Optical Anisotropy as a Probe of Structural Order by Stokes Polarimetry

Abstract

Structural order often manifests itself in the anisotropic optical phenomena birefringence and dichroism. Such properties of a material cause changes in the polarization of a probe beam. Characterization of the optical anisotropy, and subsequent inference on the structural arrangement of molecules responsible, may be accomplished in two stages. First, Stokes polarimetry is used to determine the polarization change in the transmitted light. Next, a model of the polarization transfer is used to fit the data in order to obtain values of the birefringence and dichroism which may serve as quantitative order parameters. The technique may be applied to linear as well as circular anisotropy, but is perhaps most valuable for cases in which both types coexist and therefore need to be separated. Our polarimeter is simple in construction and may be assembled from common optical elements.