红外偏振成像在众多领域具有广泛应用。偏振片作为偏振成像系统中的核心器件，其性能好坏对系统成像指标具有决定性的影响。传统的偏振片具有体积大难集成、有效入射孔径角度较小并且在中长波红外波段应用较少等缺点。而金属线栅偏振片由于其体积薄易集成、具有宽入射角范围和宽工作波段等优点得到不断关注。但国内针对中长波红外波段的金属线栅偏振片研究较少且性能一般，商用线栅偏振片也被国外公司垄断。为了改变此种局面，因此亟需对中长波红外线栅偏振片的制作方案进行研究。本论文从红外线栅偏振片的仿真计算、加工制作、性能测试以及后期优化等各个方面依次进行展开。本论文首先采用等效介质理论和严格耦合波理论分析了金属线栅偏振片的偏振分光原理和衍射效率计算原理。再辅助COMSOL软件对偏振器的基本参数进行仿真，得出参数和偏振性能的变化趋势，为后续实验提供理论支持。通过搭建洛埃镜分波前干涉光刻光路和曝光光束监测系统，完成亚微米光栅掩模制作，避免采用电子束光刻方法导致制作成本高以及制作效率低的问题。通过对比湿法腐蚀、干法刻蚀和lift-off三种常用工艺方法，最终采用单层胶lift-off工艺成功制作出槽深为200nm的亚微米银金属线栅结构，避免采用干法刻蚀会生成不挥发产物以及湿法腐蚀各向同性严重的问题。最后采用傅里叶变换红外光谱仪完成样品的偏振性能测试。结果显示制备出的双层金属线栅偏振器相比Edmund同类型偏振片，在透过率水平相当时，其消光比从24.7dB（300:1）提升至27.5dB（560:1），工作波段从8~17μm扩展到3~15μm。在此基础上，为了进一步提升偏振片性能，提出基底刻穿、双面光栅和高深宽比光栅三种优化结构：①仿真得到基底刻穿结构可将平均透过率提升至96%左右；②通过样片对准，以及采用两次单层胶lift-off工艺制作出双面单层金属线栅偏振片，测试其在3~15μm波段平均消光比相比单面单层光栅提升了8.6dB；③提出采用干涉光刻、干法刻蚀和定向侧沉积的工艺方案制作高深宽比金属银线栅，通过高功率快速干法刻蚀以及设计特定角度镀膜夹具，制作出深宽比大于15的银线栅偏振片，实验证明此方案不受金属类型限制。经过测试双面线栅结构和高深宽比结构的相对透过率分别为134.0%和129.1%，相比双层金属线栅结构的相对透过率（104.6%）有了较大提升。
The infrared polarization imaging system has been widely applied in many fields. The performance of the polarizer has decisive effect on the imaging index, which is the core device in the polarization imaging system. Traditional polarizers have the disadvantages of large volume, difficult to integrate, small effective incident aperture angle and working waveband. While the metal wire grid polarizer (WGP) is proposed to be an effective device due to its thin volume for easy integration, wide operating band, wide range of incidence angle, and long-term stability. However, there are less researches on the WGP in mid and long-wave infrared waveband in our country. Commercial WGP are also monopolized by foreign companies with expensive price and without excellent performance. In order to change this situation, it is urgent to study the fabrication scheme of the mid and long-wave infrared WGPs. It was studied in this thesis including the structure design, fabrication process, performance test and post-optimization.In this dissertation, the polarization principle and diffraction efficiency calculation procedure of the subwavelength WGP were analyzed by equivalent medium theory (EMT) and rigorous coupled-wave theory (RCWT). The basic parameters of the polarizer were simulated using COMSOL software to provide the polarization performance trends and theoretical support for subsequent experiments. Then the Lloyd's mirror interferometer and exposure beam monitoring system were built to fabricate the sub-micron grating mask, which avoid the high cost and low efficiency of electron beam lithography. By comparing the wet etching, dry etching and lift-off micro-nano processing technology, the silver film submicron gratings with a depth of 200nm were successfully produced by single layer lift-off process, which solves the problem that dry etching process is difficult to be used for the non-volatile products and avoid the serious isotropic of wet etching. Finally, it was tested by fourier transform infrared spectrometer(FTIR) that the extinction ratio of the double layer WGPs increased from 24.7dB (300:1) to 27.5dB (560:1), and the working band increased from 8~17μm to 3~15μm compared to the same type of polarizer in Edmund.Based on the preliminary work, we proposed three optimized structures to improve the polarization performance, which were substrate through-cut, double-side grating and high-aspect-ratio grating: ①It was simulated that the structure of the substrate through penetration can increase the average TM-wave transmittance to about 96%. ②The double-sided single-layer WGPs were fabricated by alignment and lift-off process twice. The average extinction ratio of the double-sided single-layer grating was 8.6dB higher than that of the single-side single-layer grating in 3~15 m band. ③It was proposed that the processes of interference lithography, dry etching and directional side deposition can be used to fabricate high-aspect-ratio WGPs. It was confirmed that the gratings with an aspect ratio greater than 15 was fabricated by high RF power dry etching and specific angle coating fixture. And it was confirmed that this scheme can be applied to other type of metals.It was tested that the average relative transmittance of the double-sided single-layer WGPs and high-aspect-ratio WGPs in the 3 ~ 15μm band were 134.0% and 129.1%, which improved a lot compared to the double layer WGPs (104.6%).
