The manufacture of a Bose-Einstein condensate
; where a collection of atoms
have the same wavelength (see wave/particle duality
) lead to experiments to produce a beam
of such atoms, in a manner similar to laser
of the same wavelength are emitted.
In an atom laser, the magnetic trap
containing the Bose-Einstein condensate is analogous
to the cavity of a conventional laser, and radio
waves or laser beams can be used to 'pump
' the atoms, until they are emitted from the trap.
This was first achieved at M.I.T
in 1997 by the research group of Wolfgang Ketterle
, in this experiment radio waves were used to flip the nuclear spin
of atoms in the trap so they were no longer confined, so they simply 'fell' out of the trap. This produced not so much a beam, as a sequence of spreading output pulses, caused by the atoms mutual repulsion
forcing them apart.
The first directional, collimated
matter laser was produced in the NIST physics
lab. by E.W. Hagley
, et al in 1999. In this experiment a condensate of sodium
atoms were driven by optical Raman
pulses from two lasers between different magnetic energy levels
. Tuning the lasers to slightly different frequencies
allowed the experimenters to cause atoms to be emitted in one direction; towards that of the lower frequency laser. The atoms emit photons preferentially towards the high frequency laser, and less so towards the lower frequency one, which in a manner similar to a rocket
gives the atoms momentum
. By increasing the difference in frequency between the Raman lasers, the atoms can be transferred into an energy level where they no longer feel the trapping potential
, and they are then ejected from the bulk of the condensate, to form (in this experiment) a beam the thickness of a human hair
, moving at 6 centimeters
The beam only lasts as long as there are atoms in the condensate
, to keep it going long enough to do really useful work
, a way would have to found to add atoms back into the condensate. Some examples of the useful work that could be done with good, continuous wave matter lasers are :-
, if these lasers could be used to make holograms of matter, that is patterns of pictures, on the surface of objects, this could lead to the production of features on silicon chips
much smaller than is possible with conventional lithographic
2. Improve the precision of atomic clocks
, leading to benifits in all experiments that rely on accurate measurements.
3. Improvements in atomic imaging
A Well Collimated Quasi-Continuous Atom Laser, E.W. Hagley, L. Deng, M. Kozuma, J. Wen, K. Helmerson, L. Rolston, and W. D. Phillips. Science
12 March 1999
An output coupler for a Bose
-condensed atoms, M.-O. Mewes, M.R. Andrews, D.M. Kurn, D.S. Durfee, C.G. Townsend, and W. Ketterle, Physical Review Letters
78, 582, 27 January 1997.