Stokes polarimeters based on Liquid Crystals

Abstract

In this work, we present a study of different Stokes polarimeters where liquid crystal devices are fundamental elements of the design. These anisotropic materials act as variable retarders controlled electronically. Therefore, it leads to a versatile setup where an optimization of some parameters of the design is essential to minimize the noise propagation. On the one hand, a polarimeter based on two parallel aligned liquid crystal is proposed. Since we can perform any polarization analyzer with this system, we achieve as optimal configuration a set of four analyzers with equispaced distribution in the Poincaré sphere, forming a regular tetrahedron. On the other hand, we analyze a second polarimeter formed by one twisted nematic liquid crystal. Although the optimum configuration is limited by the characteristic curve, we achieve a well-conditioned system with a simpler design. Once the design optimization is done, we carry out an experimental calibration to know exactly the real polarization analyzers used in the laboratory. Finally, we test and compare the two implemented polarimeters and their results are verified with a commercial Stokes polarimeter