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 tun able lasers. Photobleaching of the dye under laser excitation is an importa nt phenomenon in this application. The optical absorption and luminescence of SiO2 silica gels doped with Rhodamine B exposed to the second harmonic p ulses of a YAG:Nd laser have been studied. In addition to the characteristi c 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.