Phase dependent atom optics.
PhD thesis, University of Glasgow.
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Quantum interference in atomic media has elicited interest for a very wide range of investigations and applications. As well as being a fascinating effect in itself, it also found applications in spectroscopy, nonlinear optics and has recently been drawing attention in the field of quantum optics for the realisation of sources of entangled photons, optical switching, and quantum information storage.
The work presented in this thesis consists of two main projects centred around the theme of quantum interference in atomic processes. As cooled atomic vapours provide favourable conditions for the investigation of coherent phenomena, a magneto-optical trap was built for the future study of quantum interference in four-level link- ages. The number of trapped atoms is estimated to be ≈ 8 × 10^8, and the density to be ≈ 10^9 atoms per cubic centimetre. This represents the first stage of an ongoing study of quantum interference in four-level linkages.
However, coherent effects can also be observed in hot vapours. A spontaneous, highly efficient, frequency up-conversion arising from four-wave mixing can indeed be observed in Rubidium. This complex phenomenon was investigated experimentally and theoretically so as to improve the conversion efficiency, and understand the underlying physics. The optimum conditions found in this study yield 1 mW of converted light for 40 mW of pumping light.
As part of the study of the phase coherence of the process, the conversion of spatial modes in the four-wave mixing process was also examined. The observation of the transfer of orbital angular momentum in the process is reported, and a preliminary theoretical interpretation is presented.
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