Polarization effects in nematic liquid crystal optical phased arrays

Abstract

In a one-dimensional liquid crystal optical phased array (LCOPA), a liquid crystal layer is electrically addressed by an array of long, narrow electrodes. A spatially periodic voltage profile can be applied to the liquid crystals in order to induce a sawtooth-shaped index of refraction variation in the liquid crystal layer that will steer an optical beam in a fashion analogous to that of a blazed diffraction grating. In reality, an LCOPA is a thick, periodic, anisotropic structure with complicated polarization properties. The changes in polarization as a beam passes through an LCOPA can have negative practical effects, particularly in optical systems where LCOPAs and other polarization-sensitive optical elements are cascaded. This paper presents experimental measurements of the polarization state of the light diffracted by an LCOPA as well as a discussion of the origin of these effects.