Polarization Control by Using Anisotropic 3D Chiral Structures

TL;DR

This paper introduces a novel anisotropic 3D chiral structure that enables highly tunable polarization conversion, overcoming symmetry limitations and achieving significant linear-to-circular polarization efficiency at microwave frequencies.

Contribution

The work presents a compact, anisotropic 3D chiral design that enhances polarization control capabilities beyond symmetric structures, with practical implementation on a PCB at 9.2 GHz.

Findings

Achieves 60% linear-to-circular polarization conversion efficiency.

Demonstrates phase shift control via anisotropic chiral response.

Operates effectively at 9.2 GHz frequency.

Abstract

Due to the mirror symmetry breaking, chiral structures show fantastic electromagnetic (EM) properties involving negative refraction, giant optical activity, and asymmetric transmission. Aligned electric and magnetic dipoles excited in chiral structures contribute to extraordinary properties. However, the chiral structures that exhibit n-fold rotational symmetry show limited tuning capability. In this paper, we proposed a compact, light, and highly tunable anisotropic chiral structure to overcome this limitation and realize a linear-to-circular polarization conversion. The anisotropy is due to simultaneous excitations of two different pairs of aligned electric and magnetic dipoles. The 3D omega-like structure, etched on two sides of one PCB board and connected by metallic vias, achieves 60% of linearto- circular conversion (transmission) efficiency at the operating frequency of 9.2 GHz. The desired 90-degree phase shift between the two orthogonal linear polarization components is not only from the finite-thickness dielectric substrate but also from the anisotropic chiral response slightly off the resonance. The work enables elegant and practical polarization control of EM waves.