Electrooptic response of chiral nematic with oblique helicoidal director

TL;DR

This paper reports the experimental observation of an electro-optic effect in a cholesteric liquid crystal with an oblique-helicoidal director, revealing how electric fields influence its structure and optical properties.

Contribution

It provides the first experimental validation of the oblique helicoid structure in cholesteric liquid crystals with dimer materials and analyzes its electro-optic response.

Findings

Oblique helicoid pitch and cone angle increase as electric field decreases.

Low electric fields transform the oblique helicoid into a right-angle helicoid.

The study combines theoretical, numerical, and experimental approaches.

Abstract

Electrically induced reorientation of liquid crystals (LCs) is a fundamental phenomenon widely used in modern technologies. We observe experimentally an electro-optic effect in a cholesteric LC with a distinct oblique-helicoidal director deformation. The oblique helicoid, predicted in late 1960-ies, is made possible by recently developed dimer materials with an anomalously small bend elastic constant. Theoretical, numerical, and experimental analysis establishes that both the pitch and the cone angle of the oblique helicoid increase as the electric field decreases. At low fields, the oblique helicoid with the axis parallel to the field transforms into a right-angle helicoid (the ground state of field-free cholesteric) with the axis perpendicular to the field.