Concentration dependence of refractive index in Zn-doped LiNbO3 crystals

This paper reports the concentration dependence of the ordinary (n(o)) and extraordinary (n(e)) refractive indices in congruent ZnO-doped LiNbO3 crystals. The Zn2+ concentration in the crystals was varied from 0% to 5.9%. Although the dependencies of n(o) and n(e) with the Zn2+ content are very different, both showed singularities for ZnO concentrations in the crystal at around 4.6%. The n(o) and n(e) values measured in ZnO doped crystals doped from the melt are compared with the data reported in the literature for post-growth thermal diffusion of Zn2+ ions in LiNbO3 crystals. Both sets of data are well described by a generalised Sellmeier equation which takes into account a different Zn2+ ions sites location depending on the Zn2+ concentration and the method used for doping the crystals. (C) 1998 Elsevier Science B.V. All rights reserved.