LASER-INDUCED VAPORIZATION OF A METAL-SURFACE

The laser-induced vaporization process of a metallic surface is incorporated into a simple model which describes the phase transformation and the expansion of the metal vapour against the ambient air as a function of the laser intensity and material properties. It is shown that there exists a material-dependent minimal laser intensity, where the vapour properties at the vaporization front become independent from further expansion against the ambient gas. This laser intensity is called critical intensity and also depends on the beam waist at the vaporization front. To check the model, a comparison with an experimental situation is performed, where a metal surface is irradiated by a Nd:YAG laser beam. The position of a shock front coming from the vaporizing metal surface were detected and compared with the calculated position.