Characteristics of UV-induced bulk damage in large-aperture fused silica from full-sized beam tests

Laser-induced bulk damage in fused silica is studied on a large-aperture laser system with 6 J/cm2, 5-ns shot sequences at 351 nm. The lateral dimension of bulk damage is found to propagate exponentially with shot number in a wide range of growth rates, similar to the stochastic trend as displayed by rear-surface damage. Resemblance in the morphology between bulk and surface damage is revealed offline by microscopic observations. Arising from the accumulated effect of fluence variation, the repetitive laser exposures tend to create an increased number of bulk damage, the tendency of which is applied to evaluate the number of damage initiations via simulations.