Ablation of aluminum thin films by ultrashort laser pulses

In this study, various results are presented for laser ablation experiments on aluminum and silicon, made in ambient air by means of subpicosecond laser pulses. These results include threshold fluences for plasma formation and for the appearance of various spectral lines, and the single shot fluence required to remove aluminum layers of various specific thicknesses (ranging from 10 to 500 nm) deposited on a silicon substrate. The threshold fluence for plasma formation is of the order of 0.1 J/cm(2). Threshold fluences for the appearance of the spectral lines considered vary from 0.1 to about 5 J/cm(2). Finally, our results suggest that for high fluences, even for ultrashort laser pulses, the ablation depth is essentially determined by a long-range process, such as thermal conduction in the solid, rather than by the short range optical depth. (C) 2001 American Institute of Physics.