An axisymmetric interfacial tracking model for melting and resolidification in a thin metal film irradiated by ultrashort pulse lasers

A two dimensional axisymmetric, interfacial tracking method is developed to model rapid melting and solidification of a free standing metal film subjected to an ultra-short laser pulse. Finite volume method is employed to solve the coupled electron and lattice heat conduction equations together with the equations for ultrafast solid–liquid phase transformation, to calculate the location of solid–liquid interface and the temperature distribution in the metal film. The interfacial velocities, both melting and resolidification, in the ultra-fast phase change process are obtained by considering interfacial energy balance and the nucleation dynamics. Both the electron and lattice temperature in the metal film irradiated by Gaussian laser beams are computed and presented along the cylindrical coordinates. The effect of laser fluence and beam radius on melting and resolidification are also investigated. The results show that higher laser fluence leads to faster and deeper melting. With the distance to the center of the beam increasing, the melting depth reduces. In the early time of laser heating, larger beam radii with the same fluence will not cause higher electron temperature at the beam center but will lift the temperature in nearby area.