OPTICALLY INDUCED DIPOLE-DIPOLE INTERACTIONS IN ATOMIC ENSEMBLES

Abstract

Thanks to recent experimental advances, quantum light-matter interactions in atomic ensembles can now be studied in regimes that have hitherto been inaccessible. Of particular interest are problems involving multiple photon scattering, where effective dipole-dipole interactions between the atoms are present. A prominent example involves atoms coupled to a photonic band gap material, which strongly modifies the atomic emission and absorption properties compared to free space. The first part of this thesis describes theoretically the fundamental optical properties of such a system, including important characterisation tools in the linear regime, and applications leveraging strong non-linearity at the few-photon level.

A second example involves atoms in free space arranged in highly ordered arrays, where strong interference in the fields scattered by the atoms can give rise to remarkable collective optical phenomena. The second part of this thesis shows how strong dipole-dipole interactions can manifest themselves in the steady-state population distribution of a driven 1D array of multilevel atoms, under conditions readily accessible to current experiments. Importantly, the results illuminate how widely used control techniques for multilevel atoms - e.g. optical pumping - can be degraded by multiple scattering, and how the influence of dipole-dipole interactions may be regulated by the system geometry.