皮秒激光烧蚀Al膜的理论分析与实验验证

Abstract

In order to investigate the energy transport process in Al film irradiated by 10 ps lasers, a semi-classical two temperature model (TTM) was applied, and a 1D finite element calculation model was constructed with finite element software. Considering phase change region of material during laser ablation, reasonable expression was added to the TTM. According to the calculation, the surface lattice temperature evolutions along with time for single pulse lasers with different powers were presented. In order to investigate the surface plasma reflectivity and the heat absorption coefficient changing with lattice temperature during laser irradiation, the free-electron gas theory was applied. Moreover, the laser generated thermoelectric field and the electron drift velocity distribution map were depicted. The results verify that the thermoelectric field is the major reason for the electron drift movement, and the location of maximum velocity is changed with time. The spatial and temporal lattice temperature distribution map of Al film irradiated by 0.12 W picosecond laser was depicted. According to the calculation, the phase explosion is the reason for ablation, and it occurs during the process of laser energy deposition. The over-heated zone (OHZ) was defined, and the relationship between ablated depths and time was found. The calculated ablation depths of single pulses coincide with the experiment for 10 ps laser.