Photorefractive coupling between orthogonally polarized light beams in barium titanate

In certain crystals, photorefractive two-beam coupling is predicted for orthogonally polarized optical beams. The prediction follows from the phenomenological tensor form of the photogalvanic current. We demonstrate this coupling by measuring the complex beam-coupling coefficient in barium titanate and show that the photogalvanic current correctly predicts the form for the coefficient as a function of the beam crossing angle.