Polarization state detection method and polarization state detection system

Abstract

This application relates to the field of electromagnetic waves, specifically providing a polarization state detection method and apparatus. The method utilizes a polarization state detection device for detection and includes: inputting the beam to be detected into the polarization state detection device to obtain orthogonal first and second Bessel beams; using a polarizer to obtain the azimuth angles corresponding to the interference weakening or enhancement regions in the interference patterns of the first and second Bessel beams, and determining the phase difference between the first and second Bessel beams based on the azimuth angles; using the polarizer to obtain the first amplitude of the first Bessel beam and the second amplitude of the second Bessel beam, respectively, and obtaining the amplitude ratio based on the first and second amplitudes; and calculating the polarization state of the wave to be detected based on the phase difference and amplitude ratio. This polarization state detection method simplifies the polarization state detection process for terahertz and millimeter waves, promoting the miniaturization and integration of detection equipment.

Description

Technical Field

[0001] This application relates to the field of electromagnetic waves, and in particular to a polarization state detection method and a polarization state detection system. Background Technology

[0002] Currently, research on wave polarization states can be applied to fields such as detection, communication, and sensing. Traditional polarization state detection methods fall into two main categories: single-path measurement methods, which use rotating optical components (such as polarizers and waveplates) or introducing electro-optic modulation crystals to complete a series of polarization state measurements; and multi-path measurement methods, which use beam-splitting elements to divide the incident beam into multiple optical paths and use multiple polarizers and detectors for parallel measurements or to detect the polarization state through interferometry. Traditional polarization detection methods have complex optical systems and long optical paths. If used to detect terahertz and millimeter waves, the terahertz and millimeter waves will experience severe signal attenuation due to molecular absorption during propagation, thus affecting the accuracy of polarization state detection and hindering the miniaturization of terahertz and millimeter wave polarization detection systems. Summary of the Invention

[0003] This application provides a polarization state detection method and a polarization state detection system, aiming to miniaturize polarization state detection devices for terahertz and millimeter waves, simplify the polarization state detection steps, and improve the accuracy of polarization state detection.

[0004] In a first aspect, this application provides a polarization state detection method. This method utilizes a polarization state detection device, which includes: a metal body with a preset thickness and a waveguide array formed by multiple rectangular aperture units disposed on the metal body. Each rectangular aperture unit is used to control two orthogonally polarized beams. The method includes: inputting the beam to be detected into the polarization state detection device to obtain an orthogonal first Bessel beam and a second Bessel beam; using a polarizer to obtain the azimuth angles corresponding to the interference weakening or enhancing regions in the interference patterns of the first and second Bessel beams, and determining the phase difference between the first and second Bessel beams based on the azimuth angles; using a polarizer to obtain the first amplitude of the first Bessel beam and the second amplitude of the second Bessel beam, respectively, and obtaining the amplitude ratio based on the first and second amplitudes; and calculating the polarization state of the wave to be detected based on the phase difference and the amplitude ratio.

[0005] Secondly, this application also provides a polarization state detection system, which includes: a polarization state detection device, a polarizer, a detector, and a detection apparatus; the polarization state detection device has a metal body of a preset thickness and a waveguide array formed by multiple rectangular aperture units disposed on the metal body, wherein a single rectangular aperture unit is used to control two orthogonally polarized beams, and the polarization state detection device is used to convert the beam to be detected into an orthogonal first Bessel beam and a second Bessel beam; the detector is used to acquire the interference pattern of the first Bessel beam and the second Bessel beam, the interference pattern including an interference attenuation region and an interference enhancement region; the detector is also used to acquire the first amplitude of the first Bessel beam and the second amplitude of the second Bessel beam; the detection apparatus calculates the corresponding azimuth angle based on the interference attenuation region or the interference enhancement region of the interference pattern, and calculates the phase difference between the first Bessel beam and the second Bessel beam based on the azimuth angle, and the detection apparatus is also used to calculate the polarization state of the wave to be detected based on the phase difference, the first amplitude, and the second amplitude.

[0006] This application discloses a polarization state detection method. The method utilizes a polarization state detection device, which includes a metal body with a preset thickness and a waveguide array formed by multiple rectangular aperture units disposed on the metal body. Each rectangular aperture unit is used to control two orthogonally polarized beams. The polarization state detection method includes at least the following steps: inputting the beam to be detected into the polarization state detection device to obtain an orthogonal first Bessel beam and a second Bessel beam; using a polarizer to obtain the azimuth angles corresponding to the interference weakening or enhancement regions in the interference patterns of the first and second Bessel beams, and determining the phase difference between the first and second Bessel beams based on the azimuth angles; using a polarizer to obtain the first amplitude of the first Bessel beam and the second amplitude of the second Bessel beam, respectively, and obtaining the amplitude ratio based on the first and second amplitudes; and calculating the polarization state of the wave to be detected based on the phase difference and the amplitude ratio. The polarization state detection method proposed in this application uses a miniaturized polarization state detection device to orthogonally connect a first Bessel beam and a second Bessel beam to be detected. Since the phase difference between the two orthogonal polarized waves directly corresponds to the azimuth angle corresponding to the interference weakening or enhancement region, the phase difference is measured in real time by measuring the azimuth angle. Combined with the amplitude ratio of the first and second Bessel beams, the polarization state of the beam under test is measured. This simplifies the polarization state detection process for terahertz and millimeter waves, eliminating the need for a complex and bulky detection system and promoting the miniaturization of the detection device. Attached image description:

[0007] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0008] Figure 1 This is a schematic flowchart of a polarization state detection method provided in an embodiment of this application;

[0009] Figure 2 This is a schematic diagram of generating a Bessel beam according to an embodiment of this application;

[0010] Figure 3 This is an interference pattern provided in an embodiment of this application;

[0011] Figure 4 This is a first relation table provided in an embodiment of this application;

[0012] Figure 5 This is a second relation table provided in an embodiment of this application;

[0013] Figure 6 This is a schematic diagram of generating a Bessel beam according to an embodiment of this application;

[0014] Figure 7 This is an embodiment of the present application providing an intensity distribution diagram of an x-polarized wave in the yz section of a Bessel beam;

[0015] Figure 8 This is an embodiment of the present application providing an intensity distribution diagram of a y-polarized wave in the yz section of a Bessel beam;

[0016] Figure 9 This is an embodiment of the light intensity distribution diagram of an x-polarized wave on the xy section provided by this application;

[0017] Figure 10 This is an embodiment of the present application providing an intensity distribution diagram of a y-polarized wave on an xy cross section;

[0018] Figure 11 This is an interference pattern for a simulation experiment provided in an embodiment of this application;

[0019] Figure 12 This is an interference pattern from a physical experiment provided in an embodiment of this application;

[0020] Figure 13 This is an interference pattern for a simulation experiment provided in an embodiment of this application;

[0021] Figure 14This is an interference pattern from a physical experiment provided in an embodiment of this application;

[0022] Figure 15 This is a schematic diagram of the structure of a polarization state detection system provided in an embodiment of this application.

[0023] Main component designations and descriptions:

[0024] 100. Polarization state detection system; 11. Polarization state detection; 12. Polarizer; 13. Detector; 14. Detection device; 15. Collimating lens. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the application. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0027] It should also be further understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0028] The flowchart shown in the attached diagram is for illustrative purposes only and does not necessarily include all content and operations / steps, nor does it necessarily have to be performed in the order described. For example, some operations / steps can be broken down, combined, or partially merged, so the actual execution order may change depending on the actual situation.

[0029] In this application, terahertz and millimeter waves refer to electromagnetic waves with frequencies between 0.03 THz and 10 THz (wavelengths between 10 mm and 30 μm).

[0030] To achieve miniaturization of polarization state detection devices for terahertz and millimeter waves, simplify the polarization state detection steps, and ensure the accuracy of polarization state detection, this application provides a polarization state detection method.

[0031] Please see Figure 1 , Figure 1 A schematic flowchart of a polarization state detection method is shown. Figure 1As shown, this application provides a polarization state detection method. The polarization state detection method uses a polarization state detection device for detection. The polarization state detection device includes: a metal body with a preset thickness and a waveguide array formed by multiple rectangular aperture units disposed on the metal body. A single rectangular aperture unit is used to realize the control of two orthogonally polarized beams. The specific steps of the polarization state detection method include at least: S101-S104.

[0032] S101. Input the beam to be detected into the polarization state detection device to obtain the orthogonal first Bessel beam and second Bessel beam.

[0033] like Figure 2 As shown, a three-dimensional coordinate system is established with the plane containing the cross-section of the polarization state detection device as the plane containing the x-axis and y-axis. The z-axis is the direction perpendicular to the cross-section of the device to be detected. The beam to be detected is input into the incident surface of the polarization state detection device along the z-axis direction. Through the adjustment of the rectangular aperture unit on the device to be detected, the first and second orthogonal Bessel beams are obtained at the exit surface.

[0034] The rectangular aperture unit provided in this application is a subwavelength rectangular metal aperture, a metasurface-like structure capable of phase control, polarization control, and amplitude control, and can be considered a type of metallic waveguide. Based on waveguide theory, each rectangular aperture unit can generate two orthogonally polarized guided modes (TE01 mode and TE10 mode). Therefore, in this application, by precisely setting the size and arrangement of the rectangular aperture units, a single rectangular aperture unit can achieve the control of two orthogonally polarized beams. Furthermore, this technology can also be used in dynamic vector optical holography and for generating light with complex structures.

[0035] For example, the beam to be detected is an orthogonal terahertz and millimeter wave beam. After the beam to be detected is converted by the polarization state detection device, an orthogonally polarized first Bessel beam and second Bessel beam are obtained.

[0036] In some embodiments, the first Bessel beam and the second Bessel beam are vortex beams with the same intensity distribution. The topology numbers of the first Bessel beam and the second Bessel beam are ±1, respectively. It should be noted that by changing parameters such as the side length and layout of the rectangular aperture element, this application can also obtain a Bessel beam with a topology number of ±m, where m is a positive integer.

[0037] In some embodiments, before inputting the beam to be detected into the detection polarization device, the beam is first collimated using a collimating lens, and then the collimated beam is input into the detection polarization device. Collimating the beam improves its stability, thereby increasing the accuracy of the detection results.

[0038] In some embodiments, the beam to be detected can be a terahertz or millimeter-wave beam, or a beam in other frequency bands.

[0039] The polarization state detection device provided in this application can convert terahertz or millimeter-wave beams into Bessel beams, and the optical path required for the conversion is simple, reducing the loss of terahertz and millimeter-wave beams during transmission, thereby improving the accuracy of the detection results. Furthermore, this device can also be applied to beams in other frequency bands, showing great application potential in fields such as detection, communication, and sensing.

[0040] S102. Use a polarizer to obtain the azimuth angles corresponding to the interference weakening or interference strengthening regions in the interference patterns of the first and second Bessel beams, and determine the phase difference between the first and second Bessel beams based on the azimuth angles.

[0041] The Bessel beam is a solution to the Helmholtz wave equation in free space. It describes the m-order Bessel beam propagating along the z-axis in cylindrical coordinates by equation (1), which is:

[0042] E(r,θ,z)=A·exp(ik z z)·J m (k r r)·exp(±imθ;

[0043] In the formula, A is a constant related to the amplitude, and k z and k r Let be the wavenumbers in the radial direction and the beam propagation direction, respectively, and r be the radial radius, satisfying the equation... (λ is the wavelength), J m Let be a first-order m-th order Bessel function, where m is the topological number and θ = arctan(y / x) is the vortex phase distribution. Equation (1) shows that the transverse intensity distribution of the Bessel beam is independent of the z-coordinate, which leads to their non-diffraction properties, and the exp(±imθ) term indicates that any higher-order Bessel beam must carry orbital angular momentum.

[0044] For any given cross section (z = z0), the Bessel beam can be described by equation (2), and the formula for equation (2) is:

[0045] E(r,θ)=A0J ±m (k r r)exp(±imθ;

[0046] In the formula, A0=A·exp(ik) z (z0), where A0 represents a constant related to the complex amplitude at a given section z = z0.

[0047] Since any polarization state can be represented by a linear combination of two Jones vectors of a specific orthogonal polarization state, a pair of orthogonal monochromatic plane waves in the Cartesian coordinate system can be described by equation (3), which is:

[0048]

[0049] In the formula, A x (r,θ) and A y (r, θ) represent the amplitudes of the polarized waves along the x-axis and y-axis, respectively, and the initial phase difference between the two incident orthogonally linearly polarized waves is...

[0050] If the two orthogonal components of terahertz and millimeter waves are respectively converted into m-order Bessel beams with opposite topological numbers, the interference field distribution E at a preset angle can be described by equation (4). 45 (r,θ), the preset angle is the angle between the polarization direction (i.e., x-axis) of the first Bessel beam and the preset angle is 45°. The specific formula of equation (4) is:

[0051]

[0052] In the formula, and θ represents the amplitudes of x-polarization and y-polarization at any given cross section z = z0, respectively, and are both constants. d The azimuth angle is the interference pattern of the first Bessel vortex beam and the second Bessel beam.

[0053] Equation (5) describes the relationship between the phase difference of two orthogonal polarized waves and the azimuth angle of interference enhancement (or reduction). The specific formula of equation (5) is as follows:

[0054]

[0055] In the formula, θ d Let m be the azimuth angle of the interference pattern. When m = 1 and n = 0, equation (5) can be written as: Therefore, in this application, the phase difference between the first and second Bessel beams can be measured in real time by observing the azimuth angle of the interference pattern of the first Bessel vortex beam and the second Bessel beam. Thus, the measurement method of this application can achieve real-time measurement of unstable polarization beams, as well as real-time and non-real-time measurement of stable polarization beams. Measuring the phase difference via azimuth angle requires extremely short measurement time and can be applied to the real-time detection of continuous unstable beams, reflecting the polarization state changes of the beam in real time.

[0056] In this application, a polarizer is placed between the polarization state detection device and the detection instrument, with the polarizer positioned behind the polarization state detection device in the beam propagation direction. The interference pattern at a preset polarization angle is observed using the linear polarizer and the detection instrument. Then, the phase difference between the first Bessel beam and the second Bessel beam is calculated based on the azimuth angle corresponding to the interference weakening region or interference strengthening region in the interference pattern.

[0057] It should be noted that, in the embodiments of this application, the polarization angle of the polarizer is the angle between the polarization direction (i.e., the x-axis) of the first Bessel beam and the polarization direction (i.e., the x-axis) in the counterclockwise direction.

[0058] Please see Figure 3 , Figure 3 A schematic diagram of an interference pattern is shown. (For example...) Figure 3 As shown, in the plane containing the x-axis and y-axis, the interference pattern in the direction with a polarization angle of 45° includes an interference weakening region and an interference strengthening region. The interference strengthening region consists of two bright lobes in the interference image, and the angle between the line of symmetry of the two lobes and the x-axis is the azimuth angle corresponding to the interference strengthening region.

[0059] In other embodiments, the corresponding azimuth angle can be calculated based on the interference-attenuating regions in the interferogram, where the interference-enhancing and interference-attenuating regions form concentric rings. Within these concentric rings, the highlighted areas represent interference-enhancing regions, and the other areas represent interference-attenuating regions.

[0060] In this application, the phase difference between the first and second Bessel beams is obtained by measuring the azimuth angle of the interference weakening or interference strengthening regions in the interference patterns of the first and second Bessel beams. The steps are simple, do not require setting up a complex optical path, and simplify the measurement process.

[0061] S103. Use a polarizer to obtain the first amplitude of the first Bessel beam and the second amplitude of the second Bessel beam, and obtain the amplitude ratio based on the first amplitude and the second amplitude.

[0062] In this application, the polarization angles of the polarizer are adjusted to 0° and 90°, and the first and second patterns of the first and second Bessel beams are observed at the two polarization angles using a detection instrument, thereby obtaining the amplitude of the first Bessel beam. Amplitude of the second Bessel beam The amplitude ratio α between the first and second Bessel beams is and The ratio, where,

[0063] S104. Calculate the polarization state of the wave to be detected based on the phase difference and amplitude ratio.

[0064] For example, the polarization state of the wave to be detected is determined using the Jones matrix based on the phase difference and amplitude ratio; the formula for the Jones matrix is:

[0065]

[0066] In the formula, E x E represents the first complex amplitude of the beam to be detected in the plane containing the x-axis. x Including the amplitude and phase of the beam to be detected in the plane containing the x-axis; E y E represents the second complex amplitude of the beam to be detected in the plane containing the y-axis. y This includes the amplitude and phase of the beam to be detected in the plane containing the y-axis.

[0067] In one embodiment, after obtaining the phase difference and amplitude ratio of the first and second Bessel beams, the polarization state of the wave to be detected can be calculated using the Stokes parameter method.

[0068] For example, four parameters (S0, S1, S2, S3) are used to describe the polarization state of the beam. S0 represents the total amplitude, S1 represents the difference between the horizontal and vertical polarization amplitudes, S2 represents the difference between the +45° and -45° polarization amplitudes, and S3 represents the difference between the right-hand and left-hand circular polarization amplitudes. For fully polarized light, S0 = S1 + S2 + S3. The Stokes parameters correspond to a Stokes sphere, where each point represents a specific polarization state. The Stokes equations are:

[0069]

[0070]

[0071]

[0072] S0 = S1 + S2 + S3.

[0073] In the polarization state detection method provided in this application embodiment, a miniaturized polarization state detection device is used to orthogonalize the first and second Bessel beams to be detected. The phase difference is measured by measuring the azimuth angles of the first and second Bessel beams. Combined with the amplitude ratio of the first and second Bessel beams, the polarization state of the beam to be detected is measured. This simplifies the steps of the polarization state detection process for terahertz and millimeter waves, eliminating the need for a complex and bulky detection system and promoting the miniaturization of the detection device.

[0074] To implement the above-mentioned polarization state detection method, this application provides a design scheme for a polarization state detection device.

[0075] In this embodiment, the polarization state detection device includes: a metal body with a preset thickness and a waveguide array formed by multiple rectangular aperture units disposed on the metal body. According to waveguide theory, when the side length of the rectangular aperture of the rectangular waveguide is between λ / 2n and λ / n, where n is the refractive index of the medium in the metal aperture, the second directional polarization component of the incident beam can excite a TE10 mode polarized along the second direction, while the first directional polarization component of the incident beam can excite a TE01 mode polarized along the first direction. The TE10 mode and the TE01 mode are orthogonal to each other.

[0076] In some embodiments, the first relational table is used to characterize the mapping relationship between the side length of the rectangular aperture element and the phase delay. The side length of the rectangular aperture can be independently adjusted by COMSOL Multiphysics software, and the phase delay data obtained by parametrically scanning different side lengths of the rectangular aperture can be used to form the first relational table.

[0077] In some embodiments, the second relationship table is used to characterize the mapping relationship between the side length of the rectangular aperture unit and the transmittance. The second relationship table can be formed by parametrically scanning transmittance data with different rectangular aperture side lengths using COMSOL Multiphysics software.

[0078] For example, to verify the effect of the side length of the rectangular aperture waveguide element on the beam, an aluminum rectangular aperture waveguide element was set up using COMSOL Multiphysics simulation software. Floquet periodic boundary conditions were applied to the four sides of the aluminum rectangular aperture waveguide element to simulate an infinitely large two-dimensional rectangular aperture waveguide element array. In COMSOL Multiphysics simulation software, the first side length in the x-axis direction and the second side length in the y-axis direction of the aluminum rectangular aperture waveguide element were changed. Terahertz and millimeter-wave beams were used to scan the side length of the aluminum rectangular aperture waveguide element, and the data was processed using Origin plotting software to obtain the following results: Figure 4 The first table showing the relationship between side length and phase delay, and as shown in the table below... Figure 5 The second table showing the relationship between side length and transmittance is provided, where 'a' is the side length of the rectangular aperture element in the x-axis direction and 'b' is the side length of the rectangular aperture element in the y-axis direction. Due to the symmetry of the element, the relationship between the phase delay generated when the incident beam is polarized along the first direction and the two sides (first side length, second side length) of the rectangular aperture element is symmetrical about the diagonal compared to the relationship generated when the beam is polarized along the second direction. Similarly, the relationship between the transmittance and the two sides (first side length, second side length) of the rectangular aperture is also symmetrical about the diagonal.

[0079] In some embodiments, such as Figure 4 and Figure 5As shown, a preset number of side length combinations of rectangular hole units are selected according to the first and second relationship tables. For example, the preset number is 64. The dimensions of the 64 metal rectangular holes are... Figure 4 The position of the solid origin is indicated. The selected aperture phase delay covers 0–2π, and the interval between the x-polarization component and the y-polarization component is π / 4. Furthermore, due to anomalous transmission, the corresponding... Figure 5 The transmittance is greater than 90%, and the high transmittance makes it easy to effectively control the wave.

[0080] By increasing the preset number of the above-mentioned side length combinations, the accuracy of the rectangular aperture unit can be improved, thereby improving the accuracy of the polarization state detection unit, and further improving the accuracy of the polarization state detection results.

[0081] In some embodiments, the target side length combination of the rectangular hole element is determined based on the phase delay diagram and the aforementioned preset number of side length combinations.

[0082] In the embodiments of this application, the phase delay diagram is determined based on the preset tilt angle of the Bessel beam, the vortex phase distribution of the Bessel beam, and the Bessel beam conversion formula.

[0083] In order to form a Bessel beam, the beam needs to be emitted at a certain tilt angle, which ranges from 5° to 85°.

[0084] like Figure 6 As shown, in order to obtain a 0th-order Bessel beam at the exit surface, the phase delay of the Bessel beam along the z-axis at the exit surface should satisfy the following formula:

[0085]

[0086] In the formula: β is the tilt angle of the wavefront; k0 is the wave vector; and r is the radial radius.

[0087] For a Bessel beam of ±m order, the Bessel beam conversion formula is:

[0088]

[0089] m is the topological number, θ is the vortex phase distribution, and r is the radial cross-sectional radius of the Bessel beam on the target surface.

[0090] The phase delay diagram determines the phase delay of the element required to form a Bessel beam at the exit surface. The period of the phase delay is [0, 2π]. By selecting and arranging the rectangular aperture elements according to the phase delay diagram, a Bessel beam can be formed at the exit surface.

[0091] To obtain the target side length combination of the rectangular aperture element, the phase delay corresponding to each rectangular aperture element can be determined first based on the phase delay diagram, and then the target side length combination can be determined from the side length combination based on the phase delay corresponding to each rectangular aperture element.

[0092] In some embodiments, determining the target side length combination for each rectangular aperture element based on a phase delay map, a first relational table, and a second relational table includes:

[0093] The phase delay interval corresponding to each rectangular aperture unit is obtained based on the phase delay diagram. The period of the phase delay is [0, 2π]. The phase delay interval is divided into [0, 2π] according to a preset order. The length interval of the side length combination of the rectangular aperture unit 120 is determined based on the phase delay interval corresponding to the rectangular aperture unit and the first relationship table. The target side length combination of the rectangular aperture unit can be obtained based on the length interval of the side length combination of the rectangular aperture unit, the second relationship table, and the preset transmittance conditions. The preset conditions include: 1. The transmittance corresponding to the first side length and the second side length of the reference unit of the selected side length combination cannot be less than a preset value, for example, the preset value can be set to 90%. At the same time, the average value of the transmittance corresponding to the first side length and the second side length is the maximum or the difference between the two is the minimum. 2. The transmittance corresponding to the first side length and the second side length of the reference unit of the selected side length is the maximum within the interval.

[0094] In some embodiments, the metal body further includes processing the medium into the above-described shape and then depositing a metal film that electromagnetic waves cannot penetrate on the surface of the medium, thereby equivalently realizing the above-described polarization state detection device.

[0095] In some embodiments, a medium different from the metal body material is filled into the rectangular aperture unit 120, the medium including air, where the refractive index n = 1. To improve the beam signal modulation capability, a special medium transparent to the electromagnetic waves used can also be added to the rectangular aperture unit to achieve better phase delay modulation.

[0096] In some embodiments, the thickness of the metal body is related to the wavelength of the incident wave, and the preset thickness range is λ-10λ, where λ represents the wavelength of the incident wave, and the wavelength range is 0.03mm-10mm. In a preferred embodiment, the thickness of the metal body is 6mm.

[0097] In some embodiments, a plurality of rectangular aperture units are arranged periodically, and the corresponding spacing T between the rectangular aperture units is 0.5λ / n to λ, where λ represents the wavelength of the incident wave and n represents the refractive index of the medium in the metal aperture. In a preferred embodiment, the corresponding spacing T between the rectangular aperture units is 2 mm.

[0098] like Figure 7-10As shown, to characterize the diffraction-free properties of the Bessel beam, a Bessel beam was generated using a polarization state detection device. The intensity distributions of the first and second Bessel beams at z = 50 mm, 55 mm, and 60 mm were detected using a polarizer at polarization directions of 0° and 90°, respectively. The amplitude was the product of the intensity and a constant coefficient, thus obtaining the amplitude distributions of the first Bessel beam along the x-axis and the second Bessel beam along the y-axis. It can be seen that with increasing transmission distance, the Bessel beam exhibits a significant diffraction-free characteristic, with the polarization components displaying vortex distribution characteristics, and the central halo maintaining almost the same size. The diffraction-free properties of the Bessel beam were verified by detecting it within the diffraction-free region.

[0099] To verify the relationship between the phase difference of the orthogonal first and second Bessel beams and the azimuth angle of the interferogram, embodiments of this application provide interferograms of Bessel waves with various phase differences through COMSOL simulation. According to equation (5), when m = 1, Interference patterns were observed using a polarizer with a polarization angle of 45° and a polarization angle of 270°, yielding the following results: Figure 11 The interference pattern shown, the interference pattern in This proves the relationship between phase difference and azimuth angle.

[0100] To verify the relationship between the phase difference of the orthogonal first and second Bessel beams and the azimuth angle of the interferogram, this application also provides interferograms of Bessel waves with various phase differences through actual measurements of the polarization state detection device. For example... Figure 12 As shown, the phase difference generated by the polarization state detection device is The first Bessel beam and the second Bessel beam, Interference patterns were observed using a polarizer with a polarization angle of 45° and a polarization angle of 270°, yielding the following results: Figure 12 The interference pattern shown, the interference pattern in The experimental results are consistent with the simulation results.

[0101] To verify that the polarization state detection device can measure arbitrary polarization, in this embodiment of the application, orthogonal polarized waves with different amplitude ratios were also measured.

[0102] For example, in the simulation in COMSOL, the input amplitude ratio is... Orthogonal polarization beams, and the polarization state detector is rotated clockwise along the cut-off plane. The simulated intensity distribution of COMSOL at z = 50 mm was measured, and the measurement results are as follows: Figure 13 As shown.

[0103] To verify the actual performance of the polarization state detection device, this application also conducted physical measurements of the polarization state detection device at polarization angles of 0°, 90°, and 45° using a polarizer. Based on the conditions used in the simulation measurement process described above, a physical experiment was conducted on the polarization state detection device, and the experimental results are as follows: Figure 14 As shown.

[0104] according to Figure 13 and Figure 14 The comparison results show that the simulated intensity distribution and the actual intensity distribution are in very good agreement. The polarization state detection device provided in this application embodiment is suitable for measuring beams with inconsistent amplitude ratios of orthogonal polarization components.

[0105] like Figure 15 As shown, embodiments of this application also provide a polarization state detection system 100, which includes: a polarization state detection device 11, a polarizer 12, a detector 13, a detection apparatus 14, and a collimating lens 16.

[0106] In some embodiments, the beam to be detected is collimated by the collimating lens 15, and the collimated beam is input into the polarization state detection device 11, which helps to improve the accuracy of detection.

[0107] The polarization state detection device 11 has a metal body of preset thickness and a waveguide array formed by multiple rectangular aperture units disposed on the metal body. A single rectangular aperture unit is used to control two orthogonally polarized beams. The polarization state detection device 11 is used to convert the beam to be detected into an orthogonal first Bessel beam and a second Bessel beam. The polarization state detection device 11 can also be any polarization state detection device provided in the embodiments of this application.

[0108] Polarizer 12 is used to allow the first Bessel beam and the second Bessel beam to pass through at a preset polarization angle.

[0109] In some embodiments, the polarizer 12 is located behind the polarization state detection device 11 in the beam propagation direction, and the polarizer 12 is located in front of the detector 13 in the beam propagation direction.

[0110] The detector 13 is used to obtain the azimuth angle of the first Bessel beam and the second Bessel beam, and the detector 13 is also used to obtain the amplitude ratio of the first Bessel beam and the second Bessel beam.

[0111] In some embodiments, the detector 13 may be a PYIII camera. A PYIII camera can operate across the entire terahertz and millimeter-wave frequency range (0.03–10 THz), has an effective area of ​​1.24 cm × 1.24 cm, consists of 124 × 124 pixels, and has a pixel spacing of 0.1 mm. In this application, the detector 13 may also be a detection device other than a PYIII camera; the PYIII camera is not used to limit the detector 13 in the embodiments of this application.

[0112] The detection device 14 is used to calculate the phase difference between the first Bessel beam and the second Bessel beam based on the azimuth angle. The detection device 14 is also used to calculate the polarization state of the wave to be detected based on the phase difference and the amplitude ratio.

[0113] In some embodiments, the detection device 14 may be a terminal device or a server with computing capabilities. Terminal devices include electronic devices such as tablets, laptops, desktop computers, and personal digital assistants. The server may be a standalone server or a server cluster.

[0114] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A polarization state detection method, characterized in that, The polarization state detection method utilizes a polarization state detection device for detection. The polarization state detection device includes: a metal body with a preset thickness and a waveguide array formed by multiple rectangular aperture units disposed on the metal body. Each rectangular aperture unit is used to control two orthogonally polarized beams. The method includes: The beam to be detected is input into the polarization state detection device to obtain an orthogonal first Bessel beam and a second Bessel beam; Using a polarizer, the azimuth angles corresponding to the interference weakening or interference strengthening regions in the interference patterns of the first and second Bessel beams are obtained, and the phase difference between the first and second Bessel beams is determined based on the azimuth angles. The first amplitude of the first Bessel beam and the second amplitude of the second Bessel beam are obtained using polarizers, and the amplitude ratio is obtained based on the first amplitude and the second amplitude. The polarization state of the wave to be detected is calculated based on the phase difference and the amplitude ratio.

2. The polarization state detection method as described in claim 1, characterized in that, The step of obtaining the azimuth angles corresponding to the interference weakening or enhancing regions in the interference patterns of the first and second Bessel beams using a polarizer includes: Obtain the interference pattern obtained after the first Bessel beam and the second Bessel beam pass through a polarizer with a preset polarization angle, and obtain the azimuth angle corresponding to the interference weakening region or interference strengthening region in the interference pattern; wherein, the polarization angle is the angle between the polarization of the first Bessel beam and the polarization of the second Bessel beam.

3. The polarization state detection method as described in claim 1, characterized in that, The phase difference between the first Bessel beam and the second Bessel beam is determined according to the azimuth angle calculation formula, which is: in, For the phase difference, θ d Let m be the azimuth angle, n be the order of the Bessel beam, and m be an integer. When m = 1 and n = 0, the formula for calculating the azimuth angle is:

4. The polarization state detection method as described in claim 1, characterized in that, The polarization state of the wave to be detected is calculated based on the phase difference and the amplitude ratio, including: Using the Jones matrix, the polarization state of the wave to be detected is determined based on the phase difference and the amplitude ratio; the formula for the Jones matrix is: Among them, E x E is the first complex amplitude. y The second complex amplitude is α, where α is the amplitude ratio. This represents the phase difference.

5. The polarization state detection method as described in claim 1, characterized in that, The intensity distributions of the first Bessel beam and the second Bessel beam are consistent, and the topology numbers of the first Bessel beam and the second Bessel beam are positive and negative m, respectively, where m is a positive integer.

6. The polarization state detection method as described in claim 1, characterized in that, The side length of the rectangular aperture unit is determined according to the phase delay diagram, the first relationship table, and the second relationship table; the first relationship table is obtained based on the relationship between the side length of the rectangular aperture and the phase delay, and the second relationship table is obtained based on the relationship between the side length of the rectangular aperture and the transmittance; the phase delay diagram is determined based on the preset tilt angle of the Bessel beam, the vortex phase distribution of the Bessel beam, and the Bessel beam conversion formula.

7. The polarization state detection method as described in claim 6, characterized in that, The first relationship table is used to characterize the mapping relationship between the rectangular aperture side length and the phase delay, and the second relationship table is used to characterize the mapping relationship between the rectangular aperture size and the transmittance. The first relationship table and the second relationship table are composed of data obtained by parametric scanning of different rectangular aperture side lengths by simulation software.

8. The polarization state detection method as described in claim 1, characterized in that, The beam to be detected includes terahertz and millimeter-wave beams.

9. A polarization state detection system, characterized in that, The polarization state detection system includes: A polarization state detection device; the polarization state detection device has a metal body of a preset thickness and a waveguide array formed by multiple rectangular aperture units disposed on the metal body. A single rectangular aperture unit is used to control two orthogonal polarized beams. The polarization state detection device is used to convert the beam to be detected into an orthogonal first Bessel beam and a second Bessel beam. Polarizing filter; The detector is used to acquire the interference pattern of the first Bessel beam and the second Bessel beam, the interference pattern including interference reduction region and interference enhancement region; the detector is also used to acquire the first amplitude of the first Bessel beam and the second amplitude of the second Bessel beam; The detection device is used to calculate the corresponding azimuth angle based on the interference weakening region or interference strengthening region of the interference pattern, and to calculate the phase difference between the first Bessel beam and the second Bessel beam based on the azimuth angle. The detection device is also used to calculate the polarization state of the wave to be detected based on the phase difference, the first amplitude, and the second amplitude.

10. The polarization state detection system as described in claim 9, characterized in that, The polarizer is located behind the polarization state detection device in the beam propagation direction.

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