Light can exert optical forces on matter. In the macroscopic world these forces are minuscule, but on the microscopic or atomic scale, these forces are large enough to trap and manipulate particles. They may even be used to cool atoms to a fraction of a degree above absolute zero. This thesis details a number of experiments concerned with the optical manipulation of atoms and micron-size particles using free space light beams and photonic crystal fibres. Two atom guiding experiments are described. In the first experiment, a spatial light modulator is used to generate higher blue-detuned azimuthal Laguerre-Gaussian LG) beams, which are annular beams with a hollow core. These LG beams are then used to guide laser cooled rubidium-85 atoms within the dark core over a distance of 30 mm. The second atom guiding experiment involves attempting to guide laser cooled and thermal rubidium atoms through a hollow-core photonic crystal fibre using red-detuned light. Hollow-core photonic crystal fibres are fibres that are able to guide light with low attenuation within a hollow core. For this experiment a hot wire detection system was designed, along with a number of complex vacuum systems. The first dual-beam fibre trap for micron-size particles constructed using endlessly single-mode photonic crystal fibre (ESM-PCF) is described. The characteristics of dual-beam fibre traps are governed by the fibres used. As ESM-PCF has considerably different properties in comparison to conventional single- or multimode fibres, this dual beam ESM-PCF trap exhibits some novel characteristics. I show that the dual beam ESM-PCF trap can form trapping, repulsive and line potentials; an interference-free ‘white light’ trap; and a dual-wavelength optical conveyor belt.

Drawing of standard telecommunication-type optical fibres has been optimised in terms of optical and physical properties. Specialty fibres, however, typically have more complex dopant profiles. Designs with high dopant concentrations and multidoping are common, making control of the fabrication process particularly important. In photonic crystal fibres (PCF) the inclusion of air-structures imposes a new challenge for the drawing process. The aim of this study is to gain profound insight into the behaviour of complex optical fibre structures during the final fabrication step, fibre drawing. Two types of optical fibre, namely conventional silica fibres and PCFs, were studied. Germanium and fluorine diffusion during drawing was studied experimentally and a numerical analysis was performed of the effects of drawing parameters on diffusion. An experimental study of geometry control of PCFs during drawing was conducted with emphasis given to the control of hole size. The effects of the various drawing parameters and their suitability for controlling the air-structure was studied. The effect of air-structures on heat transfer in PCFs was studied using computational fluid dynamics techniques. Both germanium and fluorine were found to diffuse at high temperature and low draw speed. A diffusion coefficent for germanium was determined and simulations showed that most diffusion occurred in the neck-down region. Draw temperature and preform feed rate had a comparable effect on diffusion. The hole size in PCFs was shown to depend on the draw temperature, preform feed rate and the preform internal pressure. Pressure was shown to be the most promising parameter for on-line control of the hole size. Heat transfer simulations showed that the air-structure had a significant effect on the temperature profile of the structure. It was also shown that the preform heating time was either increased or reduced compared to a solid structure and depended on the air-fraction.

Drawing of standard telecommunication-type optical fibres has been optimised in terms of optical and physical properties. Specialty fibres, however, typically have more complex dopant profiles. Designs with high dopant concentrations and multidoping are common, making control of the fabrication process particularly important. In photonic crystal fibres (PCF) the inclusion of air-structures imposes a new challenge for the drawing process. The aim of this study is to gain profound insight into the behaviour of complex optical fibre structures during the final fabrication step, fibre drawing. Two types of optical fibre, namely conventional silica fibres and PCFs, were studied. Germanium and fluorine diffusion during drawing was studied experimentally and a numerical analysis was performed of the effects of drawing parameters on diffusion. An experimental study of geometry control of PCFs during drawing was conducted with emphasis given to the control of hole size. The effects of the various drawing parameters and their suitability for controlling the air-structure was studied. The effect of air-structures on heat transfer in PCFs was studied using computational fluid dynamics techniques. Both germanium and fluorine were found to diffuse at high temperature and low draw speed. A diffusion coefficent for germanium was determined and simulations showed that most diffusion occurred in the neck-down region. Draw temperature and preform feed rate had a comparable effect on diffusion. The hole size in PCFs was shown to depend on the draw temperature, preform feed rate and the preform internal pressure. Pressure was shown to be the most promising parameter for on-line control of the hole size. Heat transfer simulations showed that the air-structure had a significant effect on the temperature profile of the structure. It was also shown that the preform heating time was either increased or reduced compared to a solid structure and depended on the air-fraction.