Effect of shot number on laser damage of fused silica: experimental test of the Max-of-N model

Laser-induced damage initiation on the exit surface of fused silica optics triggered by nanosecond pulses at 351 nm is mostly studied for single laser shots. In this paper, we experimentally investigate how the number of laser shots influences the number of initiated damage sites in the case of an unstable laser beam. More precisely, our experiments question the validity of the "Max-of-N" model [Liao <i>et al.</i>, Appl. Opt.50, 3547 (2011)10.1364/AO.50.003547]. Results show that, in some cases, the modSel correctly predicts the laser damage risk. However, in other cases, it overestimates the damage. We attribute this phenomenon to an increase in the laser damage resistance of the optic, known as laser conditioning, occurring during successive laser shots.