Subpicosecond ultraviolet laser ablation of diamond: Nonlinear properties at 248 nm and time-resolved characterization of ablation dynamics

Ablation of diamond by short UV pulses is reported. The ablation threshold for 500 fs pulses at 248 nm was found to be 0.6 J/cm2 (equal to a peak intensity of 1.1 TW/cm2). Intensity-dependent transmission measurements from low intensities to 100 GW/cm2 showed that two-photon absorption is the dominant nonlinearity in this range and the two-photon absorption coefficient was measured to be (1.6±0.3) cm/GW. In the intensity regime above threshold (≳1 TW/cm2), however, low ablation rates indicate strong absorption by laser induced free carriers. The dynamics of diamond ablation was investigated time-resolved using pump probe transmission and pulse pair ablation measurements. Ablation with short pulses at 248 nm is also compared to ablation with 15 ns pulses at 193 nm.