偏振光飞秒双脉冲微加工

利用具有纳焦能量、高重复频率的偏振光飞秒双脉冲对金属铬膜样品进行微加工,样品表面都会产生微突起状结构,它们的宽度在0～400 ps的双脉冲时延范围内没有明显的变化,但高度却都在1～10 ps的双脉冲时延范围内呈现明显的下降,在此时延范围之外并没有明显的变化。通过加工样品的扫描电子显微镜(SEM)图片发现,对于偏振光,利用双脉冲方法,可以获得更好的加工质量。并且线偏振光得到的微突起状结构比较细长,在入射光束的偏振方向上有所伸长;圆偏振光得到的微突起状结构比较接近圆形。即在低脉冲能量、高重复频率情况下,具体的微加工特征形貌与入射光束的偏振状态有关。

Microbump structures were formed on the sample surface after micromachining the Cr films by polarized femtosecond double pulses with nanojoule energy and high repetition rate. Although the widths of the microbumps have no obvious variation among the 0-400 ps double pulses delay, the heights of them exhibit an obvious drop among the 1-10 ps double pulses delay and have no obvious variation beyond this delay. It is helpful to understand the electron-phonon coupling process in metal film during femtosecond laser micromaching. Furthermore, better micromachining quality was acquired with double pulses method for both linearly and circularly polarized light according to the scanning electronic microscope (SEM) images. Contrast to nearly circular microbumps fabricated by circularly polarized light, the microbumps fabricated by linearly polarized light is narrow and stretched in the direction of polarization of the incident beam. Namely, the micromachining feature is related to the polarized state of the incident beam with low pulse energy and high repetition rate.