Monitoring annealing via CO_2 laser heating of defect populations on fused silica surfaces using photoluminescence microscopy

Abstract

Photoluminescence (PL) microscopy and spectroscopy under 266 nm and 355 nm laser excitation are explored as a means of monitoring defect populations in laser-modified sites on the surface of fused silica and their subsequent response to heating to different temperatures via exposure to a CO(2) laser beam. Laser-induced temperature changes were estimated using an analytic solution to the heat flow equation and compared to changes in the PL emission intensity. The results indicate that the defect concentrations decrease significantly with increasing CO(2) laser exposure and are nearly eliminated when the peak surface temperature exceeds the softening point of fused silica (approximately 1900K), suggesting that this method might be suitable for in situ monitoring of repair of defective sites in fused silica optical components.