Classical polarimetric method revisited to analyse the modulation capabilities of parallel aligned liquid crystal on silicon displays

Abstract

Novel liquid crystal on silicon displays (LCoS) technology has found widespread use in a number of applications dealing with the spatial modulation of the properties of a light wavefront. Parallel aligned LCoS (PA-LCoS) are especially interesting since they provide phase-only modulation with no coupling of amplitude modulation. However, typically LCoS are digitally addressed and this has been proven as a drawback since it causes fluctuations in the phase modulation. In this work we concentrate on PA-LCoS. We analyse the application of a classical polarimetric method for retardance measurement, which makes use of only linearly polarized light, typically used in wave plates. We analyse the effect of phase fluctuations on the measurements and provide a refinement of the method which allows estimating both the average retardance and the magnitude of the phase fluctuation. We demonstrate both theoretically and experimental that this extension of a classical method is both simple and very well suited for the measurement of the modulation properties of novel PA-LCoS.