The dominant mechanism of gold film damage induced by near-threshold femtosecond laser: Non-thermal deformation or thermal ablation

Near-threshold femtosecond laser produces nanostructures on the gold film, which has received much attention in applications. However, the theoretical researches on the early stage of gold film excitation induced by the femtosecond laser are scarce, because of the ultrafast and non-equilibrium characteristics. In this study, stress and temperature distributions in different thicknesses of gold film induced by the near-threshold fluences were calculated. At the fluence below the melting threshold, we found that only the 30 nm gold films might be damaged by the non-thermal deformation. At the fluence of the melting threshold, the dominant damage mechanism shifted from non-thermal deformation to thermal melting as the gold film thickness increased. Our study provided a way to distinguish the dominant damage mechanism of gold film and it was valuable for the theoretical study of near-threshold processing.