A reflective metasurface unit structure for electromagnetic wave regulation

Abstract

The present invention relates to a reflective metasurface unit structure for electromagnetic wave regulation, belonging to the technical field of metasurface electromagnetic regulation, and solves the problems of narrow working frequency band, low efficiency, difficult phase modulation, single polarization regulation, and limited application scenarios of existing metasurface unit structures. The unit structure includes: a rectangular conductor sheet, a dielectric layer, and a conductor plate arranged in sequence along the direction of normal incidence of electromagnetic waves, the dielectric layer covering the conductor plate, and the rectangular conductor sheet and the conductor plate being perfect electric conductors corresponding to the electromagnetic wave frequency band; wherein, the rectangular conductor sheet, the dielectric layer, and the conductor plate have the same geometric center, and the major axis of the rectangular conductor sheet forms a predetermined angle with the horizontal axis of the conductor plate, the predetermined angle being the direction angle of the rectangular conductor sheet, and this direction angle being related to the amplitude and phase of the electromagnetic wave. The metasurface unit structure has a wide working frequency band, high efficiency, flexible regulation of phase and amplitude, and diverse polarization regulation methods, and can be applied to a variety of application scenarios.

Description

Technical Field

[0001] The present invention relates to the technical field of metasurface electromagnetic regulation, and particularly relates to a reflective metasurface unit structure for electromagnetic wave regulation. Background Art

[0002] As an electromagnetic wave regulation device, metamaterials have a certain regulation ability for the amplitude, phase, and polarization of electromagnetic waves, and have currently achieved applications in beam deflection, beam focusing, vortex beams, Bessel beams, etc. However, with the continuous improvement of beam regulation requirements, people are no longer satisfied with the single regulation of the amplitude or phase of electromagnetic waves, but pursue more functions and more flexible regulation methods, which also greatly improves the performance requirements for the metamaterial unit structure. As a 2D form of metamaterials, metasurfaces not only have the function of electromagnetic wave regulation, but also have the characteristics of thin thickness, easy miniaturization and integration, and have received extensive attention in recent years.

[0003] As a controllable electromagnetic wave device, metasurfaces can be used to generate special beams. Among them, the Airy beam, as a special beam, has characteristics such as non-diffraction, self-bending, and self-healing, and has become a research hotspot in recent years. In the prior art, the Airy beam can be generated in the following ways: First, the Airy beam is generated by optical devices. This method requires a large number of optical devices, and its defects are low space utilization rate, difficult integration, etc., which seriously limit the development of metasurface devices. Second, in the optical frequency band, a dielectric column metasurface can be used as a structural unit to generate the Airy beam. This method can only achieve the phase regulation of the beam, and the Airy beam is formed by the diffraction of spatial light; at the same time, the quality of the Airy beam generated by this method is relatively poor, and the available range of the Airy beam is extremely limited in the propagation direction. Third, in the microwave band and the infrared band, a dual-frequency Airy beam is generated by a metasurface device, and an Airy beam in the transmission form and surface plasmon polaritons can also be generated simultaneously. When using plasmon polaritons to generate the Airy beam, since the Airy beam generated in this way is on the surface of the metal layer, the use space of the beam is greatly limited. In addition, in the prior art, there are also various methods for generating the Airy beam through complex metasurface designs, such as multi-layer film designs, complex patch shapes, multi-layer complex Huygens metasurfaces, etc. These complex designs make device processing difficult, and the functions of the devices themselves are single.

[0004] The prior art has at least the following defects: First, it is impossible to simultaneously regulate the amplitude and phase of electromagnetic waves, and it is impossible to simultaneously regulate the amplitude and polarization of electromagnetic waves, and the working frequency band is narrow, the efficiency is low, the regulation method is complex, the polarization regulation method is single, and the use scenario is limited; Second, the existing metasurface structures usually need to change their structural dimensions to achieve the regulation of phase or amplitude. The regulation method has low flexibility, and the processing difficulty is large, it is not easy to integrate, and the manufacturing cost is increased. Summary of the Invention

[0005] In view of the above analysis, the present invention aims to provide a reflective metasurface unit structure for electromagnetic wave regulation, so as to solve the problems of narrow working frequency band, low efficiency, difficulty in independently modulating phase and amplitude, single polarization regulation, and limited usage scenarios of existing metasurface unit structures.

[0006] On the one hand, the present invention provides a reflective metasurface unit structure for electromagnetic wave regulation, including: a rectangular conductor sheet, a dielectric layer, and a conductor plate arranged in sequence along the direction of normal incidence of electromagnetic waves, the dielectric layer covering the conductor plate, and the rectangular conductor sheet and the conductor plate being perfect electric conductors corresponding to the electromagnetic wave frequency band;

[0007] Wherein, the rectangular conductor sheet, the dielectric layer, and the conductor plate have the same geometric center, and the major axis of the rectangular conductor sheet forms a predetermined angle with the horizontal axis of the conductor plate, the predetermined angle being the direction angle of the rectangular conductor sheet, and the direction angle being related to the amplitude and phase of the electromagnetic wave.

[0008] Further, the direction angle of the conductor sheet and the amplitude of the cross-polarization reflection coefficient of the linearly polarized incident electromagnetic wave satisfy the following relationship:

[0009] A1 = A 1(45°) |sin(2θ1)|,

[0010] Wherein, θ1 represents the direction angle of the conductor sheet, the value range of the direction angle is (-180°, 180°], A1 represents the amplitude of the cross-polarization reflection coefficient of the linearly polarized incident electromagnetic wave, and A 1(45°) represents the amplitude of the cross-polarization reflection coefficient of the linearly polarized incident electromagnetic wave when the direction angle θ1 of the conductor sheet is 45°.

[0011] Further, the direction angle of the conductor sheet and the amplitude of the co-polarization reflection coefficient of the linearly polarized incident electromagnetic wave satisfy the following relationship:

[0012] A2 = A 2(0°) |cos(2θ2)|,

[0013] Wherein, θ2 represents the direction angle of the conductor sheet, the value range of the direction angle is (-180°, 180°], A2 represents the amplitude of the co-polarization reflection coefficient of the linearly polarized incident electromagnetic wave, and A 2(0°) represents the amplitude of the co-polarization reflection coefficient of the linearly polarized incident electromagnetic wave when the direction angle θ2 of the conductor sheet is 0°.

[0014] Further, when the range of the direction angle of the conductor sheet is (-180°, -90°] or (0°, +90°], the phase value of the cross-polarization reflection coefficient of the linearly polarized incident electromagnetic wave is the first phase value; when the range of the direction angle of the conductor sheet is (-90°, 0°] or (+90°, +180°], the phase value of the cross-polarization reflection coefficient of the linearly polarized incident electromagnetic wave is the second phase value, and the phase difference between the first phase value and the second phase value is 180°

[0015] Further, when the range of the direction angle of the conductor sheet is (-45°, +45°], (-180°, -135°] or (+135°, +180°], the phase value of the co-polarization reflection coefficient of the linearly polarized incident electromagnetic wave is the first phase value; when the range of the direction angle of the conductor sheet is (-135°, -45°] or (+45°, +135°], the phase value of the co-polarization reflection coefficient of the linearly polarized incident electromagnetic wave is the second phase value, and the phase difference between the first phase value and the second phase value is 180°.

[0016] On the other hand, the present invention provides an Airy beam generator, including a two-dimensional array composed of reflective metasurface unit structures and an electromagnetic wave generating device;

[0017] Wherein, in the first dimension of the two-dimensional array, the magnitude of the direction angle of the conductor sheet of each metasurface unit structure corresponds to the aperture amplitude of the Airy beam at the position of the metasurface unit structure; the range of the direction angle of the conductor sheet of each metasurface unit structure corresponds to the aperture phase of the Airy beam at the position of the metasurface unit structure.

[0018] Further, the thicknesses of both the conductor sheet and the conductor plate are 0.018 mm, the length of the conductor sheet is 7.55 mm, the width is 2 mm, and the side length of the conductor plate is 10 mm.

[0019] Further, the side length of the dielectric layer is 10 mm and the thickness is 3 mm.

[0020] Further, the material of the dielectric layer is a lossless dielectric material.

[0021] On the other hand, the present invention provides an Airy beam generator, including a two-dimensional array composed of reflective metasurface unit structures and an electromagnetic wave generating device;

[0022] Wherein, in the first dimension of the two-dimensional array, the magnitude of the direction angle of the conductor sheet of each metasurface unit structure corresponds to the aperture amplitude of the Airy beam at the position of the metasurface unit structure; the range of the direction angle of the conductor sheet of each metasurface unit structure corresponds to the aperture phase of the Airy beam at the position of the metasurface unit structure.

[0023] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0024] 1. The reflective metasurface unit structure proposed by the present invention utilizes a three-layer structure with the properties of a half-wave plate, which improves its operating bandwidth. By changing the electrical size of the metasurface unit structure, it can operate in the microwave band, infrared band, terahertz band, and optical frequency band. In addition, by setting the direction angle of the conductor sheet, the amplitude and phase of the reflected electromagnetic wave can be adjusted separately without changing the structural dimensions of the unit structure. Among them, the adjustment range of the amplitude is [0, 1], and it can also control the phase of the transmitted electromagnetic wave to change from 0 to π, or from π to 0. The control method is simple and flexible. In addition, this metasurface unit structure can not only be used to construct a generator for generating Airy beams, but also be used to construct an electromagnetic wave beam with an arbitrary amplitude distribution form and a binary form of phase distribution of 0 or π, such as a zero-order Bessel beam.

[0025] 2. For the cases of linear polarization co-polarization and linear polarization cross-polarization, the reflective metasurface unit structure proposed by the present invention can respectively control the phase and amplitude of the reflection coefficient of the reflected electromagnetic wave by setting the angle, which improves the utilization rate of the unit structure and expands its application scenarios.

[0026] 3. The Airy beam generator based on the metasurface unit structure proposed by the present invention can generate high-quality Airy beams for linearly polarized incident electromagnetic waves in the frequency band of 12 - 17 GHz. In addition, the structural dimensions of each metasurface unit structure in the two-dimensional array of the Airy beam generator are the same, and only the direction angles of the conductor sheets are different, which simplifies the manufacturing process of the two-dimensional array and greatly reduces the manufacturing cost.

[0027] In the present invention, the above technical solutions can also be combined with each other to achieve more preferred combination schemes. Other features and advantages of the present invention will be described in the subsequent specification, and some advantages can be made obvious from the specification, or understood by implementing the present invention. The objectives and other advantages of the present invention can be realized and obtained through the content specifically pointed out in the specification and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings are only for the purpose of showing specific embodiments and are not considered as a limitation to the present invention. Throughout the drawings, the same reference signs represent the same components.

[0029] Figure 1 is a schematic diagram of the metasurface unit structure;

[0030] Figure 2 is a schematic diagram of the curve of the amplitude of the electromagnetic wave cross-polarization reflection coefficient corresponding to different direction angles in the embodiment of the present invention changing with the incident electromagnetic wave frequency;

[0031] Figure 3 Schematic diagram of the curve of the magnitude of the co-polarization reflection coefficient corresponding to different directions in the embodiments of the present invention varying with the incident electromagnetic wave frequency;

[0032] Figure 4 Schematic diagram of the curve of the magnitude of the cross-polarization reflection coefficient corresponding to incident electromagnetic waves of different frequencies in the embodiments of the present invention varying with the direction angle;

[0033] Figure 5 Schematic diagram of the curve of the phase of the cross-polarization reflection coefficient corresponding to incident electromagnetic waves of different frequencies in the embodiments of the present invention varying with the direction angle;

[0034] Figure 6 Schematic diagram of the curve of the magnitude of the co-polarization reflection coefficient corresponding to incident electromagnetic waves of different frequencies in the embodiments of the invention varying with the direction angle;

[0035] Figure 7 Schematic diagram of the curve of the phase of the co-polarization reflection coefficient corresponding to incident electromagnetic waves of different frequencies in the embodiments of the present invention varying with the direction angle;

[0036] Figure 8 Schematic diagram of the amplitude distribution of the Airy beam in the embodiments of the present invention;

[0037] Figure 9 Schematic diagram of the phase distribution of the Airy beam in the embodiments of the present invention;

[0038] Figure 10 Schematic diagram of the structure of the two-dimensional array composed of the metasurface unit structures in the Airy beam generator in the embodiments of the present invention;

[0039] Figure 11 Schematic diagram of the Airy beam obtained by simulation when the incident electromagnetic wave is 12 GHz in the embodiments of the present invention;

[0040] Figure 12 Schematic diagram of the Airy beam obtained by experiment when the incident electromagnetic wave is 12 GHz in the embodiments of the present invention;

[0041] Figure 13 Schematic diagram of the Airy beam obtained by simulation when the incident electromagnetic wave is 14 GHz in the embodiments of the present invention;

[0042] Figure 14 Schematic diagram of the Airy beam obtained by experiment when the incident electromagnetic wave is 14 GHz in the embodiments of the present invention;

[0043] Figure 15 Schematic diagram of the Airy beam obtained by simulation when the incident electromagnetic wave is 17 GHz in the embodiments of the present invention;

[0044] Figure 16Schematic diagram of Airy beam obtained from experiments when the incident electromagnetic wave is 17 GHz in the embodiments of the present invention;

[0045] Figure 17 Schematic diagram of the variation curve of the full-width at half-maximum of the main lobe intensity of the Airy beam obtained when the incident electromagnetic wave is 12 GHz in the embodiments of the present invention with the propagation distance;

[0046] Figure 18 Schematic diagram of the variation curve of the full-width at half-maximum of the main lobe intensity of the Airy beam obtained when the incident electromagnetic wave is 14 GHz in the embodiments of the present invention with the propagation distance;

[0047] Figure 19 Schematic diagram of the variation curve of the full-width at half-maximum of the main lobe intensity of the Airy beam obtained when the incident electromagnetic wave is 17 GHz in the embodiments of the present invention with the propagation distance.

[0048] Figure 20 Schematic diagram of the self-healing property of the Airy beam obtained in the embodiments of the present invention. Detailed implementation manners

[0049] The following will specifically describe the preferred embodiments of the present invention in conjunction with the accompanying drawings. The accompanying drawings form a part of this application and are used together with the embodiments of the present invention to explain the principles of the present invention, rather than to limit the scope of the present invention.

[0050] A specific embodiment of the present invention discloses a reflective metasurface unit structure for electromagnetic wave regulation.

[0051] As Figure 1 shown. The reflective metasurface unit structure includes: a rectangular conductor sheet, a dielectric layer, and a conductor plate arranged in sequence along the direction of the normal incidence of the electromagnetic wave, and the dielectric layer covers the conductor plate; wherein, the rectangular conductor sheet and the conductor plate are perfect electric conductors corresponding to the electromagnetic wave frequency band.

[0052] Specifically, the rectangular conductor sheet, the dielectric layer, and the conductor plate have the same geometric center (that is, the rectangular conductor sheet, the dielectric layer, and the conductor plate are arranged coaxially along the structure). Having the same geometric center means that when the metasurface unit structure is regarded as a plane from the direction of the normal incidence of the electromagnetic wave, the geometric centers of the rectangular conductor sheet, the dielectric layer, and the conductor plate are the same point; in addition, the major axis of the rectangular conductor sheet forms a predetermined angle with the horizontal axis of the conductor plate, and this horizontal axis is Figure 1 the x-axis in Figure 1 , so this predetermined angle is the angle between the major axis of the rectangular conductor sheet and the positive direction of the x-axis in Figure 1 . This predetermined angle is the direction angle of the rectangular conductor sheet, and this direction angle is related to the amplitude and phase of the electromagnetic wave. Therefore, the amplitude and phase of the electromagnetic wave can be regulated by setting this direction angle.

[0053] For the reflective metasurface unit structure, its polarization response to electromagnetic waves can be described by the Jones matrix:

[0054]

[0055] r j,i (i, j = x, y) represents the complex reflection coefficient corresponding to the incident polarization i and the reflected polarization j. Its magnitude represents the amplitude of the corresponding reflection coefficient (i.e., the amplitude of the reflected electromagnetic wave), and its phase represents the phase of the corresponding reflection coefficient (i.e., the phase of the reflected electromagnetic wave).

[0056] When the metasurface unit is rotated around the normal direction of the mouth surface (i.e., the direction of the normal incidence of the electromagnetic wave), its Jones matrix will be deformed into:

[0057]

[0058] When the performance of this metasurface unit structure is similar to that of a half-wave plate, its Jones matrix form is:

[0059]

[0060] Furthermore, the Jones matrix obtained after rotation can be determined as:

[0061]

[0062] From the above formula, it can be obtained that the magnitudes of the cross-polarization reflection coefficients r x,y 、r y,x satisfy the variation law of |sin2θ| with the direction angle of the conductor sheet. At the same time, the phase has two possible values of 0° and 180° within the range of the direction angle change; the magnitudes of the co-polarization reflection coefficients r x,x 、r y,y satisfy the variation law of |cos2θ| with the direction angle of the conductor sheet. At the same time, the phase has two possible values of 0° and 180° within the range of the direction angle change.

[0063] Specifically, the direction angle of the conductor sheet and the magnitude of the cross-polarization reflection coefficient of the linearly polarized incident electromagnetic wave satisfy the following relationship:

[0064] A1 = A 1(45°) |sin(2θ1)|,

[0065] where θ1 represents the direction angle of the conductor sheet, the value range of the direction angle is (-180°, 180°], A1 represents the magnitude of the cross-polarization reflection coefficient of the linearly polarized incident electromagnetic wave, and A 1(45°) represents the magnitude of the cross-polarization reflection coefficient of the linearly polarized incident electromagnetic wave when the direction angle θ1 of the conductor sheet is 45°.

[0066] In addition, when the range of the direction angle of the conductor sheet is (-180°, -90°] or (0°, +90°], the phase value of the cross-polarization reflection coefficient of the linearly polarized incident electromagnetic wave is the first phase value; when the range of the direction angle of the conductor sheet is (-90°, 0°] or (+90°, +180°], the phase value of the cross-polarization reflection coefficient of the linearly polarized incident electromagnetic wave is the second phase value, and the phase difference between the first phase value and the second phase value is 180°.

[0067] Specifically, the direction angle of the conductor sheet and the amplitude of the co-polarization reflection coefficient of the linearly polarized incident electromagnetic wave satisfy the following relationship:

[0068] A2 = A 2(0°) |cos(2θ2)|,

[0069] where θ2 represents the direction angle of the conductor sheet, the range of the direction angle is (-180°, 180°], A2 represents the amplitude of the co-polarization reflection coefficient of the linearly polarized incident electromagnetic wave, and A 2(0°) represents the amplitude of the co-polarization reflection coefficient of the linearly polarized incident electromagnetic wave when the direction angle θ2 of the conductor sheet is 0°.

[0070] At this time, for the cases of x-polarized incident co-polarization and y-polarized incident co-polarization, the direction angle of the conductor sheet and the co-polarization reflection coefficient both satisfy the following conditions:

[0071] When the range of the direction angle of the conductor sheet is (-45°, +45°], (-180°, -135°] or (+135°, +180°], the phase value of the co-polarization reflection coefficient of the linearly polarized incident electromagnetic wave is the first phase value; when the range of the direction angle of the conductor sheet is (-135°, -45°] or (+45°, +135°], the phase value of the co-polarization reflection coefficient of the linearly polarized incident electromagnetic wave is the second phase value, and the phase difference between the first phase value and the second phase value is 180°.

[0072] Specifically, when the range of the direction angle of the conductor sheet is (-45°, +45°], (-180°, -135°] or (+135°, +180°], the phase difference between the first phase value of the co-polarization reflection coefficient of the x-polarized incident electromagnetic wave and the first phase value of the co-polarization reflection coefficient of the y-polarized incident electromagnetic wave is 180°; when the range of the direction angle of the conductor sheet is (-135°, -45°] or (+45°, +135°], the phase difference between the second phase value of the co-polarization reflection coefficient of the x-polarized incident electromagnetic wave and the second phase value of the co-polarization reflection coefficient of the y-polarized incident electromagnetic wave is 180°.

[0073] Those skilled in the art can know that in the present invention, the intensity of the electromagnetic wave has the same meaning as the amplitude of the electromagnetic wave, and the intensity of the electromagnetic wave is the amplitude of the electromagnetic wave.

[0074] In this metasurface structure, the conductor sheet and the conductor plate are perfect electric conductors. The thickness of both the conductor sheet and the conductor plate is 0.018 mm. The length of the conductor sheet is 7.55 mm and the width is 2 mm. The side length of the conductor plate is 10 mm. The side length of the dielectric layer is 10 mm and the thickness is 3 mm. The dielectric layer material is set as a lossless dielectric material. Based on the above structural parameter settings, simulations are carried out, and the specific simulation results are as follows:

[0075] From Figure 2 it can be seen that within the 12 - 17 GHz frequency band, as the direction angle of the conductor sheet increases, the magnitude (i.e., the amplitude) of the corresponding electromagnetic wave cross-polarization reflection coefficient also increases, indicating that the metasurface unit structure can be applied to the cross-polarization working scenario within this working frequency band. From Figure 3 it can be seen that within the 12 - 17 GHz frequency band, as the direction angle of the conductor sheet increases, the magnitude of the corresponding electromagnetic wave co-polarization reflection coefficient decreases, indicating that the metasurface unit structure can be applied to the co-polarization working scenario within this working frequency band.

[0076] From Figure 4 it can be seen that the variation law of the magnitude of the cross-polarization reflection coefficient corresponding to the incident electromagnetic waves at 12 GHz, 14 GHz, and 17 GHz with the direction angle is the same, that is, sin2θ. Therefore, within the 12 - 17 GHz frequency band, the magnitude of the cross-polarization reflected electromagnetic wave can be regulated by setting the size of the direction angle of the conductor sheet; From Figure 5 it can be seen that when the azimuth angle is 0°, it is the phase jump point of the cross-polarization reflection coefficient. When the azimuth angle is within the range of [0°, 90°], the phases of the cross-polarization reflection coefficients obtained by the incident electromagnetic waves of the three frequencies are 180° different from the phases of the cross-polarization reflection coefficients obtained by the incident electromagnetic waves of the three frequencies when the azimuth angle is within the range of [-90, 0°]. Therefore, the phase of the cross-polarization reflected electromagnetic wave can be regulated by setting the positive and negative of the direction angle of the conductor sheet. In practical applications, within the range of [-45°, 45°], by setting the size and positive and negative of the direction angle of the conductor sheet, the amplitude adjustment range [0, 1] of the cross-polarization electromagnetic wave and the phase jumps of 0 and π can be satisfied.

[0077] From Figure 6 it can be seen that the variation law of the magnitude of the co-polarization reflection coefficient corresponding to the incident electromagnetic waves at 12 GHz, 14 GHz, and 17 GHz with the direction angle is the same, that is, cos2θ. Therefore, within the 12 - 17 GHz frequency band, the magnitude of the co-polarization reflected electromagnetic wave can be regulated by setting the size of the direction angle of the conductor sheet; From Figure 5It can be seen that the azimuth angles of 45° and -45° are the phase jump points of the co-polarization reflection coefficient. When the azimuth angle is within the range of [-45°, 45°], the phases of the co-polarization reflection coefficients obtained by the incident electromagnetic waves of the three frequencies are 180° different from the phases of the co-polarization reflection coefficients obtained by the incident electromagnetic waves of the three frequencies when the azimuth angle is within the ranges of [-90°, -45°] and [45°, 90°]. Therefore, the phase of the co-polarization reflected electromagnetic wave can be regulated by setting the value range of the conductor sheet direction angle. In practical applications, within the range of [0°, 90°], by setting the value range and magnitude of the conductor sheet direction angle, the phase jumps of 0 and π of the co-polarization electromagnetic wave and the amplitude adjustment range of [0, 1] can be satisfied.

[0078] Another embodiment of the present invention discloses an Airy beam generator, which includes a two-dimensional array composed of the aforementioned reflective metasurface unit structures and an electromagnetic wave generating device.

[0079] Among them, in the first dimension of the two-dimensional array, the magnitude of the direction angle of the conductor sheet of each metasurface unit structure corresponds to the aperture amplitude of the Airy beam at the position of the metasurface unit structure; the value range of the direction angle of the conductor sheet of each metasurface unit structure corresponds to the aperture phase of the Airy beam at the position of the metasurface unit structure.

[0080] Specifically, the Airy beam generator is designed and obtained through the following method, and simulations and tests are carried out.

[0081] Among them, the electric field distribution of the one-dimensional Airy beam can be described by the following formula:

[0082] U(ξ, s) = A·Ai(s - (ξ / 2) 2 + iaξ)exp(as - (aξ 2 / 2) - i(ξ 3 / 12) + i(a 2 ξ / 2) + i(sξ / 2))

[0083] Among them, A represents the normalized amplitude of the electric field, ensuring that the maximum value of the amplitude distribution of the initial Airy beam is 1, Ai represents the Airy function, a represents the exponential decay factor, s = (x - x0) / w represents the normalized transverse coordinate, w is the coordinate scaling value, where x is the real coordinate and x0 is the normalized relative coordinate. ξ = z / kw 2 represents the normalized propagation distance, where k = 2πn / λ0. The electric field distribution of the initial Airy beam can be described by U(0, s) when ξ = 0:

[0084] U(0, s) = A·Ai(s)exp(as),

[0085] U(0, s) represents the normalized amplitude equation, where the phase distribution along the x-axis of the array arrangement must satisfy Specifically, the amplitude distribution of the Airy beam is as Figure 8 shown, and the phase distribution is as Figure 9 shown. Specifically, based on the above formula, taking a = 0.01, w = P / 0.358, x0 = 28 cm, where P represents the lattice constant of the unit structure, which is 10 mm. Appropriate values of x0 and w are selected to obtain an Airy beam within a suitable size range. In Figure 8 and Figure 9 , 41 dots are selected along the x-axis respectively. These dots can represent the variation laws of the phase and amplitude of the Airy beam respectively. Set the direction angles of the conductor sheets of each metasurface unit structure according to the dots in the figure, so that the direction angles correspond to the amplitude and phase at the dots in Figure 8 and Figure 9 . The obtained two-dimensional array is as Figure 10 shown.

[0086] In addition, the thicknesses of both the conductor sheet and the conductor plate are 0.018 mm. The length of the conductor sheet is 7.55 mm, the width is 2 mm, and the side length of the conductor plate is 10 mm; the side length of the dielectric layer is 10 mm, and the thickness is 3 mm. The dielectric layer material is selected as a lossless dielectric material. Exemplarily, F4B can also be selected, with a dielectric constant of 2.65 and a loss tangent value of 0.0017.

[0087] When the incident electromagnetic wave frequency band is the microwave frequency band, during the simulation process, the conductor sheet and the conductor plate are set as perfect semiconductors. In the experiment, copper is selected as the material of the conductor sheet and the conductor plate.

[0088] The simulation results and experimental results are as follows:

[0089] Figure 11 and Figure 12 respectively show the schematic diagrams of the Airy beams obtained by simulation and experiment when the incident electromagnetic wave is 12 GHz; Figure 13 and Figure 14 respectively show the schematic diagrams of the Airy beams obtained by simulation and experiment when the incident electromagnetic wave is 14 GHz; Figure 15 and Figure 16 respectively show the schematic diagrams of the Airy beams obtained by simulation and experiment when the incident electromagnetic wave is 17 GHz; It can be seen that within the frequency band of 12 - 17 GHz, when electromagnetic waves of different frequencies are incident, the Airy beams obtained by simulation and field test are basically the same.

[0090] In addition, Figure 17 and Figure 18 and Figure 19The figures show the variation of the full width at half maximum (FWHM) of the main lobe intensity of the Airy beam obtained when the incident electromagnetic wave is 12 GHz, 14 GHz, and 17 GHz, respectively, with the propagation distance. It can be seen from the figures that the FWHM of the main lobe intensity bends as the propagation distance increases. At the same time, the FWHM of the main lobe intensity also changes with the increase of the propagation distance. When the propagation distance increases to a certain extent, the FWHM value also increases by a certain value, indicating that the obtained Airy beam has a certain non-diffracting distance. Figure 20 The self-repairing characteristic of the obtained Airy beam is shown. It can be seen from the figure that a metal square column is placed at a certain distance above the main lobe from the exit surface. It can be seen from the figure that the beam is disturbed to a certain extent around the metal block, but after a certain propagation distance, the characteristics of the Airy beam are restored again.

[0091] According to the above experimental and simulation results, it can be determined that the Airy beam generator proposed by the present invention can generate high-quality Airy beams in the frequency band range of 12 - 17 GHz.

[0092] Another embodiment of the present invention provides an Airy beam generator, which includes a two-dimensional array composed of the aforementioned reflective metasurface unit structures and an electromagnetic wave generating device. This Airy beam generator is applicable to the working scenario of linear polarization conversion to circular polarization.

[0093] Among them, in the first dimension of the two-dimensional array, the magnitude of the direction angle of the conductor sheet of each metasurface unit structure corresponds to the aperture amplitude of the Airy beam at the position of the metasurface unit structure; the value range of the direction angle of the conductor sheet of each metasurface unit structure corresponds to the aperture phase of the Airy beam at the position of the metasurface unit structure.

[0094] Compared with the prior art, the reflective metasurface unit structure proposed by the present invention utilizes a three-layer structure with the properties of a half-wave plate to improve its operating bandwidth. By changing the electrical size of the metasurface unit structure, it can operate in the microwave band, infrared band, terahertz band, and optical frequency band. In addition, by setting the direction angle of the conductor sheet, the amplitude and phase of the reflected electromagnetic wave can be adjusted separately without changing the structural dimensions of the unit structure. Among them, the adjustment range of the amplitude is [0,1], and it can also control the phase of the transmitted electromagnetic wave to change from 0 to π, or from π to 0, and the control method is simple and flexible. In addition, this metasurface unit structure can not only be used to construct a generator for generating Airy beams, but also be used to construct an electromagnetic wave beam with an arbitrary amplitude distribution form and a binary form of phase distribution of 0 and π, such as a zero-order Bessel beam. Secondly, for the cases of linear polarization co-polarization and linear polarization cross-polarization, the proposed reflective metasurface unit structure can adjust the phase and amplitude of the reflected electromagnetic wave by setting the angle respectively, improving the utilization rate of the unit structure and expanding its application scenarios. In addition, the Airy beam generator based on the metasurface unit structure proposed by the present invention can generate high-quality Airy beams for linearly polarized incident electromagnetic waves in the frequency band of 12-17 GHz. In addition, the structural dimensions of each metasurface unit structure in the two-dimensional array of the Airy beam generator are the same, and only the direction angles of the conductor sheets are different, simplifying the manufacturing process of the two-dimensional array and greatly reducing the manufacturing cost.

[0095] Those skilled in the art can understand that all or part of the processes of implementing the methods in the above embodiments can be completed by instructing relevant hardware through a computer program, and the program can be stored in a computer-readable storage medium. Among them, the computer-readable storage medium is a disk, an optical disc, a read-only memory, or a random access memory, etc.

[0096] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention.

Claims

1. An Airy beam generator, characterized in that, It includes a two-dimensional array composed of reflective metasurface unit structures for electromagnetic wave regulation and an electromagnetic wave generating device. The reflective metasurface unit structure includes: a rectangular conductor sheet, a dielectric layer, and a conductor plate arranged in sequence along the direction of normal incidence of the electromagnetic wave. The dielectric layer covers the conductor plate, and the rectangular conductor sheet and the conductor plate are perfect electric conductors corresponding to the electromagnetic wave frequency band. Among them, the rectangular conductor sheet, the dielectric layer, and the conductor plate have the same geometric center, the rectangular conductor sheet, the dielectric layer, and the conductor plate are arranged coaxially along the structure, and the major axis of the rectangular conductor sheet forms a predetermined angle with the horizontal axis of the conductor plate. The predetermined angle is the direction angle of the rectangular conductor sheet, and the direction angle is related to the amplitude and phase of the electromagnetic wave. The relationship between the direction angle of the conductor sheet and the amplitude of the cross-polarization reflection coefficient of the linearly polarized incident electromagnetic wave is as follows: A1 = A 1(45°) |sin(2θ1)|, Among them, θ1 represents the direction angle of the conductor sheet, and the value range of the direction angle is (-180°, 180°]. A1 represents the amplitude of the cross-polarization reflection coefficient of the linearly polarized incident electromagnetic wave, and A 1(45°) represents the amplitude of the cross-polarization reflection coefficient of the linearly polarized incident electromagnetic wave when the direction angle θ1 of the conductor sheet is 45°; The relationship between the direction angle of the conductor sheet and the amplitude of the co-polarization reflection coefficient of the linearly polarized incident electromagnetic wave is as follows: A2 = A 2(0°) |cos(2θ2)|, Among them, θ2 represents the direction angle of the conductor sheet, and the value range of the direction angle is (-180°, 180°]. A2 represents the amplitude of the co-polarization reflection coefficient of the linearly polarized incident electromagnetic wave, and A 2(0°) represents the amplitude of the co-polarization reflection coefficient of the linearly polarized incident electromagnetic wave when the direction angle θ2 of the conductor sheet is 0°; When the value range of the direction angle of the conductor sheet is (-18°, -90°] or (0°, +90°], the phase value of the cross-polarization reflection coefficient of the linearly polarized incident electromagnetic wave is the first phase value. When the value range of the direction angle of the conductor sheet is (-90°, 0°] or (+90°, +180°], the phase value of the cross-polarization reflection coefficient of the linearly polarized incident electromagnetic wave is the second phase value, and the phase difference between the first phase value and the second phase value is 180°. When the value range of the direction angle of the conductor sheet is (-45°, +45°], (-180°, -135°] or (+135°, +180°], the phase value of the co-polarization reflection coefficient of the linearly polarized incident electromagnetic wave is the first phase value. When the value range of the direction angle of the conductor sheet is (-135°, -45°] or (+45°, +135°], the phase value of the co-polarization reflection coefficient of the linearly polarized incident electromagnetic wave is the second phase value, and the phase difference between the first phase value and the second phase value is 180°. Among them, in the first dimension of the two-dimensional array, the magnitude of the direction angle of the conductor sheet of each metasurface unit structure corresponds to the aperture amplitude of the Airy beam at the position of the metasurface unit structure; the value range of the direction angle of the conductor sheet of each metasurface unit structure corresponds to the aperture phase of the Airy beam at the position of the metasurface unit structure.

2. The Eley beam generator according to claim 1, characterized in that, The thicknesses of the conductor sheet and the conductor plate are both 0.018 mm, the length of the conductor sheet is 7.55 mm, the width is 2 mm, and the side length of the conductor plate is 10 mm.

3. The Airy beam generator according to claim 2, characterized in that, The side length of the dielectric layer is 10 mm and the thickness is 3 mm.

4. The Eley beam generator according to claim 3, characterized in that, The material of the dielectric layer is a lossless dielectric material.

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