Towards an integrated atom chip

Abstract

The field of atom chips is a relatively new area of research which is rapidly becoming of great interest to the scientific community. It started out as a small branch of cold atom physics which has quickly grown into a multidisciplinary subject. It now encompasses topics from fundamental atomic and quantum theory, optics and laser science, to the engineering of ultra sensitive sensors.
In this thesis the first steps are taken towards a truly integrated atom chip device for real world applications. Multiple devices are presented that allow the trapping, cooling, manipulation and counting of atoms. Each device presents a new component required for the integration and miniaturisation of atom chips into a single device, capable of being used as a sensor.
Initially, a wire trap was created capable of trapping and splitting a cloud of BoseEinstein condensate (BEC) for use in atom interferometry. Using this chip a BEC has been successfully created, trapped and coherent splitting of this cloud has been achieved.
Subsequently, the integration and simplification of the initial trapping process was approached. In all the experiments to date, atoms are initially collected from a warm vapour by a magneto-optical trap (MOT). This thesis presents a new approach in which microscopic pyramidal MOTs’ are integrated into the chip itself. This greatly reduces the number of optical components and helps to simplify the process significantly.
Also presented is a method for creating a planar-concave micro-cavity capable of single atom detection. One such cavity consists of a concave mirror fabricated in silicon and the planar tip of an optical fibre. The performance of the resonators is highly dependent on the surface roughness and shape profile of the concave mirrors therefore a detailed study into the fabrication technique and its effects on these parameters was undertaken. Using such cavities single atom detection has been shown to be possible. These cavities have also been sccessfully integrated into an atom wire guide.
Finally a co-sputtered amorphous silicon/titanium (a-Si/Ti) nanocomposite material was created and studied for its use as a novel structural material. This material is potentially suitable for integrated circuitry (IC)/Micro-electromechanical- systems (MEMS) integration. The material’s electrical and structural properties were investigated and initial results suggest that a-Si/Ti has the potential to be a compelling structural material for future IC/MEMS integration.
To build all of these devices, a full range of standard microfabrication techniques was necessary as well as some non standard processes that required considerable process development such as the electrochemical deposition.
This thesis presents a tool box of fabrication techniques for creating various components capable of different tasks that can be integrated into a single device. Each component has been successfully demonstrated in laboratory conditions. This represents a significant step toward a real world atom chip device.

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