Bragg and non-Bragg diffraction from single beam writing and readout in photorefractive barium titanate

We demonstrate anisotropic self-diffraction in cerium doped barium titanate crystal using one incident beam. The second writing beam is derived from the internal reflection, at the incident surface, of the generated contra-propagating self-phase conjugate inside the crystal. Experimental measurements of the permissible angle(s) of incidence fit the theoretical and experimental results using two incident beams investigated by Kukhtarev et al [1]. The result also shows that anisotropic higher orders can be observed even when the ratio between both writing beams (induced and incident) is less than 10%. In the second part of the paper, we investigate the gratings created during self-diffraction originating from two writing beams in cerium doped barium titanate, using a reading beam of different wavelength. We have previously used anisotropic self-diffraction using two incident beams for image correlation [2]. The results can be separated to two different regimes, Bragg-like regime and Raman-Nath like regime. In the Raman-Nath regime, the polarizations of the generated higher order(s) are orthogonal to the polarization of the reading beam. In the Bragg like regime, the polarizations are the same. Finally the reading of self-diffraction gratings created by one writing beam will be investigated using one beam at a different wavelength.