Influence of Low Magnetic Field on Pumping Efficiency in an Optically Pumped Cesium Beam Resonator

Abstract

In this paper, we report our investigation on the influence of the magnetic field on the optical pumping of a cesium beam using coherent excitation with a broadband laser. The generation of Zeeman coherences in the ground state level when optical transitions of the cesium D2 line are excited by a linearly a polarized laser may result in a decrease of the efficiency of the optical pumping and lead to an intensity minimum in the fluorescence LJp as the applied magnetic field decreases to zero value. Accordingly the population difference An and LJp are found to depend on the magnitude B of the magnetic field. Here we describe physical basis which indicate that the fluorescence intensity variation results from the coupling of the lower level ∆m = ± 2 coherences to the excited level population. Comparison of theoretical predictions with experimental records of the fluorescence are then made. Finally guidelines are given which may influence the magnetic field design in the light-atom interaction zones of an efficient optically pumped cesium beam frequency standard.