Damage thresholds in laser‐irradiated glass

A model is developed for determining the laser fluence required to damage glass. In particular, damage thresholds for elastic stress failure and surface relaxation phenomena are determined based on the temperature and stress profiles in the glass. The temperature profile is calculated from the one‐dimensional diffusion equation with an exponential source term to account for absorption of laser radiation. An effective heat transfer coefficient is used to approximate surface heat losses due to natural convection and radiation. Stress profiles in the glass are calculated based on the plane stress approximation. The model is used to calculate damage thresholds for continuous wave DF and CO2 irradiation of BK‐7 glass for times ranging from 10−5 to several seconds. It is found that the absorption coefficient at the laser wavelength plays a significant role in determining the mode of damage and the damage threshold. The effects of surface losses and glass width on the damage threshold are also discussed.