Photon-mediated thermodynamics and density fluctuations in an ensemble of laser-cooled cesium atoms

Abstract

We present an experimental study of detuning-dependent properties of a laser-cooled cesium cloud in a magneto-optical trap. Fluorescence images are used to extract the cloud size, shot-to-shot width fluctuations, optical depth, density profiles, and spatial density fluctuation spectra as the trapping laser detuning is varied. Near resonance, the cloud exhibits larger spatial extent, increased width fluctuations, higher optical depth, and enhanced density fluctuation power, while larger detunings produce a more reproducible and spatially confined cloud. The measured density profiles are analyzed phenomenologically using a generalized Lane–Emden model with a polytropic equation of state, yielding detuning-dependent effective fit parameters in a weak interaction regime. Power spectrum and autocorrelation analyses reveal reproducible scale-dependent density correlations. The results provide a quantitative characterization of detuning-dependent radiative and collective effects in a cesium MOT and establish a basis for future measurements that can more directly test nonequilibrium transport and photon-mediated interaction models.