Laser-Induced Damage in Dielectrics with Nanosecond to Subpicosecond Pulses

We report extensive measurements of damage thresholds for fused silica and calcium fluoride at 1053 and 526 nm for pulse durations $\tau$ ranging from 270 fs to 1 ns. Qualitative differences in the morphology of damage and a departure from the diffusion-dominated ${\tau }^{1/2}$ scaling indicate that damage results from plasma formation and ablation for $\tau \le 10$ ps and from conventional melting and boiling for $\tau >100\mathrm{}$ ps. A theoretical model based on electron production via multiphoton ionization, Joule heating, and collisional (avalanche) ionization is in good agreement with experimental results.