Broadband angle- and permittivity-insensitive nondispersive optical activity based on chiral metamaterials

TL;DR

This paper introduces a chiral metamaterial with interconnected metal helix structures that achieves broadband, nondispersive optical activity insensitive to incident angles and permittivity, enabling flexible polarization control.

Contribution

The work presents a nonresonant, Drude-like chiral metamaterial design that overcomes dispersion issues, providing broadband, angle-insensitive optical activity with high transmittance.

Findings

Achieves nondispersive optical activity over a broad frequency range.

Optical activity scales with the number of layers.

Insensitivity to incident angle and substrate permittivity enhances application potential.

Abstract

Because of the strong inherent resonances, the giant optical activity obtained via chiral metamaterials generally suffers from high dispersion, which has been a big stumbling block to broadband applications. In this paper, we propose a type of chiral metamaterial consisting of interconnected metal helix structures with four-fold symmetry, which exhibits nonresonant Drude-like response and can therefore avoid the highly dispersive optical activity resulting from resonances. It shows that the well-designed chiral metamaterial can achieve nondispersive and pure optical activity with high transmittance in a broadband frequency range. And the optical activity of multi-layer chiral metamaterials is proportional to the layer numbers of single-layer chiral metamaterial. Most remarkably, the broadband behaviors of nondispersive optical activity and high transmission are insensitive to the incident angles of electromagnetic waves and permittivity of dielectric substrate, thereby enabling more flexibility in polarization manipulation.