Three physicists share Nobel prize for laser-cooling and atom-trapping

Steven Chu, Claude Cohen-Tannoudji, and William D. Phillips have won the 1997 Nobel Prize in Physics for their contributions to the development of methods to cool and trap atoms with laser light. Chu, now at Stanford University (Stanford, CA), developed a way to cool atoms using laser light while working with colleagues at Bell Laboratories (Holmdel, NJ) in 1985. Using six pairwise orthogonal laser beams they created a small pod of about a million sodium atoms moving in a thick "optical molasses" at 240 µK—a technique called Doppler cooling. Later they constructed a magneto-optical trap that counteracted the force of gravity and securely captured atoms for study and experiment.

At the National Institute of Standards and Technology (Gaithersburg, MD), Phillips built on Chu`s work and discovered new methods of measuring the temperature of the atoms in the molasses (see Laser Focus World, May 1995, p. 36). He found attainable temperatures as low as 40 µK, below the theoretically calculated Doppler limit. Cohen-Tannoudji of the École Normale Supérieure (Paris, France) was able to explain Phillips` result from theoretical studies of more-complicated cooling schemes based on an the lowest energy levels of the sodium atom, a process termed Sisyphus cooling. His group later created atomic "dark" states, cooling helium atoms to a temperature of 0.18 µK at a speed of only 2 cm/s.

The work has led to insights into the interaction of matter and radiation and a host of applications in areas such as spectroscopy, atomic clocking, atomic interferometers, optics, and lithography, and the first observation of a Bose-Einstein condensate (see Laser Focus World, Jan. 1996, p. 47).