Dispersion-free broadband optical polarization rotation based on helix photonic metamaterials.

We present a helix photonic metamaterial that exhibits nondispersive optical rotation in a broad passband at optical frequencies. Several features, including zero dispersion, zero ellipticity, and high transmission, can be simultaneously achieved in the presented structure. Pure optical rotation with extremely low dispersion is exhibited in a broad band covering the optical telecommunication wavelengths along with high transmission above 95%. We show that the chiral responses as well as the wavelength-dependent properties of the passband are governed by the behaviors of adjacent resonances. A systematic study of the optical properties with various geometrical parameters is performed, where the dependence of passband properties on resonance behaviors is examined and discussed. Such broadband dispersion-free optical rotation at optical frequencies may be of great interest for high-performance polarization manipulation and relevant applications.