The Research On Volume Holographic Storage Of Doping LiNbO₃ Crystal

Zn:Fe:LiNbO₃, Ce:Cu:LiNbO₃ and Mg:Mn:Fe:LiNbO₃ crystals were grown by Czochralski method. And the influence of varied Zn²⁺ concentration on the photorefractive properties of the crystals were investigated. At the same time, Ce:Cu:LiNbO₃ and Mg:Mn:Fe:LiNbO₃ were cut and then oxidized and reduced, the influence of oxidation and reduction treatments on the photorefractive properties of the crystals were investigated as well.The holographic storage properties including diffraction efficiency, response time and erasing time were obtained by two-beam coupling experiment. The paper presents that the holographic storage properties of the crystals were affected by the concentrations of dopants and the treating state of crystals.The light scattering resistances of the Ce:Cu:LiNbO₃ and Mg: Mn: Fe: LiNbO₃ crystals were studied by the transmission facula distortion method. The main mechanisms of photorefractive effect are different for the oxidized, reduced and as-grown crystals respectively. During a photorefractive process, for the as-grown or reduced crystals, both the diffusion mechanism and photo-induced volt effect act together and for oxidized crystals, photo-induced volt effect is dominant. In as-grown and reduced crystals the light excited carrier is the electron, and in oxidized crystal it is the cavity.The paper also conducts a research of volumn holographic storage on the tested crystals. It starts with the improvement of optical paths in laboratory. The pape finds that reducing aberration and noises of the detector used helps improve the storage quality. Furthermore, in the storage experiment of crystals, it is found that photo refractive quality of the crystals directly decides storage quality. For Zn:Fe:LiNbO₃, increasing the concentration of Zn²⁺ slows down the response speed, but it improves the time needed for information storage. For Ce:Cu:LiNbO₃, oxidation and reduction mainly change the concentrations of different ions in the crystals, and these changes will directly influence response time and erasing time. The best storage effect was gained in the as-grown Ce:Cu:LiNbO₃, and the second best was achieved in the reduced crystal, while the worst was found in oxidized crystal. At last, we conducted multiplexing storage in the crystal by employing the angle-multiplexing technology.