Enhanced wave mixing in photorefractive rhodium-doped barium titanate crystals

We present an experimental study of the self-diffraction in Rh:BaTiO3 and B aTiO3 crystals for small angle between the interfering laser beams. Much la rger diffraction efficiencies and beam amplifications are measured in the s elf-diffraction pattern of Rh:BaTiO3 than in the corresponding pattern of u ndoped BaTiO3 crystals. The enhancement increases with the Rh concentration in the barium titanate crystals, This effect cannot be explained by a simp le Raman-Nath diffraction model, although it gives acceptable predictions f or the undoped crystals, at small modulation index. In the same crystals, t he results of self-diffraction in the Bragg regime remain in a good agreeme nt with the existing theory. (C) 2000 Elsevier Science B.V. All rights rese rved.