Microscopic mechanisms of ablation and micromachining of dielectrics by using femtosecond lasers

We report measurements of damage threshold and ablation depth for SiO2 and CaF2 irradiated under lasers at wavelengths of 800 and 400 nm for duration of 45–800 fs. These results can be well understood by using a developed avalanche model. The model includes the production of conduction band electrons (CBEs), laser energy deposition, and CBE diffusion. The evolution of microexplosion is investigated based on this model.