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Optical Methods for the Measurement of Layer-Tilt and Pretilt Angles in Surface-Stabilized Ferroelectric Liquid Crystal Devices

We have used simple optical methods to determine, simultaneously, the layer-tilt, pretilt, quiescent state azimuthal, and tilt angles of surface-stabilized ferroelectric liquid crystal (SSFLC) devices as a function of temperature. In a SSFLC cell aligned by rubbed polymer films, the measured pretilt angles are small and the layer-tilt angle is, in general, less than the tilt angle for the same material at any given temperature in the smectic C phase. The measured pretilt, layer-tilt, angles show a common tendency to converge to zero as the temperature approaches the smectic C-to-A transition, while the azimuthal angle of the director in the stable quiescent state increases toward 90°. We observed that the direction of rubbing for alignment was parallel to the projection of the layer-normal onto the substrate surface within the temperature range of the smectic C and smectic A phases.