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Raman Amplification of
Matter Waves
With the realization of coherent, laser-like atoms
in the form of Bose-Einstein condensates it has become
possible to explore matter-wave amplification, a process
in which the number of atoms in a quantum state is amplified
due to bosonic stimulation. In previous amplifiers based
on superradiant Rayleigh scattering the atoms remained
in the same internal state [1, 2], a fact that severely
limited the performance since the amplified atoms were
scattered out of the final state or served as a gain
medium for higher-order processes. We have now realized
a Raman atom amplifier in which the gain medium and
the amplified atoms are in different internal states
[3]. Such a system has analogies to an optical laser
in which different transitions are used for pumping
and lasing.
The gain mechanism is provided by a polarization grating,
a coherence between two different hyperfine states.
We observed an exponential growth of this grating and
characterized its coherence time.
Fig 1.
Observation of superradiant Rayleigh scattering. (A)
Experimental configuration. A laser beam (wave vector
k) is incident perpendicularly to the long axis of the
condensate; its electric field vector E is parallel
to it and the applied magnetic field B. Each scattering
event results in a recoiling atom (momentum hq) and
a scattered photon (momentum h(k-q)). The recoiling
atoms lie on a shell of radius hk. (B) Spontaneous Rayleigh
scattering. The absorption image shows a halo of atoms.
The intensity of the beam was 1 mW/cm2; the pulse duration
was 1 ms. (C) Superradiant Raman scattering as observed
for a beam intensity of 18 mW/cm2 and a pulse duration
of 100 µs (the original condensate was fully depleted
after ~10 µs). In both cases the field of view was 1.05
mm x 1.05 mm.
- S. Inouye, T. Pfau, S. Gupta, A.P. Chikkatur, A.
Görlitz, D.E. Pritchard, and W. Ketterle, Observation
of phase-coherent amplification of atomic matter waves,
Nature 402, 641 (1999).
Link
- M. Kozuma, Y. Suzuki, Y. Torii, T. Sugiura, T.
Kuga, E.W. Hagley, and L. Deng, Phase coherent amplification
of matter waves,
Science 286, 2309 (1999).
- Dominik Schneble, Gretchen K. Campbell, Erik W.
Streed, Micah Boyd, David E. Pritchard, and Wolfgang
Ketterle: Raman Amplification of Matterwaves.
Phys. Rev A 69, 041601(R) (2004)
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