Novel schemes for the optical manipulation of atoms and molecules
The range of atoms which can be cooled by lasers is limited to those which have a closed two level structure. Several schemes have been proposed which aim to extend this range by using coherent control of the particle momenta, but none have yet been demonstrated. We hope to implement these and other coherent manipulation schemes, and we begin with a system which is well understood and over which we can exert precise control. This thesis covers the design and construction of an experiment to demonstrate coherent manipulation of cold rubidium atoms collected in a magneto-optical trap. The lower hyperfine levels of these cold atoms very closely mimic the ideal two-level atom, and we use carefully crafted laser pulses to prepare, manipulate, and read their quantum state. The hyperfine levels are coupled using two fields whose frequency difference is equal to the hyperfine splitting. The way in which these Raman coupled levels can be used to emulate a two-level atom is explored, and the experimental apparatus used to create and control the driving fields is described in detail. The amplitude, frequency and phase of these fields is programmable, and complex manipulation schemes can be implemented merely by programming a computer. We have observed Raman transitions in the cold rubidium atoms, and the experimental methods used to detect these features amidst large experimental noise are discussed. Although we have not yet seen Rabi oscillations, we are confident that we can now have sufficient control to begin to implement simple interferometric sequences. However, there remain significant challenges if we are to coherently manipulate the momentum, and the prospects for such manipulation are discussed.
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