We report direct, time-resolved observations of single-photon superradiance in a highly extended, elliptical sample of cold 87 Rb atoms. The observed rapid decay rate is accompanied by its counterpart, the cooperative Lamb shift. The rate of the strongly directional decay, and the associated shift, scale linearly with the number of atoms, demonstrating the collective nature of the observed quantities.
Based on the developed quantum microscopic theory, the interaction of weak electromagnetic radiation with dense ultracold atomic clouds is described in detail. The differential and total cooperative scattering cross sections are calculated for monochromatic radiation as particular examples of application of the general theory. The angular, spectral, and polarization properties of scattered light are determined. The dependence of these quantities on the sample size and concentration of atoms is studied and the influence of collective effects is analyzed.
We report a combined experimental and theoretical investigation of near-resonance light scattering from a high-density and ultracold atomic 87 Rb gas. The atomic sample, having a peak density ∼5 × 10 13 atoms/cm 3 , temperature ∼65 μK, and initially prepared in the F = 1 lower-energy 87 Rb hyperfine component, is optically pumped to the higher-energy F = 2 hyperfine level. Measurements are made of the transient hyperfine pumping process and of the time evolution of scattering of near-resonance probe radiation on the F = 2 → F = 3 transition. Features of the density, detuning, and temporal dependence of the signals are attributed to the high density and consequent large optical depth of the samples.
We review experimental and theoretical studies of coherent backscattering of near resonant radiation from an ultracold atomic gas in the weak localization regime. Recent accomplishments in high resolution spectroscopy of atomic ensembles based on the coherent backscattering process are discussed. We also propose several new experimental schemes for time-dependent spectroscopy as applied to multiple scattering in the regime of weak localization.A coherent backscattering image of light scattered from an atomic cloud of 85 Rb atoms in the lin ⊥ lin polarization channel
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