Researchers Move Atom Lasers Forward

CAMBRIDGE, Mass., Jan. 12 -- Operating independently, researchers at the Massachusetts Institute of Technology (MIT) and the University of Tokyo have succeeded in amplifying an atom wave while maintaining its original phase, leading to an atom laser that is the closest equivalent yet to an optical laser.
Scientists at MIT used a pair of laser pulses to strike a sodium Bose-Einstein condensate (BEC). Some of the BEC atoms absorbed a photon from the high-frequency beam and emitted a photon towards the lower-frequency beam; these atoms recoiled in the same direction, forming a weak atom wave. The lower-frequency beam was then shut off, and some of the other BEC atoms absorbed light from an intensified pulse from the high-frequency laser. The presence of the initial atom wave stimulated these BEC atoms to emit a photon in the direction of the lower-frequency beam. The end result was a phase-coherent amplified beam about four times as strong as the initial atom wave.
The Tokyo group used a rubidium-87 BEC in their experiment, which demonstrated similar results. The amplification in both cases was limited by the size of the BEC, which was depleted during the demonstrations. However, researchers hope these results will lead to improvements in such applications as atom-wave gyroscopes and lithography.