Towards interferometry with bright solitary waves in a ring

Abstract

This thesis presents the work towards the realisation of an interferometer using bright solitary waves in a ring. The splitting of a bright solitary wave, which is created from a 85Rb Bose-Einstein condensate in an optical waveguide, is realised through scattering from a narrow potential well formed from a tightly focussed red detuned laser beam. We observe reflection of up to 25% of the atoms, along with the trapping of atoms at the position of the potential. Such a reflected fraction is much larger than the theoretical predictions for a single, narrow Gaussian potential. A more detailed model, which accounts for the diffraction pattern of the laser beam, suggests that the presence of these small subsidiary intensity maxima is the cause of the enhancement in quantum reflection.

An upgrade of the apparatus sees a new set of magnetic coils, a compact coil mount, and a crossed optical dipole trap with independently controllable beams implemented. This enables the control of magnetic curvature and dipole trap position, and maximises the optical access to the science cell. To generate a ring trap for the interferometry scheme, a spatial light modulator (SLM) is incorporated into the experiment. Through underfilling the SLM panel with the laser beam, and the use of the analytical first phase guess prior to the error minimising Mixed Region Amplitude Freedom (MRAF) algorithm, we are able to generate speckle-free, high quality holograms of arbitrary shapes. Furthermore, we demonstrate atom trapping in a ring potential, which is formed at the intersection of the SLM beam and a red detuned horizontal light sheet.