Influence of magnesium concentration on the optical properties of ytterbium and holmium co-doped lithium niobate crystal

Abstract

In this paper, a series of Yb (0.5[Formula: see text]mol.%):Ho (0.5[Formula: see text]mol.%):LiNbO3 crystals doped with various concentration of Mg[Formula: see text] (1, 3, 5 and 7[Formula: see text]mol.%) were grown by the Czochralski technique. The ability of optical damage resistance of Mg:Yb:Ho:LiNbO3 crystals increases with increasing the Mg[Formula: see text] doping concentration. The optical homogeneity of Mg:Yb:Ho:LiNbO3 crystals doped with different concentration of Mg[Formula: see text] was detected using the birefringence gradient method. The results demonstrated that the optical homogeneity is getting better with the increase of the Mg[Formula: see text] doping concentration. The studies on the infrared transmission spectra indicated that Mg[Formula: see text] ions first replaces anti-site Nb[Formula: see text] in the form of Mg[Formula: see text] defect, once the concentration of Mg[Formula: see text] reaches or exceeds the threshold concentration, it begins to substitute Li-site and Nb-site of normal lattice and form defect of Mg[Formula: see text][Formula: see text]3Mg[Formula: see text]. Therefore, the change of Mg[Formula: see text] doping concentration is the fundamental reason leading to a violet shift of the OH[Formula: see text] absorption peak.