Population-grating transfer in cold cesium atoms

Optical-pumping-induced population-grating transfer between hyperfine level s of the cesium D-2 line is observed through four-wave mixing in a sample o f cold atoms. Diffraction efficiencies of order of 1% have been measured fo r a large range of angular apertures. We have studied the angular dependenc e of the diffracted signal in the limit of small atomic velocities and disc ussed its application for a nondestructive diagnostic of the trap dynamic. Image processing with nearly degenerate frequency conversion was also demon strated using this specific mechanism. [S1050-2947(99)05302-0].