CHARGE-CARRIER DIFFUSION LENGTH IN PHOTOREFRACTIVE CRYSTALS COMPUTED FROM THE INITIAL HOLOGRAM PHASE-SHIFT

The plane shift between the pattern of light onto a photorefractive cr ystal and the resulting hologram at the very beginning of the recordin g process in two-wave mixing is analyzed and measured as a function of the applied electric field. These data allow one to compute the diffu sion length of photoexcited charge carriers and to evaluate the actual electric field inside the crystal. A diffusion length of 0.14 mu m is measured in a nominally undoped photorefractive Bi12TiO20 crystal usi ng a 532 nm wavelength laser illumination, in agreement with results o btained from other methods. (C) 1997 American Institute of Physics. [S 0003-6951(97)02243-2].