Alignment and temperature effects in liquid-crystal-based active polarimetry.

It is well known that in liquid crystal (LC)-based active polarimetry, alignment and temperature effects impact polarimeter performance. Practically speaking, when constructing a polarimetric measurement system from LC variable retarders (LCVRs), unavoidable alignment and temperature uncertainties will occur, leading to systematic error that propagates to the Mueller matrix. Typical calibration methods use only a single metric to assess polarimeter performance (the condition number) and often ignore the relationship between systematic error and specific Mueller matrix elements. Here we explore alignment and temperature effects in a Stokes generator and polarimeter, each consisting of two LCVRs, through a series of simulations to calibrate the polarimeter and measure the Mueller matrix of air. We achieve this by modifying an existing LCVR model to incorporate alignment and temperature effects. This new approach offers insight into employing LCVRs individually and associating particular Mueller matrix element error with specific LCVR effects.