Photodegradation of Luminescence in SiO2 : Rh B Gels Exposed to YAG : Nd Laser Pulses

Silicate gels doped with organic dyes have been proposed as solid-state tunable lasers. Photobleaching of the dye under laser excitation is an important phenomenon in this application. The optical absorption and luminescence of SiO2 silica gels doped with Rhodamine B exposed to the second harmonic pulses of a YAG : Nd laser have been studied. In addition to the characteristic exponential decay with the number of pulses, overlapping oscillations in the intensity were observed. This behavior is explained in terms of a long lived metastable electronic excited state of the dye molecules.