Defects in Undoped and Doped Bi12GeO20

Optimization of Bi12Ge O20 (BGO) for better photorefractive performance requires a systematic physico-chemical and physical characterization in parallel with material processing, investigation of photorefractive properties and implementation of nonlinear experiments. A main aspect is to analyze the effects of unintentional and intentional doping. We are concerned by the physical characterization of defects. To this end we use novel special thermal and optical spectroscopic methods (1). These survey techniques allow to probe the forbidden gap and to monitor changes in the nature and concentration of the species.