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 l ight was examined in synthetic fused silicas made under a variety of p rocessing conditions. The SiCl4-based glass exhibited increased UV abs orption, 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 molec ular hydrogen. The damage did not correlate with the OH level. Fused s ilica produced using a hydrogen/oxygen flame showed the same damage re sistance as glass made with a natural gas/oxygen flame. Fused silica m ade with the chlorine-free precursor, octamethylcyclotetrasiloxane (OM CTS), 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.