Off-resonance absorption and dispersion in vapours of hot alkali-metal atoms.

Abstract

We study the absorptive and dispersive properties of Doppler-broadened atomic media as a function of detuning. Beginning from the exact lineshape calculated for a two-level atom, a series of approximations to the electric susceptibility are made. These simplified functions facilitate direct comparison between absorption and dispersion, and show that dispersion dominates the atom–light interaction far from resonance. The calculated absorption and dispersion are compared to experimental data for Rb vapour on the D1 transition, showing the validity of the approximations.