On pulsed laser ablation of metals: comparing the relative importance of thermal diffusion in the nanosecond-femtosecond regime

A comparative study is presented, alongside results of controlled production of sub-micron periodic surface structures in metals using a (ns) copper vapor laser. These findings demand careful consideration of the thermal diffusion process. By considering the energy deposition per unit volume u, a useful categorization of pulsed laser ablation of metals can be made. Within this framework, the relative advantages of fs vs. ns lasers are assessed, and it is shown that the degree energy deposition u defines different processing windows for different applications. Specifically, in the regime of explosive ablation, the thermal characteristics of fs and ns ablation are shown to be similar, in line with experimental results.