Repair strategies for fused silica wedged focus lens with high density filamentary damage

The National Ignition Facility (NIF) is intentionally operated with the final fused silica glass (SiO₂) optics exposed to fluences and intensities with the potential to induce damage that will grow with additional laser exposure. Therefore, the NIF operates a recycle loop to refurbish final optics by mitigating any initiated surface damage to arrest its growth. However, the morphology of filamentary damage, caused by local self-focusing in the bulk of a silica optic, adds additional complexity to optics mitigation and provides a limitation to optic reusability. This study evaluates techniques for mitigating isolated and clustered filamentary damage. Optical microscopy before and after NIF installation was used to determine the efficacy of filamentary mitigation after a series of high fluence and intensity laser exposures. The challenges and success rate of the methods are compared for various filamentary damage mitigations strategies.