Refractive index and dispersion measurements in prismatic thin film of phasmidic columnar liquid crystals

Abstract

ABSTRACTIn this work, we explore the refractive index of the phasmidic columnar liquid crystal for homeotropic oriented samples (column perpendicular to the plates). To measure the ordinary index no of the columnar liquid crystal C10, a simple and accurate method is presented using the deflection by reflection of a laser beam (λ = 633nm) through a prismatic phasmidic thin film placed between two glass plates in the homeotropic orientation. For the C10 samples, we found no = 1.5512 ± 0.0002 at T = 100°C. We used the same method to determine the isotropic index nl of the isotropic phase and found nl = 1.5301 ± 0.0002 at T = 120°C. Using the precision of the same method in polychromatic laser beam, we measured the variation of the ordinary index with the wavelength λ and characterize the dispersion by the known Cauchy's dispersion relationship no = A + B/λ2. We deduce an estimation of the birefringence for several samples.