Transient light-induced absorption in periodically poled lithium niobate: Small polaron hopping in the presence of a spatially modulated defect concentration

Abstract

The study of the transient light-induced absorption in thermally reduced, periodically poled lithium niobate doped with Y uncovers the simultaneous action of the ${\text{Nb}}_{\text{Li}}^{4+}:{\text{Nb}}_{\text{Nb}}^{4+}$ bipolaron and ${\text{O}}^{\ensuremath{-}}$ hole polaron relaxation in the blue and near-infrared spectral range. The findings can be comprehensively explained taking into account a periodic, spatial modulation of the ${\text{Nb}}_{\text{Li}}^{5+}$ antisite defect distribution, which results in a modulation of both concentrations and relaxation lifetimes of optically excited, small bound electron and hole polarons and bipolarons.