90 degree polarization rotator using a bilayered chiral metamaterial with giant optical activity

TL;DR

This paper introduces a bilayered chiral metamaterial that achieves a 90-degree polarization rotation with giant optical activity, high efficiency, and a very thin structure, advancing optical device capabilities.

Contribution

The study presents a novel bilayered chiral metamaterial with record optical activity and high polarization conversion efficiency in a very thin form factor.

Findings

Achieves over 90% polarization conversion efficiency

Optical activity of about 2700 degrees per wavelength

Structure is less than λ/30 thick

Abstract

A bilayered chiral metamaterial (CMM) is proposed to realize a 90 degree polarization rotator, whose giant optical activity is due to the transverse magnetic dipole coupling among the metallic wire pairs of enantiomeric patterns. By transmission through this thin bilayered structure of less than \lambda/30 thick, a linearly polarized wave is converted to its cross polarization with a resonant polarization conversion efficiency (PCE) of over 90%. Meanwhile, the axial ratio of the transmitted wave is better than 40 dB. It is demonstrated that the chirality in the propagation direction makes this efficient cross-polarization conversion possible. The transversely isotropic property of this polarization rotator is also experimentally verified. The optical activity of the present structure is about 2700 degree/\lambda, which is the largest optical activity that can be found in literature.