Photostability of porous silica - rhodamine 6G hybrid samples

In the last decades solid-state tunable lasers were prepared by embedding dye molecules into sol-gel matrix. The main advantage with respect to the liquid dye solution is the decrease of health and environmental hazards. However the desired dye photostability, which is mainly related to the photochemical degradation of organic molecules in their gain range, has not yet achieved. In this work we present a photostability study of porous silica - rhodamine 6G hybrids (PS-R6G) prepared via sol-gel method. Two kinds of samples were prepared: class I and II, where the dye molecules are weakly and covalently bonded to the glass matrix, respectively. Measurements were carried out by exciting PS-R6G samples with the 3rd harmonic of a Nd:YAG laser (355 nm) at different power densities. We observed the decay of the fluorescence signal as the cumulative excitation energy increases in both the sets of samples. The photobleaching rate depends both on the power density and the kind of the samples. The photoluminescence properties and the photobleaching feature reported indicate the class II samples as good candidate for solid-state dye laser.