and a thickness of 1.5 mm, and are made of F4B with a dielectric constant of 3.5; The metal gap layer (4) is a square with a side length of 10.8 mm; r =4.3mm, rw =0.2mm, w =1.6mm,0.2mm≤ rx 1≤1.1mm,0.2mm≤ rx 2≤1.1mm; in, r and rw are the inner radius and width of all metal rings respectively ，w is the length of all rectangular areas, rx 1 is the width of the rectangular area in the center of the second rectangle. rx 2 is the width of the rectangular area in the center of the fourth rectangle; 0°≤ β 1≤180°,0°≤ β 2≤180°; where β 1 and β 2 are the rotation angles of the first metal ring (1) and the second metal ring (7); 2mm≤ a ≤5.8mm, b =3mm; where a and b are the length and width of the rectangular metal patch (8) respectively; ws =0.5mm, 0.5mm≤ Ls ≤6mm; among which, ws and Ls are the width and length of the rectangular gap respectively.

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