Damage in fused-silica spatial-filter lenses on the OMEGA laser system

Amy L. Rigatti; Douglas J. Smith; Ansgar W. Schmid; Semyon Papernov; John H. Kelly

doi:10.1117/12.344444

7 April 1999 Damage in fused-silica spatial-filter lenses on the OMEGA laser system

Amy L. Rigatti, Douglas J. Smith, Ansgar W. Schmid, Semyon Papernov, John H. Kelly

Proceedings Volume 3578, Laser-Induced Damage in Optical Materials: 1998; (1999) https://doi.org/10.1117/12.344444
Event: Laser-Induced Damage in Optical Materials: 1998, 1998, Boulder, CO, United States

Abstract

Vacuum surface damage to fused-silica, spatial-filter lenses is the most prevalent laser-damage problem occurring on the OMEGA laser system. Approximately one-half of the stage C- input and output, D-input, E-input, and F-input spatial- filter lenses are currently damaged with millimeter-scale fracture sites. With the establishment of safe operational damage criteria, laser operation has not been impeded. These sol-gel-coated lenses see an average fluence of 2 to 4 J/cm² at 1053 nm/1 ns. Sol-gel coatings on fused-silica glass have small-spot damage thresholds at least a factor of 2 higher than this peak operational fluence. It is now known that the vacuum surface of OMEGA's spatial-filter lenses are contaminated with vacuum pump oils and machine oils used in the manufacture of the tubes; however, development-phase damage tests were conducted on uncontaminated witness samples. Possible explanations for the damage include absorbing defects originating form ablated pinhole materials, contamination nucleated at surface defects on the coating, or subsurface defects from the polishing process. The damage does not correlate with hot spots in the beam, and the possibility of damage from ghost reflections has been eliminated. Experiments have been initiated to investigate the long-term benefits of ion etching to remove subsurface damage and to replace sol-gel layers by dielectric oxide coatings, which do not degrade with oil contamination.

Citation Download Citation

Amy L. Rigatti, Douglas J. Smith, Ansgar W. Schmid, Semyon Papernov, and John H. Kelly "Damage in fused-silica spatial-filter lenses on the OMEGA laser system", Proc. SPIE 3578, Laser-Induced Damage in Optical Materials: 1998, (7 April 1999); https://doi.org/10.1117/12.344444

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