Simulations of CO₂laser interaction with silica and comparison to experiments

Abstract

Localized CO 2 laser heating of silica glass has demonstrated its ability to mitigate surface damage on optics used for high power laser applications. The parameters for this process such as the power, the beam size and the exposition time are however critical and some fundamental studies on the silica behavior under CO 2 laser irradiation are required to develop the processes. It is necessary for instance to understand the silica transformation, the material ejection and the thermo-mechanical stresses induced by the laser heating and subsequent cooling. A thermo-mechanical model based on finite-element method has been used to calculate the temperature of silica heated by CO 2 laser irradiation and the residual stress after cooling of the samples. The model, as the different parameters used for calculations, are detailed in this paper and the numerical results are compared to different dedicated experimental studies.