Optimization of Bose-Einstein Condensate Imaging Techniques

Abstract

Research into Bose-Einstein condensates is currently a thriving field in physics. Much of the experimental research involves the detection of cold atom clouds under various conditions. Consequently, the fundamental and technical limitations of the imaging techniques and technologies utilized will have a dramatic influence on the results of these experiments. Therefore a detailed analysis of the restrictions on a Bose-Einstein condensate imaging system is overdue and will facilitate further developments in the field due to an increase in the signal to noise ratio; hence a greater level of detail available in experimental images. ¶ The work carried out in this thesis focuses on the properties of absorption imaging techniques, in the quest for an optimized imaging system. Optimization was proposed to be achieved through maximization of the signal to noise ratio by any and all means available. A detailed investigation of the diverse influences on the signal to noise ratio was performed with a focus on eliminating technical restrictions and minimizing fundamental constraints. By studying a 2f - absorption imaging system the maximal signal to noise ratio of 35 was calculated. This corresponded to imaging a cloud of 105 87Rb atoms in a (50 micron) square box with a 31.8MHz detuned, 780nm laser at an intensity of 570W/(m.m) for 35 micro-s. These optimal imaging parameters correspond to our imaging system being limited by the well depth of our detector, not by a fundamental physical process. Furthermore, current experimental noise is identified as the most significant inhibitor to the achievement of an optimized absorption image. ¶ This study represents a first analysis of the quality of current Bose-Einstein condensate imaging techniques and limitations.