Effect of [Li]/[Nb] ratios on doping concentration and defect structure of Mg:Fe:Cu:LiNbO3 crystals

Abstract

Mg:Fe:Cu:LiNbO3 crystals with different [Li]/[Nb] ratios (0.946, 1.05, 1.20, 1.38) were prepared by the Czochralski method. The crystal structure and the occupancy of impurity ions were analyzed by X-ray diffraction (XRD). The effective segregation coefficient was analyzed by an inductively coupled plasma-atomic emission spectrometer (ICP-AES). The optical uniformity of the crystal is analyzed by birefringence gradient. The results show that the dopant ions do not change the crystal structure, and the concentration of dopant ions changes with the ratio of [Li]/[Nb]. The greater the ratio of [Li]/[Nb], the better the optical uniformity. Finally,we conclude that when the [Li]/[Nb] ratio approaches 1.20, the intrinsic defects of Mg:Fe:Cu:LiNbO3 crystals almost disappear and the crystals approach the stoichiometric ratio. When the [Li]/[Nb] ratio is 1.38, the optical uniformity of the crystal is the best.