Abstract

Near-stoichiometric copper-doped lithium niobate crystals are fabricated by in-diffusion of thin layers of evaporated copper and a subsequent vapor transport equilibration treatment. The crystals are heated in a Li-rich atmosphere to increase the Li content. To determine the photorefractive properties, holographic as well as electrical measurements are performed. Saturation values of the refractive-index changes $\mathrm{\Delta }{n}_{\mathrm{S}},$ bulk photovoltaic current densities $j_{\mathrm{phv}},$ photoconductivities ${\sigma }_{\mathrm{ph}},$ and holographic sensitivities S are measured for light intensities up to ${10}^4 \mathrm{W}/{\mathrm{m}}^2.$ Comparison with experimental data of congruent crystals indicates that the specific photoconductivity is 15 times larger after a vapor transport equilibration treatment. The specific bulk photovoltaic coefficient ${\beta }^{*}$ is 2 times larger, refractive-index changes are 7 times smaller, and the holographic sensitivity is up to 4 times larger.

© 2002 Optical Society of America

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