Guo Hanming, Weng Xiaoyu, Jiang Man, Zhao Yanhui, Sui Guorong, Hu Qi, Wang Yang, Zhuang Songlin
Engineering Research Center of Optical Instrument and System, Ministry of Education, Shanghai Key Lab of Modern Optical System, School of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, 516 Jungong Rd, Shanghai 200093, China.
Opt Express. 2013 Mar 11;21(5):5363-72. doi: 10.1364/OE.21.005363.
When the pupil filters are used to improve the performance of the imaging system, the conversion efficiency is a critical characteristic for real applications. Here, in order to take full advantage of the subwavelength focusing property of the radially polarized higher-order Laguerre-Gaussian (LG) beam, we introduce the multi-zone binary phase pupil filters into the imaging system to deal with the problem that the focal spot is split along the z axis for the small size parameter of the incident LG beam. We provide an easy-to-perform procedure for the design of multi-zone binary phase pupil filters, where the zone numbers of π phase are uncertain when the optimizing procedure starts. Based on this optimizing procedure, we successfully find the set of optimum structures of a seventeen-belt binary phase pupil filters and generate the excellent focal spot, where the depth of focus, the focal spot transverse size, the Strehl ratio, and the sidelobe intensity are 9.53λ, 0.41λ, 41.75% and 16.35% in vacuum, respectively. Most importantly, even allowing the power loss of the incident LG beam truncated by the pupil of the imaging system, the conversion efficiency is still as high as 37.3%. Theoretical calculations show that we succeed to have sufficient conversion efficiency while utilizing the pupil filters to decrease the focal spot and extend the depth of focus.
当使用光瞳滤波器来提高成像系统的性能时，转换效率是实际应用中的一个关键特性。在此，为了充分利用径向偏振高阶拉盖尔 - 高斯（LG）光束的亚波长聚焦特性，我们将多区域二元相位光瞳滤波器引入成像系统，以解决由于入射LG光束的尺寸参数较小，焦斑沿z轴分裂的问题。我们提供了一种易于执行的多区域二元相位光瞳滤波器设计程序，在优化程序开始时，π相位的区域数量是不确定的。基于此优化程序，我们成功找到了一组十七带二元相位光瞳滤波器的最佳结构，并生成了出色的焦斑，在真空中，焦深、焦斑横向尺寸、斯特列尔比和旁瓣强度分别为9.53λ、0.41λ、41.75%和16.35%。最重要的是，即使考虑到成像系统光瞳截断入射LG光束所造成的功率损失，转换效率仍高达37.3%。理论计算表明，我们在利用光瞳滤波器减小焦斑并扩展焦深的同时，成功获得了足够的转换效率。
