Time-resolved shadowgraphs of the laser ablation of silicon at probe delays on femtosecond timescale. (a–d) Shadowgraphs for the first pulse. (e–h) Shadowgraphs for the second pulse. The laser fluence is 7.27 J/cm2. The dashed line indicates the interface of silicon and air. The white arrow in (a) indicates the propagation direction of the incident laser.