Spectral narrowing via quantum coherence

Journals published by the American Physical Society can be found at http://publish.aps.org/We have studied the transmission through an optically thick Rb-87 vapor that is illuminated by monochromatic and noise-broadened laser fields in Lambda configuration. The spectral width of the beat signal between the two fields after transmission through the atomic medium is more than 1000 times narrower than the spectral width of this signal before the medium