Mechanism for photorefractive phase conjugation using incoherent beams

Two mutually incoherent extraordinary laser beams, incident upon opposite a faces of a BaTiO(3) crystal, generate a set of photorefractive holograms that channel both beams toward the +c face of the crystal, where they are internally reflected into the opposite channel. The resultant cross coupling of the two incident beams produces a pair of phase-conjugate (Phi*) beams. This new photorefractive interaction is characterized by reasonable Phi* reflectivities (~10-25%), good Phi* fidelity, and no image cross talk. The variations in Phi* reflectivity with crystal orientation, angles of incidence, and intensity ratio are presented. The formation times of the photorefractive gratings responsible for the phase conjugation are significantly shorter than those of other self-pumped phase conjugators.