Abstract

Nonlinear spectroscopy of cold atoms has recently been reported for a sample of cesium atoms confined in a magnetooptical trap.¹,² In particular, we report measurements of the spectral response of the cold sample to a weak probe beam for a range of detunings and power for the saturating trapping beams. Transmission spectra for the probe beam reveal the presence of broad absorption and gain features as well as narrow resonances. The power dependence of the broad part of the spectrum can be reasonably well described by earlier work for two-level atoms in a strong field.³ However, narrow dispersive shaped features around the frequency of the trapping beams are also observed and can have appreciable single pass gain (>20%). An exploration of the correlation between the narrow spectroscopic features and the mechanical properties of the atomic sample leads to the observation of both positive and negative radiation pressure associated with stimulated absorption from and emission to the probe beam.

© 1991 Optical Society of America