Polarimetry in turbid, birefringent, optically active media: A Monte Carlo study of Mueller matrix decomposition in the backscattering geometry

Determination of the intrinsic polarization properties of a complex turbid medium such as biological tissue in the backscattering geometry (a geometry that is convenient for in situ applications) is complicated due to the confounding influence of scattering, and due to simultaneous occurrence of several polarization effects. We have investigated the polar decomposition approach of Mueller matrices to delineate individual intrinsic polarization parameters (specifically linear retardance δ and optical rotation ψ ) of a birefringent, chiral, turbid medium in the backscattering geometry, using Mueller matrices generated with polarization-sensitive Monte Carlo simulations. The results show that near the exact backscattering direction, the interplay of the scattering-induced linear retardance and diattenuation on the intrinsic values for δ and ψ is coupled in a complex interrelated way, due to contribution of the backscattered photons. In contrast, these effects were significantly reduced for detection positions at distances larger than a transport length away from the point of illumination. Simultaneous determination of the intrinsic values for δ and ψ of a birefringent, chiral, turbid medium in the backward detection geometry can thus be accomplished by decomposing the Mueller matrices recorded at distances larger than a transport length away from the point of illumination. Determination of the intrinsic values for these polarization parameters in backscattering geometry could be significant in, for example, for quantification of tissue structural anisotropy and for noninvasive blood glucose measurements of diabetic patients.