  Using a modified self-consistent one-dimensional hydrodynamic lagrangian
fluid code, laser ablation of solid copper by ultrashort laser pulses in vacuum
was simulated to study fundamental mechanisms and to provide a guide for
drilling periodic microholes or microgratings on the metal surface. The
simulated laser ablation threshold is a approximate constancy in femtosecond
regime and increases as the square root of pulse duration in picosecond regime.
The ablation depth as a function of pulse duration shows four different regimes
and a minimum for a pulse duration of ~ 12ps for various laser fluences. The
influence of laser-induced plasma shielding on ablation depth is also studied.
