Diffraction of a Bose-Einstein Condensate and the Path to an Atom Laser
In this thesis, we study the diffraction processes of a Bose-Einstein condensate of
87Rb atoms and outline our progress toward the realisation of an atom laser. The
experiments are carried out with a condensate that is produced ‘all-optically’; this is
covered in the first part of the thesis. For our diffraction processes, we expose the
condensate to an intense, pulsed optical standing wave. We perform mean energy
measurements and interpret our results with two different theories: one treating the
condensed atoms as particles, the other focusing on the atoms’ wave properties.
The first interpretation requires knowledge of the theoretical background of the
atom-optics -kicked rotor (AOKR); in our experiments, we focus on the resonances in
the early-time behaviour of the kicked atoms. The second interpretation retrieves an
observation of the temporal Talbot effect—the atomic analogue to the optical Talbot
effect. From this point of view, the full resonances represent the integer Talbot effect,
whereas the early-time behaviour corresponds to the observation of the fractional
Talbot effect. We find for both theoretical interpretations an excellent qualitative
agreement between our experimental results and the results of our computer simulation
of the AOKR.
Furthermore, we outline our future work on the realisation of an atom laser as
a tool for coherence measurements of the condensate via atom-counting statistics.
In this context, the most current progress in our laboratory is given. We aim for a
Bragg-scattering process of our condensate as a modified version of our prospective
outcoupling technique for the atom laser; this process is modelled in a semi-classical
approach, and our first experimental implementations are presented.