Xie Hongbo, Zhao Bo, Lei Yuhao, Yu Zhi, Cheng Jinluo, Yang Jianjun
Opt Express. 2021 Sep 27;29(20):31408-31417. doi: 10.1364/OE.433035.
Elucidation of the underlying physics for laser-induced periodic surface structures (LIPSSs) is of great importance for their controllable fabrication. We here demonstrate a periodic structure transition from normal to anomalous morphology, upon femtosecond laser irradiation on 50-nm thick Cr/Si films in an air pressure-tunable chamber. As the air pressure gradually decreases, the amount of surface oxide induced by preceding laser pulses is found to reduce, and eventually triggering the structure evolution from the anomalously oriented subwavelength to normally oriented deep-subwavelength LIPSSs. The intriguing structure transition is explained in terms of the competitive excitation between the transverse-electric scattered surface wave and transverse-magnetic hybrid plasmon wave, which is ruled by the thickness of the preformed oxide layer indeed.
阐明激光诱导周期性表面结构（LIPSSs）的潜在物理机制对于其可控制造至关重要。我们在此展示了在气压可调腔内对50纳米厚的Cr/Si薄膜进行飞秒激光辐照时，周期性结构从正常形态到反常形态的转变。随着气压逐渐降低，发现先前激光脉冲诱导的表面氧化物数量减少，并最终引发结构从反常取向的亚波长LIPSSs向正常取向的深亚波长LIPSSs演变。这种有趣的结构转变是根据横向电散射表面波和横向磁混合等离子体波之间的竞争激发来解释的，而这实际上是由预先形成的氧化层厚度所决定的。
