Mueller matrix ellipsometry study of a circular polarizing filter

The authors introduce an ellipsometric data analysis strategy for a flexible polymeric circular polarizing filter consisting of a thin linear polarizer and quarter-wave plate sandwich. The circular polarizing filter is an inhomogeneous optical system exhibiting different optical responses depending on the propagation direction of light. If light enters from the linear polarizer, the transmitted beam is linearly polarized before entering the quarter-wave plate. The orientation of the quarter-wave plate is rotated 45° from the linear polarizer axis. The emerging light from the quarter-wave plate is circularly polarized. If light is circularly polarized and enters from the reserve side, the quarter-wave plate converts it into linearly polarized light. The following linear polarizer either transmits or absorbs the beam depending on the handedness of the original circular polarization. The optical response in the forward direction is utilized in photography to reduce unwanted reflections in the image. The optical response in the reverse direction is utilized in 3D eyeglasses, which consist of two orthogonal circular polarizing filters to separate the left and right images. Mueller matrix spectroscopic ellipsometry is used to observe the optical responses of a circular polarizing filter in both directions. The authors demonstrate data analysis procedures for individual layers to find the optical constants in a wide spectral range from 400 to 1700 nm. The circular polarizing filter measured in the forward direction enables ellipsometry to determine the included angle between the linear polarizer and the quarter-wave plate. The ellipsometric data analysis result is used to predict transmitted light intensity versus rotation angle (deg) with respect to any input polarization state.