Continuing investigations into the properties of Bose-Einstein condensates, a team at Massachusetts Institute of Technology in Cambridge has reported high gain and low group velocities in light injected into a dressed condensate. Previously, the researchers, who published their report in the Nov. 13, 2000, issue of Physical Review Letters, discovered that the condensates, which are illuminated with an off-resonance laser, amplify matter waves.

At a probe intensity of 0.10 mW/cm², the team observed optical gain of 2.8, the result of diffraction effects on the atoms in the dressed condensate that inject photons into the probe beam mode. The stimulated amplification process also created a pulse delay proportional to the gain. The researchers reported delays of 20 µs across the 20-µm-wide condensate; this is the smallest group velocity yet observed, at 1 m/s.