Polarimetric phase measurement for the detection of contaminants on optical surfaces

It has been shown that measuring the polarimetric phase of the field scattered from a thin film multilayer gives information on the origin of scattering. Numerous numerical simulations have shown that the behavior of the polarimetric phase can be used to separate surface and bulk scattering. In the case of stacks with correlated interfaces the polarimetric phase depend only on the origin of scattering, whatever the microstructural parameters. Slight deviations from vertical correlation within the stack lead to ripples in the polarimetric phase, that can be observed experimentally. Moreover in certain cases second order effects, due for example to localized defects, can lead to depolarization. This phenomenon has strong influence on the polarimetric phase. This can be used to detect contamination of the surface. In our communication we will present some experimental results that show that the origin of scattering can be determined.