Laser-induced bulk damage in various types of vitreous silica at 1064, 532, 355, and 266 nm: evidence of different damage mechanisms between 266-nm and longer wavelengths

Laser-induced-damage thresholds (LIDT's) with various types of vitreous sil ica at 1064, 532, 355, and 266 nm are investigated. At 1064 nm no differenc e in the LIDT was observed in any sample. At 1064-355 nm the wavelength dep endence of the LIDT of synthetic fused silica (SFS) can be described well b y the relation I-th = 1.45 lambda(0.43), where I-th the LIDT in J/cm(2) and lambda is the wavelength in nanometers. At 266 nm, however, LIDT's were sm aller than half of the calculated value from the relation above. This diffe rence can be explained by the damage mechanism; at 266 nm two-photon absorp tion-induced defects lower the LIDT as in the case of KrF-excimer-laser-ind uced defects, whereas at longer wavelengths the two-photon process does not occur. LIDT's of fused quartz (FQ) at 532 and 355 nm and that of SFS conta ining similar to 1000 ppm of Cl and no OH at 355 nm were a little lower tha n those of the other SFS's. This lower LIDT may be related to the absorptio n of metallic impurities in FQ and dissolved Cl-2 molecules in SFS. At 266 nm, on the other hand, LID's of FQ's were higher than those of most SFS's. (C) 1999 Optical Society of America.