Effects of glass forming conditions on the KrF-excimer-laser-induced optical damage in synthetic fused silica

The optical damage induced by exposure to KrF (248 nm) excimer laser light was examined in synthetic fused silicas made under a variety of processing conditions. The SiCl4-based glass exhibited increased UV absorption, increased red fluorescence and compaction after prolonged 248 nm exposure. The induced damage was most severe in glasses made with oxidizing deposition flames or in glasses with reduced levels of molecular hydrogen. The damage did not correlate with the OH level. Fused silica produced using a hydrogen/oxygen flame showed the same damage resistance as glass made with a natural gas/oxygen flame. Fused silica made with the chlorine-free precursor, octamethylcyclotetrasiloxane (OMCTS), exhibited the same general damage behavior as that seen in SiCl4-based glass except that the absorption damage shifted to a saturated condition without passing through the absorption transition prevalent in the SiCl4-based glass.