Abstract

Saturation effects affecting absorption and fluorescence spectra of an atomic vapour confined in an Extremely Thin Cell (cell thickness L< 1μm) are investigated experimentally and theoretically. It is known that in a thin cell of dilute vapour, the wall-to-wall atomic trajectories generate original sub-Doppler signatures for spectra recorded under normal incidence. An experimental study is performed on the D₂ line (λ = 852nm) of Cs. We concentrate on the two situations L = λ/2 and L = λ, because they are the simplest ones relatively to the Fabry-Perot situation intrinsic to an extremely thin cell, and because they are the most contrasted ones with respect to the linear absorption, when the cell length dependence of the coherent Dicke narrowing [1] is considered. In contrast, no such interferometric length dependence has been observed in fluorescence [2], because fluorescence is an incoherent process, even when a transient process of atomic excitation has to be considered.

© 2007 IEEE