Observation of the Bichromatic Force on Metastable Helium

M. Cashen, H. Metcalf

Chieda, Edward E. Eyler

M. Cashen, H. Metcalf

We have observed the bichromatic force on metastable He using fiber amplifiers to produce the high power of light needed at $\ensuremath{\lambda}=1.083 \ensuremath{\mu}\mathrm{m}.$ We have done deflection experiments to confirm that the very large magnitude of the force scales to He, and preliminary deceleration experiments for eventual trap loading. Our measurements support earlier experiments in Rb. Helium is ideally suited for this kind of beam slowing because its slowing length with the usual radiative force is more than a factor of 100 larger than with the bichromatic force. Thus, loading a MOT will be much more effective because of the much larger angular capture range associated with the shorter distance.

M. A. Chieda, Edward E. Eyler

We examine two approaches for significantly extending the velocity range of the optical bichromatic force (BCF), to make it useful for laser deceleration of atomic and molecular beams. First, we present experimental results and calculations for BCF deceleration of metastable helium using very large BCF detunings and discuss the limitations of this approach. We consider in detail the constraints, both inherent and practical, that set the usable upper limit of the BCF. We then show that a more promising approach is to utilize a BCF profile with a relatively small velocity range in conjunction with chirped Doppler shifts, to keep the force resonant with the atoms as they are slowed. In an initial experimental test of this chirped BCF method, helium atoms are slowed by $\ensuremath{\sim}$370 m/s using a BCF profile with a velocity width of $\ensuremath{\lesssim}$125 m/s. Straightforward scaling of the present results indicates that a decelerator for He* capable of loading a magneto-optical trap can yield a brightness comparable to a much larger Zeeman slower.

Matthew J. Partlow, Joerg Bochmann, X. Miao +1 more

Wilbert Rooijakkers, W. Vassen, W. Hogervorst