Tunable multispectral chiral effects of folded S-shaped metamaterials in mid-infrared region

Three-dimensional chiral optical metamaterials have attracted tremendous interests due to their enhanced chiroptical responses. Here we report an S-shape based folded metamaterial which can realize the tunable chiroptical property of multispectral effects in the mid-infrared region. This folded S-shaped metamaterial exhibits distinctive chiroptical responses under the irradiation of circularly polarized light with different spin states and it achieves two strong circular dichroism signals at 5 μ m and 7. 9 μ m , respectively. We attribute the spin-selective chiroptical characteristic to the intrinsic mechanism of the parallel and antiparallel coupling modes between induced electric dipoles and magnetic dipoles. Moreover, we also demonstrate that the chiroptical response is easily regulated by tuning its structural parameters. These properties promise various strong application potentials, such as spin-selective optical wavelength multiplexing, circularly polarized spectral filters, and ultrasensitive chiral sensors. • We report an S-shape based folded metamaterial which achieves two strong circular dichroism signals at 5 μ m and 7.9 μ m, respectively. • By analyzing the surface current distribution of the folded metamaterial, we find that its two distinct chiroptical responses are generated by different coupling modes between the dipoles. • We found that the chiroptical response of the folded metamaterial can be tuned.