Photorefractive properties of highly-doped lithium niobate crystals in the visible and near-infrared
Light-induced refractive-index changes, bulk-photovoltaic current densities, and photoconductivities of photorefractive iron-doped lithium niobate crystals (iron concentrations between 0.02 and 0.17 wt. %) are investigated in detail using visible and near-infrared light. It turns out that the one-center model predicts the material performance correctly for small iron concentrations (cFe<0.06 wt. % Fe2O3), only. A strong increase of the photoconductivity for higher doping levels limits the space-charge fields. Refractive-index changes up to 7×10-4 for green and 2.8×10-4 for near-infrared ordinarily polarized light are obtained. The corresponding hologram multiplexing numbers are 11 for green and 5 for near-infrared light.
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