飞秒脉冲激光烧蚀金属的机理分析

Mechanism analysis of ablation of metal by femtosecond pulsed laser

为了深入理解超短脉冲激光烧蚀金属的机理,特别是烧蚀过程中靶面电子发射带来的影响,本文分析了飞秒脉冲激光烧蚀金属的机理,并在此基础上建立了一维热传导双温模型,模型考虑了电子热导率、热容、电子-晶格耦合系数等参数随温度的变化,以及表面热电子发射和多光子电离导致靶面的能量损失。选择波长为800 nm,FWHM为100 fs,峰值功率密度为1.2×10^(17) W/m^2的高斯型单脉冲激光辐照铜靶进行数值模拟。并对计算数据进行分析,结果表明:多光子电离所导致的电子发射比热电子发射要强,但是热电子发射持续的时间长;多光子电离导致的电子发射带走的靶面能量比较大,在分析飞秒烧蚀过程中不可忽略。

In order to understand the mechanism of metal ablation by ultrashort pulsed laser,especially the effect of electron emission from the target surface during ablation,the mechanism of the interaction between femtosecond pulse laser and metal material is theoretically analyzed in this paper,and based on this,an one-dimensional two-temperature model is established.In the model,many parameters changing with temperature are taken into account,such as thermal conductivity,heat capacity,electron-lattice coupling coefficient et al,as well as the energy loss caused by thermal electron emission and multiphoton ionization emission at the boundary.The ablation process of the copper target irradiated by a Gauss type single pulse laser with a peak power density of 1.2×1017 W/m2,a wavelength of 800 nm and FWHM of 100 fs is numerically simulated.The results show that the electron emission caused by multiphoton ionization is stronger than that of heat electron emission,but the duration of the thermal electron emission is longer;The energy loss of the electron emission caused by the multiphoton ionization is very high,which should not be ignored during the analysis of the femtosecond ablation process.