Abstract
Designing and fabricating high-performance polarization converters that exhibit asymmetric transmission (AT), for light with different circularly/linearly polarized states with opposite propagating directions, are in high demand. The AT phenomenon leads to potential applications as isolators and circulators in information and communication systems. We propose a chiral metamaterial structure with high AT efficiency for two types of linearly orthogonal polarized red-near-IR light in two opposite incident directions. Theoretical results showed that the proposed chiral metamaterial structure achieves cross-polarization conversion where the polarization conversion ratio (PCR) is over 90%, in a broadband wavelength range from 715 to 810 nm, for both forward-propagating linearly polarized light and backward-propagating orthogonal linearly polarized light. The physical mechanisms of the polarization converter with the AT have been investigated. It was confirmed that the Fabry–Perot-like resonance and coupling between electric and magnetic dipoles lead to highly efficient asymmetric polarization conversion for two orthogonal linearly polarized light. Additionally, the conversion efficiency and bandwidth of the polarization converter are successfully optimized by adjusting the related structure parameters.
Highlights
The asymmetric transmission (AT) phenomenon arises from reversed polarization conversion efficiencies for light with different circularly/linearly polarized states propagating from opposite directions
We propose a polarization converter with AT effect for linearly polarized red-near-IR light based on a chiral metamaterial structure
The difference between the cross-polarization transmission coefficients tybx/f and txby/f originates from the asymmetric polarization conversion of the chiral metamaterial structure. These results demonstrate that a polarization converter with AT effect for x- and y-polarized light has been successively achieved
Summary
The asymmetric transmission (AT) phenomenon arises from reversed polarization conversion efficiencies for light with different circularly/linearly polarized states propagating from opposite directions. Dai et al realized the AT effect for linearly polarized waves in the THz region with a chiral metamaterial structure consisting of two double-T structures, where the AT parameter (the difference between the total transmitted intensities for different propagation directions) remains higher than 0.35 in 1.38–1.63 THz [17]. Wang et al theoretically propose and experimentally validate the manipulation of symmetry-assisted spectral line shapes in the dielectric double-Fano metasurfaces, which can support two kinds of channels: multipole localized resonance modes and a propagating continuum mode [19] They demonstrate highly efficient THz waveplates via all-dielectric metamaterials. Txby/f and Tybx/f represent cross-polarized transmission coefficients where the
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