Excimer-laser-induced densification of fused silica: laser-fluence and material-grade effects on the scaling law

We present results of the study of 193 nm laser-induced densification of fused silica as a function of incident laser fluence and pulse count. We describe an internally self-consistent experiment involving the simultaneous irradiation of 12 samples of two different grades, at fluences varying by two orders of magnitude and pulse counts exceeding 1.5 x 10(9). We are able to establish the existence of a dose-rate dependence of the densification phenomenon and to characterize the empirical rate constants as a function of fluence for two different grades of fused silica. (C) 1999 Published by Elsevier Science B.V. All rights reserved.