飞秒激光正交线扫描诱导表面微纳结构

通过控制激光偏振与扫描方向,利用飞秒脉冲激光正交线扫描的微加工方式,在硅和不锈钢表面诱导出了规则分布的复合表面微纳结构并分析了激光能量密度对微纳表面结构形成的影响。实验显示:当激光的能量密度接近材料烧蚀阈值时,在硅表面诱导出了周期条纹嵌套纳米孔的双层复合二维结构,在不锈钢表面则诱导出了依赖于激光偏振方向的纳米点阵列分布,分析认为纳米点阵列是由周期条纹结构边缘发生断裂而生成的。另外,当激光的能量密度大于材料烧蚀阈值时,在硅和不锈钢表面会烧蚀出规则分布的微米级孔洞结构。实验结果表明:第一次扫描诱导出的表面微纳结构增加了对入射激光的吸收,促进入射激光与表面等离子体波的耦合,加强了后扫描的烧蚀效果,使得后扫描诱导出的微纳结构占主导。文中提出的正交线扫描的加工方式为微纳表面结构的制备提供了新的思路。

Femtosecond laser induced surface micro-and nano-structures by orthogonal scanning processing

With controlling the femtosecond (fs) laser polarization and scanning direction, the regular distribution of composite micro/nano structures was induced on the surfaces of silicon and stainless steel by Orthogonal Line Scanning Processing (OLSP). The influence of laser fluence on the micro/nano structures was studied. The experimental results show that two-dimensional (2D) composite structures nested with periodic ripples and nanoholes are induced on the silicon wafer surface, however, nanorod arrays at the edge of scanning area are induced on the stainless steel surface when the laser fluence is close to the material ablation threshold. The analysis indicates that the nanorod arrays are formed by the fracture of periodic ripples. Moreover, when laser fluence is higher than the ablation threshold, the regular distribution of micro hole structures is induced both on the surfaces of silicon and stainless steel. The experimental results demonstrate that the micro/nano structures induced by the first line scanning enhances its laser absorption and promotes the coupling between the incident fs laser and the surface plasma wave, so that the ablation of the second scanning is enhanced and the later structures induced by the second scanning becomes a dominating. In conclusion, the OLSP provides a new approach for fabrication of surface micro/nano structures.