Ultra-cold atoms in far-detuned optical lattices

This thesis describes the design and construction of a laser cooling experiment for the study of optical lattices, and reports on the results of experiments aimed at 'quantum state preparation' by means of resolved-sideband Raman cooling in a far-detuned optical lattice. Preliminary experiments were performed on cold atoms in a magneto-optical trap, in an optical molasses and in an optical lattice to determine their properties and optimise the conditions for the loading of a far-detuned optical lattice. Temperature measurement techniques such as ballistic expansion and recoil-induced resonances were used. The vibrational levels and coherences of the optical lattice were investigated with conventional probe absorption spectroscopy and a novel method based on coherent transients, which revealed evidence that the anharmonicity of the potential wells is the dominant factor in determining the widths of Raman transitions between levels. A two-dimensional far-detuned (non-dissipative) lattice was loaded from a spatially coincident near-resonant lattice, and a scheme for degenerate resolved-sideband Raman cooling investigated, which was found to increase the population of the lowest motional band to several times that achievable by Sisyphus cooling alone. (author)SIGLEAvailable from British Library Document Supply Centre-DSC:D216745 / BLDSC - British Library Document Supply CentreGBUnited Kingdo