Broadband Circular Polarizers Constructed by Helix-like Chiral Metamaterials

TL;DR

This paper presents a novel helix-like chiral metamaterial design that achieves broadband circular polarization filtering with high extinction ratios and transmittance, suitable for integrated optical devices.

Contribution

The study introduces a scalable, broadband circular polarizer based on helix-like chiral metamaterials with enhanced bianisotropic response and high extinction ratios.

Findings

Maximum extinction ratio of 19.7 achieved.

Operational wavelength range from 4.69 μm to 8.98 μm.

Transmittance above 0.8 across the band.

Abstract

In this paper, a kind of helix-like chiral metamaterial, which can be realized with multiple conventional lithography or electron beam lithographic techniques, is proposed to achieve broadband bianisotropic optical response analogous to helical metamaterial. On the basis of twisted metamaterial, via tailoring the relative orientation within the lattice, the anisotropy of arc is converted into magneto-electric coupling of closely spaced arc pairs, which leads to a broad bianisotropic optical response. By connecting the adjacent upper and lower arcs, the coupling of metasurface pairs is transformed to the coupling of the three-dimensional inclusions, and provides a much broader and higher bianisotropic optical response. For only a four-layer helix-like metamaterial, the maximum extinction ratio can reach 19.7. The operation band is in the wavelength range from 4.69 {\mu}m to 8.98 {\mu}m with an average extinction ratio of 6.9. And the transmittance for selective polarization is above 0.8 in the entire operation band. Such a structure is promising for integratable and scalable broadband circular polarizers, especially has great potential to act as broadband circular micropolarizers in the field of the full-stokes division of focal plane polarimeters.