Xu Shuai, Fan Hua, Xu Si-Jia, Li Zhen-Ze, Lei Yuhao, Wang Lei, Song Jun-Feng
State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, China.
State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instrument, Tsinghua University, Beijing 100084, China.
Nanomaterials (Basel). 2020 Sep 1;10(9):1737. doi: 10.3390/nano10091737.
The nanoresolution of geometric phase elements for visible wavelengths calls for a flexible technology with high throughout and free from vacuum. In this article, we propose a high-efficiency and simple manufacturing method for the fabrication of geometric phase elements with femtosecond-laser direct writing (FsLDW) and thermal annealing by combining the advantages of high-efficiency processing and thermal smoothing effect. By using a femtosecond laser at a wavelength of 343 nm and a circular polarization, free-form nanogratings with a period of 300 nm and 170-nm-wide grooves were obtained in 50 s by laser direct ablation at a speed of 5 mm/s in a non-vacuum environment. After fine-tuning through a hot-annealing process, the surface morphology of the geometric phase element was clearly improved. With this technology, we fabricated blazed gratings, metasurface lens, vortex Q-plates and "M" holograms and confirmed the design performance by analyzing their phases at the wavelength of 808 nm. The efficiency and capabilities of our proposed method can pave the possible way to fabricate geometric phase elements with essentially low loss, high-temperature resistance, high phase gradients and novel polarization functionality for potentially wide applications.
用于可见波长的几何相位元件的纳米分辨率需要一种具有高产量且无需真空的灵活技术。在本文中，我们通过结合高效加工和热平滑效应的优点，提出了一种利用飞秒激光直写（FsLDW）和热退火制造几何相位元件的高效且简单的制造方法。通过使用波长为343 nm的飞秒激光和圆偏振，在非真空环境中以5 mm/s的速度进行激光直接烧蚀，在50 s内获得了周期为300 nm且槽宽为170 nm的自由形式纳米光栅。经过热退火过程的微调后，几何相位元件的表面形貌得到了明显改善。利用这项技术，我们制造了闪耀光栅、超表面透镜、涡旋Q波片和“M”全息图，并通过分析它们在808 nm波长处的相位来确认设计性能。我们所提出方法的效率和能力可为制造具有基本低损耗、耐高温、高相位梯度和新型偏振功能的几何相位元件铺平道路，以实现潜在的广泛应用。
