Femtosecond-laser-induced spallation in aluminum

Ultrashort laser pulses having 50 fs duration were used to cause planer fracture, i.e., spallation, in pure aluminum foils at intensities of (0.07–1)×1015 W/cm2. A linear relationship was obtained between spall depth and foil thickness, approximately corresponding to the proportions that were obtained in other relations for 300 ps and longer laser pulse irradiation. Spall thicknesses less than 5 μm were obtained in foils thinner than 50 μm, and revealed small-scale spallation at a strain rate exceeding 108 s−1. This ultrashort laser pulse evidently produced a shock wave followed by a steep unloading stress profile.