Spatial optical memory based on coherent population oscillations

We show that a system characterized by long-lived coherent population oscillations (CPOs), such as a two-level system that decays via a shelving state, can be used to construct a spatial optical memory. In the presence of a cw control field, a field is generated at the four-wave mixing (FWM) frequency with the same spatial profile as the initial probe. When the control field is switched off, these spatial profiles are encoded in the CPOs of the ground and storage states. When the control field is switched on again, the probe and FWM fields are retrieved simultaneously with the same spatial profiles as the initial probe.