Dark developing of photorefractive proton-exchanged LiNbO3 waveguides

Photorefractive measurements have been performed in proton-exchanged (PE) L iNbO3 waveguides as unannealed alpha -phase layers. Holographic recording a nd light and dark erasures have been studied. The saturation index change i s independent of the light intensity within the studied range 0.3-50 W/cm(2 ). The time dependencies of Deltan are well represented by the sum of two e xponential components. After a complete optical erasure, Deltan increases i n the dark (dark developing) up to Deltan congruent to 3 x 10(-6) and then decays to zero in about 4 h. All experimental results are reasonably well s imulated using a model in which the Fe2+/Fe3+ light-induced charge distribu tion is compensated by a light insensitive species (ionic charges or holes) mobile at room temperature. (C) 2001 Elsevier Science B.V. All rights rese rved.