Superheating in liquid and solid phases during femtosecond-laser pulse interaction with thin metal film

Superheating of the liquid phase caused by non-equilibrium evaporation during femtosecond-laser processing of a thin metal film is investigated by adopting the wave hypothesis along with the two-temperature model. The simulation results show that the superheating in the liquid occurs shortly after the evaporation. For a 100-fs laser pulse of 0.7 J/cm², the maximum degree of superheating in liquid can reach 600 K. The superheating in solid can also be captured in the current model, which can be as high as 300 K. The effects of laser fluence, pulse duration and film thickness on the degree of superheating were studied. A higher laser fluence will increase the degree of superheating in liquid significantly but has little effect for the solid part. In the range adopted in the current work, the pulse duration has little effect on the degree of superheating in both liquid and solid phases.