Study on the growth and photorefractive properties of In:Fe:Cu:LiNbO ₃ crystals

Fe(0.2 mol%):Cu(0.04 mol%):LiNbO₃ crystals with different doping concentration of In³⁺ (0, 1.0, 2.0, 3.0mol%) were grown by Czochralski method, and then oxidized and reduced. The infrared transmittance spectra of crystals were measured to investigate the location of doping ion and its threshold concentration. The photorefractive properties of the crystals were tested by two beam coupling experiment. The results showed that the threshold concentration of In ions is 2.0-3.0 mol% and In ions take the place of Nb _Li ⁴⁺ to form (In_Li ²⁺ before reaching its threshold concentration, and then the location of normal Nb ions. In the (2.0 mol%):Fe:Cu:LiNbO₃ crystal with the oxidation treatment having the highest diffraction efficiency (η = 45.8%), the photo-damage resistance threshold value R of In(3.0 mol%):Fe:Cu:LiNbO₃ was 3.67 × 10⁴ W/cm² which was two orders of magnitude higher than that of Fe:Cu:LiNbO₃ crystal (4.30×10² W/cm²). And the photo-damage resistance ability was enhanced by oxidized treatment. The In(2.0-3.0 mol%):Fe:Cu:LiNbO₃ crystals with oxidized treatment have the best photorefractive properties.