Photo dissociation of blue-light-induced VIS-centers in SBN : Ce, Cr and in BCT : Fe into small polarons at low temperatures

Abstract

The promising photorefractive single crystal systems Sr(x)Ba(1-x)N(b)2O(6) (SBN, congruent composition x = 0.61) [1] and Ba1-yCayTiO3 (BCT, congruent y = 0.23) [2], can be doped with polyvalent ions like Fe, Cr, Cc to enhance and optimize their photorefractive properties. Illumination with blue Ar+-laser light at low temperature creates light-induced NIR and VIS absorption bands [3, 4]. The NIR absorption has been identified as being due to electron polarons (Nb4+ in SBN, Ti3+ in BCT) and their properties have been investigated in some detail [3, 4]. The VIS-Centers (at about 2 eV) are less well understood and their nature is still under discussion [5]. We could show that illumination with red Kr+-laser light (647 nm) leads to a dissociation of the VIS-Centers and a simultaneous build-up of a transient NIR-polaron absorption [5]. These features give new insight into the dynamic nature of these VIS-Centers.