Absorption cross sections and number densities of electron and hole polarons in congruently melting LiNbO3

Abstract

The number densities and absorption cross sections of both optically generated and reduction-induced small electron and hole polarons in LiNbO3 are determined by means of time-resolved pump-multiprobe spectroscopy. The data are obtained for free (Nb-Nb(4+)) and bound (Nb-Li(4+)) electron polarons, bound Nb-Li(4+) : Nb-Nb(4+) electron bipolarons, and bound O- hole polarons. The peak absorption cross sections are in the range of sigma(pol) approximate to (4-14) x 10(-22) m(2), comparable to that for Fe2+. In all cases the ratio of occupied to unoccupied polaronic sites is less than 10(-2).