Stimulated Emission by Atoms Moving in a Strong Standing Wave Field

Wen-Sheng Ren

A. I. Alekseev, Ashat M. Basharov

Alain Aspect, Jean Dalibard, A. Heidmann +2 more

We have observed an efficient collimation of a cesium atomic beam crossing at right angles an intense laser standing wave. This new cooling scheme is mainly based on a stimulated redistribution of photons between the two counterpropagating waves by the moving atoms. By contrast with usual radiation pressure cooling, this "stimulated molasses" works for blue detuning and does not saturate at high intensity.

Jean Dalibard, Alain Aspect, A. Heidmann +3 more

We have observed a new type of laser cooling1mainly based on stimulated emission, which can be much more efficient than the usual laser cooling, i.e., the so-called radiation pressure optical molasses. This cooling occurs in a strong laser standing wave, detuned blue with respect to the atomic resonance. The force exerted on the atom results from a coherent redistribution of photons between the two running waves forming the standing wave. The cooling process can also be seen in the dressed atom picture as a microscopic realization of the Sisyphus myth: the atoms in this diagram see more uphill parts than downhill parts.

Ch. J. Bordé

Yaakov Shevy

The optical forces exerted on a slowly moving two-level atom in a standing wave are profoundly modified when the normal decay rates of the atom are altered. The theory presented in this paper shows that the stimulated emission force becomes dominant at a very low laser intensity. Furthermore, it can change sign to provide an additional cooling force instead of a heating force at laser detunings below the atomic resonance. These phenomena can lead to equilibrium temperatures below the Doppler limit.