Ultrafast thermalisation dynamics in an Au film excited by a polarization-shaped femtosecond laser double-pulse

We theoretically investigated the ultrafast non-equilibrium thermalisation dynamics in an Au film irradiated by a polarization-shaped femtosecond laser double-pulse. A non-equilibrium thermal relaxation model is proposed to study the relevance of the polarization of the double-pulse energy that couples to the Au film target. The phonon temperature can be greatly increased by optimizing double-pulse polarization combinations. The results are explained by an enhanced laser energy coupling with the Au film due to a synergetic effect arising from pulse-to-pulse polarization relevance. The study provides a basis for understanding ultrafast thermalisation dynamics for optimizing laser micro- and nano-fabrications by tailoring the polarization state of temporally shaped femtosecond lasers.