Rotating polarization probing of elastic and inelastic scatterings

The recent technical advances in the creation of rapidly rotating light polarizations are shown to provide new tools to explore elastic and inelastic scattering phenomena. In the case of inelastic scattering, the light fluoresced by atoms or molecules coherently excited by a rapidly rotating linear polarization is expected to exhibit new resonances. Such resonances, due to the transfer of coherence from light to atoms or molecules, are theoretically studied and experimentally observed. They provide simple methods to probe atomic internal constants, such as energy level life-times. The analogy between those resonances and the Hanle effect suggests new experiments in atomic physics. In the case of elastic scattering such as the one encountered during propagation through a dense turbid medium, the rotating linear polarization is shown to be an ideal tool to extract the ballistic photons from the large background of diffused light. This permits to image tiny objects embedded in a dense turbid medium, with an experimental resolution similar to the one obtained in usual homogeneous optical system.