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Inspired by the chiral structure from mode interaction, a chiral terahertz metamaterial and its complementary structure with the coexistence of asymmetric transmission and circular dichroism response are designed. The asymmetric transmission happens in the presence of electric and magnetic modes perpendicular to each other, resulting from intrinsic chirality under normal incidence. Circular dichroism exists in the presence of electric and magnetic modes parallel to each other under oblique incidence because of extrinsic chirality. Both asymmetric transmission and circular dichroism are enhanced by complementary structures, benefitting from the coupling between adjacent units. The maximum of chiral parameter κ can achieve 450, which is one hundred times higher than previously reported. The chiral response can be tuned by the incident angle and is sensitive to the environmental refractive index. The results highlight the potential applications of these metamaterials in chiral sensing and polarization transformation devices. [ABSTRACT FROM AUTHOR]

Chirality, as the core code of life forms, connects the ultimate secret of life and universe evolution. In article number 1900398, Changji Liu and co-workers propose an intrinsic chiral metamaterial and its complementary structures with coexistence of circular asymmetric transmission and circular dichroism in the THz region. The analysis reveals the chirality in metamaterials mainly comes from mode interaction and can be tuned by the incident angle. [Extracted from the article]