Atom-light interactions in ultracold anisotropic media

Abstract

A series of studies on atom-light interactions in ultracold anisotropic media were conducted. Methods to trap ultracold neutral atoms in novel traps with widely tunable trap frequencies and anisotropies were investigated. In comparison to conventional magnetic traps, it was found that magnetic traps generated by soft ferromagnets have various advantages such as a large dynamic range of trap confinement, an ability to create homogeneous reciprocal traps and an ability to shield ultracold atoms from deleterious surface induced effects which would otherwise lead to decoherence and loss. Such microfabricated ferromagnetic "atom chips" are promising systems for the integration of atom optic components such as high finesse cavities and single atom counters. This can, in the near future, lead to precise atom sensors for magnetometry and inertial sensing. the wide tunability of the trap parameters made such integrated atom traps and ideal system for studies of lower dimensional systems and mesoscopic physics in the ultracold regime. Ultracold anisotropic media were shown to possess many novel and attractive properties. Due to the suppression of radiation trapping in these systems, laser cooling was shown to be highly efficient leading to a dramatic increase in the phase space density of an optically cooled atomic ensemble. Subsequent confinement of the resulting ensemble in a magnetic trap and further increase of the phase space density by evaporative cooling should lead to large numbers of atoms in a Bose condensate. It is also an intriguing prospect to combine extreme trap anisotropy with sub-recoil cooling schemes to approach Bose condensation through all-optical cooling. Recoil induced resonances in these anisotropic media were shown to exhibit single pass optical amplifications on the order of 100, more than two orders of magnitude higher than observed previously. The strong dispersion associated with this resonance was used to create an ultracold optical fiber, thus overcoming the diffraction limit for atom-light interactions. With such radial confinement, strong dispersion was combined with arbitrarily large optical depths thereby rendering this system a unique medium for nonlinear optics in the single photon domain. This system was shown to exhibit pronounced nonlinear and collective effects due to the strong coupling between atoms and light.