Dual-beam differential measurement device and method for polarization sensitivity of metasurface grating

Abstract

The present application relates to the field of optical design technology, and discloses a dual-beam differential measurement device and method for the polarization sensitivity of a metasurface grating, comprising: dividing a pre-generated light beam into a first light beam and a second light beam through a fiber coupler, and dynamically switching the polarization state of the second light beam to obtain a second incident light beam, and adjusting the first light beam based on the second incident light beam to obtain a first incident light beam; passing the first incident light beam through a first path without a metasurface grating, and passing the second incident light beam through a second path including a metasurface grating to obtain a first output light beam and a second output light beam; performing time-domain differentiation on the first output light beam and the second output light beam to calculate a multi-polarization state differential signal; correcting the multi-polarization state differential signal through a preset differential correction mechanism to obtain a corrected differential signal; and calculating the polarization sensitivity of the metasurface grating based on the corrected differential signal. The present application can improve the accuracy of the calculated polarization sensitivity of the metasurface grating.

Description

Technical Field

[0001] The present invention relates to the field of optical design technology, and in particular to a dual-beam differential measurement device and method for polarization sensitivity of a metasurface grating. Background Art

[0002] A metasurface grating is an optical element with a subwavelength structure that can flexibly control the amplitude, phase, polarization and other properties of light. It has broad application prospects in optical communications, imaging, sensing and other fields. Accurately measuring the polarization sensitivity of metasurface gratings is crucial for grating applications in optical communications, imaging and sensing.

[0003] The existing technology has the following problems: measurement based on a single polarization state light beam cannot fully obtain the response of the metasurface grating in different polarization states, resulting in inaccurate and incomplete measurement results; a single error correction method is used for error correction of differential signals, and the signal correction effect is poor, resulting in large deviations in the measurement results; in order to solve at least one of the above problems, the present application proposes a dual-beam differential measurement device and method for the polarization sensitivity of metasurface gratings. Summary of the Invention

[0004] In response to the shortcomings of the prior art, the main purpose of the present invention is to provide a dual-beam differential measurement device and method for the polarization sensitivity of a metasurface grating, which can effectively solve the problems in the background art. The specific technical solutions of the present invention are as follows:

[0005] A dual-beam differential measurement method for the polarization sensitivity of metasurface gratings, including:

[0006] Splitting the pre-generated light beam into a first light beam and a second light beam through a fiber coupler, dynamically switching the polarization state of the second light beam to obtain a second incident light beam, and adjusting the first light beam based on the second incident light beam to obtain a first incident light beam;

[0007] Passing the first incident light beam through a first path without a metasurface grating and passing the second incident light beam through a second path including a metasurface grating to obtain a first output light beam and a second output light beam;

[0008] Performing time domain differentiation on the first output light beam and the second output light beam to calculate and obtain a multi-polarization state differential signal;

[0009] Correcting the multi-polarization state differential signal through a preset differential correction mechanism to obtain a corrected differential signal;

[0010] The polarization sensitivity of the metasurface grating is calculated according to the corrected differential signal.

[0011] Specifically, the method of dividing the pre-generated light beam into a first light beam and a second light beam by a fiber coupler, dynamically switching the polarization state of the second light beam to obtain a second incident light beam, and adjusting the first light beam based on the second incident light beam to obtain a first incident light beam includes:

[0012] Splitting the pre-generated light beam into a first light beam and a second light beam by a fiber coupler;

[0013] Dynamically switching the polarization state of the second light beam between a linear polarization state, a left-handed circular polarization state, or a right-handed circular polarization state within a preset time period to obtain a second incident light beam;

[0014] According to the second incident light beam, the first light beam is adjusted by controlling the optical path difference between the light beams to be less than a preset optical path difference threshold to obtain a first incident light beam.

[0015] Specifically, the first incident light beam passes through a first path without a metasurface grating, and the second incident light beam passes through a second path including a metasurface grating, to obtain a first output light beam and a second output light beam, comprising:

[0016] Launching a first incident light beam into a first path without a metasurface grating, and outputting a first output light beam after light intensity regulation and light path collimation;

[0017] The second incident light beam is emitted to a second path including the metasurface grating, and a second output light beam is output after diffraction by the grating, wherein the second path and the first path are parallelized to make the light beams of the two paths confocal.

[0018] Specifically, performing time domain differentiation on the first output light beam and the second output light beam to calculate and obtain a multi-polarization state differential signal includes:

[0019] Performing time-domain synchronous acquisition on the first output light beam and the second output light beam to obtain a first acquisition light beam and a second acquisition light beam;

[0020] The light intensity difference and phase difference between the first collection light beam and the second collection light beam are calculated to obtain a multi-polarization state differential signal.

[0021] Specifically, the multi-polarization state differential signal is corrected by a preset differential correction mechanism to obtain a corrected differential signal, including:

[0022] According to the multi-polarization state differential signal, a first corrected differential signal is obtained by correcting the common mode noise of the multiple polarization state differential signals;

[0023] Error identification and correction are performed on the differential signal of each polarization state to obtain a corrected differential signal.

[0024] Specifically, the method of obtaining a first corrected differential signal by correcting the common mode noise of a plurality of differential signals in different polarization states according to the multi-polarization state differential signal includes:

[0025] By extracting the common features of multi-polarization differential signals, a signal correlation matrix is ​​constructed;

[0026] identifying similar features associated with common mode noise based on similarities of features in the signal correlation matrix;

[0027] According to the similar characteristics, the common mode noise of the differential signals in different polarization states is corrected through a preset multi-channel correction model to obtain a first corrected differential signal.

[0028] Specifically, the error identification and correction of the differential signal of each polarization state are performed to obtain a corrected differential signal, including:

[0029] Perform frequency domain signal transformation on the differential signal of each polarization state to obtain frequency domain features;

[0030] The coupled wave analysis model preset for the metasurface grating is used to calculate the response of the metasurface grating in each polarization state and obtain the theoretical frequency domain response curve.

[0031] Comparing the frequency domain characteristics with a theoretical frequency domain response curve to obtain an error curve;

[0032] According to the error curve, the signal is corrected by a preset error correction model to obtain an error correction signal;

[0033] Performing signal fitting on the error correction signal to calculate a phase difference correction value;

[0034] The error correction signal is phase-corrected according to the phase difference correction value to obtain a corrected differential signal.

[0035] Specifically, calculating the polarization sensitivity of the metasurface grating according to the corrected differential signal includes:

[0036] According to the corrected differential signal, the reflectivity of the metasurface grating at different wavelengths is calculated using the preset reflection analysis model of the metasurface grating;

[0037] The polarization sensitivity of the metasurface grating at different wavelengths is calculated based on the reflectivity.

[0038] Specifically, the calculation of the reflectivity of the metasurface grating at different wavelengths based on the corrected differential signal and the preset reflection analysis model of the metasurface grating includes:

[0039] Extract the light intensity difference and phase difference from the corrected differential signal;

[0040] Calculating the operating wavelength range of the metasurface grating based on the light intensity difference and the phase difference and the structural parameters of the metasurface grating;

[0041] The reflectivity at different wavelengths within the working wavelength range is calculated using a preset reflection analysis model of the metasurface grating.

[0042] A dual-beam differential measurement device for the polarization sensitivity of a metasurface grating, used to implement the dual-beam differential measurement method for the polarization sensitivity of a metasurface grating, comprising:

[0043] a dual-beam generation module that splits a pre-generated beam into a first beam and a second beam through a fiber coupler, dynamically switches the polarization state of the second beam to obtain a second incident beam, and adjusts the first beam based on the second incident beam to obtain a first incident beam;

[0044] a dual-beam measurement module, which passes the first incident light beam through a first path without a metasurface grating and the second incident light beam through a second path including a metasurface grating to obtain a first output light beam and a second output light beam;

[0045] a signal analysis module, performing time domain differentiation on the first output light beam and the second output light beam to calculate and obtain a multi-polarization state differential signal;

[0046] A signal correction module, which corrects the multi-polarization state differential signal through a preset differential correction mechanism to obtain a corrected differential signal;

[0047] The polarization sensitivity calculation module calculates the polarization sensitivity of the metasurface grating according to the corrected differential signal.

[0048] Compared with the prior art, this application has the following beneficial effects:

[0049] This application combines dual-beam differential measurement of multi-polarization state light beams and performs multi-level correction on the differential signal, which can effectively resist environmental interference and common-mode noise in the system, measure the metasurface grating under different polarization states, and obtain comprehensive polarization sensitivity information. The corrected differential signal can more realistically reflect the polarization sensitivity of the metasurface grating, and the obtained measurement results are more accurate, thereby improving the accuracy of the calculated polarization sensitivity of the metasurface grating. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a flowchart of the dual-beam differential measurement method for the polarization sensitivity of a metasurface grating in Example 1 of the present invention;

[0051] Figure 2 Schematic diagram of the dual-beam emission process in Example 1 of the present invention;

[0052] Figure 3 This is a flowchart of the process of correcting the differential signal of each polarization state in Example 1 of the present invention;

[0053] Figure 4 Schematic diagram of the structure of the dual-beam differential measurement device for the polarization sensitivity of the metasurface grating in Example 2 of the present invention. DETAILED DESCRIPTION

[0054] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0055] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0056] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0057] Example 1

[0058] This embodiment provides a dual-beam differential measurement method for the polarization sensitivity of a metasurface grating, such as Figure 1 As shown, the dual-beam differential measurement method for the polarization sensitivity of the metasurface grating includes:

[0059] S101, splitting a pre-generated light beam into a first light beam and a second light beam using a fiber coupler, dynamically switching the polarization state of the second light beam to obtain a second incident light beam, and adjusting the first light beam based on the second incident light beam to obtain a first incident light beam;

[0060] S102, passing the first incident light beam through a first path without a metasurface grating, and passing the second incident light beam through a second path including a metasurface grating, to obtain a first output light beam and a second output light beam;

[0061] S103, performing time domain differentiation on the first output light beam and the second output light beam to calculate and obtain a multi-polarization state differential signal;

[0062] S104, correcting the multi-polarization state differential signal by a preset differential correction mechanism to obtain a corrected differential signal;

[0063] S105 . Calculate the polarization sensitivity of the metasurface grating according to the corrected differential signal.

[0064] This embodiment divides the light beam into two beams, one as a reference beam and the other as a measurement beam, and dynamically switches the polarization state of the measurement beam to obtain the response of the metasurface grating under multiple polarization states, thereby achieving a comprehensive measurement of the polarization sensitivity of the metasurface grating. By performing layered correction on the differential signal, environmental interference and system errors are effectively eliminated. Compared with the traditional single correction mode, the accuracy of the polarization sensitivity measurement of the metasurface grating can be improved.

[0065] In this embodiment, a pre-generated light beam is divided into a first light beam and a second light beam through a fiber coupler; the pre-generated light beam is connected to the input end of the fiber coupler, and the two output ends of the fiber coupler are respectively connected to the subsequent optical path, so that the light beam is divided into a first light beam and a second light beam of equal proportions; an electro-optical modulator is connected to the transmission path of the second light beam, and different voltage signals are applied to the electro-optical modulator through a control circuit to dynamically switch the polarization state of the second light beam to obtain a second incident light beam, and the first light beam is adjusted based on the second incident light beam to obtain a first incident light beam; by dividing the light beam and dynamically switching the polarization state of the second light beam, the response of the metasurface grating under different polarization states can be obtained, providing data support for comprehensive measurement of the polarization sensitivity of the metasurface grating.

[0066] Specifically, after obtaining the first incident light beam and the second incident light beam, two independent optical paths are constructed. The first path is the transmission path of the first incident light beam. There is no metasurface grating in the first path. It is only composed of basic optical elements such as transmission optical fiber and reflector, so that the first incident light beam can be smoothly transmitted to obtain a first output light beam; the second path is the transmission path of the second incident light beam. A metasurface grating is placed in the second path, and other optical elements (including collimator, focusing lens, etc.) are configured to enable the second incident light beam to be accurately irradiated on the metasurface grating, and after being modulated by the metasurface grating, a second output light beam is obtained; through this optical path design, the polarization state and other characteristics of the light beam passing through the first path remain basically unchanged, and the light beam passing through the second path passes through the modulation effect produced by the metasurface grating on light of different polarization states, changing the polarization state, phase, amplitude and other characteristics of the light; by comparing the output light beams of the two paths, the influence of the metasurface grating on the polarization state of light is analyzed.

[0067] Specifically, the light intensity, phase and other optical signal parameters of the first output light beam and the second output light beam are subtracted in the time domain to obtain a differential signal, including information on the polarization state modulation of the light by the metasurface grating at different times, forming a multi-polarization state differential signal; through differential calculation, the difference signal generated by the light modulation by the metasurface grating can be extracted, effectively removing the background noise and other interference signals shared by the two beams of light, highlighting the influence of the metasurface grating on the polarization state of light, and making the measurement results more accurate.

[0068] Specifically, after calculating the multi-polarization state differential signal, the differential signal is layered and corrected through a preset differential correction mechanism. First, the multi-polarization state differential signal is corrected as a whole to remove system noise. Second, the differential signal of each polarization state is corrected separately, and the phase and other parameters of the differential signal are corrected to obtain a corrected differential signal. By correcting the differential signal, the accuracy and reliability of the measurement results can be improved, and the impact of system errors and environmental factors on the measurement results can be reduced. The corrected differential signal can more realistically reflect the polarization sensitivity of the metasurface grating. Based on the corrected differential signal combined with the theoretical model and optical principles of the metasurface grating, the polarization sensitivity of the metasurface grating is calculated. By accurately calculating the polarization sensitivity of the metasurface grating, it can provide important parameter basis for the design, optimization and application of the metasurface grating, which will help promote the development and application of metasurface gratings in optical devices, optical communications and other fields.

[0069] This application combines dual-beam differential measurement of multi-polarization state light beams and performs multi-level correction on the differential signal, which can effectively resist environmental interference and common-mode noise in the system, measure the metasurface grating under different polarization states, and obtain comprehensive polarization sensitivity information. The corrected differential signal can more realistically reflect the polarization sensitivity of the metasurface grating, and the obtained measurement results are more accurate, thereby improving the accuracy of the calculated polarization sensitivity of the metasurface grating.

[0070] Furthermore, the method of dividing the pre-generated light beam into a first light beam and a second light beam by a fiber coupler, dynamically switching the polarization state of the second light beam to obtain a second incident light beam, and adjusting the first light beam based on the second incident light beam to obtain a first incident light beam includes:

[0071] S201, splitting a pre-generated light beam into a first light beam and a second light beam through a fiber coupler;

[0072] S202, dynamically switching the polarization state of the second light beam between a linear polarization state, a left-handed circular polarization state, or a right-handed circular polarization state within a preset time period to obtain a second incident light beam;

[0073] S203 . According to the second incident light beam, the first light beam is adjusted by controlling the optical path difference between the light beams to be less than a preset optical path difference threshold to obtain a first incident light beam.

[0074] In this embodiment, if Figure 2 As shown, first, a light beam is pre-generated by a light source such as a laser and transmitted through an optical fiber. Then, the optical fiber that transmits the pre-generated light beam is connected to the input end of the optical fiber coupler, while ensuring a tight connection to reduce light loss. The two output ends of the optical fiber coupler are respectively connected to two subsequent independent optical paths. According to the same splitting ratio, the light beam is divided into a first light beam and a second light beam with the same beam ratio. Splitting the light beam by the optical fiber coupler can achieve stable and accurate splitting, so that the two divided light beams can be used for different optical paths respectively.

[0075] Specifically, the polarization state of the second light beam is dynamically switched, and the polarization state of the second light beam is switched between different polarization states within a preset time period through a polarization state modulation device (such as an electro-optical modulator), including different directions of linear polarization states, left-handed circular polarization states, and right-handed circular polarization states, to obtain a second incident light beam with different polarization states; by dynamically switching the polarization state of the second light beam, the response data of the metasurface grating in different polarization states can be obtained, and data that can fully reflect the polarization sensitivity characteristics of the metasurface grating can be obtained.

[0076] Specifically, according to the second incident light beam, the optical path of the first light beam is adjusted so that the optical path difference between it and the second incident light beam is less than a preset optical path difference threshold, and the first incident light beam is obtained. By adjusting the optical path difference of the two light beams, the two light beams can effectively interfere with each other and perform accurate differential measurement. The preset optical path difference threshold can be set according to the actual calculation accuracy requirements. By installing optical path adjustment devices such as optical delay lines on the transmission path of the first light beam, the optical delay line is adjusted through the control circuit according to the measured optical path difference data, and the transmission path length of the first light beam is changed to gradually reduce the optical path difference until the optical path difference is less than the preset optical path difference threshold. Through optical path adjustment, problems such as blurred interference fringes or inability to form interference due to excessive optical path difference can be avoided, so that the measurement results can reflect the modulation effect of the metasurface grating on the polarization state of light, which helps to improve the stability of the measurement system.

[0077] Furthermore, the first incident light beam is passed through a first path without a metasurface grating, and the second incident light beam is passed through a second path including a metasurface grating, to obtain a first output light beam and a second output light beam, comprising:

[0078] S301, emitting a first incident light beam to a first path without a metasurface grating, and outputting a first output light beam after light intensity regulation and light path collimation;

[0079] S302. Launch a second incident light beam to a second path including the metasurface grating, and output a second output light beam after diffraction by the grating, wherein the second path and the first path are parallelized to make the light beams of the two paths confocal.

[0080] In this embodiment, the first path does not have a metasurface grating. When light propagates therein, its polarization state and basic optical properties are not modulated by the metasurface grating. First, the first incident light beam is aligned with the entrance of the first path to ensure that the light beam can smoothly enter the first path. A light intensity adjustment device, such as an adjustable neutral density filter, is installed in the first path. The light intensity is adjusted to a desired level by rotating the filter or changing the degree of its insertion into the light path. Next, an optical path collimation system is installed after the light intensity adjustment device. The system includes multiple lenses. For example, a convex lens is first used to converge the diverging light beam, and then a concave lens is used to collimate the converged light beam into a parallel beam. By adjusting the distance and position between the lenses, the divergence angle of the light beam is monitored in real time using a beam analyzer or other equipment. When the divergence angle of the light beam reaches the set accuracy requirement, the optical path collimation operation is completed to obtain a first output light beam. The light intensity adjustment and optical path collimation operations can avoid damage to the detector due to excessive light intensity or unclear measurement signals due to insufficient light intensity, reduce energy loss and directional deviation of the light beam during transmission, and improve measurement accuracy and stability.

[0081] Specifically, the second incident light beam is emitted to the second path including the metasurface grating, and the first path and the second path are parallelized and confocal adjusted so that the light beams of the two paths remain parallel in space and can converge on the same focus, ensuring that the two beams of light can be accurately superimposed and compared during the differential measurement process, thereby improving the accuracy of the measurement results; the second incident light beam is aligned with the entrance of the second path so that the light beam is accurately irradiated on the metasurface grating, and corresponding optical elements (including lenses, reflectors, etc.) are configured after the metasurface grating to collect and guide the light beam after diffraction by the grating to obtain a second output light beam, and the second path is parallelized and confocal adjusted. High-precision position The stage and angle adjustment device adjust the position and angle of the optical elements in the first path and the second path respectively. The parallelism and focal position of the light beams in the two paths are monitored in real time through equipment such as confocal microscopes and interferometers. The optical elements are continuously fine-tuned until the light beams in the two paths remain parallel during the entire transmission process and can accurately converge on the same focus. At this time, the second output light beam obtained meets the measurement requirements. Through parallelism calibration and confocal adjustment, the accurate spatial correspondence and superposition of the first output light beam and the second output light beam are ensured, avoiding measurement errors caused by beam position deviations, improving the accuracy and reliability of differential measurement, and enabling the measurement results to truly reflect the modulation effect of the metasurface grating on the polarization state of light.

[0082] Furthermore, performing time domain differentiation on the first output light beam and the second output light beam to calculate and obtain a multi-polarization state differential signal includes:

[0083] S401, performing time-domain synchronous acquisition on the first output light beam and the second output light beam to obtain a first acquisition light beam and a second acquisition light beam;

[0084] S402: Calculate the intensity difference and phase difference between the first acquisition light beam and the second acquisition light beam to obtain a multi-polarization state differential signal.

[0085] In this embodiment, the first output light beam and the second output light beam are synchronously collected in the time domain to ensure that the collected data can truly reflect the status of the two beams of light at the same time; first, photoelectric detectors with matching performance are installed at the ends of the transmission paths of the first output light beam and the second output light beam respectively to ensure that the response characteristics of the two detectors to the optical signal are consistent and to avoid additional errors introduced due to differences in the detectors, and the output ends of the two photoelectric detectors are connected to a high-precision data acquisition card, and the trigger mode of the data acquisition card is set to external trigger or synchronous trigger mode; for example, a stable clock signal is used as an external trigger source, and is connected to the data acquisition card and other related equipment at the same time to ensure that the acquisition card samples the electrical signals converted from the two beams of light at precise time intervals; the data acquisition program is started, and the first output light beam and the second output light beam are collected at the same sampling frequency to obtain the data of the first collection beam and the second collection beam; the time consistency of the data of the first collection beam and the second collection beam can be guaranteed by time domain synchronous acquisition, thereby improving the accuracy and reliability of the collected data.

[0086] Specifically, the light intensity values ​​and phase values ​​of the first collection light beam and the second collection light beam at the same moment are subtracted to obtain a multi-polarization state differential signal. First, the light intensity data of the two beams of light are subtracted point by point in the order of collection time to obtain a light intensity difference sequence. Then, the electrical signals of the two beams of light are Fourier transformed to convert the time domain signals into frequency domain signals, and the phase information of the signals is extracted. By calculating the phase values ​​of the two beams of light on the same frequency component, a phase difference sequence is obtained. The light intensity difference sequence and the phase difference sequence are integrated to obtain a multi-polarization state differential signal including light intensity and phase difference information. By calculating the light intensity difference and phase difference, the key information after the metasurface grating modulates the light is fully obtained, and the influence of the metasurface grating on the light intensity and phase under different polarization states is comprehensively reflected. The modulation difference of the metasurface grating on the light is effectively extracted, avoiding the limitations of single light intensity or phase analysis, and making the measurement results more comprehensive and accurate.

[0087] Furthermore, the multi-polarization state differential signal is corrected by a preset differential correction mechanism to obtain a corrected differential signal, including:

[0088] S501, obtaining a first corrected differential signal by correcting common mode noise of multiple differential signals in different polarization states according to a multi-polarization differential signal;

[0089] S502 : Perform error identification and correction on the differential signal of each polarization state to obtain a corrected differential signal.

[0090] In this embodiment, based on the multi-polarization state differential signal, multiple polarization state differential signals are analyzed, the common noise part is identified, the common noise is removed from the signal, and the influence of the noise on the differential signal is reduced; by analyzing the similarity of the common mode noise in the multiple differential signals, the common mode noise is extracted and eliminated to obtain a first corrected differential signal; by correcting the common mode noise, the interference of the noise on the multi-polarization state differential signal can be significantly reduced, and the signal-to-noise ratio of the signal can be improved. The corrected differential signal can more truly reflect the polarization sensitivity characteristics of the metasurface grating and reduce the influence of noise on the accuracy of the measurement results.

[0091] Specifically, after removing the common-mode noise, the errors existing in the differential signal of each polarization state are identified and corrected respectively. The measurement results of the measurement system on the standard sample under the same conditions are used as the reference standard. The differential signal of each polarization state is compared with the standard signal, and the differences in the signal in terms of light intensity, phase, etc. are analyzed. The different differences are corrected respectively to obtain the final corrected differential signal; the separate error identification and correction of the differential signal of each polarization state can fully take into account the error conditions of the signal under different polarization states, realize the refined processing of the signal, and make the corrected differential signal more accurately reflect the true response of the metasurface grating under different polarization states, thereby improving the accuracy and reliability of the measurement results.

[0092] Furthermore, the method of obtaining a first corrected differential signal by correcting the common mode noise of a plurality of differential signals in different polarization states according to the multi-polarization state differential signal includes:

[0093] S601, constructing a signal correlation matrix by extracting common features of multi-polarization state differential signals;

[0094] S602, identifying similar features related to common mode noise based on similarities of features in the signal correlation matrix;

[0095] S603 : According to the similarity characteristics, the common mode noise of the differential signals of different polarization states is corrected by using a preset multi-channel correction model to obtain a first corrected differential signal.

[0096] In this embodiment, feature extraction is performed on the common features in the multi-polarization state differential signals. First, the obtained multi-polarization state differential signals are preprocessed, including removing outliers, normalizing, and other preprocessing, so that the differential signals of different polarization states are on the same comparison scale. Then, a feature extraction method is selected, including principal component analysis, independent component analysis, and the like. This embodiment adopts principal component analysis to perform principal component transformation on the preprocessed multi-polarization state differential signals, calculate the covariance matrix of the signals, and perform eigenvalue decomposition on the covariance matrix to extract the main eigenvectors and eigenvalues ​​to obtain the common features of the signals. Based on the extracted common features, a signal correlation matrix is ​​constructed, wherein the rows and columns of the signal correlation matrix correspond to different polarization state differential signals, respectively, and the elements in the matrix are the correlation coefficients of different signals on the common features. By extracting the common features and constructing the signal correlation matrix, the characteristics of common mode noise can be highlighted, thereby improving the efficiency and accuracy of noise identification.

[0097] Specifically, based on the signal correlation matrix, the similarity between features is calculated. In this embodiment, cosine similarity is used. For the common feature corresponding to each column in the signal correlation matrix, the cosine similarity of the differential signals in different polarization states on the feature is calculated, and a similarity threshold is set. Common features whose cosine similarity is greater than the similarity threshold are identified as similar features related to common-mode noise. By identifying the common-mode noise features, a precise target is provided for noise removal, ensuring that the real signal components are not mistakenly deleted during the correction process.

[0098] Specifically, based on similar features, the common-mode noise in the differential signals of different polarization states is corrected through a preset multi-channel correction model. The multi-channel correction model can be a linear regression model, a neural network model, or other models. In this embodiment, the multi-channel correction model is a convolutional neural network model. The convolutional neural network model is trained using a large amount of historical data to obtain a pre-trained convolutional neural network model. The identified similar features are input into the pre-trained convolutional neural network model. The model identifies and removes the common-mode noise in each signal based on the learned noise feature pattern, outputs the corrected signal, and combines the corrected signals to obtain a first corrected differential signal. By correcting the common-mode noise, the corrected differential signal can more accurately reflect the true response of the metasurface grating.

[0099] Further, such as Figure 3 , the error identification and correction of the differential signal of each polarization state are performed respectively to obtain a corrected differential signal, including:

[0100] S701, performing frequency domain signal transformation on the differential signal of each polarization state to obtain frequency domain features;

[0101] S702, calculating the response of the metasurface grating in each polarization state using a coupled wave analysis model preset for the metasurface grating, and obtaining a theoretical frequency domain response curve;

[0102] S703, comparing the frequency domain characteristics with a theoretical frequency domain response curve to obtain an error curve;

[0103] S704: Correct the signal using a preset error correction model according to the error curve to obtain an error correction signal;

[0104] S705, performing signal fitting on the error correction signal to calculate a phase difference correction value;

[0105] S706 : Perform phase correction on the error correction signal according to the phase difference correction value to obtain a corrected differential signal.

[0106] In this embodiment, a frequency domain signal transformation is performed on the differential signal of each polarization state. The differential signal of each polarization state is converted from the time domain to the frequency domain through Fourier transform to obtain frequency domain characteristics, which can quickly identify noise components and abnormal frequency components in the signal. The theoretical response of the grating is analyzed using a coupled wave analysis model preset for the metasurface grating. First, the detailed structural parameters of the metasurface grating (including grating period, groove depth, duty cycle, etc.) and the optical parameters of the material (including refractive index, extinction coefficient, etc.) are obtained, and these parameters are input into the pre-established coupled wave analysis model. The coupled wave analysis model is based on Maxwell's equations and combines the structural parameters and material properties of the metasurface grating to calculate the response of the metasurface grating to light in different polarization states by solving the electromagnetic field coupling equation. The input conditions of the model are set according to different polarization states. The model calculates the theoretical frequency domain response data of the metasurface grating in each polarization state, and obtains the theoretical frequency domain response curve, which provides an accurate theoretical reference for the actual measurement signal.

[0107] Specifically, the frequency domain characteristics are compared with the theoretical frequency domain response curve to obtain the amplitude difference between the actual measured signal and the theoretical expectation, and the amplitude error values ​​are arranged in frequency order to obtain an error curve; according to the error curve, the signal error is corrected by a preset error correction model. The error correction model can be a polynomial fitting model, a neural network model, or other models. The error correction model in this embodiment is a polynomial fitting model. The error curve data is used to fit the polynomial, and the coefficient of the polynomial is determined. According to the fitted polynomial, the frequency domain signal is corrected and calculated to obtain an error-corrected signal; by comparing the frequency domain characteristics with the theoretical frequency domain response curve to obtain the error curve, and using the error correction model to perform signal correction, the error components in the actual measured signal can be eliminated in a targeted manner, the accuracy of the signal correction can be improved, and the corrected error correction signal can more truly reflect the actual response of the metasurface grating.

[0108] Specifically, the error correction signal is fitted using the least squares method combined with a sine function to obtain the signal's phase information. This information is then compared with the theoretical phase to calculate the phase difference correction value. Based on the calculated phase difference correction value, the error correction signal is phase-adjusted to bring the signal's phase closer to the actual phase of the metasurface grating under actual operating conditions. The frequency domain signal is then converted back to the time domain via an inverse Fourier transform to obtain a phase-corrected signal. Phase correction enables the corrected differential signal to more accurately reflect the actual response of the metasurface grating in both amplitude and phase. This fully corrected signal provides high-quality data for accurately calculating the polarization sensitivity of the metasurface grating, helping to improve the accuracy of the measurement results.

[0109] Furthermore, the polarization sensitivity of the metasurface grating is calculated according to the corrected differential signal, including:

[0110] S801. Calculate the reflectivity of the metasurface grating at different wavelengths based on the corrected differential signal and a preset reflection analysis model of the metasurface grating;

[0111] S802: Calculate the polarization sensitivity of the metasurface grating at different wavelengths based on the reflectivity.

[0112] In this embodiment, based on the corrected differential signal, the structural parameters and material properties of the metasurface grating are analyzed to calculate the reflection of light on the metasurface grating and obtain the reflectivity at different wavelengths. First, the corrected differential signal is preprocessed to extract data related to the reflectivity calculation, including light intensity, phase and other data, and the detailed structural parameters of the metasurface grating (including grating period, groove depth, duty cycle, etc.) and the optical parameters of the material (including refractive index, extinction coefficient, etc.) are obtained. The preprocessed corrected differential signal data and the structural and material parameters of the metasurface grating are input into a preset reflection analysis model to solve the reflection of light on the metasurface grating and obtain the reflectivity of the metasurface grating at different wavelengths. The calculated reflectivity provides a reference for calculating polarization sensitivity.

[0113] Specifically, based on the calculated reflectivity, for each wavelength, reflectivity data corresponding to two or more different polarization states (such as horizontal polarization and vertical polarization) are selected. According to the polarization sensitivity calculation formula, the polarization sensitivity values ​​of the metasurface grating at different wavelengths are calculated. The polarization sensitivity calculation formula is as follows:

[0114] ;

[0115] Where, 、 are the reflectivities of two different polarization states, is the polarization sensitivity; the numerator calculates the difference in reflectivity of the two polarization states, reflecting the difference in the reflectivity of the metasurface grating to the two polarized lights; the denominator calculates the average of the reflectivity of the two polarization states, which plays a normalization role. By dividing the reflectivity difference by the average, the result is a relative value, which eliminates the influence of the overall reflectivity of the metasurface grating on the calculation result, making the polarization sensitivities of different metasurface gratings comparable, and more accurately reflecting the selective reflection characteristics of the metasurface grating to light in different polarization states; calculating the polarization sensitivity through reflectivity can clearly reflect the response difference of the metasurface grating to light in different polarization states, and obtain polarization sensitivity data at different wavelengths, so as to fully understand the change law of the polarization sensitivity characteristics of the metasurface grating with wavelength, and provide important parameter basis for the application of metasurface grating in optical sensing, optical communication, polarization optical devices and other fields.

[0116] Furthermore, the calculation of the reflectivity of the metasurface grating at different wavelengths based on the corrected differential signal and the preset reflection analysis model of the metasurface grating includes:

[0117] S901, extracting the light intensity difference and phase difference from the corrected differential signal;

[0118] S902, calculating the operating wavelength range of the metasurface grating based on the light intensity difference and the phase difference and the structural parameters of the metasurface grating;

[0119] S903 , calculating the reflectivity at different wavelengths within the operating wavelength range using a preset reflection analysis model of the metasurface grating.

[0120] In this embodiment, the intensity difference and phase difference are extracted from the corrected differential signal. The intensity difference reflects the degree of change of the metasurface grating on the intensity of light in different polarization states, and the phase difference reflects the change in the phase of light after passing through the metasurface grating. In the time domain, the intensity difference is obtained by directly measuring the amplitude change of the corrected differential signal; in the frequency domain, the phase difference is obtained using the phase spectrum after Fourier transform; based on the intensity difference and phase difference, it is analyzed that when the intensity difference and phase difference have specific change patterns, it corresponds to the metasurface grating having a good modulation effect on light of certain wavelengths, and the working wavelength range is obtained. range; first, the detailed structural parameters of the metasurface grating are obtained, including grating period, groove depth, duty cycle and other parameters. According to the existing optical theoretical model in the prior art (such as the coupled wave theoretical model), the extracted intensity difference and phase difference data are input into the coupled wave theoretical model to calculate the wavelength range that meets the specific conditions of intensity difference and phase difference; the working wavelength range is calculated by combining the intensity difference, phase difference and structural parameters, which can accurately determine the effective working wavelength range of the metasurface grating, help avoid blindly selecting the wavelength range in the subsequent calculation of reflectivity, and improve the calculation efficiency and accuracy.

[0121] Specifically, based on Maxwell's equations in electromagnetism and combined with the structure and material properties of the metasurface grating, a preset reflection analysis model of the metasurface grating is constructed. Within a certain working wavelength range, the reflection analysis model is used to solve the electromagnetic field distribution of light in the metasurface grating, calculate the reflection of light, and obtain the reflectivity data corresponding to each wavelength within the working wavelength range. By calculating the reflectivity within the working wavelength range, the amount of calculation can be reduced and the calculation efficiency can be improved compared to calculating within the full wavelength range.

[0122] Example 2

[0123] In this embodiment, if Figure 4 , providing a dual-beam differential measurement device for the polarization sensitivity of a metasurface grating, for implementing the dual-beam differential measurement method for the polarization sensitivity of a metasurface grating, comprising:

[0124] a dual-beam generation module that splits a pre-generated beam into a first beam and a second beam through a fiber coupler, dynamically switches the polarization state of the second beam to obtain a second incident beam, and adjusts the first beam based on the second incident beam to obtain a first incident beam;

[0125] a dual-beam measurement module, which passes the first incident light beam through a first path without a metasurface grating and the second incident light beam through a second path including a metasurface grating to obtain a first output light beam and a second output light beam;

[0126] a signal analysis module, performing time domain differentiation on the first output light beam and the second output light beam to calculate and obtain a multi-polarization state differential signal;

[0127] A signal correction module, which corrects the multi-polarization state differential signal through a preset differential correction mechanism to obtain a corrected differential signal;

[0128] The polarization sensitivity calculation module calculates the polarization sensitivity of the metasurface grating according to the corrected differential signal.

[0129] In this embodiment, a dual-beam generation module generates dual beams for measurement, and dynamically switches the polarization state of one of the beams of light. The pre-generated single beam is split into two beams through a fiber coupler to obtain a first beam and a second beam, and the polarization state of the second beam is dynamically switched, so that the measurement process is closer to the actual application scenario where the metasurface grating encounters various polarization states of light; the dual-beam measurement module guides the first incident beam and the second incident beam through different paths respectively to obtain an output beam containing information about the metasurface grating effect. The first incident beam passes through a first path without a metasurface grating as a reference path to provide an optical signal without the influence of the metasurface grating. The second incident beam passes through a second path containing a metasurface grating. The metasurface grating affects the light. By analyzing the specific effect of the metasurface grating on the light, the polarization sensitivity of the metasurface grating is calculated.

[0130] Specifically, the signal analysis module performs time domain differential processing on the first output light beam and the second output light beam to obtain a multi-polarization state differential signal, ensures that the collected first collection light beam and the second collection light beam are corresponding in time through time domain synchronous collection, calculates the light intensity difference and phase difference between the first collection light beam and the second collection light beam, and obtains the modulation information of the metasurface grating on light in different polarization states, which is used to analyze the response difference of the metasurface grating to light in different polarization states; the signal correction module corrects the multi-polarization state differential signal to improve the accuracy of the measurement result. Through the layered correction method, first, the common mode noise of multiple polarization state differential signals is corrected to remove the common mode noise in the signal due to the measurement system itself or The same noise components caused by environmental factors are removed, and then the error identification and correction are performed on the differential signal of each polarization state to further eliminate the existing errors that are not related to the actual response of the metasurface grating. The obtained corrected differential signal can more accurately reflect the true performance of the metasurface grating; the polarization sensitivity calculation module calculates the polarization sensitivity of the metasurface grating based on the corrected differential signal, and calculates the reflectivity of the metasurface grating at different wavelengths through the preset reflection analysis model of the metasurface grating, combined with the light intensity difference and phase difference in the corrected differential signal and the structural parameters of the metasurface grating. Based on the reflectivity data, the polarization sensitivity of the metasurface grating at different wavelengths is calculated to reflect the polarization characteristics of the metasurface grating.

[0131] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A dual-beam differential measurement method for polarization sensitivity of a metasurface grating, characterized in that: include: Splitting a pre-generated light beam into a first light beam and a second light beam through a fiber coupler, dynamically switching the polarization state of the second light beam to obtain a second incident light beam, and adjusting the optical path length of the first light beam based on the second incident light beam by adjusting the transmission path length of the first light beam so that the optical path difference between the first light beam and the second light beam is less than a preset optical path difference threshold to obtain a first incident light beam; Passing the first incident light beam through a first path without a metasurface grating and passing the second incident light beam through a second path including a metasurface grating to obtain a first output light beam and a second output light beam; Performing time domain differentiation on the first output light beam and the second output light beam to calculate and obtain a multi-polarization state differential signal; Correcting the multi-polarization state differential signal through a preset differential correction mechanism to obtain a corrected differential signal; The polarization sensitivity of the metasurface grating is calculated according to the corrected differential signal.

2. The dual-beam differential measurement method for polarization sensitivity of a metasurface grating according to claim 1, wherein: The method comprises: dividing a pre-generated light beam into a first light beam and a second light beam by a fiber coupler, dynamically switching the polarization state of the second light beam to obtain a second incident light beam, and adjusting the first light beam based on the second incident light beam to obtain a first incident light beam, comprising: Splitting the pre-generated light beam into a first light beam and a second light beam by a fiber coupler; Dynamically switching the polarization state of the second light beam between a linear polarization state, a left-handed circular polarization state, or a right-handed circular polarization state within a preset time period to obtain a second incident light beam; According to the second incident light beam, the first light beam is adjusted by controlling the optical path difference between the light beams to be less than a preset optical path difference threshold to obtain a first incident light beam.

3. The dual-beam differential measurement method for polarization sensitivity of a metasurface grating according to claim 1, wherein: The first incident light beam is passed through a first path without a metasurface grating, and the second incident light beam is passed through a second path including a metasurface grating, to obtain a first output light beam and a second output light beam, comprising: Launching a first incident light beam into a first path without a metasurface grating, and outputting a first output light beam after light intensity regulation and light path collimation; The second incident light beam is emitted to a second path including the metasurface grating, and a second output light beam is output after diffraction by the grating, wherein the second path and the first path are parallelized to make the light beams of the two paths confocal.

4. The dual-beam differential measurement method for polarization sensitivity of a metasurface grating according to claim 1, wherein: Performing a time domain difference on the first output light beam and the second output light beam to calculate and obtain a multi-polarization state differential signal, including: Performing time-domain synchronous acquisition on the first output light beam and the second output light beam to obtain a first acquisition light beam and a second acquisition light beam; The light intensity difference and phase difference between the first collection light beam and the second collection light beam are calculated to obtain a multi-polarization state differential signal.

5. The dual-beam differential measurement method for polarization sensitivity of a metasurface grating according to claim 1, wherein: The method of correcting the multi-polarization state differential signal by a preset differential correction mechanism to obtain a corrected differential signal includes: According to the multi-polarization state differential signal, a first corrected differential signal is obtained by correcting the common mode noise of the multiple polarization state differential signals; Error identification and correction are performed on the differential signal of each polarization state to obtain a corrected differential signal.

6. The dual-beam differential measurement method for polarization sensitivity of a metasurface grating according to claim 5, wherein: The method of obtaining a first corrected differential signal by correcting the common mode noise of a plurality of differential signals in different polarization states according to the multi-polarization state differential signal includes: By extracting the common features of multi-polarization differential signals, a signal correlation matrix is ​​constructed; identifying similar features associated with common mode noise based on similarities of features in the signal correlation matrix; According to the similar characteristics, the common mode noise of the differential signals in different polarization states is corrected through a preset multi-channel correction model to obtain a first corrected differential signal.

7. The dual-beam differential measurement method for polarization sensitivity of a metasurface grating according to claim 5, wherein: The error identification and correction of the differential signal of each polarization state are performed respectively to obtain a corrected differential signal, including: Perform frequency domain signal transformation on the differential signal of each polarization state to obtain frequency domain features; The coupled wave analysis model preset for the metasurface grating is used to calculate the response of the metasurface grating in each polarization state and obtain the theoretical frequency domain response curve. Comparing the frequency domain characteristics with a theoretical frequency domain response curve to obtain an error curve; According to the error curve, the signal is corrected by a preset error correction model to obtain an error correction signal; Performing signal fitting on the error correction signal to calculate a phase difference correction value; The error correction signal is phase-corrected according to the phase difference correction value to obtain a corrected differential signal.

8. The dual-beam differential measurement method for polarization sensitivity of a metasurface grating according to claim 1, wherein: Calculating the polarization sensitivity of the metasurface grating according to the corrected differential signal includes: According to the corrected differential signal, the reflectivity of the metasurface grating at different wavelengths is calculated using the preset reflection analysis model of the metasurface grating; The polarization sensitivity of the metasurface grating at different wavelengths is calculated based on the reflectivity.

9. The dual-beam differential measurement method for polarization sensitivity of a metasurface grating according to claim 8, wherein: The method of calculating the reflectivity of the metasurface grating at different wavelengths based on the corrected differential signal and using a preset reflection analysis model of the metasurface grating includes: Extract the light intensity difference and phase difference from the corrected differential signal; Calculating the operating wavelength range of the metasurface grating based on the light intensity difference and the phase difference and the structural parameters of the metasurface grating; The reflectivity at different wavelengths within the working wavelength range is calculated using a preset reflection analysis model of the metasurface grating.

10. A dual-beam differential measurement device for polarization sensitivity of a metasurface grating, characterized in that: A dual-beam differential measurement method for realizing the polarization sensitivity of a metasurface grating according to any one of claims 1 to 9, comprising: a dual-beam generation module that splits a pre-generated beam into a first beam and a second beam through a fiber coupler, dynamically switches the polarization state of the second beam to obtain a second incident beam, and adjusts the first beam based on the second incident beam to obtain a first incident beam; a dual-beam measurement module, which passes the first incident light beam through a first path without a metasurface grating and the second incident light beam through a second path including a metasurface grating to obtain a first output light beam and a second output light beam; a signal analysis module, performing time domain differentiation on the first output light beam and the second output light beam to calculate and obtain a multi-polarization state differential signal; A signal correction module, which corrects the multi-polarization state differential signal through a preset differential correction mechanism to obtain a corrected differential signal; The polarization sensitivity calculation module calculates the polarization sensitivity of the metasurface grating according to the corrected differential signal.

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