Toward cold atom guidance in a hollow-core photonic crystal fibre using a blue detuned hollow laser bea

This thesis describes advances and techniques toward the efficient coupling of cold 85Rb atoms into a low loss hollow core photonic crystal fibre using a blue-detuned first order hollow beam. In the proposed system, the low diffraction of the blue-detuned first order hollow beam acts as a repulsive potential optical funnel that allows the coupling of cold atoms under the influence of gravity into the fibre's hollow core. Using a low loss fibre with a blue detuned hollow beam shows potential for guiding atoms over an arbitrary path and longer distances on the laboratory scale, which would enable several new applications in nanofabrication and optical metrology.;To realize this objective, a Magneto-Optical Trap of 85Rb was built from scratch and by using advanced polarization gradient cooling techniques was turned into a 9 muK cold optical molasses containing 10 7 atoms. These cold atoms were guided over 23 cm in a collimated blue detuned hollow beam tunnel and through a focused hollow beam mimicking as closely as possible the coupling conditions for a hollow core optical fibre. Three classes of atoms were observed: lost, trapped and guided atoms. The dynamics of the system as well as the optimal coupling conditions were identified through the use of a numerical model.;A novel approach to modelling cold atom dynamics in an optical funnel was developed during the course of this thesis. This new model was not only able to reproduce the dynamics of atoms in the experiment but also simulate dense cold atoms cooled into the MOT and predict final temperatures attained. This was achieved by 3D modelling of the conservative and non-conservative components of optical forces acting on atoms but also through the implementation of known heat mechanisms: light scattering and momentum diffusion. The model identified the best coupling conditions of this system, confirmed by experiment, and an optimal light potential for a given distance of coupling that must not be exceeded.;A single mode, high purity, LG01 beam was generated with over 50% conversion efficiency from a Gaussian mode using a complex-valued computer generated hologram (CGH) rendered on a phase-only liquid-crystal spatial light modulator (SLM). A system-wide 35% conversion efficiency was achieved from the laser output to the vacuum chamber input.;Several micro-structured polymer optical fibres and silica hollow-core band-gap photonic crystal fibres with Kagome claddings were evaluated. A single defect, large hollow core (∼ 5mum diameter) Kagome cladding fibre was identified as a suitable solution for guiding cold 85Rb atoms. The LG01 mode generated by the SLM was coupled into a single first order hollow mode with a high efficiency of 43% and 76% for the Gaussian mode by controlling the blazed grating period and the input beam size with the CGH.;All these achievements opened a way for the challenging realisation of cold atom fibre guidance in this optimal system which has shown to have an order of magnitude less heating than in comparable red-detuned coupling and guidance. This guiding scheme also allows the keeping of the coldest atoms within the distribution to interact minimally with the guiding potential, showing promise of enabling single mode atomic wave guiding with less experimental constraints than red detuned schemes.