Photorefractive charge compensation in α-phase proton-exchanged LiNbO3 waveguides

Photorefractive recording and light and dark erasures have been measured in unannealed alpha-phase proton-exchanged LiNbO3 waveguides. The saturation index change, Delta n(s) congruent to 9 x 10(-6), is independent of the light intensity within the studied range, 0.3-50 W/cm(2). The time dependencies are well represented by the sum of two exponential components. After complete optical erasure, diffraction efficiency eta increases in the dark (i.e., dark developing) up to similar to 17% of the saturation value eta(s) congruent to 0.12 and then decays to zero in similar to 4 h. All experimental results are reasonably well simulated by a model in which the Fe2+/Fe3+ light-induced charge distribution is compensated for by a light-insensitive species (ionic charges or holes) that is mobile at room temperature. (C) 2000 Optical Society of America [S0740-3224(00)01908-1] OCIS codes: 190.4400, 190.5330, 130.3130, 130.3730.