Because of radiation pressure, an optical cavity with harmonically bound mirrors has an intensitydependent length and behaves as an effective Kerr medium. We determine the quantum fluctuations of the field reflected by such a cavity" taking into account the input field fluctuations and the mirror Brownian motion. In the regions of parameter space close to bistability turning points, we obtain a significant quantum-noise reduction effect.PACS number(s): 42.50.Lc, 42.65.Vh

We derive the modifications of the quantum fluctuations of a coherent field after it has interacted with an optical cavity containing an ensemble of two-level atoms. The fluctuations in the output field are separated into two parts: the first one is linked to the parametric transformation of the fluctuations of the incoming field by the atomic medium; the second one is associated with the resonance fluorescence of the atoms driven by the mean intracavity field and coupled with the empty modes of a bath field. We calculate the squeezing spectra and we compare them to the ones obtained with Kerr media having similar dynamic nonlinearities.PACS number(s): 42.50. Lc, 42.65.Pc, 42.50.Dv

We have observed a laser oscillation when a cloud of magneto-optically trapped cesium atoms is inserted in an optical cavity. The laser oscillation occurs at a frequency which is detuned from the trapping beam frequency by 150 kHz. The gain mechanism is due to stimulated Raman processes recently observed in such media.

Laser-cooled and trapped cesium atoms have been used as a nonlinear medium in a nearly resonant cavity. A study of the semiclassical dynamics of the system was performed, showing bistability and instabilities. In the quantum domain, squeezing in a probe beam having interacted with this system was demonstrated.Comment: 6 pages, 6 figures, LaTe