THE EFFECT OF AN ELECTRIC-FIELD ON A HOMEOTROPICALLY ALIGNED SMECTIC-C LIQUID-CRYSTAL

A homeotropically aligned layer of smectic C liquid crystal has been s tudied using optical excitation of half leaky guided modes. Under the application of an AC voltage, the director configuration changes over a time-scale of the order of seconds. Fitting model results to the rec orded angle dependent reflectivity data indicates firstly a change of tilt angle of the primary director, suggesting perhaps a layer tilt, a nd secondly a reduction of the imaginary part of the optical permittiv ity, implying a suppression of fluctuations. There is no evidence for a Helfrich-like deformation in the liquid crystal layer. Detailed anal ysis finally shows that the results are correctly interpreted as an in crease in cone angle, not layer tilt, with field. Then from the fitted data, the change of tilt angle with field is obtained and hence infor mation on the mean-field theory parameters.