Xu Shuai, Fan Hua, Li Zhen-Ze, Hua Jian-Guan, Yu Yan-Hao, Wang Lei, Chen Qi-Dai, Sun Hong-Bo
Opt Lett. 2021 Feb 1;46(3):536-539. doi: 10.1364/OL.413177.
We systematically studied femtosecond laser-inscribed self-organized nanogratings and geometric phase elements such as a polarization diffraction focusing lens and Q-plate in sapphire crystal. Besides the void structures observed in the focus, nanogratings with periods of 150~300 nm were observed, depending on a nanoslit that took the role of a seeding effect by localized light field enhancement. The non-polarized refractive index change and birefringence were measured with values around 1∼2×10 and 6×10, respectively. Based on the laser-inscribed form birefringence, a geometric phase lens and Q-plate were successfully demonstrated in sapphire with high imaging and a focusing effect. We expect that our findings may promote the understanding of laser-induced nanogratings in bulk and potential applications in geometric phase elements.
我们系统地研究了飞秒激光写入的自组织纳米光栅以及蓝宝石晶体中的几何相位元件，如偏振衍射聚焦透镜和Q波片。除了在焦点处观察到的空洞结构外，还观察到周期为150~300 nm的纳米光栅，这取决于一个纳米狭缝，该纳米狭缝通过局部光场增强起到种子效应的作用。测量了非偏振折射率变化和双折射，其值分别约为1∼2×10和6×10。基于激光写入的形状双折射，在蓝宝石中成功展示了具有高成像和聚焦效果的几何相位透镜和Q波片。我们期望我们的发现可能会促进对体材料中激光诱导纳米光栅的理解以及几何相位元件的潜在应用。
