Effect of the oxidation state of LiNbO3:Fe on the diffraction efficiency of multiple holograms

Abstract

We show that the oxidation state of Fe in LiNbO3 has two competing effects on the diffraction efficiency of multiple holograms in 90 degree-geometry holographic storage. For crystals with moderate absorption, the saturation space-charge field is larger after high-temperature reduction treatment. However, reduction also increases absorption, which reduces the overall diffraction efficiency. We develop a theoretical model that predicts achievable diffraction efficiency as a function of oxidation state, doping level, photovoltaic field, crystal length, and region of beam overlap. We compare this model with experimental results for achievable diffraction efficiency and erasure-time constant.