Excitation dependence of resonance line self-broadening at different atomic densities

We study the dipole-dipole spectral broadening of a resonance line at high atomic densities when the self-broadening dominates. The selective reflection spectrum of a weak probe beam from the interface of the cell window and rubidium vapour is recorded in the presence of a far-detuned pump beam. The excitation due to the pump reduces the self-broadening. We found that the self-broadening reduction dependence on the pump power is atomic density independent. These results provide experimental evidence for the disordered exciton based theory of self-broadening, and can be useful for the description of the interaction of a strong optical field with a dense resonance medium.