Ab initio molecular dynamics simulation of the effect of impurities on laser-induced damage of fused silica

The damages of fused silica surface after laser irradiation can be caused by the impurities introduced during manufacture processes. In this paper, Fe and Ce impurities are considered in fused silica. The first-principles method is employed to simulate the process of high-power ultraviolet laser irradiation to fused silica. The bond angle distribution, pair distribution function, the density of state (DOS) and other information of fused silica structures are calculated. There is a remarkable difference in bond length and bond angle distribution between pure and doped fused silica. New defect states are also observed in DOS with the narrower band gap, and new optical absorption peaks appear in the dielectric function for the fused silica with the dopants after laser irradiation. This means that fused silica with impurities has more significant absorption for laser energy than pure fused silica. FeO bonds are found more stable than CeO ones after irradiation. This indicates the damage of Fe doping is greater than that of Ce doping. So, doping of metal indeed leads to a decrease in damage resistance to laser for fused silica, and Fe is more harmful than Ce.