Effect of the dielectric transition on laser-induced phase explosion in metals

Phase explosion is an explosive liquid to vapor phase change that occurs during laser ablation as the surface approaches 90% of the thermodynamic critical temperature (0.9Tc), which is the upper limit of superheating. Large variations in properties are expected to occur near 0.8Tc, transforming the electrically conductive metal into a nearly transparent dielectric, an effect that has been neglected in previous models of laser ablation. The work presented in this paper numerically investigates the possible effect of the dielectric transition using a one dimensional heat transfer model. The results show that accurate knowledge of the absorption coefficient above 0.8Tc is critical for predicting the laser fluence at which phase explosion occurs.