基于矢量光衍射理论的低偏振光学薄膜的研究

According to National Outline for Medium and Long Term Science and Technology Development, the large –numerical- aperture (LNA) optical systems with polarization-sensitive property have gradually attracted intensive attention. In LNA polarized systems, the inappropriate design of optical coating can disturb the original polarization property of the incident light field and induce extra polarization aberrations. Meanwhile, such systems are always characterized in optical surfaces with large curvatures, resulting in homogeneous problem of coating deposition. In this project, based on vectorical diffraction theory, the model of coating induced polarization aberrations in the LNA system is established. We further propose a method to optimize the diattenuation and retardance of coating. In this way, the coating induced polarization variation is simultaneously concerned with residual polarization of the optical system, and the coating design with that of the optical system to mutually compensate the aberrations is integrated. The deposited properties of coatings on large curvature substrates by ALD are comprehensively considered, and the optimized parameters are determined. With the parameters, the database included the relationship between substrate curvatures and deposited parameters is established. Thereafter, in relatively simple experiment condition of ALD, we plan to fabricate the low polarization aberrations coating with low optical loss on LNA system. By establishing test systems, the sizes of focal spot along radial and axial directions are measured, and polarization properties of coating are evaluated.

国家中长期科学和技术发展的需求中，各类偏振敏感的大数值孔径光学系统逐渐成为研究的重点和热点。大数值孔径偏振光学系统中，不合理的光学薄膜设计将明显扰动入射光场的偏振特性，引发额外的偏振像差。同时，此类光学系统较大的曲率，对薄膜制备的均匀性也带来了较大挑战。本项目基于矢量光衍射理论，构建大数值孔径光学系统中光学薄膜诱导偏振像差的模型，将薄膜诱导的光场偏振态改变与光学系统的残余偏振相结合，对薄膜诱导的偏振分离和位相延迟进行优化设计，实现光学系统和光学薄膜偏振像差的整合设计和相互补偿。在实验方面，摸索大曲率基板上，原子层沉积的优化工艺参数，建立基板曲率与原子层沉积参数关系的数据库。利用原子层沉积,在较为简单的沉积条件下,实现大曲率或大面积基板表面，高均匀性、低损耗的低偏振像差光学薄膜的制备。搭建测试系统,对镀膜前后系统聚焦光斑轴向和径向特征尺寸的进行测量,完成对光学薄膜偏振特性的评价。

利用Debye矢量光衍射理论，建立了光学薄膜各参量与光学系统聚焦光场的模型，对薄膜诱导偏振像差对的光学系统聚焦光场的扰动进行了理论研究。在此基础上，探讨了应用了不同约束条件下得到的光学薄膜对最终聚焦光场的影响，确定了减小薄膜扰动光学系统光斑的设计方法。相比于普通减反膜而言, 对系统聚焦光场中心强度的提升可达约12.5%。在此基础之上，开展了矢量光衍射理论在位相编码技术中的拓展应用研究，对不同振幅编码条件对于受激发射抑制超分辨显微技术中抑制光形成中空聚焦光斑聚焦质量的影响的研究。采用边缘光进行光束整形，使STED（Stimulated Emission Depletion）显微系统分辨率提高约20%。理论分析的基础之上，进行了压缩透镜球差的光学薄膜的研究方面，建立波前差和入射角之间的函数关系后，对波前差进行离散化处理，针对数个离散区间，分别优化设计相应的膜系。实现对单透镜的球差优异的补偿，将波前差压缩近43%。 原子层沉积实验方面，大曲率基板上原子层沉积光学薄膜的实验研究方面，通过对反应腔内部脉冲与清洗时间内的气体源的传输过程进行了数值分析，确定了优化沉积区间。在此基础上，开展了原子层沉积光学薄膜的实验研究。低偏振光学薄膜的实验测试方面，搭建了测试系统，对优化前后的二色镜进行了测试。通过分析经过优化前后二色镜对激光光束聚焦光斑的影响，评估了使用低偏振二色镜对于光束偏振状态的保偏作用。