Precision of retroreflection in quasidegenerate four-wave interaction

An experimental determination was made of the direction of propagation of a reflected wave in the case of a quasidegenerate four-photon interaction. This direction was different from the exact retroreflection of the signal wave. Characteristics of the deviation from the exact retroreflection were determined and it was found that the magnitude of the deviation depended strongly on the angle of incidence of the signal wave on the boundary of a nonlinear interaction region.