Wang Fei, Zhao Bo, Lei Yuhao, Yang Jianjun, Guo Chunlei
Opt Lett. 2020 Mar 15;45(6):1301-1304. doi: 10.1364/OL.382322.
We report on producing unprecedentedly uniform periodic structures on chromium thin films in vacuum conditions with irradiation of femtosecond laser pulses. In sharp contrast to the observations in air, the achieved surface structures of the ablated groove arrays are surprisingly found to have not only an extraordinarily uniform distribution but also a deep-subwavelength period of 360 nm. The measured both width and depth of the ablated periodic grooves are 150 and 120 nm, respectively, showing a large depth-to-width ratio and sharp-edge profiles. Remarkably, such well-organized nanostructures can be enabled to robustly extend into an infinitely long range via the sample scanning and even have a large-area production with a cylindrical lens. Raman spectral analyses reveal that the regular formation of such nanostructures benefits from avoiding the material oxidation and thermal disturbance of the air plasma on the sample surface.
我们报道了在真空条件下，通过飞秒激光脉冲辐照在铬薄膜上制备出前所未有的均匀周期性结构。与在空气中的观察结果形成鲜明对比的是，令人惊讶地发现，烧蚀凹槽阵列所形成的表面结构不仅具有极其均匀的分布，而且具有360纳米的深亚波长周期。所测量的烧蚀周期性凹槽的宽度和深度分别为150纳米和120纳米，显示出大的深宽比和尖锐的边缘轮廓。值得注意的是，通过样品扫描，这种组织良好的纳米结构能够稳健地延伸到无限长的范围，甚至可以使用柱面透镜进行大面积生产。拉曼光谱分析表明，这种纳米结构的规则形成得益于避免样品表面的材料氧化和空气等离子体的热干扰。
