IMPROVEMENT OF NONVOLATILE BLUE PHOTOREFRACTIVE PROPERTIES IN In:Ce:Cu:LiNbO3 CRYSTALS

Abstract

The In : Ce : Cu : LiNbO 3 crystals used in this work were grown by Czchralski method. The key parameters: the exponential gain coefficient Γ, the diffraction efficiency ηS, the response time τw, the dynamic range M/#, the sensitivity S and the maximal refractive index change Δn max were measured with conventional two beam coupling. The optimal values of Γ, ηS, M/#, S and Δn max achieved are 44.7, 68.6%, 6.02, 0.471 cm/J and 5.37 × 10-5, respectively. It was found that the blue light photorefractive properties of Γ, ηS, M/#, S and Δn max increased with increasing In 3+ ions concentration, while the red light photorefractive properties of Γ, ηS, Δn max decreased with increasing In 3+ ions concentration. The nonvolatile holographic storage properties were measured by both the dual wavelength and two color techniques. The maximal diffraction efficiency and fixing diffraction efficiency using the dual wavelength technique were doubled compared to those obtained in using the two color technique. The sensitivity and nonvolatile sensitivity were one order of magnitude higher than those by the two color technique. The photorefractive property enhancement by the dual wavelength technique was investigated.