EFFECTS OF GAMMA-IRRADIATION AND ANNEALING ON THE OPTICAL-PROPERTIES OF YALO3, YALO3-ND, AND YALO3-ER CRYSTALS

The effects of gamma irradiation and anneals in oxidizing and reducing atmospheres on the optical properties of YAP, YAP:Nd, and YAP:Er crys tals are investigated. The difference absorption spectra of annealed a nd as-grown crystals and the irradiation-induced absorption spectra ex hibit five bands each. The intensity of these bands depends on the con centration of defects responsible for the formation of the correspondi ng color centers. The effects of air annealing at different temperatur es are interpreted in terms of the thermally activated changes in the charge state of existing defects and the diffusion mechanisms for the formation of new defects. Irrespective of the type of crystal, the sam e defects are responsible for the changes produced in the absorption s pectrum by annealing or gamma irradiation.