Structure-Mediated Excitation of Air Plasma and Silicon Plasma Expansion in Femtosecond Laser Pulses Ablation

Time-resolved shadowgraphs of the plasma at probe delays on picosecond timescale. (a–e) Shadowgraphs for the first pulse. (f–j) Shadowgraphs for the second pulse. The laser fluence is 7.27 J/cm². The dashed line indicates the interface of silicon and air.