Effects of nonlinear absorption in BK7 and color glasses at 355 nm

Abstract

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 8.0x10-18 ± 20% cm 2 , 2.8x10-16 ± 20% cm 2 , and 5x10-17 ± 20% cm 2 , respectively, and solarization coefficients of 8.5x10-20 ± 20% cm 2 , 2.5x10-18 ± 20% cm 2 , and 1.3x10-19 ± 20% cm 2 , respectively. For our application, nonlinear effects in 10-cm of BK7 are small (≤ 2%) for 355-nm fluences < 0.2 J/cm 2 for flat-top pulses. However, nonlinear effects are noticeable for 355-nm fluences at 0.8 J/cm 2. 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/cm 2. For 0.5-cm of UG1 absorbing glass the non-linear absorption has a similar effect as that from 10cm of BK7 on the pulse shape; however, the effects in UG11 are much smaller.

Characterization of BG28 and KG3 filter glass for Drive Diagnostic Attenuators

“…[6] This was attributed to some phase-toamplitude conversion coupled with non-linear absorption in the BG28. In another case, tests ( Figure 3) by John Adams et al [7] at 355 nm showed that solarization in BG28 did indeed occur-tens of J/cm 2 changed the transmittance noticeably. Solarization in copper-containing filters has been reported [8,9] and the Schott catalog specifically mentions its occurrence in BG28.…”

“…3. Data of Adams et al [7] on solarization of BG28 at 355 nm. Gaussian pulses 7.2 nsec wide were used in the experiments.…”