Pumping light intensity transmitted through an inhomogeneously broadened line system: application to passive rubidium frequency standards

Abstract

This paper presents a theoretical evaluation of the pumping light intensity transmitted through an inhomogeneously broadened line system submitted to a coherent microwave excitation. A model is developed for the case of rubidium 87 atoms interacting with a buffer gas and optically pumped by all components of the D1 and D2 lines. The light generated by an electrodeless lamp is considered incoherent and the coherent signal is produced in a microwave cavity. The spatial distribution of the light intensity transmitted through the absorption cell is shown to be related to the microwave magnetic-field axial-component distribution. Then the resonance curve obtained with a photodetector is a function of its shape and location. When applied to the case of a passive rubidium frequency standard, this model allows the calculation of the ultimate short-term frequency stability of the device.