PROCEEDINGS ARTICLE | June 10, 2004
Proc. SPIE. 5273, Laser-Induced Damage in Optical Materials: 2003
KEYWORDS: Mirrors, Cameras, Signal attenuation, Glasses, Ultraviolet radiation, Diagnostics, Refraction, Color centers, National Ignition Facility, Absorption
We have demonstrated a simple experimental technique that can be used to measure the nonlinear absorption coefficients in glasses. We determine BK7, UG1, and UG11 glasses to have linear absorption coefficients of 0.0217 ± 10% cm-1, 1.7 ± 10% cm-1, and 0.82 ± 10% cm-1, respectively, two-photon absorption cross-sections of 0.025 ± 20% cm/GW, 0.035 ± 20% cm/GW, and 0.047 ± 20% cm/GW, respectively, excited-state absorption cross-sections of 8.0 x 10-18 ± 20% cm2, 2.8 x 10-16 ± 20% cm2, and 5 x 10-17 ± 20% cm2, respectively, and solarization coefficients of 8.5 x 10-20 ± 20% cm2, 2.5 x 10-18 ± 20% cm2, and 1.3 x 10-19 ± 20% cm2, respectively. For our application, nonlinear effects in 10-cm of BK7 are small (≤ 2%) for 355-nm fluences < 0.2 J/cm2 for flat-top pulses. However, nonlinear effects are noticeable for 355-nm fluences at 0.8 J/cm2. In particular, we determine a 20% increase in the instantaneous absorption from linear, a solarization rate of 4% per 100 shots, and a 10% temporal droop introduced in the pulse, for 355-nm flat-top pulses at a fluence of 0.8 J/cm2. For 0.5-cm of UG1 absorbing glass the non-linear absorption has a similar effect as that from 10-cm of BK7 on the pulse shape; however, the effects in UG11 are much smaller.
