A weak measurement based metasurface parameter characterization system and method

Abstract

The application discloses a kind of based on weak measurement's metasurface parameter characterization system and method, including in order along the direction of light beam propagation: light source, front selection unit, focusing transmission unit, to be measured metasurface, rear selection unit and detection unit.The rear selection unit is used to amplify spin-related lateral displacement, and the detection unit is used to collect the output light spot amplified after rear selection and read its centroid offset.The application no longer relies on topography observation to infer metasurface function indirectly, but the spin-related displacement induced by phase gradient is regarded as weak coupling signal, and the direct characterization of phase gradient metasurface optical parameter is realized by rear selection amplification and response map construction.The application does not judge whether device meets design requirement according to topography image, but directly utilizes metasurface transmission optical readout to carry out parameter inversion.

Description

Technical Field

[0001] This invention relates to the field of optical measurement technology, and in particular to a metasurface parameter characterization system and method based on weak measurement. Background Technology

[0002] Metasurfaces achieve optical functions by designing geometric structures, but in actual manufacturing processes, manufacturing defects such as dimensional errors and material inhomogeneities can cause the actual optical response to deviate from the ideal design [1], manifested as changes in the amplitude and phase of the superatomic transmission [2].

[0003] Currently, electron microscopy is commonly used to inspect the morphology of metasurfaces[3]. However, for dielectric samples, a conductive coating is usually applied during imaging to reduce charge accumulation. This sample preparation step alters the surface state, and if the coating cannot be completely removed, it may affect subsequent optical testing. The true optical response of metaatoms cannot be determined solely by electron microscopy morphology data, and direct optical measurement is still required to confirm whether the device meets the design specifications.

[0004] In metasurface devices, the Pancharatnam–Berry phase is often used to introduce a geometric phase gradient through spatial variations in the orientation of superatoms. This phase gradient can cause the left-hand and right-hand circularly polarized components to shift in opposite transverse directions, which is regarded as the optical spin Hall effect in real space [4]. Under the pre-selection and post-selection effects of weak measurement schemes, this displacement can be mapped to a measurable centroid shift, thereby converting the weak signal into an optical reading [5]. The centroid shift in weak measurement is affected by the complex transmission response and geometric phase gradient of the metasurface. The complex transmission response corresponds to the transmission amplitude and transmission phase of the superatoms and is related to the size, shape and material properties of the superatoms. The geometric phase gradient is the rate of change of the rotation angle with position [6]. Based on this, the centroid shift obtained by weak measurement can be used as an optical readout for characterizing metasurface parameters.

[0005] In existing technologies, SEM morphology inspection is destructive and cannot directly characterize the optical properties of metasurfaces; moreover, existing optical characterization methods are difficult to simultaneously and quickly decouple multiple parameters such as amplitude, phase and phase gradient of metaatoms, and cannot meet practical measurement needs.

[0006] [1].Yu N, Genevet P, Kats MA, et al. Light propagation with phasediscontinuities: generalized laws of reflection and refraction. Science, 2011, 334(6054): 333–337.

[0007] [2]. Khorasaninejad M, Chen W T, Devlin R C, et al. Metalenses at visible wavelengths: diffraction limited focusing and subwavelength resolution imaging. Science, 2016, 352(6290): 1190–1194.

[0008] [3]. Goldstein J I, Newbury D E, Michael J R, et al. Scanning electron microscope (SEM) instrumentation. In: Scanning Electron Microscopy and X Ray Microanalysis. New York, NY: Springer, 2017: 65–91.

[0009] [4]. Zhou J, Qian H, Chen C F, et al. Optical edge detection based on high efficiency dielectric metasurface. Proceedings of the National Academy of Sciences, 2019, 116(23): 11137–11140.

[0010] [5]. Chen S, Zhou X, Mi C, et al. Dielectric metasurfaces for quantum weak measurements. Applied Physics Letters, 2017, 110(16).

[0011] [6]. Liu S, Fan F, Chen S, et al. Computing liquid crystal photonics platform enabled wavefront sensing. Laser & Photonics Reviews, 2023, 17(8): 2300044. Summary of the Invention

[0012] The purpose of this invention is to provide a metasurface parameter characterization system and method based on weak measurement, which can perform non-contact functional characterization of the optical response of phase gradient metasurfaces.

[0013] The technical solution adopted in this invention is as follows:

[0014] The metasurface parameter characterization system based on weak measurement, along the beam propagation direction, includes, in sequence:

[0015] A light source, used to generate an incident light beam;

[0016] A pre-selection unit is used to adjust the polarization state of the incident beam to a fixed initial polarization state;

[0017] A focusing and transmission unit is used to control the spot size of the beam at the metasurface under test;

[0018] The metasurface to be tested is a phase-gradient Pancharatnam–Berry metasurface, which is used to provide weak coupling and introduce spin-dependent lateral displacement during propagation.

[0019] The post-selection unit, which consists of a quarter-wave plate and a linear polarizer, is used to amplify the spin-related transverse displacement.

[0020] The detection unit is used to acquire the output light spot after post-selection and amplification and to read its centroid offset.

[0021] The pre-selection unit is a linear polarizer used to fix the initial polarization state as horizontal linear polarization.

[0022] The focusing transmission unit consists of a first lens and a second lens located in front of and behind the metasurface to be tested, with the metasurface to be tested positioned near the focal plane of the first lens and the second lens.

[0023] In the post-selection unit, the definition is... The deflection angle of the quarter-wave plate. is the relative rotation angle between the transmission axis of the linear polarizer and the optical axis of the quarter-wave plate; where, Angle as the magnified imaginary part of a weak measurement system Angle is used as the real part magnification angle of a weak measurement system.

[0024] The light source is a single-wavelength helium-neon laser with a working wavelength of 632.8 nm, and the incident beam is modeled as a fundamental Gaussian beam.

[0025] The detection unit is a charge-coupled device used to record the intensity distribution or centroid shift image of the emitted beam after post-selective modulation.

[0026] It also includes a half-wave plate, which is located between the light source and the front selection unit and is used to adjust the incident polarization in conjunction with the front selection unit.

[0027] A metasurface parameter characterization method based on the aforementioned weak measurement-based metasurface parameter characterization system includes the following steps:

[0028] The first step is to turn on the light source, and the light beam is prepared as horizontally linearly polarized light after passing through the pre-selection unit;

[0029] In the second step, the horizontally polarized light is irradiated onto the metasurface to be tested through a focusing and transmission unit. The metasurface to be tested is positioned near the focal plane of the transmission unit in order to control the size of the light spot at the metasurface location.

[0030] The third step involves the beam of light passing through the metasurface under test entering the post-selection unit, and adjusting the deflection angle of the quarter-wave plate. Relative rotation offset angle of the linear polarizer This allows for adjustment of different weak-value amplification states;

[0031] The fourth step is to use the detection unit to collect the output light spot after selection and amplification, and read the offset of the light spot centroid along the lateral direction, i.e., the pointer displacement.

[0032] Fifth step: Simultaneously scan the deflection angle in a two-dimensional plane. Angle and relative rotation offset angle Record the centroid offset under various angle combinations and construct a two-dimensional pointer centroid displacement response map;

[0033] The sixth step is to characterize the response characteristics of the metasurface under test based on the two-dimensional pointer centroid displacement response diagram.

[0034] In the fourth step, the lateral offset of the light spot centroid is: , , and Represents horizontal spatial coordinates. The intensity distribution is represented; the sign distribution, mirror symmetry features, local extremum locations, and contour density of the response map change with the amplitude ratio, phase difference, and rotation angle step parameters.

[0035] The parameters of the metasurface to be inverted in the sixth step include: the amplitude ratio and phase difference describing the optical response of a single metaatom, and the rotational angular step parameter describing the geometric phase gradient of the metasurface.

[0036] This invention utilizes a pre-selection unit to adjust the incident light to a defined polarization state, and leverages the Pancharatnam–Berry phase-gradient metasurface to introduce a spin-dependent transverse displacement due to the photon spin Hall effect during propagation. This displacement is then weakly amplified by a post-selection unit composed of a quarter-wave plate and a linear polarizer. A detection unit records the amplified light spot and extracts the centroid shift. Based on this, a two-dimensional response map is constructed, and the amplitude ratio, phase difference, and rotation angle parameters of the metasurface are characterized accordingly. The distinguishing technical approach of this scheme lies in its departure from relying on morphological observation for indirect judgment of metasurface function. Instead, it uses the phase gradient-induced spin-dependent displacement as a weakly coupled signal, achieving direct characterization of the optical parameters of the phase-gradient metasurface through post-selection amplification and response map construction. Compared to traditional morphological detection, this invention directly utilizes the optical readout after metasurface transmission for parameter characterization. While traditional morphological detection can observe structural periodicity and arrangement, it cannot uniquely determine the actual transmission amplitude and phase response of the superatoms, thus still requiring direct optical measurement. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the structure of the present invention;

[0039] Figure 2 This is a flowchart of the present invention. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] like Figure 1 As shown, the present invention comprises, in sequence along the beam propagation direction:

[0042] The light source, a single-wavelength helium-neon laser, is used to generate the incident beam;

[0043] A pre-selection unit is used to prepare the polarization state of the incident beam into a fixed initial polarization state;

[0044] A focusing and transmission unit is used to control the spot size of the beam at the metasurface under test;

[0045] The metasurface to be tested is a phase-gradient Pancharatnam–Berry metasurface, which is used to provide weak coupling and introduce spin-dependent lateral displacement during propagation.

[0046] The post-selection unit, which consists of a quarter-wave plate and a linear polarizer, is used to amplify the spin-related transverse displacement.

[0047] The detection unit is used to acquire the output light spot after post-selection and amplification and to read its centroid offset.

[0048] In the Pancharatnam–Berry phase-gradient metasurface, the geometric phase gradient causes the left-handed and right-handed circularly polarized components to shift in opposite directions laterally. This shift manifests as a photon spin Hall effect in real space. Since this shift is small and difficult to measure directly, a pre-selection and post-selection process in weak measurement is introduced. This spin-related lateral shift can be used as a weakly coupled signal, and then weak amplification is achieved through post-selection. Ultimately, the originally difficult-to-distinguish minute shift is converted into a spot centroid shift that can be read by the detector. Thus, the metasurface's transmission response and geometric phase gradient information are mapped to a measurable spatial shift reading, providing a basis for subsequent parameter inversion.

[0049] Based on the above principles, the characterization system constructed in this invention comprises, sequentially along the optical path, a light source, a pre-selection unit, a focusing and transmission unit, a metasurface under test, a post-selection unit, and a detection unit. The light source generates the incident beam, employing a single-wavelength helium-neon laser. The incident beam is modeled as a Gaussian beam in theoretical processing. The pre-selection unit modulates the incident beam to a defined initial polarization state. The pre-selection unit consists of a linear polarizer 1 (LP1). The focusing and transmission unit controls the beam spot size at the metasurface under test, ensuring the incident beam effectively passes through the metasurface. The metasurface under test is a Pancharatnam–Berry phase-gradient metasurface, which provides weak coupling and introduces spin-dependent lateral displacement during propagation. The post-selection unit amplifies this lateral displacement and consists of a quarter-wave plate (QWP) and a linear polarizer 2 (LP2). The detection unit acquires the output beam spot and reads the centroid shift. The acquired beam intensity distribution or centroid shift results can be used for subsequent parameter characterization. The aforementioned units are not independent of each other, but rather form a continuous relationship around the goal of weak measurement readout.

[0050] The pre-selection unit uses a linear polarizer to adjust the incident beam to the desired linear polarization state, which is fixed as horizontal linear polarization. The focusing and transmission unit consists of a lens system located before and after the metasurface under test. Two lenses control beam propagation, and the metasurface under test is placed near the focal plane to control the spot size of the beam at the metasurface. The metasurface under test is located between the pre-selection and post-selection units, and it serves both as an optical modulation unit and as a generator of weakly coupled signals. The metasurface directly introduces spin-dependent lateral displacement during propagation.

[0051] The post-selection unit, located after the metasurface under test, consists of a quarter-wave plate (QWP) and a linear polarizer 2 (LP2). In the experiment, The deflection angle of the quarter-wave plate (QWP) The relative rotation angle between the transmission axis of linear polarizer 2 (LP2) and the optical axis of the quarter-wave plate (QWP) is given. The initial optical axis of the quarter-wave plate (QWP) is set in the y-direction. The function of this post-selection unit is to change the post-selection state of the system, thereby adjusting the weak amplification state and causing the output spot to exhibit centroid shift under different amplification conditions. Angles are considered as magnified imaginary angles in weak measurement systems. The real part magnification angle is considered to be that of a weak measurement system.

[0052] After the output light field, modulated by the metasurface under test and passed through the post-selection unit, propagates to the detector surface, the detector unit records its intensity distribution and reads the centroid shift of the light spot along the lateral direction. The change in the centroid of the light spot under different post-selection angle conditions is used as the basis for parameter characterization. This is achieved through simultaneous scanning. and A two-dimensional offset response map can be constructed on the magnified angular plane. This two-dimensional response map changes with variations in amplitude ratio, phase difference, and phase gradient parameters, and therefore can serve as a characteristic response of the metasurface under test for parameter characterization.

[0053] In practical use, the pre-selection unit is a linear polarizer used to fix the initial polarization state to horizontal linear polarization. The focusing transmission unit consists of lens 1 (Lens1) and lens 2 (Lens2) located before and after the metasurface under test. Lens 1 (Lens1) and lens 2 (Lens2) are used to control the spot size of the beam at the metasurface under test; the metasurface under test is located near the focal plane of lens 1 (Lens1) and lens 2 (Lens2). In the post-selection unit, a definition is defined. The deflection angle of the quarter-wave plate (QWP) is the relative rotation angle of the transmission axis of linear polarizer 2 (LP2) with respect to the optical axis of the quarter-wave plate (QWP); where, Angle as the magnified imaginary part of a weak measurement system The angle serves as the real amplification angle for the weak measurement system. A quarter-wave plate (QWP) is used in combination with linear polarizer 2 (LP2) to change the post-selection state of the system, thereby adjusting the weak amplification state;

[0054] The light source is a single-wavelength helium-neon laser with an operating wavelength of 632.8 nm, and the incident beam is modeled as a fundamental mode Gaussian beam. The detection unit is a charge-coupled device (CCD) used to record the intensity distribution or centroid shift image of the emitted beam after post-selection modulation, thereby realizing the detection and data acquisition of weak amplification effects. It also includes a half-wave plate (HWP), located between the light source and the pre-selection unit, used to adjust the incident polarization in conjunction with the pre-selection unit.

[0055] A metasurface parameter characterization method based on a weak measurement-based metasurface parameter characterization system includes the following steps:

[0056] The first step is to turn on the light source, and the light beam is prepared as horizontally linearly polarized light after passing through the pre-selection unit;

[0057] In the second step, the horizontally polarized light is irradiated onto the metasurface to be tested through a focusing and transmission unit. The metasurface to be tested is positioned near the focal plane of the transmission unit in order to control the size of the light spot at the metasurface location.

[0058] The third step involves the beam of light passing through the metasurface under test entering the post-selection unit, and adjusting the deflection angle of the quarter-wave plate. The relative rotation offset angle of linear polarizer 2 This allows for adjustment of different weak-value amplification states;

[0059] The fourth step is to use the detection unit to collect the output light spot after selection and amplification, and read the offset of the light spot centroid along the lateral direction, i.e., the pointer displacement.

[0060] Fifth step: Simultaneously scan the deflection angle in a two-dimensional plane. Angle and relative rotation offset angle The centroid offset under each angle combination is recorded, and a two-dimensional pointer centroid displacement response map is constructed. The obtained two-dimensional pointer centroid displacement response map is compared and fitted with the theoretical formula results to obtain the parameters of the metasurface under test.

[0061] In the fourth step, the lateral offset of the light spot centroid is: , , and Represents horizontal spatial coordinates. The intensity distribution; the sign distribution, mirror symmetry features, local extremum locations, and contour density of the response map change with the amplitude ratio, phase difference, and rotation angle step parameters.

[0062] The parameters of the metasurface to be inverted in the fifth step include: the amplitude ratio and phase difference describing the optical response of a single metaatom, and the rotational angular step parameter describing the geometric phase gradient of the metasurface.

[0063] The following specific examples further illustrate this application:

[0064] Theoretical implementation of weak measurement characterization:

[0065] The incident beam is described using a fundamental Gaussian beam. At the beam waist plane, the incident electric field can be expressed as:

[0066]

[0067] in, Indicates the waist radius, and Representing the transverse spatial coordinates, this expression defines the normalized incident field entering the system, satisfying the power normalization condition. For a single superatom in the metasurface under test, its response in the local principal axis coordinate system is described by the Jones matrix:

[0068]

[0069] in, The amplitude ratio between the two intrinsic polarization channels. The phase difference between the two intrinsic polarization channels is represented by , where i represents the imaginary unit. Therefore, the local optical response of the metasurface under test can be expressed by the amplitude ratio. Phase difference Two parameters characterize the process. To introduce a geometric phase gradient in the plane, the superatom undergoes a spatial rotation along a predetermined direction. The Jones matrix in the laboratory coordinate system is represented as:

[0070]

[0071] in, The polarization transmission matrix of a single superatom in its intrinsic coordinate system. Indicates the rotation angle is The coordinate rotation matrix is ​​expressed as follows:

[0072]

[0073] in, , This represents the rotation angle as a function of position. This represents the position coordinates within the metasurface plane along the phase gradient direction. Indicates the lattice period, This represents the rotation angle step parameter between adjacent units. The spatial orientation change of local superatoms is achieved through the rotation angle function. This is reflected in the discrete arrangement of superatomic arrays. From lattice period and the rotation angle step parameters between adjacent units Confirmed. Lattice period. With rotation angle step parameters It is not an explicit variable in the formula, but rather a variable contained in the rotation angle function. In the construction relationship, the rotation angle step parameter... Reflecting the magnitude of the geometric phase gradient is one of the target parameters that this invention needs to characterize.

[0074] The weak measurement system consists of three stages: pre-selection, weak coupling, and post-selection. In the pre-selection stage, the incident polarization is fixed as horizontal linear polarization, corresponding to the Jones vector. .

[0075] The post-selection stage consists of a quarter-wave plate (QWP) and linear polarizer 2 (LP2). The azimuth angle of the quarter-wave plate (QWP) is defined as... The relative offset angle of linear polarizer 2 (LP2) with respect to the quarter-wave plate is defined as The transmission axis direction of linear polarizer 2 (LP2) is... The zero-angle reference is taken in the vertical direction. The combination matrix of the subsequently selected elements is denoted as... The output field on the metasurface plane can be written as:

[0076]

[0077] in, Indicates the choice angle after selection. and The output light intensity distribution on the detection plane under certain conditions and To detect planar coordinates, This indicates the quarter-wave plate (QWP) at the azimuth angle. The Jones matrix below, This indicates that the linear polarizer 2 (LP2) is in the transmission axis direction. The Jones matrix below, This indicates that the metasurface under test varies with position in the laboratory coordinate system. The changing local Jones matrix contains the result of the rotation angle function. Introduced spatial changes, This represents the Jones vector of incident polarization after pre-selection. This represents the scalar amplitude distribution of the incident beam in the transverse space.

[0078] In this embodiment, the weak measurement readout is defined as along... Displacement of the center of mass in the direction:

[0079]

[0080] in, Indicates the choice angle after selection. and The output light intensity distribution on the detection plane under certain conditions This represents the position coordinates within the metasurface plane along the phase gradient direction. By adjusting different post-selection angles... and By sampling the output light spot, a two-dimensional pointer displacement response diagram can be obtained. The two-dimensional response plot shows variations in sign distribution, approximate mirror symmetry, local extremum locations, and contour density with amplitude ratio. Phase difference and rotation angle step parameters It changes with the parameters, and therefore can be used as a basis for parameter inversion.

[0081] This invention provides an optical measurement system for characterizing the parameters of a Pancharatnam–Berry phase gradient metasurface. The system, along the beam propagation direction, sequentially includes a light source, a half-wave plate (HWP), a linear polarizer 1 (LP1), a lens 1 (Lens1), the phase gradient metasurface to be measured, a lens 2 (Lens2), a quarter-wave plate (QWP), another linear polarizer 2 (LP2), and a detector. The half-wave plate (HWP) is used to adjust the beam intensity. The linear polarizer 1 (LP1) constitutes the incident polarization adjustment and pre-selection unit, while the quarter-wave plate (QWP) and the linear polarizer 2 (LP2) constitute the post-selection unit. The phase gradient metasurface to be measured is located between lens 1 (Lens1) and lens 2 (Lens2). The detector is positioned after the post-selection unit to acquire the output beam spot and read the centroid position of the beam spot.

[0082] The above-mentioned devices constitute a complete experimental measurement device, in which the lens group is used to control the beam size at the metasurface to be measured, and the detector is used to record the intensity distribution of the output beam after post-selective amplification.

[0083] In actual use, the above system includes the following steps:

[0084] The first step is to turn on the light source, enabling the helium-neon laser to emit light. The beam passes sequentially through a half-wave plate and linear polarizer 1 (LP1). The incident polarization is pre-selected and fixed as horizontal linear polarization by linear polarizer 1 (LP1). The half-wave plate is located between the light source and linear polarizer 1 (LP1) to work with linear polarizer 1 (LP1) to achieve light intensity modulation; linear polarizer 1 (LP1) performs the pre-selection function.

[0085] In the second step, the pre-selected linearly polarized beam is focused by lens 1 (Lens1) and then illuminates the metasurface under test, before continuing to propagate through lens 2 (Lens2). To ensure that the beam passes completely through the metasurface aperture, the metasurface under test is positioned near the focal plane to control the spot size at the metasurface location.

[0086] The third step involves the light beam passing through the metasurface under test into the post-selection unit. The orientation angle of the quarter-wave plate (QWP) is denoted as... The relative offset angle of linear polarizer 2 (LP2) with respect to the quarter-wave plate (QWP) is denoted as... The detector collects and amplifies the output light spot, then the pointer displacement is obtained directly using the centroid readout function.

[0087] The fourth step is to record the measurement data. This involves simultaneous scanning in two dimensions. and Construct a two-dimensional pointer centroid displacement response diagram This is to record the complete response information on the magnified angular plane.

[0088] Fifth step, based on the two-dimensional pointer centroid displacement response diagram The amplitude ratio, phase difference, and rotation angle parameters of the metasurface under test are characterized.

[0089] Compared to detection methods that rely on morphological observation, this invention directly uses the optical readout of the metasurface under test as the characterization basis, avoiding the limitation of indirectly inferring the optical function of the device based solely on structural morphology. Compared to measurement methods that read a single offset at a single back-selection angle, this invention scans the azimuth angle of the quarter-wave plate. relative offset angle with linear polarizer A two-dimensional pointer centroid displacement response map is constructed to obtain richer characterization information. Under the implementation conditions of this invention, the amplitude ratio, phase difference, and geometric phase gradient related parameters of the metasurface under test can be mapped to the centroid displacement characteristics of the far-field spot. Therefore, multiple optical parameters can be characterized in the same weak measurement optical path. This invention adopts a non-contact optical measurement method, which does not require sample pretreatment, thus avoiding the influence that traditional tests may have on the sample.

[0090] In the description of this invention, it should be noted that for directional terms, such as "center," "lateral," and "vertical," the appropriate terms may be used.

[0091] The directions and positional relationships indicated by symbols such as "direction", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", and "counterclockwise" are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description. They are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and should not be construed as limiting the specific protection scope of the present invention.

[0092] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification and claims of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0093] Note that the above description is merely a preferred embodiment and application of the technical principles of the present invention. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the specific embodiments described herein, and may include many other effective embodiments without departing from the concept of the present invention. The scope of the present invention is determined by the scope of the appended claims.

Claims

1. A metasurface parameter characterization system based on weak measurement, characterized in that, Along the direction of beam propagation, the following are included in sequence: A light source, used to generate an incident light beam; A pre-selection unit is used to adjust the polarization state of the incident beam to a fixed initial polarization state; A focusing and transmission unit is used to control the spot size of the beam at the metasurface under test; The metasurface to be tested is a phase-gradient Pancharatnam–Berry metasurface, which is used to provide weak coupling and introduce spin-dependent lateral displacement during propagation. The post-selection unit, which consists of a quarter-wave plate and a linear polarizer, is used to amplify the spin-related transverse displacement. The detection unit is used to acquire the output light spot after post-selection and amplification and to read its centroid offset.

2. The metasurface parameter characterization system based on weak measurement according to claim 1, characterized in that, The pre-selection unit is a linear polarizer used to fix the initial polarization state as horizontal linear polarization.

3. The metasurface parameter characterization system based on weak measurement according to claim 1, characterized in that, The focusing transmission unit consists of a first lens and a second lens located in front of and behind the metasurface to be tested, with the metasurface to be tested positioned near the focal plane of the first lens and the second lens.

4. The metasurface parameter characterization system based on weak measurement according to claim 1, characterized in that, In the post-selection unit, the definition is... The deflection angle of the quarter-wave plate. is the relative rotation angle between the transmission axis of the linear polarizer and the optical axis of the quarter-wave plate; where, Angle as the magnified imaginary part of a weak measurement system Angle is used as the real part magnification angle of a weak measurement system.

5. The metasurface parameter characterization system based on weak measurement according to claim 1, characterized in that, The light source is a single-wavelength helium-neon laser with a working wavelength of 632.8 nm, and the incident beam is modeled as a fundamental Gaussian beam.

6. The metasurface parameter characterization system based on weak measurement according to claim 1, characterized in that, The detection unit is a charge-coupled device used to record the intensity distribution or centroid shift image of the emitted beam after post-selective modulation.

7. The metasurface parameter characterization system based on weak measurement according to claim 1, characterized in that, It also includes a half-wave plate, which is located between the light source and the front selection unit and is used to adjust the incident polarization in conjunction with the front selection unit.

8. A metasurface parameter characterization method based on the weak measurement-based metasurface parameter characterization system according to any one of claims 1 to 7, characterized in that, Includes the following steps: The first step is to turn on the light source, and the light beam is prepared as horizontally linearly polarized light after passing through the pre-selection unit; In the second step, the horizontally polarized light is irradiated onto the metasurface to be tested through a focusing and transmission unit. The metasurface to be tested is positioned near the focal plane of the transmission unit in order to control the size of the light spot at the metasurface location. The third step involves the beam of light passing through the metasurface under test entering the post-selection unit, and adjusting the deflection angle of the quarter-wave plate. Relative rotation offset angle of the linear polarizer This allows for adjustment of different weak-value amplification states; The fourth step is to use the detection unit to collect the output light spot after selection and amplification, and read the offset of the light spot centroid along the lateral direction, i.e., the pointer displacement. Fifth step: Simultaneously scan the deflection angle in a two-dimensional plane. Angle and relative rotation offset angle Record the centroid offset under various angle combinations and construct a two-dimensional pointer centroid displacement response map; The sixth step is to characterize the response characteristics of the metasurface under test based on the two-dimensional pointer centroid displacement response diagram.

9. The method for characterizing phase gradient Pancharatnam–Berry metasurface parameters according to claim 8, characterized in that, In the fourth step, the lateral offset of the light spot centroid is: , , and Represents horizontal spatial coordinates. The intensity distribution is represented; the sign distribution, mirror symmetry features, local extremum locations, and contour density of the response map change with the amplitude ratio, phase difference, and rotation angle step parameters.

10. The method for characterizing phase gradient Pancharatnam–Berry metasurface parameters according to claim 8, characterized in that, The parameters of the metasurface to be inverted in the sixth step include: the amplitude ratio and phase difference describing the optical response of a single metaatom, and the rotational angular step parameter describing the geometric phase gradient of the metasurface.

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