Heat transfer in femtosecond laser ablation of metal
The short time-scales and high intensities obtained during femtosecond laser irradiation of metals require
that heat transfer calculations take into account the non-equilibrium that exists between electrons and the lattice
during the initial laser heating period. Thus, two temperature fields are necessary to describe the process –the electron and the lattice temperature. In this work, the parabolic two step model is solved numerically to predict
heating, melting, and evaporation of metal under femtosecond laser irradiation. Kinetic relations at the phase-change
interfaces are included in the model. The numerical results show close agreement with experimental melting threshold fluence data. Further, it is predicted that the solid phase has a large amount of superheating and that a distinct melt phase develops with duration of the order of nanoseconds.