Time-Resolved Pump–Probe Imaging of Ablation Phenomena in Silica Glass Using Visible Femtosecond Laser

The ablation phenomena in silica glass were investigated using a visible femtosecond laser and time-resolved pump–probe imaging. A pump pulse with a wavelength of 400 nm was employed. Only gentle ablation occurred at a peak fluence of 6.88 J/cm², and gentle ablation and strong ablation occurred at a peak fluence of 8.23 J/cm². At both peak fluences, reflectivity increased owing to excitation at a delay time of ~1 ps. At a delay time of ~30 ps, a decrease in reflectivity due to melting was observed only at the local fluence that generated strong ablation. The ablation that occurred after melting was considered to correspond to strong ablation.