Abstract

We present recent experimental results on subrecoil laser cooling of caesium and helium atoms, using Raman cooling and velocity selective coherent population trapping (VSCPT). Raman cooling of caesium was optimized using a new approach based on Lèvy flight statistics. In a one-dimensional experiment temperatures below 3 nK, less than 1/70 of the single photon recoil temperature, were obtained. In the periodic potential of an optical standing wave these atoms are delocalized and under the influence of an inertial force Bloch oscillations have been observed. VSCPT of metastable helium atoms has led to the first demonstration of subrecoil laser cooling in three dimensions. Adiabatic passage was used to transform the resulting set of coherent wavepackets into a single one, producing an ultracold spin-polarized atomic beam with a de Broglie wavelength of 1.08 μm and a coherence length of ~ 5 μm, which will be of considerable interest for future work in atom optics.

© 1996 Optical Society of America