Study on Ultra-Short Laser Pulse Ablation of Metals by Molecular Dynamics Simulation

摘要

The dynamical progresses involved in ultra-short laser pulse ablation of face-centered cubic metals under stress confinement condition are described completely using molecular dynamics method. The laser beam absorption and thermal energy turning into kinetics energy of atoms are taken into account to give a detailed picture of laser metal interaction. Superheating phenomenon is observed, and the phase change from solid to liquid is characterized by a destroyed atom configuration and a decreased number density. The steep velocity gradients are found in the systems of Cu and Ni after pulse in consequence of located heating and exponential decrease of fluences following the Lambert-Beer expression. The shock wave velocities are predicted to be about 5000m/s in Cu and 7200m/s in Ni. The higher ablation rates are obtained from simulations compared with experimental data as a result of a well-defined crystalline surface irradiated by a single pulse. Simulation results show that the main mechanisms of ablation are evaporation and thermoelastic stress due to located heating.