Photoselective reactions of H2 with germanosilicate glass

With the possibilities of creating large (>10(^-3)) photoinduced refractive index changes in germanosilicate glass now well established one would like to understand better the detailed mechanisms by which these effects are realized. More specifically, the relative importance of 1-photon or 2-photon defect state resonant transitions (and subsequent chemical reactions), in addition to light induced thermal reactions are sought. While the most common technique to achieve index modification for device fabrication utilizes high-intensity (ca. 10⁷ W/cm²) pulsed UV light, this unfortunately represents the most complex situation with regard to the number of different mechanisms that could be taking place. To conceptually separate out individual effects, therefore, we have chosen a set of experimental conditions where only 1-photon resonant photochemical reactions can play a role