Photorefractive charge compensation in alpha-phase proton-exchanged LiNbO3waveguides

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 lig ht intensity within the studied range, 0.3-50 W/cm(2). The time dependencie s are well represented by the sum of two exponential components. After comp lete optical erasure, diffraction efficiency eta increases in the dark (i.e ., dark developing) up to similar to 17% of the saturation value eta(s) con gruent 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+ lig ht-induced charge distribution is compensated for by a light-insensitive sp ecies (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, 1 90.5330, 130.3130, 130.3730.