Propagation of an optical beam in a photorefractive medium in the presence of a photogalvanic nonlinearity or an externally applied electric field

We consider propagation of a light beam in photorefractive media in the framework of a three-dimensional model. We formulate equations governing three-dimensional distribution of a nonlinear refractive index. The distributions of electric charge, potential, current, refractive index, and the near- and far-field output intensities of the beam are calculated. The conditions necessary for observing self-focusing in photorefractive media are discussed.