Large Chiroptical Effects in Planar Chiral Metamaterials

TL;DR

This paper demonstrates that single-layer planar chiral metamaterials can produce large chiroptical effects through multimode interference, offering a simpler alternative to complex 3D structures for polarization control.

Contribution

It introduces a novel mechanism of multimode interference in planar chiral metamaterials to achieve strong chiroptical effects without complex 3D designs.

Findings

Large transmittance difference for LCP and RCP in planar metamaterials

Effect independent of dielectric loss and reciprocity

Potential applications in chiral light manipulation

Abstract

Chiroptical effects, characterized by different optical responses for left- (LCP) and right- handed circularly polarized light (RCP), are powerful and valuable tools in optics with wide applications in polarization resolved imaging and sensing. Previously observed strong chiroptical effects are limited to metamaterials with complex three-dimensional chiral structures at the sub-wavelength scale. Although asymmetrical transmission of LCP and RCP have been investigated in planar chiral metasurfaces, the observed weak chiroptical effects result from anisotropic Ohmic dissipation of the metal constituents. Here, we demonstrate by theory and proof-of-concept experiments that large difference in transmittances of LCP and RCP can be attained in a single-layer planar chiral metamaterial with a sub-wavelength thickness. Without violating the reciprocity and mirror symmetry, the strong chiroptical effect, independent of dielectric loss, arise from a novel mechanism of multimode interference. The described effect may lead to new gateway towards chiral manipulations of light and chiral optical devices.