Confirmation of an Electron Avalanche Causing Laser-induced Bulk Damage at 106 μm

Measurements have been made on intrinsic optical bulk breakdown in ten alkali halides at 1.06 microm and in one at 0.69 microm. By comparing the results to previously reported experiments conducted at 10.6 microm and at direct current, it has been possible to identify the damage mechanism as electron avalanche breakdown. Self-focusing has been controlled by restricting the probe powers to well below the critical powers for catastrophic self-focusing, and damage from inclusions has been distinguished from intrinsic damage. Implications of this work for surface damage studies are explored.