2D dynamic ionization simulation from ultrashort pulses in multilayer dielectric interference coatings

The interaction of ultrafast laser pulses and dielectric materials has been under intensive research for improvement of laser induced damage of optics for high intensity lasers. A 2D model based on Keldysh photoionization and finite-different time-domain (FDTD) algorithm are used to simulate the ionization processes in multilayer interference coatings, taking nonlinear photoionization, impact ionization, and plasma collision into account. Simulation and experimental results of bulk fused silica with different pulse durations and angles of incidence are compared and discussed. We also simulated the interaction of a 40-layer SiO2/Ta2O5 high reflective interference coating designed for 45° angle of incidence and a p-polarized 5-fs pulse at a wavelength of 800 nm, and the damage threshold of the coating is estimated.