短脉冲激光刻蚀加工铜材料的机制

Mechanism of ablation in short-pulse laser-copper target interaction

利用数值模拟方法，研究波长1064nm、脉冲宽度介于1～20ps的激光在刻蚀铜靶时，单次脉冲作用下非平衡场刻蚀和热平衡刻蚀两种机制的竞争过程。结果表明：随着脉冲宽度的增加，刻蚀过程由非平衡电荷分离场刻蚀占主导地位转变为热平衡刻蚀起主要作用，且脉冲宽度和激光峰值功率密度增大到一定程度后，各种电子加速机制在不同时刻开始突显，电子能量分布出现多峰结构。在能量密度为15J／cm^2的激光作用下，1和5ps脉宽对应的非平衡场刻蚀深度分别为110和101nm，10和20ps脉宽分别为25和18nm。

Using 1D MED101 code, the competition mechanism between nonequilibrium electrostatic field ablation and thermal equilibrium ablation was analyzed when the pulsed laser with wavelength 1 064 nm, pulse duration 1-20 ps, ablated copper in vacuum. Numerical simulation results revealed that when the pulse duration was short（1 -5 ps）, the nonequilibrium electrostatic field ablation occupies the ablation process, and that when the pulse duration become longer（10-20 ps）, the thermal equilibrium ablation is the main process in the whole ablation. It also demonstrates that the maximum temperature of electrons versus time will have multi-peaks as the pulse duration and peak power density increase. Especially, the ablation depths of the nonequilibrium electrostatic field are 110 nm and 101 nm for pulse duration 1 ps and 5 ps respectively, 25 nm and 18 nm for pulse duration 10 ps and 20 ps respectively under the energy fluenee 15 J/cm^2.