Polarimetric characterization of optically anisotropic flexible substrates

Phase Modulated Spectroscopic Ellipsometry as well as Liquid Crystal Mueller Matrix Polarimetry in reflection and in transmission configurations were used to systematically study five types of anisotropic polymer sheets: polyethylene-terephtalate (PET), polyethylene-naphtalate (PEN), polycarbonate (PC), polypropylene (PP) and triacetylcellulose (TAC). The measurements were performed at different sample azimuths in two ellipsometric configurations giving access to both standard ellipsometric data as well as to the entire Mueller matrix. Biaxial anisotropy, a common characteristic to all polymer types, as well as the in-depth optical properties, inhomogeneity present in the sheets were clearly evidenced. The data were interpreted in terms of a model consisting of a thick substrate (several microns) coated with a simple layer. Both, substrate and layer were anisotropic and characterized by a triplet of principal refractive indexes. The orientation of the principal indexes of the bulk and the layer were different revealing the in-depth inhomogeniety of the samples.