Balanced detection for low-noise precision polarimetric measurements of optically active, multiply scattering tissue...

The use and advantages of balanced detection for making low-noise polarimetric measurements in turbid materials are demonstrated. The technique reduces the intensity noise originating from the laser and, in addition, makes possible a direct measurement of a component of the Stokes vector. When phase-locked detection is used with either amplitude or polarization modulation for polarimetric measurements in turbid media, one can obtain elements of the scattering matrix of very small magnitude. This methodology is used to measure optical activity and surviving linear polarization fractions in clear and turbid media containing glucose at physiologically relevant concentrations. The results are in agreement with Monte Carlo simulations of polarized light propagation in turbid media.