Effect of zirconium content on defect structure and optical uniformity of dysprosium-doped lithium niobate crystals

Four Zr: Dy: LiNbO3 crystals doped with different concentrations of Zr4+ (0, 1, 2, 4, mol%) have been grown by Czochraski technique. The effect of doping concentration of Zr4+ ions on the actual concentration of Zr4+ and Dy3+ ions in doped crystal was studied by the inductively coupled plasma-atomic emission spectrometry (ICP-AES). The results of X-ray diffraction and ultraviolet absorption spectroscopy showed that the Zr: Dy: LiNbO3 crystal still maintained the original lattice structure of the pure lithium niobate crystal, and the doped ions entered the crystal by preferential substitution of NbLi4+, and doped ions entered the crystal When NbLi4+ is completely replaced, ions are doped to replace the normal Nb and Li positions into the crystal. The lattice constant with the increase of Zr content shows a trend of first becoming larger and then smaller. Finally, the optical uniformity of Zr4+ doped concentration on Zr: Dy: LiNbO3 crystals was studied by birefringence gradient method. The results showed that with the increase of Zr4+ ion doping concentration, the crystal optical uniformity of Zr: Dy: LiNbO3 gradually increased, and the optical uniformity reached the highest when doped at a concentration of 4 mol%. Based on the Li-site vacancy model, the experimental results are discussed in detail.