Numerical simulations of ultrashort laser pulse ablation and plasma expansion in ambient air

Using a self-consistent one-dimensional Cartesian Lagrangian fluid code, we modeled the ultrashort laser pulse ablation of solid aluminum and the subsequent plasma expansion in ambient air. A laser fluence of approximately 10 J/cm2 is considered. The code axial plasma temperature and density are strongly inhomogeneous and the maximum radiation emission generally occurs in the front of the plasma. The code average plasma temperature is in good agreement with the experiments for all times, while larger discrepancies with respect to the experiments are observed at late times for the plasma density. Experimental results are in reasonable agreement with the condition of thermodynamic equilibrium, which is an important assumption in the model.