用于光束长焦深、超分辨聚焦调制的微光学元件设计及其曲面纳米压印加工技术研究

In this project, We design and fabricate complex amplitude filter micro-optics elements(MOE) aimed at the both extended focal depth and super-resolution focusing in laser direct writing technology. We develop a design model for complex amplitude filter in which cosine function is introduced to separate single focus into several focuses axially. Through adjustment of the focuses distribution on the axis, both extended focal depth and super-resolution focusing can be obtained by amplitude filter; soft nanoimprint lithography is employed to fabricate microstructure on curved surface, so that the complex amplitude filter can be integrated onto the surface of optic elements; We proposed an approach to predict the surface deformation of soft mould covered on curved surface, mainly by numerical iteration solution of nonlinear finite element analysis. And numerical result will be used in the mould design after being corrected by vision measurement. Thiol-ene is used as resist, because its curing occurs after its volume shrinkage. Therefore, the fabrication error caused by shrinkage can be compensated by the relaxation of resist in the residue layer. We will complete the design of complex amplitude filter which can be used to focus laser beam with focal depth longer than 10λand full width at half maximum of focus field wider than 0.38λ. Furthermore, we can integrated MOE onto the surface of lens and the replication error for MOE less thanλ/10.

以激光直写技术中的光束长焦深、超分辨聚焦为背景，开展曲面基底复振幅滤波器微光学元件的设计与加工研究。提出基于余弦函数复振幅滤波器设计模型，适量余弦函数调制环节的引入，将单一焦点在轴向分裂为多个焦点，合理调整各光点轴向分布，实现兼顾长焦深和超分辨聚焦要求的幅滤波器设计；利用柔性纳米压印技术，在光学曲面上构建微细结构，提高复振幅滤波器与传统光学镜组的系统集成度；通过基于非线性有限元分析的迭代求解方法，对柔性平面薄片压模的曲面铺覆变形进行预测，结合双目立体视觉的图像测量实验方法，对数值计算结果予以修正，从而在设计环节予以精确补偿；引入硫醇-烯作为压印胶，利用其固化滞后于体积收缩的特性，通过流动弛豫，对固化过程中体积收缩导致的形貌误差予以补偿。预期实现焦深长度优于10λ，聚焦光场的半高宽优于0.38λ的滤波器设计；及传统光学透镜与微光学元件的集成加工，微纳结构复制精度优于λ/10。

本项目以激光直写技术中的长焦深、超分辨聚焦光束为背景，对复振幅滤波实现超分辨聚焦和曲面基底的复振幅滤波器元件的设计和加工方法等开展了研究。对基于三角函数基滤波器的超分辨聚焦展开了研究。研究了光束振幅分布、涡旋相位对聚焦场的影响；研究了4Pi系统对超分辨聚焦的作用；并提出了一种全局快速优化算法；对曲面微结构加工方法进行了研究，并加工了透镜阵列和多环带波带片滤波器。同时还对表面等离子激发对亚波长聚焦的影响进行了研究。通过这些研究，确定了光束参数对于获得长焦深和亚波长超分辨聚焦的影响，对于正确选择聚焦系统和相应的光束参数具有重要意义；对于加工复杂曲面微结构元件提供了重要的理论和技术支持。