Spatial shifts of the conjugate beam generated by a nondegenerate photorefractive phase-conjugate mirror

We, demonstrate that the phase conjugation of a beam during nondegenerate four-wave mixing is accompanied by a spatial shift relative to the degenerate conjugate-beam location. Experiments with a photorefractive phase-conjugate mirror reveal that the phase-conjugate beam shifts have a nonmonotonic dependence on the probe's detuning frequency and comprise both lateral displacements of up to 218 mu m and angular tilts of up to 34 are sec. An approximate theory based on spatial dispersion coefficients is in partial agreement with the experimental results. (C) 1998 Optical Society of America OCIS codes: 190.5040, 190.4380, 190.5330, 190.4420.