A thermodynamic model of plasma generation by pulsed laser irradiation in vacuum

Abstract

This paper introduces a thermodynamic model to determine composition, temperature and pressure of the plasma cloud induced by pulsed laser irradiation in the case where a relevant thermal sputtering mechanism is operating at the surface of a molten layer. The model concerns in particular pulse lengths of the order of several nanoseconds and completes the results of a previous paper concerning the physics of the evaporation and boiling driven thermal sputtering (Tosto S 2002 J. Phys. D: Appl. Phys. 35); the recession rate and temperature at the molten surface are linked to the pulse fluence and plasma properties in the frame of a unique physical model. This paper shows that the plasma properties depend critically on the non-equilibrium character of the surface evaporation and boiling mechanisms. The extension of the model to the case of continuous laser irradiation is also discussed. Some examples of computer simulation aim to show the results available in the particular case of a metal target; the comparison between calculated and experimental data supports the validity of the model.

Observation of different mass removal regimes during the laser ablation of an aluminium target in air

“…However, because of the complex interplay of the matrix, ambient and experimental parameters, it is very difficult to draw an accurate picture of the process, which fits adequately the observations in all the situations. Most of the models presented in the literature tackle the issue of ablation in vacuum or at a low pressure background gas, [1][2][3] where the process is simplified by the absence of interactions between the laser beam and the induced plasma with the ambient gas atoms.…”