Contrast Saturation Resonances in the Absorption Band of Rubidium Molecules.

We study Doppler-free saturation resonances in the absorption band $$ {{\mathrm{B}}^1}{\Pi_{\mathrm{u}}}-{{\mathrm{X}}^1}\Sigma_{{^{\mathrm{g}}}}^{+} $$ of rubidium diatomic molecules in the frequency range near the D 2 line of lithium atoms (671 nm). We observe contrast saturation resonances and record a variation in the laser light transmission of 4% due to optical saturation. The large optical nonlinearities in the molecular diatomic gas can be used for investigating the four-wave mixing and other nonlinear effects. [ABSTRACT FROM AUTHOR]