Design method of mid-wave infrared multispectral polarizer array of si-based metasurface structure

Abstract

This invention discloses a design method for a mid-wave infrared multispectral polarizer array based on a Si-based metasurface structure, belonging to the fields of micro-nano optics, multispectral, and polarization imaging technology. This invention achieves linear polarization-selective response by designing a nanoscale metasurface structure and utilizing it to modulate the spectrum, enabling the integration of a photodetector with a high linear polarization extinction ratio at key wavelengths. This achieves spectral manipulation without the need for traditional filters, offering advantages such as simple optical path, high integration density, and device miniaturization. This invention integrates a Si wire-grating metasurface, which exhibits ultra-wide absorption spectrum characteristics with full transmission in the TM polarization direction and wavelength-selective opacity in the TE polarization direction, with a photodetector, solving the problem of low absorptivity in photodetectors. By changing the dimensional parameters of the Si wire-grating metasurface structure, this invention modulates the absorption spectrum of the photodetector, achieving multispectral narrowband detection with a high linear polarization extinction ratio in the mid-wave infrared, which is beneficial for improving the spectral selectivity of infrared polarization detectors.

Description

Technical Field

[0001] This invention belongs to the fields of micro-nano optics, multispectral and polarization imaging technology, and relates to a design method for a mid-wave infrared multispectral polarizer array of a Si-based metasurface structure for mid-wave infrared spectral polarization modulation. Background Technology

[0002] Multispectral polarization imaging technology can acquire multispectral information of ground objects by simultaneously polarizing several or a dozen spectral bands, enabling the synchronous acquisition of spatial radiation, spectral, and polarization information of ground objects. It has important applications in target detection and identification, biomedical imaging, and ecological environment monitoring and analysis. Traditional multispectral imaging methods mainly include dispersive, interferometric, and filter-based dispersion.

[0003] In infrared multispectral imaging, utilizing the polarization characteristics of target radiation can effectively suppress background clutter, improve the contrast between the target and the background, and increase the amount of information about the target, thus facilitating target detection and identification. Currently, various technologies for acquiring target polarization information have been developed, mainly including time-division polarization imaging, amplitude-division polarization imaging, aperture-division polarization imaging, and focal-plane polarization imaging. However, the first three traditional polarization imaging systems, as well as traditional multispectral spectral dispersion methods, suffer from drawbacks such as complex system structure, large size, and poor stability, making it difficult to meet the demands of modern device integration and miniaturization.

[0004] Acquiring multispectral polarization information provides richer multidimensional data than traditional imaging, significantly improving target recognition and imaging quality. In the mid-infrared band, multispectral polarization imaging plays a crucial role in missile guidance, forest fire monitoring, and industrial non-destructive testing. Traditional methods for acquiring mid-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 at different bands and polarization angles through the switching and splitting of filters or polarizers, but they face challenges such as mechanical movement, speed limitations, and system complexity.

[0005] Novel micro-polarizer arrays can simultaneously capture multispectral polarization information within a single shutter cycle, significantly improving imaging speed and synchronization. With recent advancements in focal plane array technology, micro-polarizing elements can be directly integrated onto the focal plane array, enabling a focal plane polarization imaging system. This system offers advantages such as good real-time performance, small size, compact structure, and high integration. Metasurfaces, as an emerging planar optical structure, can highly integrate multiple functions within an ultrathin plane, demonstrating great potential in various beam manipulation applications. Therefore, integrating metasurface arrays as multispectral polarization elements with photodetectors creates filter-free multispectral polarization photodetectors. By designing the transmission spectrum of the metasurface array and matching it with the detector's absorption spectrum, multi-channel, narrow-bandwidth, low-crosstalk photoelectric polarization detection and imaging in the mid-infrared band can be achieved, providing more possibilities for mid-infrared multispectral polarization detection and imaging. Summary of the Invention

[0006] To achieve the aforementioned small-sized, highly integrated focal plane polarization imaging system, the present invention aims to provide a design method for a mid-wave infrared multispectral polarizer array based on a Si-based metasurface structure. By designing a Si wire grating 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 multispectral polarizer array with linear polarization response and narrowband high extinction ratio in the mid-wave infrared is realized.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] The present invention discloses a design method for a mid-wave infrared multispectral polarizer array of a Si-based metasurface structure, comprising the following steps:

[0009] Step 1: Construct a Si wire grating metasurface structure. Parameterize the geometric dimensions of the Si wire grating metasurface, including the period, height, and duty cycle of the Si wire grating. Simulate the metasurface structure using the finite-difference time-domain method. Scan different Si wire grating metasurface structure parameters in the mid-infrared band to achieve linear polarization-selective response. Plot extinction ratio curves corresponding to different metasurface structure parameters and analyze the relationship between the dimensions of different Si wire grating metasurfaces and their corresponding extinction ratios. Based on the obtained extinction ratio curves corresponding to the dimensions of the Si wire grating metasurface, determine the dimensions of Si wire grating metasurface structures with high linear polarization extinction ratios at several key wavelengths.

[0010] Step one specifically includes the following steps:

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

[0012] Step 1.2: The finite-difference time-domain method was used to perform range scanning optimization for each parameter to obtain the transmittance of the Si wire grating metasurface structure for TM-polarized and TE-polarized light. The extinction ratio was calculated according to formula (1), and the wavelength-extinction ratio curve was plotted. First, the duty cycle and period were fixed, and the Si wire grating height parameter was scanned and optimized in the mid-infrared band.

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

[0014] Where ER (Extinction Ratio) is the linear polarization extinction ratio of the Si wire-gate metasurface structure, and T TM T represents the transmittance of the Si wire-gate metasurface structure for TM-polarized light. TE The transmittance of the Si wire grating metasurface structure for TE polarized light is given.

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

[0016] Step 1.4: After determining the optimal results of the height and duty cycle of the Si wire grating metasurface structure parameters, fix the two parameters of height and duty cycle, and perform a scanning optimization of the Si wire grating period parameter in the mid-wave infrared band.

[0017] As a preferred option, the Si wire grating structure parameters with a TM polarization transmittance close to 1 and a TE polarization transmittance close to 0 at the selected wavelength are selected as the optimal results sought in the scan.

[0018] Step 2: Based on the extinction ratio curves corresponding to the preferred structural parameters of the Si wire grating metasurface obtained from scanning, determine the structural dimensions of the Si wire grating metasurface with high linear polarization extinction ratio at several key wavelengths in the mid-infrared range.

[0019] As a preferred option, 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 results of the Si wire grating metasurface structural parameter scanning optimization.

[0020] Step 3: Construct the photodetector structure and an integrated unit structure of the photodetector and Si wire-grid metasurface structure, comprising a three-layer structure. From bottom to top, the three-layer structure mainly consists of the photodetector, SiO2, and the Si wire-grid metasurface array. Based on the Si wire-grid metasurface structures with high linear polarization extinction ratios 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] As a preferred option, based on the obtained absorptivity spectrum, the optimal distance between the metasurface and the detector is selected when the absorptivity is close to 80%.

[0022] As a preferred option, based on the obtained extinction ratio curve, a Si wire grating metasurface structure with an extinction ratio bandwidth of less than 100 nm is selected and integrated with a photodetector structure to obtain a detector structure with a narrow-band high linear polarization extinction ratio. The extinction ratio bandwidth refers to the wavelength interval corresponding to the extinction ratio dropping 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 height, duty cycle, and period of the Si wire grating metasurface structure realizes the linear polarization response of the metasurface structure. The dimensions of the Si wire grating metasurface structure with a narrow band high linear polarization extinction ratio at several key wavelengths are determined to design an infrared polarization detector structure with a narrow band high linear polarization extinction ratio. By changing the dimensional parameters of the Si wire grating metasurface structure, the absorption spectrum of the photodetector can be modulated, enabling the Si wire grating metasurface structure to possess infrared polarization detection capability with tunable wavelengths over a wide wavelength range and a narrow band high linear polarization extinction ratio.

[0024] Preferably, the Si wire gate metasurface structure described in step one is constructed from 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 design method of mid-wave infrared multispectral polarizer array of Si-based metasurface structure disclosed in this invention achieves linear polarization selective response by designing nanoscale metasurface structure and using it to modulate the spectrum, realizing the integration of photodetector with high linear polarization extinction ratio at key wavelength, without the need for traditional filters to achieve spectrum modulation, and has the advantages of simple optical path, high integration and device miniaturization.

[0027] 2. The design method of mid-wave infrared multispectral polarizer array of Si-based metasurface structure disclosed in this invention integrates Si wire grating metasurface with ultra-wide absorption spectrum characteristics of full transmission in the TM polarization direction and wavelength selective non-transmission in the TE polarization direction with photodetector, which can solve the problem of low absorption rate of photodetector polarization detector.

[0028] 3. The design method of mid-wave infrared multispectral polarizer array of Si-based metasurface structure disclosed in this invention can control the absorption spectrum of photodetector by changing the various dimensional parameters of Si wire grating metasurface structure, so as to realize multispectral narrow-band high linear polarization extinction ratio detection in mid-wave infrared, which is beneficial to improve the spectral selectivity of infrared polarization detector and can be applied to the field of multispectral polarization detection. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the spectral modulation method for a multispectral polarization photodetector based on a Si wire grating metasurface structure array.

[0030] Figure 2 This is a schematic diagram of the periodic structure of the Si wire-gate metasurface in an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of the narrowband multispectral polarization photodetector structure unit provided in an embodiment of the present invention;

[0032] Figure 4 It represents the transmittance of Si wire grating for TM-polarized light and TE-polarized light under different periodic structural parameters in the mid-wave infrared region.

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

[0034] Figure 6 The absorption rates of a single-layer InSb photodetector for TM-polarized light and TE-polarized light, respectively, when using a mid-wave infrared metasurface array without Si wire grids.

[0035] Figure 7 The absorption rates of Si wire-gate metasurface arrays and InSb photodetectors in the mid-wave infrared region for TM-polarized and TE-polarized light, respectively.

[0036] Figure 8 It is the linear polarization extinction ratio after integrating a Si wire-grid metasurface array with an InSb photodetector in the mid-wave infrared.

[0037] Figure 9 This is a schematic diagram of the structure of a multi-pixel multispectral polarization detector for multispectral imaging in an embodiment of the present invention.

[0038] Wherein: 1—Si-based metasurface structure, 2—Si wire grid unit structure, 3—quartz substrate, 4—SiO2 capping layer, 5—infrared polarization detector. Detailed Implementation

[0039] To more fully describe and illustrate the technical solutions and advantages of the present invention, the specific embodiments of the present invention will be described below in conjunction with the accompanying drawings and examples.

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

[0041] Step 1: Construct a Si wire grating metasurface structure. Parameterize the geometric dimensions of the Si wire grating metasurface, including the period, height, and duty cycle of the Si wire grating. Simulate the metasurface structure using the finite-difference time-domain method. Scan different Si wire grating metasurface structure parameters in the mid-infrared band to achieve linear polarization-selective response. Plot extinction ratio curves corresponding to different metasurface structure parameters and analyze the relationship between the dimensions of different Si wire grating metasurfaces and their corresponding extinction ratios. Based on the obtained extinction ratio curves corresponding to the dimensions of the Si wire grating metasurface, determine the dimensions of Si wire grating metasurface structures with high linear polarization extinction ratios at several key wavelengths.

[0042] Step one specifically 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 grating metasurface. Its structure consists of periodically arranged Si nanowire gratings, 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 width to the wire period in the Si wire grid unit structure. By setting the boundary conditions in the software, it is set as a periodic boundary condition, so only one unit structure in the periodic structure needs to be built to solve the problem. Its spectral response can be solved separately using the finite-difference time-domain (FDTD) method.

[0044] Step 1.2: The finite-difference time-domain method is used to perform range scanning optimization for each parameter, obtaining the transmittance of the Si wire-gate metasurface structure for TM-polarized and TE-polarized light respectively. For example... Figure 2As shown, in the set rectangular coordinate system O-xyz, the grating strips extend along the y-axis, the x-axis 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 light direction. Among them, the TM polarization direction is perpendicular to the grating groove direction, that is, along the x-direction, while 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. First, the duty cycle and period are fixed, and the Si wire grating height parameter is scanned and optimized in the mid-wave infrared band within the range of 400-700nm.

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

[0046] Where ER (Extinction Ratio) is the linear polarization extinction ratio of the Si wire-gate metasurface structure, and T TM T represents the transmittance of the Si wire-gate metasurface structure for TM-polarized light. TE The transmittance of the Si wire grating metasurface structure for TE polarized light is given.

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

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

[0049] The Si wire grating structure parameters with a transmittance close to 1 for TM polarized light and a transmittance close to 0 for TE polarized light at a selected wavelength were selected as the optimal results sought in the scan.

[0050] Step 2: Based on the extinction ratio curves corresponding to the preferred structural parameters of the Si wire grating metasurface obtained from scanning, determine the structural dimensions of the Si wire grating metasurface with high linear polarization extinction ratios at several key wavelengths in the mid-infrared range. For example... Figure 4 The figure shows the transmittance of Si wire grating metasurface structures for TM-polarized and TE-polarized light at mid-wave infrared inner Si wire grating periods of 2240 nm, 2350 nm, 2500 nm, and 2760 nm, respectively. Figure 5 The figure shows the extinction ratio curves of the mid-wave infrared inner Si wire grating metasurface structure under the above four periods.

[0051] Based on the obtained extinction ratio curve, a linear polarization extinction ratio higher than 1000 was selected as the required high linear polarization extinction ratio, and the corresponding structural parameters were selected as the results of the Si wire grating metasurface structural parameter scanning optimization.

[0052] Step 3: Construct the photodetector structure and build a unit structure integrating the photodetector with the Si wire-gate metasurface structure, such as... Figure 3 As shown, it comprises a three-layer structure, mainly consisting of a photodetector, SiO2, and a Si wire-grating metasurface array from bottom to top. The SiO2 capping layer serves to form a uniform and stable insulating layer, smoothing the substrate surface and providing a protective layer. Photodetectors typically have a wide spectral response to the target wavelength, limiting their application in the multispectral field. However, by integrating them with a Si wire-grating metasurface array that features narrowband high extinction, narrowband multi-channel spectral polarization detection can be achieved.

[0053] Based on the Si wire-gate metasurface structures with high linear polarization extinction ratios at several key wavelengths determined in step two, the preferred Si wire-gate metasurface structures are integrated on top of a photodetector. In this photodetector embodiment, an InSb photodetector is selected. The absorption rate of the single-layer photodetector for linearly polarized light is simulated using the finite-difference time-domain method, where the InSb photodetector thickness is set to 20 μm. Figure 6 The figure shows the absorption rates of a single-layer InSb photodetector for TM-polarized and TE-polarized light, respectively, when using a Si-lined metasurface array in the mid-wave infrared region. The distance between the metasurface and the detector was set, and the absorption spectrum of the photodetector structure was simulated to obtain the optimal distance.

[0054] Based on the obtained absorptivity spectrum, the optimal distance between the metasurface and the detector is selected when the absorptivity is close to 80%. Based on the obtained extinction ratio curve, the Si wire-gate metasurface structure with an extinction ratio bandwidth of less than 100 nm is selected and integrated with the photodetector structure to obtain a detector structure with a narrow-band high linear polarization extinction ratio. 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: Based on the simulation analysis results of the integrated photodetector structure, such as... Figure 7 The figure shows the absorption rates of the integrated Si wire-gate metasurface array with an InSb photodetector for TM-polarized and TE-polarized light in the mid-infrared range. Figure 8The figure shows the linear polarization extinction ratio of the integrated Si wire-grid metasurface array with an InSb photodetector in the mid-infrared range. The combined design of the height, duty cycle, and period of the Si wire-grid metasurface structure achieved the linear polarization response of the metasurface structure, and determined the dimensions of the Si wire-grid metasurface structure with a narrow-band high linear polarization extinction ratio at several key wavelengths, thus enabling the design of an infrared polarization detector structure with a narrow-band high linear polarization extinction ratio. By changing the dimensional parameters of the Si wire-grid metasurface structure, the absorption spectrum of the photodetector can be modulated, enabling the Si wire-grid metasurface structure to possess infrared polarization detection capabilities with tunable wavelengths over a wide wavelength range and a narrow-band high linear polarization extinction ratio.

[0056] The Si wire-gate metasurface structure described in step one is constructed from a semiconductor material with a refractive index higher than 1.7, such as Si, Ge, or TiO2. Its fundamental purpose is to combine the inherent refractive index characteristics of the material with the control of the nano-metasurface structure to achieve linear polarization response and a high extinction ratio. In this embodiment, Si is preferred because it is a traditional semiconductor material with a high refractive index, exhibiting high transmittance in the infrared band, making it an ideal choice for use with infrared photodetectors.

[0057] The detector materials of the photodetectors in the embodiments described in step three include, but are not limited to, InSb, InAs, HgCdTe, etc., and the detectors include, but are not limited to, traditional planar detectors and novel micro / nano structure / material detectors.

[0058] By integrating multiple metasurface structure array pixels optimized using the above method onto a single chip, direct multi-wavelength gating can be achieved. Each single pixel generates a photocurrent within a selective wavelength range in the mid-infrared region, and every four pixels can compute the polarization information of the current selective wavelength. It also possesses a large number of mid-infrared wavelength channels. A schematic diagram of the designed multi-pixel multispectral polarization detector for multispectral imaging is shown below. Figure 9 As shown.

[0059] Therefore, the Si-based metasurface structure mid-wave infrared multispectral polarizer array design method disclosed in this embodiment achieves linear polarization-selective response by designing nanoscale metasurface structures and using them to modulate the spectrum. This enables the integration of a photodetector with a high linear polarization extinction ratio at key wavelengths, eliminating the need for traditional filters and offering advantages such as simple optical path, high integration, and device miniaturization. Furthermore, integrating several Si wire-gate metasurface structure array pixels corresponding to key wavelengths onto the same chip and integrating them with a photodetector allows for modulation of the photodetector's absorption spectrum, achieving multispectral narrowband high linear polarization extinction ratio detection in the mid-wave infrared region. This improves the spectral selectivity of the infrared polarization detector and can be applied to the field of multispectral polarization detection.

[0060] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. It should be understood that the above description 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 within the scope of protection of the present invention.

Claims

1. A design method for a mid-wave infrared multispectral polarizer array based on a Si-based metasurface structure, characterized by: Includes the following steps, Step 1: Construct a Si wire grating metasurface structure and parameterize the geometric 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-infrared band to achieve a linear polarization selective response. Plot extinction ratio curves corresponding to different metasurface structure parameters and analyze the relationship between the size of different Si wire grating metasurfaces and their corresponding extinction ratios; based on the obtained extinction ratio curves corresponding to the size of Si wire grating metasurfaces, determine the size of Si wire grating metasurface structures with high linear polarization extinction ratios at several key wavelengths. Step 2: Based on the extinction ratio curves corresponding to the preferred structural parameters of the Si wire grating metasurface obtained by scanning, determine the structural dimensions of the Si wire grating metasurface with high linear polarization extinction ratio at several key wavelengths in the mid-wave infrared. Step 3: Construct the photodetector structure and build a unit structure integrating the photodetector and the Si wire grating metasurface structure, including a three-layer structure. The three-layer structure mainly consists of the photodetector, SiO2, and the Si wire grating metasurface array from bottom to top. Based on the Si wire grating metasurface structure with high linear polarization extinction ratio at several key wavelengths determined in Step 2, the preferred Si wire grating metasurface structure is integrated on top of 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. Step 4: Based on the simulation analysis results of the integrated photodetector structure, the combination design of the three structural parameters of the Si wire grating metasurface structure—height, duty cycle, and period—is used to realize the linear polarization response of the metasurface structure. The dimensions of the Si wire grating metasurface structure with high linear polarization extinction ratio at several key wavelengths are determined to design an infrared polarization detector structure with narrowband spectral response. By changing the dimensional parameters of the Si wire grating metasurface structure, the absorption spectrum of the photodetector can be controlled, enabling the Si wire grating metasurface structure to have infrared polarization detection capability with narrowband spectral response.

2. The design method for a mid-wave infrared multispectral polarizer array of a Si-based metasurface structure as described in claim 1, characterized in that: Step one specifically includes the following steps: Step 1.1: Use simulation design software to model the structure of the Si wire grid metasurface. Its structure is a periodically arranged Si nanowire grid, and the structural parameters are periodic pitch, height H and duty cycle r. Step 1.2: Use the finite-difference time-domain method to perform range scanning optimization for each parameter, and obtain the transmittance of the Si wire grating metasurface structure for linearly polarized light in the TE and TM directions. Calculate the extinction ratio according to formula (1) and plot the wavelength-extinction ratio curve. First, fix the duty cycle and period parameters, and perform scanning optimization for the Si wire grating height parameter in the mid-wave infrared band. IS=T TE / T TM (1) Where ER is T TE T represents the linear polarization extinction ratio of the Si wire-gate metasurface. TM T represents the transmittance of the Si wire-gate metasurface structure for TM-polarized light. TE The transmittance of the Si wire-grid metasurface structure for linearly polarized light in the TE direction; Step 1.3: After determining the optimal result of the structural parameter height, fix the two parameters of height and period, and scan and optimize the parameter of Si grid duty cycle in the mid-wave infrared band. Step 1.4: After determining the optimal results of the height and duty cycle of the Si wire grating metasurface structure parameters, fix the two parameters of height and duty cycle, and perform a scanning optimization of the Si wire grating period parameter in the mid-wave infrared band.

3. The design method for a mid-wave infrared multispectral polarizer array of a Si-based metasurface structure as described in claim 1, characterized in that: The Si wire grating structure parameters with TM polarized light transmittance close to 1 and TE polarized light transmittance close to 0 at the selected wavelength were selected as the optimal results sought by the scan.

4. The design method for a mid-wave infrared multispectral polarizer array of a Si-based metasurface structure as described in claim 1, characterized in that: Based on the obtained extinction ratio curve, a polarization extinction ratio higher than 1000 was selected as the required high polarization extinction ratio, and the corresponding structural parameters were selected as the results of the Si wire grating metasurface structural parameter scanning optimization.

5. The design method for a mid-wave infrared multispectral polarizer array of a Si-based metasurface structure as described in claim 1, characterized in that: Based on the obtained absorptivity spectrum, the optimal distance between the metasurface and the detector is selected when the absorptivity is close to 80%.

6. The design method for a mid-wave infrared multispectral polarizer array of a Si-based metasurface structure as described in claim 1, characterized in that: Based on the obtained extinction ratio curve, the Si wire grating metasurface structure corresponding to the extinction ratio bandwidth of less than 100nm was selected and integrated with the photodetector structure to obtain a detector structure with narrowband spectral response. The extinction ratio bandwidth refers to the wavelength interval corresponding to the extinction ratio dropping to half of the peak extinction ratio.

7. The design method for a mid-wave infrared multispectral polarizer array of a Si-based metasurface structure as described in claim 1, characterized in that: The Si wire gate metasurface structure described in step one is constructed from a semiconductor material with a refractive index higher than 1.7, such as Si, Ge, or TiO2.

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