Theory of atomic wave-guidance in dark hollow beam

Firstly the interaction of a three-level /spl Lambda/-type atom with a blue-detuning dark hollow beam is described in the dressed-atom picture. The dipole potential and radiation pressure forces are derived, and the spontaneous emission processes between both adjacent manifolds are analyzed in detail. Then through Monte Carlo simulation, the relations between the guiding efficiency and the detuning in varieties of conditions are acquired. We found that the guiding efficiency also depends on guiding direction relative to the propagation direction of the hollow beam except for the intensity and configuration of the hollow beam and pressure of the chamber, when both directions are opposite, the optimal detuning is in high detuning region, the value is similar to the experimental value. Furthermore, we calculated the final velocity distribution of atoms guided by the hollow beam, we found that in same direction case, even though in low detuning region the guiding efficiency is high, but the radial and longitudinal coherence are seriously destroyed, the most atoms are much heated. It is not useful in application to atom optics experiments. The main factors are the radiation pressure forces and photon scattering effects. Finally we found that the atoms can only be guided in the high detuning region, and their coherence will be held whether same or opposite direction.