LASER-INDUCED PLASMA FORMATION DURING PULSED-LASER DEPOSITION

The ablation of Al2O3 by CO2 laser radiation is investigated both theo retically and experimentally. The model connects the laser-induced pha se transition from condensed to vaporized state of the target and the dynamic of the emerging process plasma. The plasma is described in a t wo-fluid approximation by use of non-dissipative gas-dynamical equatio ns incorporating absorption of laser radiation in the plasma and the d ynamic of its ionization state. In the experimental part, the geometry of the luminous process plasma above the target at different instance s is detected and the weight loss of the target as a function of the f luence is measured. At an Ar-base pressure below 1 mbar, both calculat ed and measured results reveal that there exist two zones in the proce ss plasma: one which is directly attached to the target surface throug hout the whole process, and another which is recognized as an outward moving shock front. Further, it is seen from both approaches that, due to absorption of laser radiation by the plasma, the weight loss has a local maximum.