Arresting UV-Laser Damage in Fused Silica

26 LLE Review, Volume 77 Deciding when to replace spot-damage-afflicted fused-silica optics or, in the case of inaccessible, space-based lasers, predicting the useful service life of fused-silica optics before catastrophic, pulsed-laser-driven crack growth shatters a part has recently become simpler. By empirically deriving a rule for laser-driven crack growth in fused silica as a function of the number of constant-fluence laser pulses, Dahmani et al.1 provided laser systems designers and operators with guidance on the crack-growth kinetics as well as on the stress-related ramifications such a laser-driven crack entails. Specifically, a hoop stress in the immediate vicinity of a crack growing along the beam propagation direction was identified as strongly coupling to both the laser fluence and the crack.2 It prompted the question of whether or not breaking the hoop-stress symmetry by some external perturbation will accelerate or stymie crack growth or, alternatively, will have no effect at all.