Quantification of the azimuthal anchoring of a homogeneously aligned nematic liquid crystal using fully-leaky guided modes

A novel optical guided mode technique, the fully-leaky guided mode techniqu e, has been used to investigate the director distortion under the applicati on of an in-plane electric field of a homogeneously aligned conventional ce ll filled with the nematic liquid crystal E7. The liquid crystal is aligned using polyimide rubbed along the direction of the gold electrode edges. A weak field is applied across a 3 mm gap between the gold electrodes to indu ce small changes in the twist angle of the director. These distortions are determined by fitting to the angle-dependent reflectivity and transmissivit y data and are compared with continuum theory. From careful analysis of the results, both the twist elastic constant, k(22), and the azimuthal anchori ng strength, W-a, of the system are obtained. At 23.5 degrees C for E7 on r ubbed polyimide we find that k(22) = (6.50 +/- 0.05) x 10(-12) N and W-a = (2.9 +/- 0.2) x 10(-5) J m(-2).