Chemical etching mechanisms and crater morphologies pre-irradiated by temporally decreasing pulse trains of femtosecond laser
Chemical etching mechanisms and crater morphologies pre-irradiated by temporally decreasing pulse trains of femtosecond laser
复制标题
飞秒激光暂时减少脉冲串预照射的化学蚀刻机制和凹坑形态
DOI：
10.1016/j.apsusc.2018.10.272
复制
发表时间：
2019
影响因子：
6.7
通讯作者：
Lu Yongfeng
中科院分区：
文献类型：
--
作者：
Du Kun;Jiang Lan;Li Xiaowei;Zhang Hao;Wang Andong;Yao Zhulin;Pan Changji;Wang Zhi;Li Ming;Grigoropoulos Costas P.;Lu Yongfeng
我们报告了暂时减少的脉冲序列对熔融石英的飞秒激光诱导化学蚀刻（FLICE）的影响。对用于 FLICE 的飞秒激光的不成形脉冲和递减脉冲序列进行了系统比较，并使用等离子体模型解释了差异。结果表明，减少脉冲序列不仅影响刻蚀效率，而且影响刻蚀坑的形貌。当通过减少脉冲序列预辐照蚀刻坑时，它在蚀刻过程的早期阶段呈现漏斗状形状，这与通过非整形脉冲预辐照的坑形成对比。在蚀刻过程的后期，漏斗状形状逐渐消失，凹坑尺寸增大。与相同加工条件下的未整形脉冲相比，减少的脉冲序列使蚀刻坑体积增加了约18倍。基于等离子体模型的理论计算表明，在最初的几百飞秒内，使用未成形脉冲产生的自由电子密度远高于样品皮肤层中减少的脉冲序列产生的自由电子密度。高自由电子密度增加了样品皮层的反射率；因此，入射脉冲的尾部被强烈反射。因此，沉积到熔融石英样品中的激光能量减少，最终导致蚀刻效率低。
We report the influence of temporally decreasing pulse trains on femtosecond laser-induced chemical etching (FLICE) of fused silica. A systematic comparison of the unshaped pulse and decreasing pulse trains of femtosecond laser for FLICE was conducted, and the differences were interpreted using a plasma model. The results revealed that the decreasing pulse trains not only affected the etching efficiency but also affected the morphology of the etched crater. When an etched crater was pre-irradiated by decreasing pulse trains, it presented a funnel-like shape at the early stage of the etching process, which contrasted with the one pre-irradiated by unshaped pulse. At the later stage of the etching process, the funnel-like shape gradually disappeared, and the crater increased in size. Compared with the unshaped pulse under the same processing conditions, the decreasing pulse trains enhanced the etched crater volume by approximately 18 times. Theoretical calculations based on the plasma model indicated that the free-electron density generated using the unshaped pulse was much higher than that generated by the decreasing pulse trains in skin layer of the sample during the first few hundred femtoseconds. The high free-electron density increased the reflectivity in skin layer of the sample; thus, the tail part of the incident pulse was strongly reflected. Consequently, the laser energy deposition into the fused silica sample decreased, eventually led to a low etching efficiency.