Fast-axis orientation dependence on driving voltage for a Stokes polarimeter based on concrete liquid-crystal variable retarders.

Nowadays liquid-crystal variable retarders (LCVRs) are widely used in optical systems because of their capacity to provide a controlled variable optical retardance by means of an applied voltage, without the need of any moving mechanical part. Nevertheless, the main disadvantages of these components, reported by users in several papers, are the necessity of using a temperature control system for precise measurements, the degradation under UV irradiation, and the lack of spatial retardance homogeneity. In this paper, we report that the orientation of the LCVR fast axis may also be dependent on applied voltage. The consideration of this phenomenon improves the performances of an imaging polarimeter. In this work, we present the problem, introduce the method of calibration that was used for the experiment, and discuss the results.