Light storage in an optically thick atomic ensemble under conditions of electromagnetically induced transparency and four-wave mixing

We study the modification of a traditional electromagnetically induced
transparency (EIT) stored light technique that includes both EIT and four-wave
mixing (FWM) in an ensemble of hot Rb atoms. The standard treatment of light
storage involves the coherent and reversible mapping of one photonic mode onto
a collective spin coherence. It has been shown that unwanted, competing
processes such as four-wave mixing are enhanced by EIT and can significantly
modify the signal optical pulse propagation. We present theoretical and
experimental evidence to indicate that while a Stokes field is indeed detected
upon retrieval of the signal field, any information originally encoded in a
seeded Stokes field is not independently preserved during the storage process.
We present a simple model that describes the propagation dynamics of the fields
and the impact of FWM on the spin wave.