Non-invasive tracking of polarization rotation from speckle contrast measurement

A technique based on speckle contrast measurement is proposed and demonstrated to track the polarization rotation of an optical beam behind a scattering layer. It is shown that with the help of a reference speckle pattern with a known linear polarization, it is possible to track the polarization rotation behind a scattering layer in a non-invasive manner by measuring the contrast of the resultant speckle pattern. Working principle and experimental demonstration are presented, and results are compared with the theoretically known results in certain cases. Performance of the proposed technique is quantitatively evaluated by determining the polarization vector rotation behind the scattering layer for two different cases, namely polarization rotation by a half wave plate and sugar solution of different concentrations, and good match are found between the experimental results and theoretical prediction. Issues like resolution of determination of the polarization vector rotation and sugar solution concentration are also discussed in the context of the recovered results. The proposed technique can have potential application in non-invasive sensing and biomedical imaging.