Photoproduction and relaxation of long-lived active charges in Ca3Mn2Ge3O12 garnet revealed through optical absorption

Photoillumination causes an augmentation of optical absorption within the b and corresponding to a forbidden transition. The observed kinetics of photo induced absorption displays a broad continuous distribution of absorption c enters over relaxation times, which cannot be explained, with allowance for the temperature dependence of the relaxation kinetics, in terms of absorpt ion centers associated with impurities or lattice defects. The experimental picture, including its temperature changes, is described by the model of a ctive charges (hole polarons) which arise under light pumping and produce r andom electric fields. These fields play a double role: they partly elimina te the forbiddenness of the optical transition, thus enhancing its oscillat or strength, and significantly shorten the lifetime of active charges. A br oad continuous distribution of random fields over magnitudes entails the co rresponding lifetime distribution of active charges covering several orders of magnitude.