Growth and optical photorefraction of Zr:Fe:LiNbO3 crystals with various [Li]/[Nb] ratios at 532 nm wavelength

Zr:Fe:LiNbO3 crystals were grown in air by the Czochralski technique with various [Li]/[Nb] ratios of 0.85, 1.05, and 1.38 in melt. Based on the ICP-AES (inductively coupled plasma atomic emission spectrometry) analyzed results, the chemical formulas of Zr:Fe:LiNbO3 crystals were obtained. The sign of the dominate charge carriers as well as the two-wave coupling gain coefficient as a function of the [Li]/[Nb] ratios in crystal were investigated by using the typical two-wave coupling experimental setup. The results show that electrons are the dominate charge carriers and the gain coefficient is the largest when the recording angle 2θ=21° in the sample with [Li]/[Nb]=0.7111 in crystal. In addition, the dependence of the light-induced birefringence on the [Li]/[Nb] ratios was measured in Zr:Fe:LiNbO3 crystals, which shows that the optical damage resistance of Zr:Fe:LiNbO3 crystals increases with the increasing of [Li]/[Nb] ratios at 532 nm wavelength. The dependences of the green photorefraction on the defect structure of Zr:Fe:LiNbO3 crystals are discussed in detail based on the obtained chemical formulas.