Electric-field-induced nematic-cholesteric transition and 3-D director structures in homeotropic cells

TL;DR

This study explores how electric fields induce phase transitions and complex three-dimensional director structures in cholesteric liquid crystals with negative dielectric anisotropy confined in thin homeotropic cells, using advanced microscopy.

Contribution

It provides a detailed phase diagram of director configurations in cholesteric liquid crystals under electric fields, revealing new insights into their tunable 3D structures.

Findings

Electric fields induce nematic-cholesteric transitions.

Identified specific director structures depending on d/p and voltage.

Potential applications in switchable optical devices.

Abstract

We study the phase diagram of director structures in cholesteric liquid crystals of negative dielectric anisotropy in homeotropic cells of thickness d which is smaller than the cholesteric pitch p. The basic control parameters are the frustration ratio d/p and the applied voltage U. Fluorescence Confocal Polarising Microscopy allows us to directly and unambiguously determine the 3-D director structures. The results are of importance for potential applications of the cholesteric structures, such as switchable gratings and eyewear with tunable transparency based.