Enhanced confocal microscopy imaging of the in-plane switching of cholesteric liquid crystal cells

Abstract

The recently developed fluorescence confocal polarizing microscopy (FCPM) imaging technique allows 3D images of the director structure in a liquid crystal cell to be resolved with sub-micron resolution. Results are presented on imaging the response of 5-micron pitch cholesteric liquid crystals to an in-plane electric field applied between two silver electrodes. The results show, in exquisite detail, how the application of an in-plane field causes the cholesteric helix to tilt through 90° either within, or immediately adjacent to, the electrode gap depending on the sign of the dielectric anisotropy of the liquid crystal. Furthermore, imaging the cholesteric material above the silver electrodes reveals a previously unreported optical intensity enhancement. This phenomenon is discussed along with its possible benefits to the existing imaging technique. The effects of the point spread function of the system are discussed and a ray optics model is used to produce model data highlighting the influence of this phenomenon on the recorded results.