Liquid-crystal based drift-free polarization modulators: Part I. Design and operation.

We report a new design for temperature-stable polarization modulators. Each modulator is composed of two liquid crystal variable retarders (LCVRs) positioned in such a way that their temperature drifts mutually compensate. We propose a model for the temperature-dependent polarization response of LCVRs, which permits us to establish expressions for the operating point of the system and for its accessible retardance range. We have validated such a model experimentally by thorough analyses of LCVR temperature responses, and we have built a polarization modulator that is stable over a wide range of temperature with commercially available LCVRs.