采用可调节延迟、共线的双束飞秒激光脉冲列烧蚀ZnO表面,验证随着延迟时间的变化,其表面周期波纹结构的转变及结构转变的机理。在ZnO表面上可以分别观察到低空间频率的周期波纹结构(LSFL)和高空间频率的周期波纹结构(HSFL)。随着延迟时间的增加,发现低空间频率的周期波纹结构开始向高空间频率的周期波纹结构转变的现象。利用电子产生的速率方程分别去计算由800 nm激光和400 nm激光辐照所激发的电子密度。最终的计算结果结合Sipe理论可以对该现象的发生进行解释。该研究表明,可以通过可调节延时的双束激光脉冲列来控制激发的电子水平从而改变飞秒激光辐照在材料表面诱导的周期波纹结构。

In this paper, ZnO surface is ablated by an adjustable time-delay dual-pulse train with a repetition rate of 1kHz, produced by collinear two beams. Low-spatial-frequency LIPSS (LSFL) and high-spatial-frequency LIPSS (HSFL) are respectively observed and LSFL switches to HSFL with increasing delay time. Rate equations of electron generation are used to calculate electron density irradiated respectively by 800 nm and 400 nm femtosecond laser. By combining Sipe theory, morphology transition phenomenon is explained. The research proves that we can control the excited electron level to change the LIPSS morphology by an adjustable time-delay double femtosecond pulses.