Hu Kailin, Guo Ziyue, Cao Tao, Liu Shaozhen, Liu Zhihong, Li Zhou, Xu Qi, Chen Kun, Peng Jiahui
Opt Express. 2022 Mar 14;30(6):8949-8958. doi: 10.1364/OE.449608.
By studying the nonlinear absorption of ultrafast laser pulses in fused silica, we examine, both with experiments and numerical simulations, the different polarization dependence of multiphoton ionization and avalanche ionization. Results show multiphoton ionization and avalanche ionization play different roles in femtosecond and picosecond laser micromachining, and the contribution via avalanche ionization increases with pulse duration. Meanwhile, the spatial distribution of the free carriers generated by circularly polarized pulses is more concentrated than those generated by linear polarization for picosecond laser pulses. These properties make the circular polarized ultrafast laser a possible way to improve the ultrafast laser micromachining efficiency and spatial quality, and can help to reduce some problematic nonlinear effects in ultrafast laser micromachining of low energy band materials.
通过研究飞秒激光脉冲在熔融石英中的非线性吸收，我们通过实验和数值模拟研究了多光子电离和雪崩电离的不同偏振依赖性。结果表明，多光子电离和雪崩电离在飞秒和皮秒激光微加工中发挥着不同的作用，并且通过雪崩电离的贡献随着脉冲持续时间的增加而增加。同时，对于皮秒激光脉冲，圆偏振脉冲产生的自由载流子的空间分布比线偏振产生的自由载流子的空间分布更集中。这些特性使得圆偏振超快激光成为提高超快激光微加工效率和空间质量的一种可能途径，并且有助于减少低能带材料超快激光微加工中一些有问题的非线性效应。
