Prof. William D. Phillips
Nobel Laureate in Physics
William D. Phillips, American physicist whose experiments using laser light to cool and trap atoms earned him the Nobel Prize for Physics in 1997. He shared the award with Steven Chu and Claude Cohen-Tannoudji, who also developed methods of laser cooling and atomtrapping.
Phillips received his doctorate in physics (1976) and completed his postdoctoral research at the Massachusetts Institute of Technology. In 1978 he joined the staff of the National Bureau of Standards (now the National Institute of Standards and Technology) in Gaithersburg, Md., and it was there that he conducted his award-winning research. Building on Chu’s work, Phillips developed new and improved methods for measuring the temperature of laser-cooled atoms. In 1988 he discovered that the atoms reached a temperature six times lower than the predicted theoretical limit. Cohen-Tannoudji refined the theory to explain the new results, and he and Phillips further investigated methods of trapping atoms cooled to even lower temperatures.
Research Interests
Laser beam
Atom
Optical Molasses
and many more...
Paper Published
In 1978, while I was a postdoctoral fellow at MIT, I read a paper by Art Ashkin (1978) in which he described how one might slow down an atomic beam of sodium using the radiation pressure of a laser beam tuned to an atomic resonance. After being slowed, the atoms would be captured in a trap consisting of focused laser beams, with the atomic motion being damped until the temperature of the atoms reached the microkelvin range. That paper was my first introduction to laser cooling, although the idea of laser cooling (the reduction of random thermal velocities using radiative forces) had been proposed three years earlier in independent papers by Hänsch and Schawlow (1975) and Wineland and Dehmelt (1975). Although the treatment in Ashkin’s paper was necessarily over-simplified, it provided one of the important inspirations for what I tried to accomplish for about the next decade. Another inspiration appeared …
Quantum phase engineering is demonstrated with two techniques that allow the spatial phase distribution of a Bose-Einstein condensate (BEC) to be written and read out. A quantum state was designed and produced by optically imprinting a phase pattern onto a BEC of sodium atoms, and matter-wave interferometry with spatially resolved imaging was used to analyze the resultant phase distribution. An appropriate phase imprint created solitons, the first experimental realization of this nonlinear phenomenon in a BEC. The subsequent evolution of these excitations was investigated both experimentally and theoretically.
We have measured the temperature of a gas of sodium atoms released from” optical molasses” to be as low as 43±20 μK. Surprisingly, this strongly violates the generally accepted theory of Doppler cooling which predicts a limit of 240 μK. To determine the temperature we used several complementary measurements of the ballistic motion of atoms released from the molasses.
Deceleration and velocity bunching of Na atoms in an atomic beam have been observed. The deceleration, caused by absorption of counterpropagating resonant laser light, amounts to 40% of the initial thermal velocity, corresponding to about 15 000 absorptions. Atoms were kept in resonance with the laser by using a spatially varying magnetic field to provide a changing Zeeman shift to compensate for the changing Doppler shift as the atoms decelerated.
We report the first observation of electromagnetically trapped neutral atoms. Laser cooled and stopped sodium atoms are confined in a magnetic quadrupole trap formed by two opposed, separated, coaxial current loops. The decay time constant for atoms in the trap is 0.83 (7) s and is limited mainly by collisions with background gas atoms.