Remarkable optics of short-pitch deformed helix ferroelectric liquid crystals: symmetries, exceptional points and polarization-resolved angular patterns

TL;DR

This paper investigates the complex polarization patterns in deformed helix ferroelectric liquid crystals under electric fields, revealing symmetry relations, polarization singularities, and enhanced electro-optic responses near exceptional points.

Contribution

It introduces a combined transfer matrix and dielectric tensor approach to analyze polarization singularities and symmetry properties in DHFLCs under electric fields, highlighting exceptional points.

Findings

Symmetry axis of L lines aligns with the major in-plane optical axis.

C points form symmetric chains of star-monstar pairs at certain angles.

Enhanced electro-optic response observed near exceptional points.

Abstract

In order to explore electric-field-induced transformations of polarization singularities in the polarization-resolved angular (conoscopic) patterns emerging after deformed helix ferroelectric liquid crystal (DHFLC) cells with subwavelength helix pitch, we combine the transfer matrix formalism with the results for the effective dielectric tensor of biaxial FLCs evaluated using an improved technique of averaging over distorted helical structures. Within the framework of the transfer matrix method, we deduce a number of symmetry relations and show that the symmetry axis of L lines (curves of linear polarization) is directed along the major in-plane optical axis which rotates under the action of the electric field. When the angle between this axis and the polarization plane of incident linearly polarized light is above its critical value, the C points (points of circular polarization) appear in the form of symmetrically arranged chains of densely packed star-monstar pairs. We also emphasize the role of phase singularities of a different kind and discuss the enhanced electro-optic response of DHFLCs near the exceptional point where the condition of zero-field isotropy is fulfilled.