Light depolarization effects during the Fréedericksz transition in nematic liquid crystals

Abstract

This work is aimed to the photopolarimetric characterization of the disorder evolution occurring in homeotropically aligned nematic liquid crystal films during the electrically induced Fréedericksz transition. The molecular director dynamics and the transversal reorientation modes are investigated by the analysis of the depolarization of the light beam emerging from the sample. Our measurements reveal unexpected depolarization effects at the transition, which we interpret in terms of director field unhomogeneity and defects creation.

Fréedericksz transition in homeotropically aligned liquid crystals: a photopolarimetric characterization

“…We use a new theoretical approach to explain our experimental results and gain further understandings. During the transition we observed an unexpected light depolarization of the transmitted light beam [1]. Recently, it was observed a substantial difference between the homeotropic and planar cases of initial configuration of the nematic film [1].…”

“…During the transition we observed an unexpected light depolarization of the transmitted light beam [1]. Recently, it was observed a substantial difference between the homeotropic and planar cases of initial configuration of the nematic film [1]. The depolarization effects during Fréedericksz transition occurs only in the homeotropic case.…”

“…These fluctuations around the regular behaviour are due to the domains formation and P MIN ~ 0.05 corresponds to ξ = (2 ± 1) µm. We observe depolarization in presence of defectantidefect pattern [1]. We show an image of this pattern in Fig.…”

“…3 the function According to Ref. [1] and related references we suppose that the domains director relaxation time is…”

“…This symmetry breaking produces a local director orientation which is different in the various points of the cell. As a consequence the wave-front of the transmitted light undergoes a local phase displacement and light depolarization occurs [1].…”