Characterization of Mueller matrices in retroreflexellipsometry

Ellipsometry is a widely-used technique for characterizing materials and thinfilms. The principle is based on the polarization changes after light is reflectedor transmitted at a sample. In general, the shape of the sample should be flat ornearly flat because ellipsometry is sensitive to the angle of incidence, tilt angleand the sample position (height variation). For nonplanar surfaces, retroreflexellipsometry was proposed to solve the problem of the alignment. Despite ofthe Mueller matrix, the coherency matrix is often used for depolarization andnoise reduction. In retroreflex ellipsometry, the measured Mueller matrix can beseen as a dual-rotation transformation. Therefore, it is important to discuss thechanges of reference frames for Mueller matrices. In this report, the polarizationmodel of retroreflex ellipsometry will be introduced. Decompositions andinvariant quantities of a Mueller matrix with a dual-rotation transformation willbe discussed.