Optical characterization of Ho³⁺ions in LiNbO₃and in LiNbO₃:MgO crystals

Abstract

A detailed study of the optical absorption and emission spectra of Ho3+ ions in LiNbO3 crystals in the visible spectral region is presented. The positions of the crystal-field levels are given for the 5F5, 5S2+5F4, 5F3 and 5G6 multiplets of Ho3+ ions. The type and character of the Stark transitions have been determined by polarized absorption measurements. Optical absorption measurements and site-selective spectroscopy have shown the existence of two crystal-held sites for Ho3+ in the LiNbO3 matrix. The effect of co-doping with MgO on the optical spectra of Ho3+ ions has also been studied and a new Ho3+ Site perturbed by the presence of a neighbouring Mg2+ ion is evidenced.