Mid-infrared circular polarization switching in helical metamaterials

Circular polarization switching in helical metamaterial structures in the mid-infrared regime is numerically demonstrated. The low loss and broad transmission of right-and left-circularly polarized waves is found within the circular polarization switching bands. The switching behavior is maintained until the helix pitch or helix height reaches a quarter of the operating wavelength in the conventional and connected 4-layer planar helices, while the electromagnetic couplings among the four quarter helical parts conserve the 'helical-like' properties for the free-stand 4-layer planar helices, when the helix height is up to one eighth of the operating wavelength. These different helical orientations can be favorable in circular polarization switching and optical and light applications. Since the transmission switching bands are greater than 25% bandwidth, these switching designs could operate in the broadband spectral domain.