GAS-FLOW DYNAMICS IN LASER ABLATION DEPOSITION

The gas flow dynamics of laser ablation plumes is investigated experimentally and theoretically. Experimentally, angular-resolved time-of-flight (ARTOF) measurements are performed on a model system (laser etching of copper in a chlorine environment). The TOF spectra obtained can be fitted by elliptical Maxwell-Boltzmann distributions on a stream velocity. Theoretically, an analytical model is constructed, based on the hydrodynamical problem of an expanding elliptical gas cloud. The model allows semiquantitative prediction of ARTOF distributions and angular intensity distributions. Observed trends in laser ablation deposition such as independence of the angular intensity distribution on mass of the atom and laser fluence, and dependence of the angular distribution on spot dimensions are explained.