Influence of the dopant concentration on the OH− absorption band in Fe-doped LiNbO3 single-crystal fibers

Abstract The growth of iron-doped single-crystal fibers of lithium niobate was performed by the laser heated pedestal growth technique for different Fe2O3 contents in the feed rods. The infra-red optical absorption spectra (OH− band) were investigated by IR transmission microscopy. To explain the evolution of the OH− ions concentration in the crystals, a model is proposed involving the partial dissociation of LiNbO3 in the melt into Li2O and Nb2O5. The constitution of the OH− absorption band is also discussed on the basis of the Nb-vacancy structural model of lithium niobate.