Probing intrinsic anisotropies of fluorescence: Mueller matrix approach

We demonstrate that information on “intrinsic” anisotropies of fluorescence originating from preferential orientation/organization of fluorophore molecules can be probed using a Mueller matrix of fluorescence. For this purpose, we have developed a simplified model to decouple and separately quantify the depolarization property and the intrinsic anisotropy properties of fluorescence from the experimentally measured fluorescence Mueller matrix. Unlike the traditionally defined fluorescence anisotropy parameter, the Mueller matrix-derived fluorescence polarization metrics, namely, fluorescence diattenuation and polarizance parameters, exclusively deal with the intrinsic anisotropies of fluorescence. The utility of these newly derived fluorescence polarimetry parameters is demonstrated on model systems exhibiting multiple polarimetry effects, and an interesting example is illustrated on biomedically important fluorophores, collagen.