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Publication Citation: A Well-Collimated Quasi-Continuous Atom Laser

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Author(s): Edward W. Hagley; Lu Deng; M M. Kozuma; J T. Wen; Kristian Helmerson; S L. Rolston; William D. Phillips;
Title: A Well-Collimated Quasi-Continuous Atom Laser
Published: March 01, 1999
Abstract: One of the most exciting and significant inventions of the 20th century is the laser. The differences between laser light and the light from an incandescent lamp, are apparent to anyone who has seen a laser pointer. The laser emits a narrow beam of collimated light that does not spread out much, even when projected across a large auditorium. By contrast even the best flashlight beam spreads significantly in a short distance. The laser light is very pure in color (frequency), but the lamp emits white light, a mixture of all the colors of the rainbow. Less apparent, but just as important, is that the light waves from the laser are all in step (a property known as coherence), like a well-trained drill team marching in strict cadence, while the light bulb emits waves in a haphazard manner, like a crowd of disorderly school children running across a playground.Beams of atoms have much in common with beams of light. Each can be thought of as a stream of particles (called photons in the case of light), or as a beam of waves. Until recently, however, atomic beams have always been like the light beams from flashlights--a disorderly jumble of different waves, not the orderly coherence of a laser beam. The 1995 achievement of Bose-Einstein condensation in the laboratory of Eric Cornell and Carl Wieman at the National Institute of Standards and Technology (NIST) in Boulder, Colorado changed all that. A Bose-Einstein condensate is a collection of atoms all in the same quantum state. That means that all the atoms are doing exactly the same thing, much as all the light inside a laser is doing the same thing, with all the waves marching in step. When atoms are drawn out of a Bose-Einstein condensate, they can form a beam of atoms that is like a laser beam, as different from ordinary atomic beams as lasers are from light bulbs. A rudimentary atom laser was first made in the laboratory of Wolfgang Ketterle at MIT in Cambridge, Massachussets in 1997.In our laboratory at NIST in Gaithersburg, Maryland we have made a significant advance in the art of atom lasers. The MIT atom laser produced a series of pulses of atoms, with each pulse spreading out in an expanding arc, like the ripples on a pond into which a series of rocks is thrown. We modified the process of extracting the atoms so that the spreading became negligible--not much worse than in a usual laser pointer. In addition, we pulse the laser so quickly that the pulses overlap, effectively making a continuous beam of atoms. The key to our method is that it kicks the atoms out in a chosen direction with a chosen speed, while the older method caused the atoms to trickle out under the influence of gravity. Just as some advanced lasers can be tuned to deliver different colors of light, our technique allows the atom laser to be tuned to deliver different velocity atoms.As when the laser was invented 40 years ago, the potential applications of the atom laser may not be apparent, but some of them can be anticipated. Atom interferometers, devices that use the wave-like properties of atoms, may be significantly improved by the use of laser-like atomic beams. This could allow improved measurements of gravity or make for better inertial navigation. The invention of lasers ushered in the common use of holographic imaging, and atom lasers may do the same for atom holograms, possibly allowing advances in lithography--the process by which ultraminiature electronic circuitry is made.A paper by E. Hagley, L. Deng, M. Kozuma, J. Wen, K. Helmerson, S. Rolston and W. Phillips, detailing the atom laser development appears in the 12 March 1999 issue of the journal Science.
Citation: Science
Volume: 283
Issue: No. 5408
Keywords: atom laser;atomic particles;atomic wave beam;Bose-Einstein condensation;laser
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