Damage to fused silica windows while under simultaneous exposure to flowing solvents and laser radiation and 308nm

This paper reports the results of a study to determine the degrading effects of flowing dye solvents on the laser damage threshold of fused-silica windows at 308nm. Thresholds were measured at the SiO/sub 2/solvent interface in a test cell. Bare SiO/sub 2/ tested in air at 308nm (20ns) typically exhibits a threshold ranging from 4 to 10 Jcm/sup 2/; with the solvent cyclohexane in contact, a threshold as low as 0.3 Jcm/sup 2/ was measured. The damage data indicate that window lifetime (number of shots) is dependent of fluence at higher levels, and asymptotically approaches infinity at levels near threshold. Dielectric coatings were tested as possible damage-resistent barriers between the solvent and SiO/sub 2/; the results show some improvement in damage threshold. When cyclohexane is replaced with the solvent dioxane, thresholds measured for SiO/sub 2/ windows are within the range cited above for thresholds measured in air

Laser deposition and laser modification of high-temperature superconducting thin films

Applications of high-temperature superconductors (HTSC) may require epitaxial films with {Tc}{ge}77 K, and J{sub c}{ge}10{sup 6} A/cm{sup 2}. In situ pulsed laser deposition (PLD) is suitable for fabrication of such films. We report parametric studies on the effect of laser and processing parameters on the crystallinity, epitaxy and electrical properties of laser-deposited HTSC thin films. In addition, several laser-based processes were used to modify the electrical properties ({Tc} and J{sub c}) of PLD thin films. A direct-write laser heating (1.06 {mu}m at {approx}0.5 kW/cm{sup 2} for {approx}5 min) process in an oxygen atmosphere at {approx}590 Torr was shown to selectivity regenerate high-{Tc} material in microscopic domains from films that were partially deoxygenated. In separate work, electrical responses and crystallinity of HTSC films were measured as a function of excimer laser exposure using fluences in the range 20--150 mJ/cm{sup 2}. The critical current and boundary layer could be modified with a high degree of accuracy. 17 refs., 4 figs