  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.
