Multiscale modeling of phase changes during femtosecond laser metal interaction

A multiscale model is developed to study the femtosecond laser single pulse and pulse train processing of metal films. In our model, molecular dynamics simulation combined with the improved two-temperature model is employed in the ablation area and the improved two-temperature model is applied in the heat-affected zone. This paper extends the improved two-temperature model to describe higher laser fluence processing by including phase change consideration. The phase change mechanisms of the non-equilibrium thermal melting and vaporization are both analyzed, which has a strong impact on the lattice temperature prediction. The model can simulate the phase change process of gold with higher accuracy. It is demonstrated that a pulse train could improve the fabrication accuracy, repeatability, and controllability.