Ablation of aluminum with GHz bursts of temporally stitched laser filaments

Ablation of aluminum by ultra-high repetition rate trains of ultrashort pulses is investigated using bursts of up to 32 150 fs pulses with sub-nanosecond inter-pulse delays generated by a custom titanium:sapphire-based laser architecture. Single-shot interactions of several burst configurations with up to ∼0.4 J of energy are investigated and compared to single femtosecond pulse interactions. White-light interferometry measurements of the ablated volume and images of the single-shot ablation craters are presented. These interactions are conducted in air with the pulses undergoing nonlinear filamentation. The ultrafast pulse trains employed in this investigation utilize repetition rates >1 GHz and uniquely propagate in the nonlinear regime with continuous plasma and precise coaxial overlap between pulses over extended ranges due to the “stitching” of consecutive pulses' filament plasmas, previously described by Reyes et al. [J. Opt. Soc. Am. B Opt. Phys. 36, G52 (2019)]. The large craters generated by a single filament burst provide a promising means for long-range stand-off ablation applications.