Determination of film thickness and anisotropy of the refractive indices in 4-octyl-4′-cyanobiphenyl liquid crystalline free-standing films

The layer structure of 4-octyl-4'-cyanobiphenyl (8CB) liquid crystalline free-standing films (FSFs) was studied. By transmission ellipsometry using a photoelastic modulator (PEM), the incidence angle dependence of the phase difference was measured with high resolution. The theoretical characteristics in the smectic A (SmA) phase structure were calculated by the geometric analysis method, changing the film thickness and the anisotropy of the refractive indices as parameters. Then, we were able to accurately determine the film thickness and the anisotropy of the refractive indices (n(parallel to) = 1.665, n(perpendicular to) = 1.523) of 8CB-FSF, by fitting the simulated characteristics to the experimental characteristics using the least-squares method.