面向全斯托克斯偏振成像的超表面像素式微偏振片阵列的研究

In recent development, polarimetric imaging of integrated with pixelated micro-polarizer arrays and CCD is a new type of integrated polarimetric imaging technology. Theoretically, full Stokes polarimetric imaging requires four polarization components, of which three polarization components are related to linear polarization and the fourth is circular polarization. Due to the lack of circular polarization dichroism devices that are highly efficient, highly selective and easily integrated, the existing integrated polarimetric imaging is limited to the detection of linear polarization components. In this project, we propose to study metasurface circular polarization dichroism devices for full-Stokes polarimetric imaging. Based on this technology, an overall design and fabrication of a pixelated micro-polarizer array will be achieved. The major works are as follows: (1) The mechanism of circular polarization dichroism of the metasurface, especially the physical mechanism and conditions of circular polarization dichroism (the difference transmission between left and right circular polarization light are greater than 70%) (2) The overall design and optimization scheme, which includes the relationship between the polarization performance of the circular polarization dichroism structures and the linear polarization structures with different structures, match of the interface layer material and the polarization state of the incident light. (3) The fabrication method of the circular polarization dichroism nanostructure, which to form a uniform fabrication process of wire grid microstructure and circular polarization dichroism microstructure and to provide the key technology and theoretical basis for truly integrated full Stokes polarimetric imaging on the one chip.

像素式微偏振片阵列与CCD集成的偏振成像是近年来发展的一种新型集成式偏振成像技术。理论上，全斯托克斯偏振成像需要四个分量，其中三个分量与线偏振有关，第四个与圆偏振有关。由于高效高选择性又易于集成的圆偏振光器件的缺乏，现有集成式偏振成像仅限于线偏振分量的探测。本项目提出和研究一种面向全斯托克斯偏振成像的超表面圆偏振二色性器件，并在此基础上实现像素式微偏振片阵列的全局性设计与制备。重点研究：（1）超表面圆偏振二色性的产生机理，特别是高选择圆偏振二色性（左右旋区分度大于70%）的物理机理和条件（2）像素式微偏振片阵列总体性设计优化方案，包括圆偏振二色性结构和线偏振结构的偏振性能与结构，界面层材料匹配、入射光偏振态等因素的关系（3）圆偏振二色性纳米结构实验制备工艺，形成微线栅结构和圆偏振二色性结构的统一性制备方法,为同一芯片上真正实现集成式全斯托克斯偏振成像提供关键技术和器件理论基础。

分焦平面偏振成像技术是近几年发展起来的一种集成微纳偏振器件与光电成像器件的新型偏振成像技术。该技术中焦平面CCD上的每一个像素单元都对应一个不同的微纳偏振元件，通过一次曝光就可获得目标的多种偏振分量信息，进而获得全斯托克斯偏振图像。该技术探测速度快，可用于快速目标的探测，不受探测目标和系统自身相互运动以及外界环境影响，是偏振成像技术的发展方向。然而高性能圆偏振二色性器件的缺乏，特别是能与线偏振器件兼容在同一个芯片上并能与CCD集成耦合的圆偏振二色性器件的缺乏，导致目前基本上还停留在线偏振分量的成像测量上。.该项目提出并研究了一种面向全斯托克斯偏振成像的超表面圆偏振二色性器件，重点研究了超表面圆偏振二色性的产生机理，特别是高选择圆偏振二色性的物理机理和条件,并在此基础上实现了像素式微偏振片阵列的全局性设计与制备。理论设计上，线栅偏振片在较宽的波段（1.47-1.70µm）对TM光的透过率接近100%，消光比（10log(TM/TE)）最低在20dB以上，最高可达到75dB。而圆偏振二色性器件在较宽的波段（1.49-1.61µm）平均圆二色性在75%以上。最后，研究了圆偏振二色性纳米结构实验制备工艺，形成线栅结构和圆偏振二色性结构的兼容性制备方法，完成了对像素式微偏振片阵列器件的制备。实验检测结果与理论设计结果匹配较好，全介质“Z”型圆偏振二色性器件在1.48-1.53µm的圆偏振二色性为55%，并且1.6µm波长处圆偏振二色性可达70%。实验得到该全介质光栅线偏振器件在1.47-1.55µm对TM光的透过率在80%左右，消光比可达20dB以上，同时在1.6µm波长处也接近20dB。因此该器件在1.48-1.53µm波段以及1.6µm，可以实现全斯托克斯偏振成像的要求。