Focal plane polarization detector based on collaborative design of metasurface and pixel mesa

Abstract

The invention discloses a focal plane polarization detector based on collaborative design of a metasurface and a pixel mesa, and the detector comprises a metasurface structure which selects a pixel-level full-Stokes polarization sensitive metasurface structure, comprises a plurality of metasurface structure units which are distributed in an array, and is used for the preliminary polarization decoupling and directional convergence; the focal plane pixel element array is in pixel-level registration with the metasurface structure and comprises a multi-element plane array composed of a plurality of pixel elements, and each pixel element is provided with a table board; and the side length of each table surface is in a range of 2-3 times of the full width at half maximum of a light spot converged by the metasurface structure unit, so that the energy utilization efficiency of each pixel on a light field is considered, optical signal crosstalk of a non-convergence center area and even adjacent pixels is inhibited, and the polarization extinction ratio is further improved on the basis of polarization decoupling of the metasurface structure. According to the invention, preliminary polarization decoupling is realized, crosstalk between adjacent pixels is suppressed by combining the collaborative design of a secondary pixel table, and the polarization extinction performance of a single metasurface is broken through.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanophotonics and photoelectric detectors, and in particular relates to a split-focus plane polarization detector based on the synergistic effect of a super surface and a pixel table. Background Art

[0002] Infrared detection refers to the technical process of converting incident infrared radiation signals into electrical signal outputs. Compared with visible light and near-infrared detection, infrared detection uses the object's own radiation and has unique advantages such as all-day and strong anti-interference. It can detect targets in low illumination or dark environments and plays an important role in military, civilian and medical fields.

[0003] Infrared polarization detection technology is a new type of photoelectric detection technology that obtains target information by analyzing the polarization characteristics of infrared radiation. Infrared polarization detection technology is based on the polarization characteristics of light waves. It can obtain the polarization characteristics of target infrared radiation light waves on the basis of intensity detection, and can reflect its medium material, surface morphology and physical and chemical properties. Traditional polarization detection technologies include time-sharing, amplitude-sharing and aperture-sharing schemes, which have the disadvantages of large size, complex system and low stability.

[0004] Based on the requirements of lightweight, high integration, high stability, and real-time full polarization detection, the DoFP polarization integrated detection solution based on pixel-level polarization sensitive structure has also become the key development direction of the new generation of infrared detection technology. The DoFP based on pixel-level polarization sensitive structure is an efficient polarization imaging technology, which captures the polarization characteristics of the scene by integrating a tiny polarization element array on the focal plane of the camera. It can obtain information on multiple polarization states at the same time, thereby greatly improving the imaging speed and accuracy.

[0005] However, since the wavelength of infrared light is at the same order of magnitude as the size of the absorption pixel, simply integrating the pixel-level polarization-sensitive micro-nanostructure on the traditional pixel will cause the diffraction effect to cause serious interference in the reception of orthogonal information between adjacent pixels, and the dispersion effect will also make it difficult to achieve high-efficiency spectroscopy and polarization extinction over a wide spectrum. Infrared detection is inherently a weak signal. If it is due to dispersion effects or microstructure energy loss, it is easy to lead to low energy utilization and low polarization discrimination, limiting its application. Thanks to the powerful phase control capability of the metasurface structure, the transmission of the detected optical signal and the directional convergence of the local channels of the light field can be customized at the pixel level. The light field components carrying different polarization and spectral information are transmitted directionally to the corresponding pixel absorption area. At the same time, the directional spatial compression of the light field also avoids interference with the orthogonal information between adjacent pixels.

[0006] In the split-focus plane polarization detection scheme, especially in the infrared band, since the pixel size is comparable to the wavelength, the signal crosstalk between adjacent pixels is large and difficult to suppress efficiently, so it is difficult to improve the polarization extinction ratio; the existing polarization / spectral functional layers based on planar micro-nano structures mainly focus on achromaticity, or monochromatic full polarization, or wide-spectrum partial polarization, or optimization of shorter wavelengths or large-size lenses. There is rarely any coordinated optimization of the planar optical functional layer from the perspective of integrated devices, making it difficult to integrate and efficiently apply it in the split-focus plane detector with a small infrared pixel size. For the split-focus plane detector with a small infrared pixel size, it has extremely strict requirements on the area, thickness, weight and most importantly, performance indicators of the optical functional layer. In this context, traditional optical components optimized for large size or single wavelength are difficult to be directly applied to miniaturized infrared detection systems.

[0007] Therefore, how to solve the problems of signal crosstalk and difficulty in improving the polarization extinction ratio in the prior art, and provide a method for improving the accuracy of polarization detection and improving its performance and application scope are technical problems that need to be urgently solved by those skilled in the art. Summary of the invention

[0008] The purpose of the present invention is to propose a focal plane polarization detector based on the coordinated design of a metasurface and a pixel table in order to solve the problems in the prior art.

[0009] To this end, the above-mentioned purpose of the present invention is achieved through the following technical solutions: A focal plane polarization detector based on the coordinated design of a metasurface and a pixel table, comprising: The metasurface structure uses a pixel-level full-Stokes polarization-sensitive metasurface structure, including a number of metasurface structural units distributed in an array, for preliminary polarization decoupling and directional focusing; A focal plane pixel array aligned with the metasurface structure at the pixel level, comprising a multi-element plane array composed of a plurality of pixels, each pixel being provided with a table; The side length of the table of the focal plane pixel array is 2-3 times the half-height full width of the light spot focused by the metasurface structure unit, so as to take into account the energy utilization efficiency of each pixel for the light field, suppress the crosstalk of optical signals in the non-converging central area or even adjacent pixels, and further significantly improve the polarization extinction ratio on the basis of polarization decoupling of the metasurface structure.

[0010] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions: As a preferred technical solution of the present invention: the metasurface structure includes an all-dielectric substrate and a metasurface structure unit on the all-dielectric substrate, the metasurface structure unit is a nanocolumn array of micro-nano scale formed by micro-nano processing, and every 2×1 metasurface structure units constitute an orthogonal polarization multiplexing subunit to achieve polarization state regulation and light splitting and convergence; each focal plane pixel matches the metasurface structure directly above it to form a subunit, and every 2×3 subunits constitute a superpixel structure to achieve full Stokes regulation of 6 polarization states.

[0011] As a preferred technical solution of the present invention: each orthogonal polarization multiplexing subunit realizes the splitting and convergence of 0 degree / 90 degree linear polarization, 45 degree / 135 degree linear polarization, left-handed / right-handed circularly polarized light, and the converged target focus is located at the center of the absorption area of ​​the two pixels matching the 2×1 unit; In each orthogonal polarization multiplexing subunit, the spatial distribution of the required phase is:

[0012] in, is any spatial position in the lens plane, is the spatial position of the lens focus in the focal plane, is the working wavelength, is the target focal length.

[0013] As a preferred technical solution of the present invention: each nanorod in the nanorod array adopts an anisotropic structure to produce different phase control effects for different polarizations. The nanorods are achromatized in the target working band. If the target working band is λ∈{λ_min,λ_max}, the phase required for the central wavelength λ_cen is regarded as the basic phase, and the phase difference at the boundary of the target working band is regarded as the dispersion phase. If both are satisfied at the same time, it can ensure that the meta-atom satisfies the phase of each wavelength at the same time.

[0014] The side length of the nanorod base is P, which is set to be equivalent to 1 / 2 of the working wavelength, and is arranged in a hexagonal or square array; The height of the nanopillar is H, which is set to be equivalent to the working wavelength; The nanocolumns are elliptical or rectangular, and multi-frequency scanning of the target working band is performed on each nanocolumn to extract the basic phase and dispersion phase.

[0015] As a preferred technical solution of the present invention: the metasurface structure introduces an anti-reflection interface on the non-microstructure side, and the anti-reflection interface is an anti-reflection microstructure or an optical anti-reflection film, which is used to reduce the reflection loss of light energy during transmission.

[0016] As a preferred technical solution of the present invention: the mesa is a semiconductor protruding structure where the pixel is located, the pixel is square, and the mesa is square.

[0017] Compared with the prior art, the focal plane polarization detector based on the collaborative design of a metasurface and a pixel table of the present invention has the following beneficial effects: utilizing a primary pixel-level full-Stokes polarization-sensitive metasurface structure to achieve preliminary polarization decoupling and directional convergence, combining and utilizing a secondary focal plane pixel array whose table size is set to 2-3 times the half-height full width of the light spot converged by the metasurface structure, taking into account the energy utilization efficiency of each pixel for the light field, and suppressing the crosstalk of optical signals in the non-converging central area or even adjacent pixels, further significantly improving the polarization extinction ratio on the basis of the primary polarization decoupling, solving the problem that the polarization extinction ratio of a primary small-size metasurface structure is difficult to reach the application level due to phase discontinuity and micro-nano processing errors, especially when the working wavelength is in the infrared band and above, providing a collaborative design method that can break through the performance limitations of small-size metasurfaces, breaking through the polarization extinction ratio limit that can be achieved by a single metasurface, and achieving a high polarization extinction ratio at the application level.

[0018] In the present invention, the pixel-level alignment between the metasurface structure and the focal plane pixel array ensures the on-chip integration capability of the device and helps to improve the stability of the device detection performance; through the coordinated design of the metasurface and the pixel table, the "filtering" light mode of the ordinary microlens metasurface is converted into a light splitting mode, which more effectively distributes and utilizes the energy of the incident light, reduces energy loss, and significantly improves the energy utilization efficiency; through the metasurface orthogonal polarization multiplexing subunit, the light of different polarization states is separated and converged to the central area of ​​the corresponding pixel, so as to achieve efficient pixel-level focusing, reduce the interference between adjacent pixels, and improve the polarization detection accuracy; based on the superpixel composed of 2×3 subunits, the full Stokes control of 6 polarization states is realized, and the comprehensive control of the polarization state of the light wave is realized, and the detector is used for real-time detection, so that a large amount of polarization information can be captured in a short time, providing key information for subsequent light processing, greatly improving the imaging speed and efficiency, and realizing the real-time snapshot working mode, which has broad application prospects in many fields such as photonic communication, satellite remote sensing, bio-optical imaging, sensing and detection, quantum optics, integrated optical systems, security monitoring and anti-counterfeiting. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of the three-dimensional structure of the focal plane polarization detector based on the collaborative design of the metasurface and the pixel table of the present invention; Figure 2 It is a top view of the 2×3 table surface in the present invention; Figure 3 A schematic diagram of the three-dimensional structure of a superpixel formed by a 2×3 supersurface and a corresponding focal plane pixel array in the present invention; Figure 4 A schematic diagram of a polarization splitting longitudinal cross section of a metasurface structure for splitting linearly polarized light at 0 / 90 degrees; Figure 5 The simulation results of the wide-spectrum full-polarization detection performance of the present invention are as follows; Figure 6 The full width at half maximum of the focused light spot changes with wavelength after the 0-degree linear polarized light passes through the metasurface structure with 0 / 90-degree linear polarized light splitting; Figure 7 The energy utilization efficiency on the focal plane when the table size changes after 4 micron 0 degree linear polarized light passes through the metasurface structure; Figure 8 It is the result of the polarization extinction ratio (S parameter, the two can be converted) of the present invention under the incidence of linear polarized light with the size of the table; Fig. 9 It is the change result of polarization extinction ratio (S parameter, the two can be converted) with the size of the table under left-handed circularly polarized light incident on the present invention; In the accompanying drawings, there is a metasurface structure 1; a table 2; and a focal plane pixel array 3. DETAILED DESCRIPTION

[0020] The implementation method, principle design and technical effects of the present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0021] The purpose of the present invention is to provide an on-chip split-focus plane polarization detector with the advantages of high integration, high energy utilization, high polarization extinction ratio, real-time snapshot acquisition, etc.

[0022] The invention discloses a focal plane polarization detector based on the collaborative design of a metasurface and a pixel table, which mainly includes two functional structures: a metasurface structural unit for regulating the full polarization sensitivity of the detected scene light signal; and a focal plane pixel array 3 structure for photoelectric conversion that is pixel-level aligned with the metasurface structural unit.

[0023] The super surface structural unit comprises: A full-Stokes polarization-sensitive super-pixel unit structure is formed by 2×3 sub-pixels. The 2×3 super-pixel structure includes three 2×1 structures, namely a 0 degree / 90 degree linear polarization splitting structure, a 45 degree / 135 degree linear polarization splitting structure, and a left-handed / right-handed circular polarization splitting structure; each group of 2×1 structures can realize the separation and directional convergence of a group of orthogonal polarizations.

[0024] The design method of the metasurface structure is as follows: The first step is to calculate the phase response distribution and transmittance distribution of the super-atom unit structure under different input light sources (polarization, spectrum). The phase response (transmission phase) of super-atoms with different geometric sizes to input light sources with fixed wavelength and polarization is calculated by the time-domain finite difference method, and the wavelength and polarization are changed to collect the phase response of super-atoms to different input light sources to form a super-atom library.

[0025] In the second step, the target light field control effect is determined according to the geometric size of the pixel, the integration distance between the metasurface and the table, the pixel center distance and other parameters, and the required phase space distribution is calculated according to the following metalens phase formula:

[0026] in, is any spatial position in the lens plane, is the spatial position of the lens focus in the focal plane, is the working wavelength, is the target focal length.

[0027] In the third step, through the particle swarm optimization algorithm, the superatom that matches the required target phase is selected from the superatom database, the size of the superatom at each spatial position is determined, and the supersurface design is formed.

[0028] The 0 degree / 90 degree linear polarization splitting structure only introduces the transmission phase, that is, the major and minor axis dimensions of the elliptical cylinder are changed to match the wide spectrum splitting and converge the required phase; the 45 degree / 135 degree linear polarization splitting structure is obtained by rotating the 0 degree / 90 degree linear polarization splitting structure by 45 degrees; The left-handed / right-handed circular polarization splitting structure introduces a geometric phase based on the transmission phase, that is, changes the major and minor axis sizes of the elliptical column and the rotation angle around the center of the ellipse.

[0029] The focal plane pixel array 3 structure has a physical structure mainly including an upper contact layer, a light absorption area, and a lower contact layer. The table structure corresponding to each pixel usually refers to the semiconductor protrusion structure where the pixel is located after the air groove is removed. It is usually composed of an epitaxial layer of semiconductor material. It is the area where each pixel absorbs light for photoelectric conversion, and plays the role of electrical isolation between adjacent pixels.

[0030] It is worth noting that since the pixel size is closely related to the spatial resolution, and the size of the pixel tends to decrease gradually, the limited discrete phase points on a limited size cannot ensure ideal continuous phase control, and errors are inevitable in micro-nano processing. From the perspective of design and preparation, it is currently difficult for single metasurface structures to achieve a high polarization extinction ratio.

[0031] The collaborative design scheme proposed in the present invention can break through the design and processing limitations of a single metasurface, and the key lies in the design of the size of the mesa 2 of the pixel array.

[0032] Considering that the pixel shape is square, the pixel center distance, i.e., the side length of the square pixel, is D, and the square table size is d. In the present invention, the side length of the table specifically refers to the side of the pixel that receives light, which is responsible for capturing the incident light and converting it into an electrical signal. Reasonable design of the size of the square table is conducive to breaking through the polarization extinction ratio of the single metasurface. The specific design method of the square table size is as follows: The metasurface has a converging effect on the light field. The converging effect is generally measured by two important indicators: focusing efficiency and half-height full width of the focused light spot. These two indicators are closely related to the determination of the table size proposed in the present invention. The focusing efficiency is generally defined as the ratio of the light spot intensity within the range of 2-3 times the half-height full width to the total light intensity on the focal plane. Theoretically, the half-height full width FWHM of the focused light spot on the focal plane is DL=0.514λ / NA, and the calculated half-height full width of the focused light spot is generally close to the theoretical limit. Setting the table size within the range of 2-3 times the half-height full width can not only ensure the focusing efficiency and energy utilization efficiency, but also suppress the influence of the diffracted light caused by imperfect focusing on the polarization extinction ratio.

[0033] The mesa 2 structure corresponding to the pixel usually refers to the semiconductor protrusion structure where the pixel is located after the air groove is removed. It is usually composed of an epitaxial layer of semiconductor material. It is the area where each pixel absorbs light for photoelectric conversion and plays the role of electrical isolation between adjacent pixels.

[0034] The pixels in large-area array detectors are generally square or rectangular, which is convenient for arrangement and processing and improves the fill ratio of the entire pixel area. The pixel center distance is generally selected based on factors such as spatial resolution, manufacturing process limitations, optical interference, electrical isolation, and heat dissipation. The present invention discusses the case of a 30 μm pixel center distance. If the pixel shape or center distance is adjusted, the table size selection scheme is also applicable. Combined with the optimization of the table size, the half-width at half-maximum FWHM of the focused spot on the focal plane is DL=0.514 λ / NA, where NA is the numerical aperture. We propose to set the square table size to 2-3 times the half-width at half-maximum, which can take into account both the focusing efficiency and further suppress the crosstalk between adjacent pixels on the receiving surface, thereby improving the polarization extinction ratio.

[0035] A focal plane polarization detector based on the coordinated design of a metasurface and table size comprises: a metasurface structural unit for regulating the full polarization sensitivity of a detected scene light signal; and a focal plane structural unit aligned with the metasurface at the pixel level.

[0036] The super surface structural unit comprises: A super pixel structure of full Stokes polarization splitting and convergence is formed by 2×3 sub-pixels, and the super pixel structure includes three 2×1 splitting and convergence structures, namely, a 0 degree / 90 degree linear polarization splitting structure, a 45 degree / 135 degree linear polarization splitting structure, and a left-handed / right-handed circular polarization splitting structure; The 0 degree / 90 degree linear polarization splitting structure only introduces the transmission phase, that is, the major and minor axis dimensions of the elliptical cylinder are changed to match the wide spectrum splitting and converge the required phase; The 45 degree / 135 degree linear polarization splitting structure is obtained by rotating the 0 degree / 90 degree linear polarization splitting structure by 45 degrees; The transmission phase and geometric phase are introduced into the left-handed / right-handed circular polarization splitting structure, that is, the major and minor axis sizes of the elliptical column and the rotation angle around the center of the ellipse are changed.

[0037] The focal plane structural unit comprises: A periodic pixel array, wherein the semiconductor protrusion structure where the pixel is located after removing the air slot is a mesa structure, and the mesa size is an important parameter emphasized in this patent; Compared with the prior art, the focal plane polarization detector based on the collaborative design of the metasurface and the pixel table of the present invention has the following beneficial effects: the metasurface realizes preliminary polarization decoupling and focusing performance, but due to the discontinuity of the phase under the small-sized pixel and the error of micro-nano processing and three-dimensional integration, it is very difficult to achieve the application-level high polarization extinction ratio by relying solely on the metasurface, especially in the infrared band. The metasurface decomposes and converges the polarization on three sets of orthogonal polarization basis vectors, and the light spot converges in the pixel table, and the half-height full width of the converged light spot is about DL=0.514 λ / NA. The present invention innovatively proposes to collaboratively design the size of the metasurface and the pixel table. When the pixel table size is set to 2-3 times the half-height full width of the metasurface converged light spot, the energy utilization efficiency can be taken into account, the diffraction light crosstalk in the non-central area or even the adjacent pixel area can be suppressed, and the polarization extinction ratio can be further significantly improved, and the signal crosstalk between adjacent pixels can be reduced, thereby improving the detection accuracy and imaging quality.

[0038] Among them, the polarization detection method based on the focal plane type can ensure high integration; the superpixel can detect the entire Stokes polarization information at one time, ensuring real-time snapshot-style full polarization detection; the spectroscopic working mode is used instead of the filtering mode to ensure high energy utilization efficiency; the polarization-decoupled metasurface structure is collaboratively designed with the pixel table to break through the polarization extinction ratio limit that can be achieved by a single metasurface, ensuring a high polarization extinction ratio.

[0039] The primary metasurface proposed in the present invention realizes preliminary polarization decoupling, and the coordinated design of the secondary pixel table further suppresses crosstalk between adjacent pixels, breaking through the polarization extinction performance of the single metasurface.

[0040] The method proposed by the present invention is easy to be integrated on a chip.

[0041] In the present invention, the design method of pixel-level alignment ensures the integration degree, and the conversion from the "filtering" mode of ordinary microlenses to the splitting mode ensures the energy utilization efficiency; the further pixel-level focusing performance reduces the information crosstalk between adjacent pixels; the super-pixel simultaneously decomposes and detects the full polarization mode to enable the real-time snapshot working mode. Example 1

[0042] The present invention is a focal plane polarization detector based on the coordinated design of a metasurface and a pixel table. The following describes the working principle and method of the device from the two sequential parts of all-medium metasurface regulation to focal plane polarization detection: like Figure 1 As shown in FIG. 1 , the detected optical signal is incident on the metasurface structure 1. Here, the target working band is 3.5-4.5 μm. The structure can perform directional focusing and control of the full Stokes polarization. Since the polarization information of the light field can be completely decomposed on three sets of orthogonal polarization basis vectors, a super pixel is set to 2×3, as shown in FIG. Figure 3 As shown, each 2×1 orthogonal polarization multiplexing subunit realizes the splitting and convergence of 0 / 90 degree linear polarization light, 45 / 135 degree linear polarization light, and left-handed / right-handed circular polarization light.

[0043] like Figure 4 As shown, the measured light signal passes through the metasurface structure, and the signal is decomposed on the 0 / 90 degree pair of orthogonal polarization bases. The 0 degree polarized light converges to the left table structure, and the 90 degree polarized light converges to the right table structure. The table 2 structure includes a photosensitive layer, and the three groups of orthogonal polarizations are split and converged on the 2×1 pixel, respectively. Finally, the 0 degree linear polarized light / 90 degree linear polarized light, 45 degree linear polarized light / 135 degree linear polarized light, left-handed circular polarized light / right-handed circular polarized light are respectively converged on the table 2 area of ​​the 6 pixels of the 2×3 super pixel.

[0044] Figure 4 The specific process of 2×1 pixel (corresponding to 0-degree linear polarized light / 90-degree linear polarized light) splitting and converging the light field is demonstrated. After the light field carrying polarization information passes through the metasurface, the 0-degree and 90-degree polarized light are decomposed and converged to the table area of ​​the two pixels respectively. The table structure is generally composed of an upper contact layer, a light absorption layer, a lower contact layer, etc. from top to bottom. The area pointed by the arrow of the converged light field is the light absorption area in the table. The vertical distance between the location of the light absorption area and the location of the metasurface represents the integration distance, and the specific value depends on the integration method and process.

[0045] like Figure 2It is a top view of the 2×3 table plane of the present invention, the table shape is a square, and the side length of the square is the table size described in the present invention; the square dotted line shows a sub-pixel area, the side length of the pixel is equal to the center distance between adjacent pixels, which is the pixel center distance described in the present invention; the focal plane position corresponding to the 2×3 super pixel is concentrated in the central area of ​​the table 2 of the focal plane pixel array 3.

[0046] Figure 5 The simulation results of the wide-spectrum full-polarization detection performance of the present invention are demonstrated, including five working wavelengths of 3.5, 3.75, 4.0, 4.25, and 4.5 μm, and the focal plane convergence light field under six polarization states of incidence.

[0047] Due to the design error of the pixel-level microlens part and the processing error of the micro-nano structure, the convergence efficiency and achromatic effect of the microlens are somewhat different from the theory. Ideally, the micropolarizer efficiently decouples each polarization signal and converges it in the absorption area of ​​the target pixel. However, due to the imperfect design and processing, in fact, there will be some polarized diffracted light in the pixel corresponding to the entire absorption area of ​​the micropolarizer, that is, in addition to the focused light spot, there is light field energy distribution in the entire focal plane.

[0048] Since the focused spot on the focal plane is at the same order of magnitude as the pixel size, the size of the pixel table will also seriously affect the polarization extinction ratio. Appropriate groove width and sidewall passivation can achieve the effect of light field isolation. The present invention proposes to accurately design the table size of the detection pixel. Figure 8 The results of the change of polarization extinction ratio with the size of the table under the incidence of linear polarized light in the present invention are shown. It can be seen that as the size of the pixel table decreases, the polarization extinction ratio is significantly improved in the current design, taking D=30 μm pixel center distance as an example. When the side length of the square table is reduced from 30 microns to 5 microns, the polarization extinction ratio of the central wavelength increases from 19.8 to 157.5, an increase of 8 times; the minimum extinction ratio in the wide spectrum range increases from 4.1 to 16.4, also an increase of 4 times. It can be seen that the closer the table size is to the focused spot size, the more effectively the influence of diffracted light on the extinction ratio can be suppressed. The selection of the optimal table size takes into account the size of the microlens focused spot and the integration error at the same time, so as to maximize the polarization detection effect. Fig. 9 It is demonstrated that the polarization extinction ratio of the present invention changes with the size of the table under the incidence of circularly polarized light, showing the same trend.

[0049] Ideally, the half-width FWHM of the focused spot on the focal plane is DL=0.514 λ / NA, where NA is the numerical aperture. The theoretical half-width FWHM of the focused spot of this structure is as follows: Figure 6 The final simulation result of the example design of the invention is shown as follows Figure 6 As shown in the circular data, Figure 6The half-width of the converged light spot after the 0-degree linear polarized light passes through the metasurface structure with 0 / 90-degree linear polarized light splitting varies with wavelength. The half-width value is extracted from the light field envelope of the midpoint of the short axis along the long axis direction of the metasurface structure with 0 / 90-degree linear polarized light splitting. The dots represent the simulation results of 0-degree linear polarized light (XLP), and the dotted straight line represents the theoretical calculation results. Figure 6 The full width at half maximum of the focused spot of 0-degree linearly polarized light XLP of different wavelengths after passing through the example structure was calculated, and the comparison showed that it was close to the theoretical calculated value.

[0050] Taking a wavelength of 4.0 microns as an example, the light field envelope of the metasurface structure along the long axis direction and the midpoint of the short axis along the 0 / 90 degree linear polarization light splitting is taken to analyze the utilization efficiency of the light field energy. Figure 7 In Figure 6 The focal spot at 4 microns shown in the figure is measured as FWHM. 0 , if the horizontal axis is num, num×FWHM 0 The ratio of the energy in the area to the total transmitted energy is defined as the energy utilization rate of the focal plane. Obviously, the larger the area where energy is collected, the greater the energy utilization rate of the focal plane, and the greater the utilization efficiency of the transmitted light energy. Generally, at least 2 to 3 areas of the half-height full width of the focused spot are considered, that is, the recommended table size, which can better guarantee the energy utilization efficiency and polarization extinction ratio. The specific design can weigh the energy utilization efficiency and polarization extinction ratio effects according to the actual situation to determine the final table size.

[0051] The above-mentioned specific implementation methods are used to explain the present invention and are only preferred embodiments of the present invention, rather than limiting the present invention. Any modifications, equivalent substitutions, improvements, etc. made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A focal plane polarization detector based on the collaborative design of a metasurface and a pixel table, characterized by: include: The metasurface structure uses a pixel-level full-Stokes polarization-sensitive metasurface structure, including a number of metasurface structural units distributed in an array, for preliminary polarization decoupling and directional focusing; A focal plane pixel array aligned with the metasurface structure at the pixel level, comprising a multi-element plane array composed of a plurality of pixels, each pixel being provided with a table; The side length of each table is 2-3 times the half-height full width of the light spot gathered by the metasurface structure unit, so as to take into account the energy utilization efficiency of each pixel for the light field, suppress the crosstalk of optical signals gathered in non-central areas or even adjacent pixels, and further improve the polarization extinction ratio on the basis of polarization decoupling of the metasurface structure.

2. The focal plane polarization detector based on the coordinated design of the metasurface and the pixel table as claimed in claim 1, characterized in that: The metasurface structure includes an all-dielectric substrate and a metasurface structure unit on the all-dielectric substrate. The metasurface structure unit is a nanocolumn array formed by micro-nano processing at a micro-nano scale. Every 2×1 metasurface structure units constitute an orthogonal polarization multiplexing subunit to achieve polarization state regulation and light splitting and convergence. Each focal plane pixel matches the metasurface structure directly above it to form a subunit, and every 2×3 subunits constitute a superpixel structure to achieve full Stokes regulation and detection of 6 polarization states.

3. The focal plane polarization detector based on the coordinated design of the metasurface and the pixel table as claimed in claim 2, characterized in that: Each orthogonal polarization multiplexing subunit realizes the splitting and convergence of 0 degree / 90 degree linear polarization, 45 degree / 135 degree linear polarization, left-handed / right-handed circularly polarized light, and the converged target focus is located at the center of the absorption area of ​​the two pixels matching the 2 X 1 unit; In each orthogonal polarization multiplexing subunit, the spatial distribution of the required phase is: ,in, is any spatial position in the lens plane, is the spatial position of the lens focus in the focal plane, is the working wavelength, is the target focal length.

4. The focal plane polarization detector based on the coordinated design of the metasurface and the pixel table as claimed in claim 2, characterized in that: Each nanorod in the nanorod array adopts an anisotropic structure to produce different phase control effects for different polarizations; The nanorods are achromatized in the target working band, which is λ∈{λ_min,λ_max}. The phase required by the central wavelength λ_cen is regarded as the basic phase, and the phase difference at the boundary of the target working band is regarded as the dispersion phase. If both are satisfied at the same time, the meta-atom can simultaneously satisfy the phase of each wavelength. The side length of the nanorod base is P, which is set to be equivalent to 1 / 2 of the working wavelength, and is arranged in a hexagonal or square array; The height of the nanopillar is H, which is set to be equivalent to the working wavelength; The nanocolumns are elliptical or rectangular, and multi-frequency scanning of the target working band is performed on each nanocolumn to extract the basic phase and dispersion phase.

5. The focal plane polarization detector based on the coordinated design of the metasurface and the pixel table as claimed in claim 1, characterized in that: The metasurface structure introduces an anti-reflection interface on the non-microstructure side. The anti-reflection interface is an anti-reflection microstructure or an optical anti-reflection film, which is used to reduce the reflection loss of light energy during transmission.

6. The focal plane polarization detector based on the coordinated design of the metasurface and the pixel table as claimed in claim 1, characterized in that: The mesa is a semiconductor protruding structure where the pixel is located. The pixel is square and the mesa is square.

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