Growth and optical damage resistance properties of In:Ho:LiNbO₃ crystals

A series of In:Ho:LiNbO₃ crystals were grown by the Czochralski method in congruent LiNbO₃ melt doped with 0, 1%(in mole, the same below), 3% and 5% In₂O₃ and 1%Ho₂O₃, respectively. The ultraviolet-visible absorption spectra, birefringence gradient and optical damage resistance threshold of the In:Ho:LiNbO₃ crystals were measured. The results show that the absorption edge continuously violet shifts with the increase of the In³⁺ content in the crystals. The 5%In:1%Ho:LiNbO₃ crystal possessed a superior optical homogeneity. The optical damage resistance of the 5%In:1%Ho:LiNbO₃ was two orders of magnitude higher than that of 1%Ho:LiNbO₃. The mole contents of In³⁺ and Ho³⁺ in the crystal were determined by an inductance coupled plasma atomic emission spectrum technique, and the segregation coefficients of In³⁺ and Ho³⁺ in the crystals were calculated. The segregation coefficients of Ho³⁺ increased from 0.36 to 0.71 with increasing the In³⁺ content in the crystal. The experimental results were analyzed based on the Li-vacancy defect model.