Formation of small polaron and excitation transfer in niobate crystals

Abstract Using a ps-YAG laser operated at 532 nm as a light source for luminescence and degenerate-four-wave-mixing (DFWM) measurements on niobate crystals such as S 0.61 B 0.39 Nb 2 O 6 (SBN), KNaSBN, KTN family (KTa 1− x Nb x O 3 )and KNbO 3 , a broad emission at 400–700 nm with lifetime of ~ 10 ns was observed. It is due to the charge carriers produced in conduction band by two-photon absorption (TPA), trapped at Nb 5+ center to form Nb 4+ − O − small polarons. In Ce 3+ -doped niobate crystals the DFWM experiment shows that the excitation of niobate host can transfer to cerium, resulting in Ce +3 emission which would otherwise not be able to be observed by direct excitation of cerium at 532 nm.