Absorption cross sections and number densities of electron and hole polarons in congruently meltingLiNbO3

Abstract

The number densities and absorption cross sections of both opticallygenerated and reduction-induced small electron and hole polarons inLiNbO3 aredetermined by means of time-resolved pump–multiprobe spectroscopy. The data are obtained for free(NbNb4+) and bound(NbLi4+) electron polarons,bound NbLi4+:NbNb4+ electronbipolarons, and bound O− hole polarons. The peak absorption cross sections are in the range ofσpol≈(4–14) × 10−22 m2, comparableto that for Fe2+. In all cases the ratio of occupied to unoccupied polaronic sites is less than10−2.