Transverse Modulation of a Laser Beam in Cerium-Doped BaTiO₃

An extraordinarily polarized Gaussian beam, after passing through a photorefractive crystal with an external electric field, shows transverse spatial modulation and self-focusing due to the in-phase component of the refractive index change relative to the intensity profile of the beam. Besides that the beam shifts toward the Crystal c-axis due to the π / 2 out-of-phase component.