Liu Dong, Chuansong Chen, Man Baoyuan, Meng Xue, Sun Yanna, Li Feifei
J Nanosci Nanotechnol. 2017 Feb;17(2):1287-295. doi: 10.1166/jnn.2017.12630.
Two kinds of laser-induced periodical structures observed on metal titanium plate irradiated by femtosecond laser (fs-laser) are reported, including the fs-laser-induced concentric rings and periodical subwavelength ripples. The rings can be produced only when the titanium target is located before the focal plane. The period and distribution of the rings stay almost fixable with the change of laser fluence and pulse number. The average cross section area (ACSA) is introduced to investigate the material removal behavior with the growth of the rings. The rings grow with the accumulation of laser pulses and the increase of the laser fluence, but the growth rate will be moderated with the increase of the pulse number. The ripples are obtained in an annular region when powerful multi-pulses irradiate on the target surface. The ripple period varies with laser fluence and location. And the annular region migrates outward when the laser fluence increases. We suggest that the formations of ripples are attributed to the propagation of the laser-stimulated surface plasma wave (SPW) on the air/ti interface. The dependence of the ripple period on the pulse fluence calculated by the SPW model agrees well with our experimental observation. The investigation improves the understanding of the two kinds of periodical surface structures both in their appearances and mechanisms.
报道了在飞秒激光（fs-激光）辐照的金属钛板上观察到的两种激光诱导周期性结构，包括fs-激光诱导的同心环和周期性亚波长波纹。只有当钛靶位于焦平面之前时才能产生同心环。同心环的周期和分布几乎不会随激光能量密度和脉冲数的变化而改变。引入平均横截面积（ACSA）来研究随着同心环的生长材料的去除行为。同心环随着激光脉冲的积累和激光能量密度的增加而生长，但生长速率会随着脉冲数的增加而减缓。当强多脉冲辐照在靶表面时，在环形区域会获得波纹。波纹周期随激光能量密度和位置而变化。当激光能量密度增加时，环形区域向外迁移。我们认为，波纹的形成归因于激光激发的表面等离子体波（SPW）在空气/钛界面上的传播。通过SPW模型计算得到的波纹周期与脉冲能量密度的关系与我们的实验观察结果吻合良好。该研究增进了对这两种周期性表面结构的外观和形成机制的理解。
