The influence of collective effects on the propagation of electromagnetic radiation in dense ultracold atomic ensembles

Abstract

Based on the already developed general theory (I.M. Sokolov, D.V. Kupriyanov, and M.D. Havey, JETP 112 (2), 246 (2011)), we have studied the spatial distribution of excited atoms and of the atomic polar ization that a weak monochromatic field creates in a dense ultracold atomic medium. We show that, in the case of a homogeneous random spatial distribution of atoms, the amplitude of atomic polarization averaged over spatial configurations decreases outside boundary regions according to an exponential law, while its phase linearly increases. Based on this, we have numerically determined the extinction coefficient and the light wavelength in the medium, as well as its dielectric permittivity. The dispersion of the permittivity at dif ferent concentrations has been studied. We show that, for dense clouds, the real part of the dielectric permit tivity acquires negative values in a certain frequency range. Based on the calculation of the spatial distribution of excited atoms, we have analyzed the character of the transfer and trapping of quasi resonant radiation in atomic clouds of differing density.

Near-resonance light scattering from a high-density ultracold atomic87Rb gas

“…Such scaling rules are useful because the samples explored experimentally contain several orders of magnitude more atoms, making direct numerical simulations impractical. The details of the theoretical approach have been laid out and applied in several previous papers [43,61,64,66], and are briefly summarized in the Appendix.…”

“…Experimental results are compared to theoretical ones obtained for atomic samples of nearly the same peak density, but fewer atoms. The theoretical approach used has been described elsewhere [43,61,64,65], and for the convenience of the reader is summarized in the appendix. To have possibilities to contrast results of the theory with experiments, we choose the density of our motionless four levels atoms in such a way that photons would have the same mean free path as in the 87 Rb samples.…”

Generalised hyper-Ramsey spectroscopy of two-level atoms in an optically dense medium

“…The ensemble is assumed to be quite dilute, such that the wavelength of the incident radiation is less than average interatomic distance ( 3 1 a n   , where  is the wavelength of the incident radiation). It allows us to neglect the effects of recurrent light scattering [33][34][35][36] and to consider the interaction of each atom with radiation independently in terms of quantum correlations. However, the interaction of radiation with each atom of the ensemble is not completely independent due to its optical density.…”

Cooperative effects in one-dimensional random atomic gases: Absence of single-atom limit

“…These effects show up as a multi-atomic coherent emission which is qualitatively different from that of a single atom [3,4]. Cooperative effects have been studied both theoretically and experimentally in various systems, such as quantum dots [5], Bose-Einstein condensate [6,7], cold atoms [8,9] and Rydberg gases [10].…”