Total internal reflection from nematic liquid crystals

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Abstract
The attenuated total internal reflection (ATIR) conditions for a plane monochromatic wave, incident on the interface flint-glass prism-deformed homeotropic nematic layer with applied d.c. or high frequency a.c. electric field are considered. The theoretical results obtained with the aid of WBK method show that there are two essential conditions for the wave behaviour : the condition for the exponential variations of the electromagnetic wave components and the ATIR condition obtained from the requirement for equality between the moduli of the incident and the reflected amplitudes. Estimates for the influence of the lower limiting glass plate (e.g. the penetration depth of the evanescent wave) are made. The first two terms in the ATIR condition were used in the experiment performed with MBBA films. The surface energy of the liquid crystal molecules interacting with a thin lecithin layer giving a homeotropic orientation was determined to be in the range of 2 x 10-2 erg/cm2. The accuracy of the method is low in the range of deformation angles 0-5° (∼ 1°) and higher for the other regions. The total internal reflection measurements give new and important information about the formation of the double electric layers, the inhomogeneity of the electric field and the flexoelectric properties of the investigated liquid crystals