Narrow-bandwidth paired photons with controllable waveform

This study reports the experimental demonstration of a high-brightness source of paired photons based on an double-/spl Lambda/ atomic level configuration in cold /sup 87/Rb atoms. The source is capable of producing pairs of correlated photons with bandwidths as small as 5 MHz at into a single spatial mode. Strong counter-propagating coupling and pump lasers are applied and the system spontaneously emits pairs of photons at Stokes and anti-Stokes frequencies. The backward-wave geometry ensures that a spontaneously emitted photons will be oppositely directed and that they can be detected without additional filtering.