A linearly polarized vortex beam generator and a beam generation method thereof

Abstract

The application discloses a linear polarization vortex beam generator and relates to the technical field of metasurfaces. The generator device is a silicon dioxide substrate, a plurality of rectangular columns are arranged on the substrate, the cubic columns are distributed in a matrix mode, and the length and width of the cubic columns are composed of eight different parameters. 01 The beam generation method comprises expanding a standard W waveband waveguide port to realize TE 01 mode output, generating linear polarization vortex beam output under normal incidence. The amplitude and phase of the transmitted electromagnetic field are changed by controlling the geometric size and rotation angle of the rectangular column. The application further discloses a beam generation method of the linear polarization vortex beam generator. The bifunctional metasurface structure is simple, light, small, convenient for generating vortex beams in practical application, and can be used for deflection of quasi-light beams and output of high-power special light beams.

Description

Technical Field

[0001] This invention relates to the field of metasurface technology, and in particular to a linearly polarized vortex beam generator and its beam generation method. Background Technology

[0002] Orbital angular momentum (OAM) vortex beams, possessing a vortex phase wavefront, hold significant promise for applications in high-capacity optical communication, super-resolution imaging, and particle detection. Methods for generating OAM vortex beam arrays include helical phase plates and spatial light modulators. Gyrotrons can generate high-power electromagnetic fields. TE (Transient Electromagnetic Field) generated by gyrotrons... 01 The output of the vortex beam realized by the mode exhibits high power characteristics. High-power vortex beams show promising applications in microwave anti-stealth radar and in interactions with plasma. Currently, there are two methods for realizing high-power vortex beams based on gyrotubes. The first method involves first realizing the TE (Transient Electron) pattern using optical devices. 01 The quasi-optical output of the mode is then phase-modulated based on a spiral phase plate to achieve the output of a vortex beam. This method involves a complex optical system that occupies a large area. Chao Zhang et al. redesigned the gyro to directly achieve vortex beam output by having microwave photons interact with vortex quanta. This novel gyro design is complex and difficult to implement on a large scale.

[0003] Metasurfaces, as two-dimensional arrays of periodic artificial microstructures, can effectively manipulate the phase, amplitude, and polarization of electromagnetic waves based on generalized Fresnel's laws. They are widely used in beam polarization, superlens design, holographic imaging, and other fields. Bifunctional metasurfaces can control both polarization direction and propagation phase. However, in most applications of these metasurfaces, the incident beam is either linearly or circularly polarized. For electromagnetic wave modes in circular waveguides, the polarization direction is often related to the radial direction, and the polarization direction of the electromagnetic field differs at different locations. Summary of the Invention

[0004] The technical problem to be solved by this invention is to overcome the shortcomings of the prior art and provide a linearly polarized vortex beam generator and its beam generation method, based on a dual-functional metasurface and a circular waveguide TE. 01 A linearly polarized vortex beam generator with a feed mode and its beam generation method; this dual-functional metasurface can realize beam generation for circular waveguides TE 01 The polarization direction of the mode is simultaneously modulated with the transmission phase, enabling quasi-optical output and vortex phase output to be achieved simultaneously.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A linearly polarized vortex beam generator according to the present invention includes a metasurface and a substrate. The metasurface is disposed on the substrate and comprises a plurality of periodically arranged cubic pillars. An external waveguide power output window outputs TE. 01 When the mode is incident perpendicularly on the metasurface, a linearly polarized vortex beam is generated by simultaneously modulating the polarization direction and phase of the electric field.

[0007] As a further optimization of the linearly polarized vortex beam generator described in this invention, the substrate and metasurface are placed at a predetermined distance behind the external waveguide power transmission window; the length a and width b of each cubic pillar are determined, TE 01 electric field of the mode Characterized as Where A represents amplitude, J′0(Tρ) represents zero-order Bessel function, e is the natural base, j is the imaginary unit, β represents wave number, z represents the Z direction, and the Z direction represents the direction of electromagnetic field propagation. Indicates TE 01 The electric field polarization direction at each location is axial linear polarization.

[0008] As a further optimization scheme for the linearly polarized vortex beam generator described in this invention, the method for determining the length a and width b of each cubic cylinder is as follows:

[0009] Based on the Jones matrix, the geometric parameters of the cube prism are scanned to determine its length and width, such that δ xy =±π,δ xy The phase difference between the incident and emitted electromagnetic waves of x-polarization and the emitted electromagnetic waves of y-polarization is represented. The scanning range of a and b is 0.3mm-1.3mm. Then, the amplitude and phase of each parameter scanned are determined. All parameters are arranged into a matrix array for visualization. The amplitude distribution map and phase distribution map of the matrix array composed of different parameters are obtained. From the amplitude distribution map and phase distribution map, eight (a,b) arrays that can uniformly cover the 2π phase and have a transmittance greater than 80% are found.

[0010] As a further optimization of the linearly polarized vortex beam generator described in this invention, the cubic pillar is a subwavelength cubic pillar, and the substrate is a silicon dioxide substrate.

[0011] As a further optimization of the linearly polarized vortex beam generator described in this invention, the electric field of the incident metasurface is the TE output from the waveguide power window of the W-band gyrotube. 01 The waveguide power window radius is r0 = 16 mm, the waveguide length is d2 = 3 mm, and the distance between the waveguide power window and the substrate of the metasurface is d0 = 8 mm.

[0012] As a further optimization of the linearly polarized vortex beam generator described in this invention, the cubic pillar is a dielectric pillar made of alumina with a dielectric constant of 9.4.

[0013] As a further optimization of the linearly polarized vortex beam generator described in this invention, the substrate of the cubic pillar includes multiple substrate unit structures, the cross-section of the substrate unit structure is square, the thickness of the substrate unit structure is h = 0.5 mm, and the period is P = 1.5 mm.

[0014] As a further optimization scheme for the linearly polarized vortex beam generator described in this invention, the rotation angle of each cubic cylinder on the metasurface varies depending on its position. A rectangular coordinate system is established with the center of the metasurface as the origin. The rotation angles of the cubic structures in the first, second, third, and fourth quadrants are arctan(x / y) / 2-π / 2, arctan(x / y) / 2+π, arctan(x / y) / 2-π, and arctan(x / y) / 2+π / 2, respectively. Wherein, x is the x-coordinate of the coordinate system established with the midpoint of the metasurface as the center, and y is the y-coordinate of the coordinate system established with the midpoint of the metasurface as the center.

[0015] As a further optimization of the linearly polarized vortex beam generator described in this invention, the phase distribution of the metasurface satisfies the classical vortex phase distribution: Φ OAM (x,y)=l*arctan(y / x), where l represents the number of OAM modes, Φ OAM (x,y) represents the phase distribution of the vortex beam.

[0016] Based on the above-described method for generating a linearly polarized vortex beam generator, and using a circular waveguide TE based on a dual-functional metasurface... 01 This is a linearly polarized vortex beam generator with a feed mode. The cubic pillar rotates at different angles depending on its location, and the TE at the W-band waveguide port... 01 The mode is output mode, which generates a linearly polarized vortex beam output under vertical incidence. The amplitude and phase of the transmitted electric field are changed by controlling the geometric dimensions and rotation angle of the cubic cylinder.

[0017] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects:

[0018] This invention discloses a circular waveguide TE based on a dual-functional metasurface. 01A linearly polarized vortex beam generator with a feed mode and its beam generation method are presented. A dual-functional metasurface combining polarization and propagation phase control is designed. This metasurface is composed of periodically arranged subwavelength cubic prism units, with dimensions on the order of a few wavelengths. The output of a linearly polarized vortex beam can be achieved by considering only the length, width, and rotation angle of the cubic prisms. The device design is simple and lightweight, providing significant advantages for generating high-power vortex beams. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the bifunctional metasurface in this invention.

[0020] Figure 2 This is a schematic diagram of the rotation angle and phase transformation of the unit structure of the bifunctional metasurface in this invention; where (a) represents the rotation angle, and different gray values ​​represent different rotation angles, and (b) represents the phase transformation, with different gray values ​​representing different transmission phases.

[0021] Figure 3 In this invention, when incident along the x-polarization direction, the 90GHz transmission amplitude T xx A schematic diagram showing how the side lengths a and b of the metasurface unit structure change.

[0022] Figure 4 In this invention, when incident along the y-polarized direction, the 90GHz transmission amplitude T yy A schematic diagram showing how the side lengths a and b of the metasurface unit structure change.

[0023] Figure 5 This refers to the 90GHz phase when incident in the x-polarization direction in this invention. A schematic diagram showing how the side lengths a and b of the metasurface unit structure change.

[0024] Figure 6 This refers to the 90GHz phase when incident in the y-polarized direction in this invention. A schematic diagram showing how the side lengths a and b of the metasurface unit structure change.

[0025] Figure 7 This is a schematic diagram of the transmittance of the eight unit structures designed in this invention.

[0026] Figure 8 This is a schematic diagram of the phases of the eight unit structures designed in this invention.

[0027] Figure 9 This is a schematic diagram of the waveguide structure and metasurface position distribution and specific dimensions designed in this invention; wherein, (a) is the waveguide structure and metasurface position distribution, and (b) is a schematic diagram of the metasurface structure.

[0028] Figure 10 This refers to the mode purity in this invention when the orbital angular momentum l = ±1 and the frequency is 85 GHz. The insets show the intensity and phase distribution of the electromagnetic wave in the transmission direction when the orbital angular momentum l = 1 and l = -1, respectively.

[0029] Figure 11 This refers to the mode purity in this invention when the orbital angular momentum l = ±1 and the frequency is 90 GHz. The insets show the intensity and phase distribution of the electromagnetic wave in the transmission direction when the orbital angular momentum l = 1 and l = -1, respectively.

[0030] Figure 12 This refers to the mode purity in this invention when the orbital angular momentum l = ±1 and the frequency is 95 GHz. The insets show the intensity and phase distribution of the electromagnetic wave in the transmission direction when the orbital angular momentum l = 1 and l = -1, respectively.

[0031] Figure 13 This is a far-field radiation diagram at three frequency points: 85GHz, 90GHz, and 95GHz, when the orbital angular momentum l = 1 in this invention. Among them, (a) is the energy distribution in different radiation directions at a frequency of 85GHz, (b) is the energy distribution in different radiation directions at a frequency of 90GHz, (c) is the energy distribution in different radiation directions at a frequency of 90GHz, (d) is the axial ratio distribution in different radiation directions at a frequency of 85GHz, (e) is the axial ratio distribution in different radiation directions at a frequency of 90GHz, and (f) is the axial ratio distribution in different radiation directions at a frequency of 95GHz.

[0032] Figure 14 This invention describes the distribution of axial force in the radiation directions at three frequency points: 85GHz, 90GHz, and 95GHz, when the orbital angular momentum l = -1. Specifically, (a) represents the energy distribution in different radiation directions at 85GHz; (b) represents the axial force distribution in different radiation directions at 90GHz; (c) represents the energy distribution in different radiation directions at 90GHz; (d) represents the axial force distribution in different radiation directions at 85GHz; (e) represents the axial force distribution in different radiation directions at 90GHz; and (f) represents the axial force distribution in different radiation directions at 95GHz. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0034] This invention proposes a linearly polarized vortex beam generator, comprising a metasurface and a substrate. The metasurface is disposed on the substrate and includes multiple periodically arranged cubic pillars. The substrate and the metasurface are placed behind a waveguide power transfer window, which outputs a TE beam. 01 A mode is incident perpendicularly on a metasurface, and a linearly polarized vortex beam is generated by simultaneously modulating the polarization direction and phase of the electric field. The substrate and the metasurface are positioned at a certain distance behind the external waveguide power transmission window. This invention achieves two functions in a single-layer structure: simultaneously modulating the polarization direction and phase of the electric field.

[0035] As a further optimization scheme for the linearly polarized vortex beam generator described in this invention, the length a and width b of each cubic cylinder are determined, TE 01 electric field of the mode Characterized as Where A represents amplitude, J′0(Tρ) represents the zeroth-order Bessel function, e is the natural base, j is the imaginary unit, and β represents the wavenumber. z The Z-direction indicates the direction of electromagnetic field propagation. Indicates TE 01 The electric field polarization direction at each location is axial linear polarization.

[0036] As a further optimization scheme for the linearly polarized vortex beam generator described in this invention, the method for determining the length a and width b of each cubic cylinder is as follows:

[0037] Based on the Jones matrix, the geometric parameters of the cube prism are scanned to determine its length and width, such that δ xy =±π,δ xy The phase difference between the incident and emitted electromagnetic waves of x-polarization and the emitted electromagnetic waves of y-polarization is represented. The scanning range of a and b is 0.3mm-1.3mm. Then, the amplitude and phase of each parameter scanned are determined. All parameters are arranged into a matrix array for visualization. The amplitude distribution map and phase distribution map of the matrix array composed of different parameters are obtained. From the amplitude distribution map and phase distribution map, eight (a,b) arrays that can uniformly cover the 2π phase and have a transmittance greater than 80% are found.

[0038] As a further optimization of the linearly polarized vortex beam generator described in this invention, the cubic pillar is a subwavelength cubic pillar, and the substrate is a silicon dioxide substrate.

[0039] As a further optimization of the linearly polarized vortex beam generator described in this invention, the electric field of the incident metasurface is the TE output from the waveguide power window of the W-band gyrotube. 01 The waveguide power window radius is r0 = 16 mm, the waveguide length is d2 = 3 mm, and the distance between the waveguide power window and the substrate of the metasurface is d0 = 8 mm.

[0040] As a further optimization of the linearly polarized vortex beam generator described in this invention, the cubic pillar is a dielectric pillar made of alumina with a dielectric constant of 9.4.

[0041] As a further optimization of the linearly polarized vortex beam generator described in this invention, the substrate of the cubic pillar includes multiple substrate unit structures, the cross-section of the substrate unit structure is square, the thickness of the substrate unit structure is h = 0.5 mm, and the period is P = 1.5 mm.

[0042] As a further optimization scheme for the linearly polarized vortex beam generator described in this invention, the rotation angle of each cubic cylinder on the metasurface varies depending on its position. A rectangular coordinate system is established with the center of the metasurface as the origin. The rotation angles of the cubic structures in the first, second, third, and fourth quadrants are arctan(x / y) / 2-π / 2, arctan(x / y) / 2+π, arctan(x / y) / 2-π, and arctan(x / y) / 2+π / 2, respectively. Wherein, x is the x-coordinate of the coordinate system established with the midpoint of the metasurface as the center, and y is the y-coordinate of the coordinate system established with the midpoint of the metasurface as the center.

[0043] As a further optimization of the linearly polarized vortex beam generator described in this invention, the phase distribution of the metasurface satisfies the classical vortex phase distribution: Φ OAM (x,y)=l*arctan(y / x), where l represents the number of OAM modes, Φ OAM (x,y) represents the phase distribution of the vortex beam.

[0044] Based on the above-described method for generating a linearly polarized vortex beam generator, and using a circular waveguide TE based on a dual-functional metasurface... 01 This is a linearly polarized vortex beam generator with a feed mode. The cubic pillar rotates at different angles depending on its location, and the TE at the W-band waveguide port... 01 The mode is output mode, which generates a linearly polarized vortex beam output under vertical incidence. The amplitude and phase of the transmitted electric field are changed by controlling the geometric dimensions and rotation angle of the cubic cylinder.

[0045] In addition to converting the TE01 mode into a linearly polarized vortex beam, the method of this invention can also convert other circular waveguide modes, such as TE11 and TE21 modes, into linearly polarized vortex beams. The difference lies in the different designs of the metasurface based on the distribution characteristics of different modes.

[0046] Example as follows:

[0047] Based on a dual-functional metasurface, a circular waveguide TE 01A linearly polarized vortex beam generator with a feed mode and its beam generation method are disclosed. The generator includes a silicon dioxide substrate on which multiple cubic pillars are disposed. The length of each cubic pillar is *a*, and the width of each cubic pillar is *b*. The TE output from the W-band cyclotron power window is also described. 01 The mode is the input electromagnetic field mode, which generates a linearly polarized vortex beam under vertical incidence.

[0048] The aforementioned circular waveguide TE based on a dual-functional metasurface 01 The mode is a linearly polarized vortex beam generator with a feed source, and the electric field of the incident metasurface is a W-band TE. 01 The input port radius is r0 = 16 mm. The waveguide length is d2 = 3 mm; the distance from the output port to the metasurface substrate is d0 = 8 mm.

[0049] The aforementioned circular waveguide TE based on a dual-functional metasurface 01 The mode is a linearly polarized vortex beam generator with a feed source. The cubic pillar is a dielectric pillar made of alumina with a dielectric constant of 9.4.

[0050] The aforementioned circular waveguide TE based on a dual-functional metasurface 01 The linearly polarized vortex beam generator with feed mode has a cubic pillar substrate composed of multiple substrate unit structures. The substrate structure has a square cross-section, and the thickness of the substrate unit is h = 0.5 mm, with a period of P = 1.5 mm.

[0051] The aforementioned circular waveguide TE based on a dual-functional metasurface 01 The mode is a linearly polarized vortex beam generator with a feed source. The rotation angle of each cubic cylinder on the metasurface is different depending on its position. A rectangular coordinate system is established with the center of the metasurface as the origin. The rotation angles of the cubic structures in the first, second, third and fourth quadrants are arctan(x / y) / 2-π / 2, arctan(x / y) / 2+π, arctan(x / y) / 2-π and arctan(x / y) / 2+π / 2.

[0052] The aforementioned circular waveguide TE based on a dual-functional metasurface 01 The mode is a linearly polarized vortex beam generator with a feed source. The phase distribution of the bifunctional metasurface satisfies the classical vortex phase distribution: l*arctan(y / x). Here, x and y represent the positions of the cubic cylinder, and l represents the number of OAM modes.

[0053] like Figure 1 As shown, the metasurface structure consists of 24×24 metasurface unit structures. The substrate material for the metasurface unit structures is silicon dioxide, and multiple cubic pillars with length 'a' and width 'b' are arranged on the substrate. Under perpendicular incident light, a linearly polarized vortex beam is generated.

[0054] The cubic pillar is a dielectric pillar made of alumina with a dielectric constant of 9.4.

[0055] The substrate of the cubic pillar is composed of multiple substrate unit structures. The cross-section of the substrate structure is square, the thickness of the substrate unit is h = 0.5 mm, and the period is P = 1.5 mm.

[0056] Any polarized electric field can be decomposed into two mutually perpendicular polarized waves along the x and y directions. The polarization transition process in a microwave field can be represented by the Jones matrix. Where T xx and T yy This is a common polarization transformation. T xy and T yx This is a cross-polarization transform. E i E represents the incident electric field. t Let represent the final electric field. Here, k is the wave number, and ω is the electromagnetic field frequency. The required function mentioned in this invention only requires linear polarization transformation. Therefore, the complex amplitude in the Jones matrix needs to satisfy the following condition: |T xx |=|T yy |=1,|T xy |=|T yx |=0,δ xy =±π, where δ xy The phase difference between the x-polarized and y-polarized electromagnetic waves after decomposition.

[0057] TE 01 The electric field of the mode can be characterized as: E ρ =0, E z =0. Where A is the amplitude of the input wave; J′0 represents the first derivative of the zeroth-order Bessel function; T is the TE value in the cylindrical waveguide. 01 The eigenvalues ​​of the mode; β represents the wavenumber of the input wave. Therefore, TE... 10 The polarization direction at any position of the mode is perpendicular to the radial direction of that position.

[0058] like Figure 2 As shown in (a) of the figure, the different grayscale values ​​represent the rotation angles of the metasurface unit structures at different locations. Based on TE 01 The quasi-optical output process of the mode can be considered as the inverse process of radial vector field generation. The rotation angle of each cubic cylinder on the metasurface varies depending on its position. When the rotation angle of the metasurface unit cell makes an angle θ with the polarization direction of the incident electric field, the polarization direction of the electric field will rotate by 2θ. By changing the rotation angle of the metasurface unit cell at different positions, quasi-optical output can be achieved. TE 01The electric field polarization direction at each location in the model is distributed along the axial direction. Therefore, a rectangular coordinate system is established with the center of the metasurface as the origin. The rotation angles of the cubic structures in the first, second, third, and fourth quadrants are arctan(x / y) / 2-π / 2, arctan(x / y) / 2+π, arctan(x / y) / 2-π, and arctan(x / y) / 2+π / 2, respectively.

[0059] like Figure 2 As shown in (b) of the figure, the different gray values ​​represent the phase of the metasurface unit structure at different locations.

[0060] The phase distribution satisfies the classical vortex phase distribution: Φ OAM (x,y)=l*arctan(y / x). Where x and y represent the positions of the cubic cylinder, and l represents the orbital angular momentum mode number. Figure 2 The orbital angular momentum number l = 2 for the phase diagram shown in (b).

[0061] like Figure 3 Figures 4, 5, and 6 show how the transmission phase and transmission amplitude changes corresponding to different values ​​of a and b are obtained by scanning parameters by changing the length a and width b of the metasurface unit structure. Eight values ​​that can simultaneously achieve uniform phase distribution and a phase span of 2π are found.

[0062] The eight determined combinations of (a, b) values ​​are: (0.54mm, 1.14mm), (0.48mm, 1.05mm), (0.3mm, 1.3mm), (1.26mm, 0.57mm), (1.14mm, 0.54mm), (1.05mm, 0.48mm), (1.3mm, 0.3mm), and (0.57mm, 1.26mm), which correspond to the eight different metasurface unit structures designed. Figure 7 The transmittance of the eight structures was characterized: all of them had a transmittance greater than 80%. Figure 8 The phases of the eight structures are characterized: their phases satisfy a 2π phase modulation.

[0063] like Figure 9 As shown, the electric field incident on the metasurface is represented by the TE output from the W waveguide. 01 The mode, whose output port is the commonly used output port of a gyrotube, Figure 9 In (a) of the simulation, the radius of the waveguide power window is r0 = 16 mm; the distance between the waveguide power window and the metasurface substrate is d0 = 8 mm; and the waveguide length in the simulation example is d1 = 3 mm. Figure 9 In (b), the length of the metasurface structure is S = 36 mm.

[0064] The electric and magnetic field monitors were placed 50 mm behind the metasurface.

[0065] Figure 10 The mode purity is defined as follows: frequency 85 GHz, orbital angular momentum l = ±1.

[0066] Figure 11 The mode purity is defined as follows: frequency 90 GHz, orbital angular momentum l = ±1.

[0067] Figure 12 The mode purity is defined as follows: frequency 95 GHz, orbital angular momentum l = ±1.

[0068] Figure 10 , 11 The left inset in Figure 12 shows the intensity and phase distribution on the monitor plane when l = -1. The right inset shows the intensity and phase distribution on the monitor plane when l = 1. It can be seen that the intensity distribution is a hollow ring shape, and the phase distribution is a spiral shape. This distribution conforms to the characteristics of a vortex beam.

[0069] Figure 13 This is the far-field radiation diagram and axial index when the orbital angular momentum l = -1. Specifically, Figure 13 (a), (b), and (c) in the figure are far-field radiation diagrams at frequencies of 85 GHz, 90 GHz, and 95 GHz, respectively. Figure 13 In this context, (d), (e), and (f) represent the axial ratios at frequencies of 85 GHz, 90 GHz, and 95 GHz, respectively. Figure 14 This is the far-field radiation diagram and axial index when the orbital angular momentum l = -1. Specifically, Figure 14 (a), (b), and (c) in the figure are far-field radiation diagrams at frequencies of 85 GHz, 90 GHz, and 95 GHz, respectively. Figure 14 In the figure, (d), (e), and (f) are the axial ratios at frequencies of 85 GHz, 90 GHz, and 95 GHz, respectively; it can be seen that it has good polarizability in the direction of electromagnetic field radiation and can achieve good linear polarizability.

[0070] This invention introduces a circular waveguide TE based on a dual-functional metasurface. 01 A linearly polarized vortex beam generator with a feed mode and its beam generation method are disclosed, wherein the cubic pillar rotates at different angles depending on its location. The beam generation method includes using the TE at the W-band waveguide port. 01 The mode is output mode, generating a linearly polarized vortex beam output under perpendicular incidence. The amplitude and phase of the transmitted electric field are changed by controlling the geometric dimensions and rotation angle of the rectangular pillar. Compared to the traditional two-step process of first achieving quasi-beam output through the optical path and then achieving vortex beam output through a spiral phase plate, this dual-function metasurface structure is simpler, lighter, and more miniaturized, bringing convenience to the generation of high-power vortex beams and other high-power special beams in practical applications.

[0071] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A linearly polarized vortex beam generator, characterized in that, It includes a metasurface and a substrate, with the metasurface disposed on the substrate and comprising multiple periodically arranged cubic pillars; an external circular waveguide power transmission window outputs TE. 01 When the mode is incident perpendicularly on the metasurface, a linearly polarized vortex beam is generated by simultaneously modulating the polarization direction and phase of the electric field. The substrate and metasurface are placed at a predetermined distance behind the external waveguide power transfer window; the length a and width b of each cubic pillar are determined, TE 01 electric field of the mode Characterized as Where A represents amplitude, J0(Tρ) represents zero-order Bessel function, e is the natural base, j is the imaginary unit, β represents wave number, z represents the Z direction, and the Z direction represents the direction of electromagnetic field propagation. Indicates TE 01 The electric field polarization direction at each location is axial linear polarization; The method for determining the length 'a' and width 'b' of each cubic prism is as follows: Based on the Jones matrix, the geometric parameters of the cube prism are scanned to determine its length and width, such that δ xy =±π,δ xy The phase difference between the incident and emitted electromagnetic waves of x-polarization and the emitted electromagnetic waves of y-polarization is represented. The scanning range of a and b is 0.3mm-1.3mm. Then, the amplitude and phase of each parameter scanned are determined. All parameters are arranged into a matrix array for visualization. The amplitude distribution map and phase distribution map of the matrix array composed of different parameters are obtained. From the amplitude distribution map and phase distribution map, eight (a,b) arrays that can uniformly cover the 2π phase and have a transmittance greater than 80% are found. The rotation angle of each cubic cylinder on the hypersurface varies depending on its position. A rectangular coordinate system is established with the center of the hypersurface as the origin. The rotation angles of the cubic structures in the first, second, third, and fourth quadrants are arctan(x / y) / 2-π / 2, arctan(x / y) / 2+π, arctan(x / y) / 2-π, and arctan(x / y) / 2+π / 2, respectively. Here, x is the x-coordinate of the coordinate system established with the midpoint of the hypersurface as the center, and y is the y-coordinate of the coordinate system established with the midpoint of the hypersurface as the center.

2. The linearly polarized vortex beam generator according to claim 1, characterized in that, The cubic pillars are subwavelength cubic pillars, and the substrate is a silicon dioxide substrate.

3. A linearly polarized vortex beam generator according to claim 1, characterized in that, The electric field incident on the metasurface is the TE output from the waveguide transport window of the W-band gyrotube. 01 The waveguide power window radius is r0 = 16 mm, the waveguide length is d2 = 3 mm, and the distance between the waveguide power window and the substrate of the metasurface is d0 = 8 mm.

4. A linearly polarized vortex beam generator according to claim 1, characterized in that, The cubic pillar is a dielectric pillar made of alumina with a dielectric constant of 9.

4.

5. A linearly polarized vortex beam generator according to claim 1, characterized in that, The substrate of the cubic pillar consists of multiple substrate unit structures. The cross-section of each substrate unit structure is square, the thickness of the substrate unit structure is h = 0.5 mm, and the period is P = 1.5 mm.

6. A linearly polarized vortex beam generator according to claim 1, characterized in that, The phase distribution of the metasurface satisfies the classical vortex phase distribution: Φ OAM (x,y)=l*arctan(y / x), where l represents the number of OAM modes, Φ OAM (x,y) represents the phase distribution of the vortex beam.

7. A beam generation method based on the linearly polarized vortex beam generator according to claim 1, characterized in that, Based on metasurfaces, circular waveguide TE 01 This is a linearly polarized vortex beam generator with a feed mode. The cubic pillar rotates at different angles depending on its location, and the TE at the W-band waveguide port... 01 The mode is output mode, which generates a linearly polarized vortex beam output under vertical incidence. The amplitude and phase of the transmitted electric field are changed by controlling the geometric dimensions and rotation angle of the cubic cylinder.

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