Nonlinear spectroscopy of cold cesium in a magneto-optical trap

In this paper an overview of recent results on nonlinear spectroscopy of cold atoms is presented. Probe-beam amplification and absorption spectra are reported for cesium atoms cooled and confined in a magneto-optical trap. In addition to the well known spectrum of Mollow, novel spectral features with subnatural linewidths and single-pass gain of 20% are also observed. These narrow resonances can be qualitatively understood in terms of stimulated Raman processes in a three-level system. Negative radiation pressure is demonstrated as a mechanical consequence of optical gain. (author). 19 refs, 7 figs