Cesium atomic resonance filter.

Abstract

An atomic resonance filter (ARF), composed of a cell containing an absorbing gas and two interference/absorption filter stacks, is designed to be both wide angle and ultra-narrowband. The bandwidth of this filter, in the range of 1-10mA, is determined by the absorption linewidth of the absorbing gas. Light entering the ARF within this bandwidth excites the gas to a highly excited state, and the fluorescence cascade back to the ground state emerges from the gas cell as the detected signal. The interference/absorption filter stacks insure that light not interacting with the gas does not pass through the ARF. The ARF is necessarily wide-angle due to the isotropic absorption properties of the gas. This dissertation models the processes involved in atomic absorption to determine the performance of an ARF that uses cesium as the absorbing gas. This model uses the Voigt absorption profile to obtain a correlation between the frequency of the traveling photon and the velocity of the absorbing atom. Results of computer simulations based on this model are presented along with experimental measurements. The ARF characteristics of importance include its efficiency and the temporal response of the filter. These characteristics are determined as a function of temperature and the input photon frequency. The effect of an additional buffer gas, which is included to decrease the ARF response time is investigated.