Phase imprinting of vortices in Bose-Einstein condensates using shaped light
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Vorticity in superfluids has been studied for decades. In atomic BECs, vorticity was induced by stirring with laser beams. In this thesis, phase imprinting is introduced as an alternative method to induce vorticity in a BEC. By using a Liquid Crystal-on-Silicon spatial light modulator the phase of a laser beam can be shaped into any spatial profile, limited only by the imaging resolution. By using this shaped light in a two-photon Raman transfer, the phase of the electromagnetic field is transferred on to the Bose-condensed atoms. Simulations are performed for light containing a single phase winding, taking into account that the vortex in this beam has a finite vortex core size due to limited imaging resolution. It follows that the finite core size has an incomplete transfer as a result, but the phase winding is imprinted on to the atoms transferred to the second component. Also, experimentally the two-photon Raman transition which is needed has been realised. However, the transfer process is impeded by a different two-photon process occuring at the same time, and by superradiant Rayleigh scattering. Recommendations are given to suppress these effects and successfully imprint the phase from the shaped light on to the atoms.