Dark developing of photorefractive proton-exchanged LiNbO3 waveguides

Abstract Photorefractive measurements have been performed in proton-exchanged (PE) LiNbO3 waveguides as unannealed α-phase layers. Holographic recording and light and dark erasures have been studied. The saturation index change is independent of the light intensity within the studied range 0.3–50 W/cm 2 . The time dependencies of Δn are well represented by the sum of two exponential components. After a complete optical erasure, Δn increases in the dark (dark developing) up to Δn≅3×10−6 and then decays to zero in about 4 h. All experimental results are reasonably well simulated using a model in which the Fe2+/Fe3+ light-induced charge distribution is compensated by a light insensitive species (ionic charges or holes) mobile at room temperature.