Entwicklung eines neuartigen, laserbasierten, photonischen Wellenleiters für ultrakalte Atome

Abstract

In the field of ultracold quantum gases atom optics has been established as a completely new discipline in the last years. This led to fundmentally new results in the field of research of atom optical systems. In modern experiments especially strongly interacting nonlinear systems are of great interest. Such a strongly correlated system consists of a cold atomic quantum gas and a light field both embedded into a nonlinear medium. This thesis documents for the first time that a two-dimensional photonic crystal fiber can be used as a novel nonlinear medium for atom optical experiments. It shows that cold atoms can be guided optically through this fiber with high efficiency and density. In order to study this system a new experiment for creating cold optically guided atoms has been built up. This complex experimental setup consists of high-stable laser sources, optics and electronics for generating, manipulating and detecting cold atomic rubidium ensembles as well as further elements for implementing photonic band gap fibers as matter wave guides. One focal point of the thesis has been the detailed investigation of the atomic flux through the fiber. This analysis demonstrates that the experimental parameters governing the atomic flux are in a good agreement with a self-developed numerical model as well as with other theoretical predictions. For applying this system as injector for other quantum gas experiments or for atom interferometry, a continuous, coherent atomic flux is necessary. Studies demonstrate that such a regime can be reached by using an additional dipole trap in front of the fiber. By properly chosen trap parameters this trap can be used as a reservoir of cold atoms. With this optical setup the atomic flux can be kept up significantly longer than in a pulsed guiding system. Further the experimental possibilities of this nearly one-dimensional, cold, dense and tightly embedded atomic system are of great interest. The analysis shows that because of the generated atomic density and the energetic distribution of the atoms in the fiber potential a coherent atom optics is feasible with this system. So this experiment paves the way towards a novel, coherent matter wave guide. By exploiting the strongly photonic interaction in the fiber other physical regimes especially in the field of nonlinear optics can be reached. This includes for example the studies of four-wave-mixing processes in the photonic band gap fiber. In a recent theoretical paper it has been suggested to use the tunability of the atom-light-interaction to reach a photonic regime of extremely strong repulsion. This possibly leads to decelerated or even stopped light forming a so-called Tonks-Girardeau gas.