Four-wave mixing in dressed cold cesium atoms

Quasi-degenerate four-wave mixing optical phase conjugation was investigate d in cold cesium atoms confined in a magneto-optical trap. Broad and narrow resonances were observed in the corresponding spectrum. The broad resonanc es reveal directly the dressed levels structure of the composite system for med by atoms and trapping laser field. However, the observed narrow resonan ces can only be qualitatively understood in terms of Raman processes involv ing nearly degenerate ground-state levels, indicating the important role pl ayed by the level degeneracy. (C) 2000 Published by Elsevier Science B.V.