Ablation mechanism of fused silica under femtosecond laser pulse

Based on the avalanche model, the mechanism of femtosecond laser-induced ablation in fused silica was investigated. The three microscopic processes, including the production of conduction band electrons (CBE), the deposition of laser energy, and the diffusion of CBE and energy, were solved by a finite element method (FEM) of two-dimension cylinder coordinate. The conduction band electrons (CBE) were produced through photoionization and impact ionization, which were calculated via Keldysh theory and Double-flux model, respectively. The accumulated charge and the electrostatic field were also calculated, and the evolution of microexplosion was discussed based on this model. The results indicate that the CBE and energy diffusion plays an important role in the ablation of dielectrics by femtosecond laser pulse.