Two-beam cross coupling from mutually incoherent lasers

The cross coupling of two mutually incoherent sources in photorefractive materials is described. It is shown that when there are two mutually incoherent pump beams that are not counterpropagating, the respective outputs are cones of light whose parameters depend on the interaction angle of both pump beams. The phase-matching equations are solved, and the cones are analytically represented. Additionally, the coupled-wave equations are solved to give the intensity of light along the coordinates of the cones. These cones are experimentally observed as ellipses on a screen. Preliminary experiments are reported in which the intensities of the cones are measured and compared with theory. How this applies to other cases of mutually incoherent two-beam cross coupling is discussed.