Mitigation of 351nm laser-induced damage sites on fused silica exit surfaces by selective CO₂ treatment has been shown to effectively arrest the exponential growth responsible for limiting the lifetime of optics in high-fluence laser systems. However, the perturbation to the optical surface profile following the mitigation process introduces phase contrast to the beam, causing some amount of downstream intensification with the potential to damage downstream optics. Control of the laser treatment process and measurement of the associated phase modulation is essential to preventing downstream 'fratricide' in damage-mitigated optical systems. In this work we present measurements of the surface morphology, intensification patterns and damage associated with various CO₂ mitigation treatments on fused silica surfaces. Specifically, two components of intensification pattern, one on-axis and another off-axis can lead to damage of downstream optics and are related to rims around the ablation pit left from the mitigation process. It is shown that control of the rim structure around the edge of typical mitigation sites is crucial in preventing damage to downstream optics.

Date Published: 16 January 2008
PDF: 9 pages
Proc. SPIE 6720, Laser-Induced Damage in Optical Materials: 2007, 67200A (16 January 2008); doi: 10.1117/12.752948

Published in SPIE Proceedings Vol. 6720:
Laser-Induced Damage in Optical Materials: 2007
Gregory J. Exarhos; Arthur H. Guenther; Keith L. Lewis; Detlev Ristau; M. J. Soileau; Christopher J. Stolz, Editor(s)