Optical Mode Characterization of the Configuration of a Thin Ferroelectric Liquid Crystal Cell Under an Applied Electric Field

It is possible to probe directly the optic dielectric tensor configuration within a thin (about 3·5 μm) smectic layer of a ferroelectric liquid crystal (FLC) by the propagation of prism-coupled leaky Fabry-Perot optic modes. Incident monochromatic polarized light couples into the resonant modes of the system which are then observed as sharp dips in the reflected signal at specific incident angles. This work has shown that the FLC has an optic tensor profile which is consistent with the chevron formation of the smectic layers observed in X-ray scattering measurements. Also it is shown that under the application of a low d.c. applied field the optic dielectric tensor configuration distorts in a manner consistent with the retention of the chevron structure up to fields of about 106 Vm−1.