Mechanisms of short-pulse laser induced damage in dielectric based on Fokker-Planck equation

Based on the Fokker-Planck equation, a theoretical computational model is established to describe the change with time of the energy distribution of conduction electrons in a dielectric material under the irradiation of short laser pulses. Using this model, the evolution of electron density in a dielectric material (taking SiO2 glass as an example) is calculated; with the critical plasma density damage criterion, the material damage thresholds are determined for various laser wavelengths and pulse durations. For laser wavelengths of 1 060, 800 and 532 nm, the obtained damage threshold curves of SiO2 are rather close to each other. The role of impact ionization and photoionization in material damage is also investigated. It is found that when the laser pulse duration is greater than 1 ps, i