On the saturation of excitation-dependent dipole-dipole broadening in dense Rb vapour

\nWe study dependence of dipole-dipole interaction in dense Rb vapour on optical excitation. We measure the dipole-dipole contribution to the selective reflection spectrum of D2 line. Optical excitation is created by intense laser beam, which depletes the 5S1/2 population and decreases the dipole-dipole interaction, narrowing the observed spectrum. The limit of the dipole-dipole interaction change is determined by the optical saturation of the D2 transition and corresponds to the 5S1/2 population approximately equal to 1/3.\n