Theory of electrically controlled exhibition of circular Bragg phenomenon by an obliquely excited structurally chiral material

TL;DR

This paper develops a theoretical framework for electrically controlling the circular Bragg phenomenon in structurally chiral materials, enabling tunable optical filtering and polarization rejection through applied voltage.

Contribution

It formulates a boundary-value problem for wave reflection and transmission in electro-optic chiral materials, revealing how voltage and symmetry class influence the circular Bragg phenomenon.

Findings

Voltage enhances or induces the circular Bragg phenomenon.

Electrical control allows for thinner optical filters.

The effect depends on the material's crystallographic symmetry.

Abstract

The boundary-value problem of the reflection and transmission of a plane wave due to a slab of an electro-optic structurally chiral material (SCM) is formulated in terms of a 4x4 matrix ordinary differential equation. The SCM slab can be locally endowed with one of 20 classes of point group symmetry, and is subjected to a dc voltage across its thickness. The enhancement (and, in some cases, the production) of the circular Bragg phenomenon (CBP) by the application of the dc voltage has either switching or circular-polarization-rejection applications in optics. The twin possibilities of thinner filters and electrical manipulation of the CBP, depending on the local crystallographic class as well as the constitutive parameters of the SCM, emerge.