Analysis of energy deposition and damage mechanisms in single layer optical thin films irradiated by IR and UV femtosecond pulses

We report on the sub-picosecond laser-induced damage of optical thin films of different thickness made by Magnetron sputtering, Ion assisted deposition and Ion plating, and submitted to single irradiation of the first and the third harmonics of an Ytterbium laser (1030 and 343nm). Using a single rate equation approach for free electron excitation coupled with calculation of the spatial and temporal distribution of the electric field, we investigate numerically the spatial density distribution of the absorbed energy and evaluate its capacity to describe damage phenomena especially damage threshold and morphologies (damage diameter, ablation deepness). Laser-induced damage thresholds are compared for different film thicknesses and different irradiation conditions.