Design method of medium-wave infrared multispectral polarizer array of Si-based metasurface structure

Abstract

The invention discloses a method for designing a medium-wave infrared multispectral polarizer array of a Si-based metasurface structure, and belongs to the technical field of micro-nano optics, multispectral and polarization imaging. Linear polarization selective response is realized by designing a nanoscale metasurface structure, the spectrum is regulated and controlled by using the nanoscale metasurface structure, integration of a photoelectric detector with a high linear polarization extinction ratio at a key wavelength is realized, regulation and control of the spectrum can be realized without a traditional optical filter, and the photoelectric detector has a wide application prospect. The device has the advantages of simple optical path, high integration level and device miniaturization. According to the invention, the Si wire grating metasurface which has a full-transmission ultra-wide absorption spectrum characteristic in the TM polarization direction and is not transparent in wavelength selectivity in the TE polarization direction is integrated with the photoelectric detector, so that the problem of low absorption rate of the photoelectric polarization detector can be solved. The absorption spectrum of the photoelectric detector is regulated and controlled by changing the size parameters of the Si wire grid metasurface structure, multispectral narrow-band high-linear polarization extinction ratio detection in medium-wave infrared is achieved, and the spectral selectivity of the infrared polarization detector is improved.

Description

Technical Field

[0001] The invention belongs to the technical fields of micro-nano optics, multi-spectrum and polarization imaging, and relates to a method for designing a medium-wave infrared multi-spectrum polarizer array of a Si-based supersurface structure for medium-wave infrared spectral polarization regulation. Background Art

[0002] Multispectral polarization imaging technology can obtain multispectral information of ground objects through simultaneous polarization imaging of several or dozens of spectral bands, and achieve synchronous acquisition of ground object spatial radiation information, spectral information, and polarization information. It has important applications in target detection and recognition, biomedical imaging, ecological environment monitoring and detection analysis, etc. Traditional multispectral imaging spectroscopy methods mainly include dispersion type, interference type, and filter type spectroscopy.

[0003] In infrared multi-spectral imaging detection, the polarization characteristics of target radiation can be used to effectively suppress background clutter, improve the contrast between the target and the background, and increase the amount of information about the target, which is beneficial to the detection and identification of the target. At present, a variety of technologies for obtaining target polarization information have been developed, mainly including time-sharing polarization imaging technology, amplitude-sharing polarization imaging technology, aperture-sharing polarization imaging technology, and focal plane-sharing polarization imaging technology. However, the first three traditional polarization imaging systems and traditional multi-spectral spectrometry methods have the disadvantages of complex system structure, large size, poor stability, etc., which are difficult to meet the development needs of modern device integration and miniaturization.

[0004] Acquiring multispectral polarization information can provide richer multidimensional data than traditional imaging, significantly improving target recognition and imaging quality. In the mid-infrared band, multispectral polarization imaging plays an important role in missile guidance, forest fire monitoring, and industrial non-destructive testing. Traditional methods for acquiring mid-wave infrared multispectral polarization imaging information mainly include the use of multispectral filter wheels, liquid crystal or acousto-optic tunable filters, multi-channel beam splitters, and polarizer wheels. These methods achieve imaging of different bands and polarization angles by switching and splitting filters or polarizers, but face problems such as mechanical movement, speed limitations, and system complexity.

[0005] The new type of micro-polarizer array can simultaneously capture multi-spectral polarization information within one shutter cycle, greatly improving the imaging speed and synchronization. With the latest progress in focal plane array technology, micro-light polarization elements can be directly integrated into the focal plane array to realize a split-focal plane polarization imaging system, which has the advantages of good real-time performance, small size, compact structure, and high integration. As an emerging planar optical structure, metasurface can highly integrate multiple functions in an ultra-thin plane and show great potential in various beam control applications. Therefore, the metasurface structure array is used as a multi-spectral polarization element and integrated with a photodetector to realize a multi-spectral polarization photodetector without a filter. By designing the transmission spectrum of the metasurface structure array and matching it with the absorption spectrum of the detector, multi-channel, narrow bandwidth, and low crosstalk photoelectric polarization detection and imaging in the mid-infrared band can be realized, providing more possibilities for realizing mid-infrared multi-spectral polarization detection and imaging. Summary of the invention

[0006] In order to realize the above-mentioned small-sized and highly integrated split-focus plane polarization imaging system, the purpose of the present invention is to provide a design method for a mid-wave infrared multi-spectral polarizer array with a Si-based metasurface structure, by designing a Si wire grid metasurface structure with a broadband full transmission spectrum in the TM polarization direction and wavelength selective non-transmission in the TE polarization direction, a nanostructured multi-spectral polarizer array with linear polarization response and narrowband high extinction ratio in the mid-wave infrared is realized.

[0007] The objective of the present invention is achieved through the following technical solutions:

[0008] The method for designing a medium-wave infrared multi-spectral polarizer array of a Si-based metasurface structure disclosed in the present invention comprises the following steps:

[0009] Step 1. Construct a Si wire grating metasurface structure, parameterize the geometric structure dimensions of the Si wire grating metasurface, including the period, height, and duty cycle of the Si wire grating; use the finite-difference time-domain method to simulate the metasurface structure, and scan different Si wire grating metasurface structure parameters in the mid-wave infrared band to achieve linear polarization selective response; draw extinction ratio curves corresponding to different metasurface structure parameters, and analyze the relationship between the sizes of different Si wire grating metasurfaces and their corresponding extinction ratios; determine the Si wire grating metasurface structure size with a high linear polarization extinction ratio at several key wavelengths based on the obtained Si wire grating metasurface size corresponding extinction ratio curve.

[0010] The specific implementation method of step 1 includes the following steps:

[0011] Step 1.1: Use simulation design software to model the structure of the Si wire grid metasurface, whose structure is a periodically arranged Si nanowire grid, and the structural parameters are period (Pitch), height (H) and duty cycle (r).

[0012] Step 1.2: Use the time-domain finite difference method to scan the range of each parameter to find the best, and obtain the transmittance of the Si wire grid metasurface structure for TM polarized light and TE polarized light respectively. Calculate the extinction ratio according to formula (1), and draw the wavelength-extinction ratio curve. First, fix the two parameters of duty cycle and period, and scan the Si wire grid height parameter in the mid-wave infrared band to find the best.

[0013] ER=T TM / T TE (1)

[0014] Among them, ER (Extinction Ratio) is the linear polarization extinction ratio of the Si wire grid metasurface structure, T TM is the transmittance of Si wire grid metasurface structure for TM polarized light, T TE is the transmittance of Si wire grid metasurface structure for TE polarized light.

[0015] Step 1.3: After determining the optimal result of the structural parameter height, fix the two parameters of height and period, and scan the Si wire grid duty cycle parameter in the mid-wave infrared band to find the optimal value.

[0016] Step 1.4: After determining the optimal results of the height and duty cycle of the Si wire grid metasurface structure parameters, fix the two parameters of height and duty cycle, and scan the Si wire grid period parameter in the mid-wave infrared band to find the optimal value.

[0017] Preferably, the Si wire grid structure parameters with a TM polarized light transmittance close to 1 and a TE polarized light transmittance close to 0 at a selected wavelength in the simulation results are selected as the optimal result to be scanned.

[0018] Step 2: According to the extinction ratio curve corresponding to the optimal structural parameters of the Si wire grid metasurface obtained by scanning, the structural dimensions of the Si wire grid metasurface with high linear polarization extinction ratio at several key wavelengths in the mid-wave infrared are determined.

[0019] Preferably, based on the obtained extinction ratio curve, a linear polarization extinction ratio higher than 1000 is selected as the required high linear polarization extinction ratio, and the corresponding structural parameters are selected as the Si wire grid metasurface structural parameter scanning optimization results.

[0020] Step 3: construct a photodetector structure, and construct a unit structure integrating the photodetector and the Si wire grid metasurface structure, including a three-layer structure, which is mainly composed of a photodetector, SiO2, and a Si wire grid metasurface array from bottom to top. According to the Si wire grid metasurface structure with a high linear polarization extinction ratio at several key wavelengths determined in step 2, the preferred Si wire grid metasurface structure is integrated above the photodetector, the distance between the metasurface and the detector is set, and the absorption spectrum of the photodetector structure is simulated using the finite difference time domain method to obtain the optimal distance.

[0021] Preferably, based on the obtained absorption rate spectrum, the distance between the metasurface and the detector corresponding to an absorption rate close to 80% is selected as the preferred optimal distance.

[0022] Preferably, according to the obtained extinction ratio curve, the Si wire grid metasurface structure corresponding to the extinction ratio bandwidth lower than 100nm is selected and integrated with the photodetector structure to obtain a detector structure with a narrowband high linear polarization extinction ratio, wherein the extinction ratio bandwidth refers to the wavelength interval corresponding to when the extinction ratio drops to half of the peak extinction ratio.

[0023] Step 4: Based on the simulation analysis results of the integrated photodetector structure, the combination design of the three structural parameters of the height, duty cycle and period of the Si wire grid metasurface structure realizes the linear polarization light response of the metasurface structure, and determines the size of the Si wire grid metasurface structure with a narrowband high linear polarization extinction ratio at several key wavelengths, so as to design an infrared polarization detector structure with a narrowband high linear polarization extinction ratio. By changing the size parameters of the Si wire grid metasurface structure, the absorption spectrum of the photodetector can be regulated, so that the Si wire grid metasurface structure has infrared polarization detection capabilities that are tunable in a wide band and have a narrowband high linear polarization extinction ratio.

[0024] Preferably, the Si wire grid supersurface structure in step one is constructed of a semiconductor material with a refractive index higher than 1.7, and the semiconductor material is Si, Ge or TiO2.

[0025] Beneficial effects:

[0026] 1. The method for designing a medium-wave infrared multi-spectral polarizer array of a Si-based metasurface structure disclosed in the present invention realizes linear polarization selective response by designing a nanoscale metasurface structure, and uses it to regulate the spectrum, thereby realizing the integration of photodetectors with high linear polarization extinction ratio at key wavelengths. The spectrum can be regulated without traditional filters, and has the advantages of simple optical path, high integration, and miniaturized devices.

[0027] 2. The method for designing a medium-wave infrared multi-spectral polarizer array of a Si-based metasurface structure disclosed in the present invention integrates a Si wire-grid metasurface with full transmission and ultra-wide absorption spectrum characteristics in the TM polarization direction and wavelength selective non-transmission in the TE polarization direction with a photodetector, which can solve the problem of low absorption rate of the photoelectric polarization detector.

[0028] 3. The method for designing a mid-wave infrared multi-spectral polarizer array of a Si-based metasurface structure disclosed in the present invention controls the absorption spectrum of the photodetector by changing the various size parameters of the Si wire grid metasurface structure, thereby realizing multi-spectral narrow-band high linear polarization extinction ratio detection in the mid-wave infrared, which is beneficial to improving the spectral selectivity of infrared polarization detectors and can be applied to the field of multi-spectral polarization detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic flow chart of a spectrum control method based on a Si wire grid metasurface structure array multi-spectral polarization photodetector;

[0030] Figure 2 Schematic diagram of a Si wire grid supersurface periodic structure in an embodiment of the present invention;

[0031] Figure 3 Schematic diagram of a narrow-band multi-spectral polarization photodetector structure unit provided by an embodiment of the present invention;

[0032] Figure 4 is the transmittance of Si wire grating for TM polarized light and TE polarized light under different periodic structure parameters in the mid-wave infrared;

[0033] Figure 5 is the linear polarization extinction ratio of Si wire grating under different periodic structure parameters in the mid-wave infrared;

[0034] Figure 6 is the absorptivity of the single-layer InSb photodetector for TM polarized light and TE polarized light in the mid-wave infrared without Si wire grid metasurface array;

[0035] Figure 7 It is the absorption rate of TM polarized light and TE polarized light after integrating Si wire grid metasurface array with InSb photodetector in mid-wave infrared;

[0036] Figure 8 It is the linear polarization extinction ratio of the Si wire grid metasurface array integrated with the InSb photodetector in the mid-wave infrared;

[0037] Fig. 9 It is a schematic diagram of the structure of a multi-pixel multi-spectral polarization detector for realizing multi-spectral imaging in an embodiment of the present invention.

[0038] Among them: 1—Si-based supersurface structure, 2—Si wire grid unit structure, 3—quartz substrate, 4—SiO2 covering layer, 5—infrared polarization detector. DETAILED DESCRIPTION

[0039] In order to more completely describe and illustrate the technical solutions and advantages of the present invention, the specific implementation methods of the present invention will be described below in conjunction with the accompanying drawings and embodiments.

[0040] like Figure 1 As shown, the method for designing a medium-wave infrared multi-spectral polarizer array of a Si-based metasurface structure disclosed in this embodiment is specifically implemented as follows:

[0041] Step 1. Construct a Si wire grating metasurface structure, parameterize the geometric structure dimensions of the Si wire grating metasurface, including the period, height, and duty cycle of the Si wire grating; use the finite-difference time-domain method to simulate the metasurface structure, and scan different Si wire grating metasurface structure parameters in the mid-wave infrared band to achieve linear polarization selective response; draw extinction ratio curves corresponding to different metasurface structure parameters, and analyze the relationship between the sizes of different Si wire grating metasurfaces and their corresponding extinction ratios; determine the Si wire grating metasurface structure size with a high linear polarization extinction ratio at several key wavelengths based on the obtained Si wire grating metasurface size corresponding extinction ratio curve.

[0042] The specific implementation method of step 1 includes the following steps:

[0043] Step 1.1: Use the FDTD module of the optoelectronic simulation design software to model the structure of the Si wire grid metasurface, whose structure is a periodically arranged Si nanowire grid, such as Figure 2 As shown, the structural parameters are period (Pitch), height (H) and duty cycle (r), where the duty cycle is defined as the ratio of the wire grid width to the wire grid period in the Si wire grid unit structure. By setting the boundary condition in the software, it is set as a periodic boundary condition, so that only one unit structure in the periodic structure needs to be established to solve, and its spectral response can be solved separately by the finite difference time domain method (FDTD).

[0044] Step 1.2: Use the finite difference time domain method to perform range scanning and optimization on each parameter, and obtain the transmittance of the Si wire grid metasurface structure for TM polarized light and TE polarized light. Figure 2As shown in the figure, in the set rectangular coordinate system O-xyz, the grating strips extend along the y-axis direction, the x-axis direction is the periodic change direction of the grating, and the z-axis is perpendicular to the interface between the grating layer and the substrate material and parallel to the incident direction of the light. Among them, the TM polarization direction is perpendicular to the grating groove direction, that is, along the x-direction, and the TE polarization direction is consistent with the grating groove direction, that is, along the y-direction. The extinction ratio is calculated according to formula (1), and the wavelength-extinction ratio curve is obtained by plotting. First, the two parameters of duty cycle and period are fixed, and the Si wire grating height parameter is scanned in the range of 400 to 700 nm in the mid-wave infrared band to find the optimal value.

[0045] ER=T TM / T TE (1)

[0046] Among them, ER (Extinction Ratio) is the linear polarization extinction ratio of the Si wire grid metasurface structure, T TM is the transmittance of Si wire grid metasurface structure for TM polarized light, T TE is the transmittance of Si wire grid metasurface structure for TE polarized light.

[0047] Step 1.3: After determining the optimal result of the structural parameter height, fix the two parameters of height and period, and scan the Si wire grid duty cycle parameter in the range of 0.1 to 0.9 in the mid-wave infrared band to find the optimal value.

[0048] Step 1.4: After determining the optimal results of the height and duty cycle of the Si wire grid metasurface structure parameters, fix the two parameters of height and duty cycle, and scan the Si wire grid period parameter in the range of 1700 to 2800nm ​​in the mid-wave infrared band to find the optimal value.

[0049] The Si wire grid structure parameters with a TM polarized light transmittance close to 1 and a TE polarized light transmittance close to 0 at the selected wavelength in the simulation results are selected as the optimal result to be found by scanning.

[0050] Step 2: According to the extinction ratio curve corresponding to the optimal structural parameters of the Si wire grid metasurface obtained by scanning, determine the size of the Si wire grid metasurface structure with high linear polarization extinction ratio at several key wavelengths in the mid-wave infrared. Figure 4 The figure shows the transmittance of Si wire grid metasurface structure for TM polarized light and TE polarized light at the period of Si wire grid in mid-wave infrared at 2240nm, 2350nm, 2500nm and 2760nm, respectively. Figure 5 Shown is the extinction ratio curve of the Si wire grid metasurface structure in the mid-wave infrared under the above four periods.

[0051] According to the obtained extinction ratio curve, a linear polarization extinction ratio higher than 1000 is selected as the required high linear polarization extinction ratio, and the corresponding structural parameters are selected as the scanning optimization results of the Si wire grid metasurface structural parameters.

[0052] Step 3: construct a photodetector structure, and construct a unit structure integrating the photodetector and the Si wire grid metasurface structure, such as Figure 3 As shown in the figure, it includes a three-layer structure, which is mainly composed of photodetectors, SiO2 and Si wire grid metasurface arrays from bottom to top. The SiO2 cover layer is used to form a uniform and stable insulating layer, flatten the substrate surface and provide a protective layer. The spectral response of the photodetector to the target band is usually wide, which limits its application in the multi-spectral field. By integrating it with a Si wire grid metasurface array with narrow-band high extinction, narrow-band multi-channel spectral polarization detection can be achieved.

[0053] According to the Si wire grid metasurface structure with high linear polarization extinction ratio at several key wavelengths determined in step 2, the preferred Si wire grid metasurface structure is integrated above the photodetector, and the photodetector embodiment uses InSb photodetector. The absorption rate of the single-layer photodetector for linear polarized light is simulated by using the time-domain finite difference method, wherein the thickness of the InSb photodetector is set to 20μm. Figure 6 The figure shows the absorptivity of a single-layer InSb photodetector for TM polarized light and TE polarized light in the mid-wave infrared without a Si wire grid metasurface array. The distance between the metasurface and the detector is set, and the absorptivity spectrum of the photodetector structure is simulated to obtain the optimal distance.

[0054] According to the obtained absorption rate spectrum, the distance between the metasurface and the detector corresponding to the absorption rate close to 80% is selected as the optimal distance. According to the obtained extinction ratio curve, the Si wire grid metasurface structure corresponding to the extinction ratio bandwidth below 100nm is selected for integration with the photodetector structure to obtain a detector structure with a narrowband high linear polarization extinction ratio, where the extinction ratio bandwidth refers to the wavelength interval corresponding to the extinction ratio dropping to half of the peak extinction ratio.

[0055] Step 4: According to the simulation analysis results of the integrated photodetector structure, Figure 7 The figure shows the absorption rate of TM polarized light and TE polarized light after integrating Si wire grid metasurface array with InSb photodetector in the mid-wave infrared. Figure 8The figure shows the linear polarization extinction ratio of the Si wire grid metasurface array integrated with the InSb photodetector in the mid-wave infrared. The combined design of the three structural parameters of the Si wire grid metasurface structure, namely the height, duty cycle and period, realizes the linear polarization light response of the metasurface structure, and determines the size of the Si wire grid metasurface structure with a narrowband high linear polarization extinction ratio at several key wavelengths, so as to design an infrared polarization detector structure with a narrowband high linear polarization extinction ratio. By changing the size parameters of the Si wire grid metasurface structure, the absorption spectrum of the photodetector can be regulated, so that the Si wire grid metasurface structure has the infrared polarization detection capability that is wavelength tunable in a wide band and has a narrowband high linear polarization extinction ratio.

[0056] The Si wire grid metasurface structure described in step 1 is constructed of semiconductor materials with a refractive index higher than 1.7, and the semiconductor materials are Si, Ge or TiO2. The fundamental purpose is to combine the inherent refractive index characteristics of the material and achieve linear polarization response and high extinction ratio by controlling the structure of the nano-metasurface. The material used in this embodiment is preferably Si, because it is a traditional semiconductor material with a high refractive index, and it has the advantage of high transmittance in the infrared band, which is an ideal choice for cooperation with infrared photodetectors.

[0057] The detector materials of the photoelectric detector in the embodiment described in step 3 include but are not limited to InSb, InAs, HgCdTe and other materials, and the detectors include but are not limited to traditional planar detectors and new micro-nano structure / material detectors.

[0058] Integrating multiple metasurface structure array pixels optimized by the above method onto the same chip can achieve direct multi-wavelength gating. Each single pixel generates a photocurrent in a selective wavelength range in the mid-infrared range. Every four pixels can resolve the polarization information of the current selective wavelength and have a large number of mid-wave infrared wavelength channels. The structural schematic diagram of the designed multi-pixel multi-spectral polarization detector to achieve multi-spectral imaging is shown in the figure. Fig. 9 shown.

[0059] It can be seen that the method for designing a medium-wave infrared multi-spectral polarizer array of a Si-based metasurface structure disclosed in this embodiment realizes linear polarization selective response by designing a nanoscale metasurface structure, and uses it to control the spectrum, so as to realize the integration of a photodetector with a high linear polarization extinction ratio at a key wavelength, and can control the spectrum without a traditional filter, and has the advantages of simple optical path, high integration, and miniaturization of devices. In addition, the Si wire grid metasurface structure array pixels corresponding to several key wavelengths are integrated into the same chip, and integrated with the photodetector, and the absorption spectrum of the photodetector is controlled to realize multi-spectral narrow-band high linear polarization extinction ratio detection in the medium-wave infrared, which is beneficial to improve the spectral selectivity of the infrared polarization detector and can be applied to the field of multi-spectral polarization detection.

[0060] The specific description above further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for designing a medium-wave infrared multi-spectral polarizer array of a Si-based metasurface structure, characterized in that: The following steps are included: Step 1: Construct a Si wire grid metasurface structure and parameterize the geometric structure dimensions of the Si wire grid metasurface, including the period, height, and duty cycle of the Si wire grid; simulate the metasurface structure using the finite difference time domain method, and scan different Si wire grid metasurface structure parameters in the mid-wave infrared band to achieve linear polarization selective response; Draw the extinction ratio curve corresponding to different metasurface structure parameters, and analyze the relationship between the size of different Si wire grid metasurfaces and their corresponding extinction ratios; According to the obtained Si wire grid metasurface size corresponding to the extinction ratio curve, determine the size of the Si wire grid metasurface structure with high linear polarization extinction ratio at several key wavelengths; Step 2: According to the extinction ratio curve corresponding to the optimal structural parameters of the Si wire grid metasurface obtained by scanning, the size of the Si wire grid metasurface structure with high linear polarization extinction ratio at several key wavelengths in the mid-wave infrared is determined; Step 3: construct a photodetector structure, and construct a unit structure integrating the photodetector and the Si wire grid metasurface structure, including a three-layer structure, which is mainly composed of a photodetector, SiO2 and a Si wire grid metasurface array from bottom to top; according to the Si wire grid metasurface structure with a high linear polarization extinction ratio at several key wavelengths determined in step 2, integrate the preferred Si wire grid metasurface structure above the photodetector, set the distance between the metasurface and the detector, use the finite difference time domain method to simulate the absorption spectrum of the photodetector structure, and obtain the optimal distance; Step 4: Based on the simulation analysis results of the integrated photodetector structure, the combination design of the three structural parameters of the height, duty cycle and period of the Si wire grid metasurface structure realizes the linear polarization light response of the metasurface structure, and determines the size of the Si wire grid metasurface structure with a narrowband high linear polarization extinction ratio at several key wavelengths, so as to design an infrared polarization detector structure with a narrowband high linear polarization extinction ratio. By changing the size parameters of the Si wire grid metasurface structure, the absorption spectrum of the photodetector can be regulated, so that the Si wire grid metasurface structure has infrared polarization detection capabilities that are tunable in a wide band and have a narrowband high linear polarization extinction ratio.

2. The method for designing a medium-wave infrared multi-spectral polarizer array of a Si-based metasurface structure according to claim 1, characterized in that: The specific implementation method of step 1 includes the following steps: Step 1.1: Use simulation design software to model the structure of the Si wire grid metasurface, whose structure is a periodically arranged Si nanowire grid, and the structural parameters are period (Pitch), height (H) and duty cycle (r); Step 1.2: Use the time-domain finite difference method to scan the range of each parameter to find the best, and obtain the transmittance of the Si wire grid metasurface structure for TM polarized light and TE polarized light respectively. Calculate the extinction ratio according to formula (1), and draw the wavelength-extinction ratio curve. First, fix the two parameters of duty cycle and period, and scan the Si wire grid height parameter in the mid-wave infrared band to find the best. IS=T TM / T TE (1) Among them, ER (Extinction Ratio) is the linear polarization extinction ratio of the Si wire grid metasurface structure, T TM is the transmittance of Si wire grid metasurface structure for TM polarized light, T TE is the transmittance of Si wire grid metasurface structure for TE polarized light. Step 1.3: After determining the optimal result of the structural parameter height, fix the two parameters of height and period, and scan the parameter of Si wire grid duty cycle in the mid-wave infrared band to find the optimal value; Step 1.4: After determining the optimal results of the height and duty cycle of the Si wire grid metasurface structure parameters, fix the two parameters of height and duty cycle, and scan the Si wire grid period parameter in the mid-wave infrared band to find the optimal value.

3. The method for designing a medium-wave infrared multi-spectral polarizer array of a Si-based metasurface structure according to claim 1, characterized in that: The Si wire grid structure parameters with a TM polarized light transmittance close to 1 and a TE polarized light transmittance close to 0 at the selected wavelength in the simulation results are selected as the optimal result to be found by scanning.

4. The method for designing a medium-wave infrared multi-spectral polarizer array of a Si-based metasurface structure according to claim 1, characterized in that: According to the obtained extinction ratio curve, a linear polarization extinction ratio higher than 1000 is selected as the required high linear polarization extinction ratio, and the corresponding structural parameters are selected as the scanning optimization results of the Si wire grid metasurface structural parameters.

5. The method for designing a medium-wave infrared multi-spectral polarizer array of a Si-based metasurface structure according to claim 1, characterized in that: According to the obtained absorption rate spectrum, the distance between the metasurface and the detector corresponding to an absorption rate close to 80% is selected as the preferred optimal distance.

6. The method for designing a medium-wave infrared multi-spectral polarizer array of a Si-based metasurface structure according to claim 1, characterized in that: According to the obtained extinction ratio curve, the Si wire grid metasurface structure corresponding to the extinction ratio bandwidth lower than 100nm is selected and integrated with the photodetector structure to obtain a detector structure with a narrowband high linear polarization extinction ratio, where the extinction ratio bandwidth refers to the wavelength interval corresponding to when the extinction ratio drops to half of the peak extinction ratio.

7. The method for designing a medium-wave infrared multi-spectral polarizer array of a Si-based metasurface structure according to claim 1, characterized in that: The Si wire grid super surface structure described in step 1 is constructed of a semiconductor material with a refractive index higher than 1.7, and the semiconductor material is Si, Ge or TiO2.

8. The method for designing a medium-wave infrared multi-spectral polarizer array of a Si-based metasurface structure according to claim 1, characterized in that: The detector materials of the photoelectric detector in the embodiment described in step 3 include but are not limited to InSb, InAs, HgCdTe and other materials, and the detectors include but are not limited to traditional planar detectors and new micro-nano structure / material detectors.

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