Conditions for femtosecond laser melting of silicon

Conditions defining melting fluence thresholds for silicon under pulsed laser irradiation are introduced in this paper. The melting conditions include both thermal and non-thermal contributions. Furthermore, a definition of the non-thermal melting threshold is given as the laser fluence above which the non-thermal contribution dominates over the thermal one and a short-lived non-thermal liquid phase appears in the femtosecond time scale. Numerical values of thresholds obtained through a two-temperature model are in good agreement with experimental data. The dependence of fluence thresholds on both wavelength and pulse width is explored and discussed in detail.