Atomic Funnel Using HE₁₁-mode Output Hollow Beam And Atomic Guide In A Beam Of Single-mode Optical Fibers

The definition of dark hollow beam (DHB) and its generation are introduced in this thesis. At the same time, the principle, methods and experimental progress of atomic guiding in hollow optical fibers, blue-detuned evanescent wave and dark hollow beams are reviewed in some detail. Finally, the basic definition of the angular momentums of all kinds of the hollow beams and their application are discussed.The physical mechanism to generate a dark hollow beam from the output beams of a LP01 mode (scalar model) and a HE11 mode (vector model) in a micro-sized hollow optical is analyzed. Under the weakly guiding approximation, we derive the electric-field distribution of the LP01 mode in the hollow fiber. The far- and near-field distribution of the LP01-mode output beam in free space is calculated numerically from Fraunhofer and Fressnel diffraction theory. On the other hand, the electric field and intensity distributions of the HE11 mode in the hollow fiber are calculated by using the exact solutions of Maxwell Equations based on the vector model, and the diffracted near- and far-field distributions of the HE11 -mode output beam under the Fresnel approximation are studies. We derive an analytical expression on the far- field distribution of the HE n -mode output beam in free space and discuss its applicable condition. We also analyze and compare the differences between the HE11- and LP01 -mode output beams, and find that the near-field distribution of the LPoi-mode output beam is a Gaussian-like one, but the near-field distribution of the HE11 -mode output beam is a doughnut-like one, whereas the far-field distribution of both the LP01- and HE11 -mode output beams are a doughnut one. We also discuss some potential applications of the HE11-mode output beam in atom optics, such as atomic funnel and guiding, and so on.Finally, we propose two schemes to guide cold atoms in the beam of single-mode fibers. One is evanescent-wave atomic guiding by using four single-mode fibers. We derive the intensity distribution of the evanescent light-wave in the rectangular hollow space of the four single-mode fibers, and calculate the optical potential for guided coldatoms. The other scheme is evanescent-wave atomic guiding by using three single-mode fibers, and calculate the intensity distribution of the evanescent light-wave in the triangular hollow space and the optical potential for guided cold atoms. Our study shows that these schemes can be used to realize single-mode atomic wavdguide only when the input laser power is equal to a few mW.