Broadband dispersionless polarization rotation with composite chiral metamaterials

We propose a planar composite chiral metamaterial (CCMM) by symmetrically inserting a metallic mesh between two layers of conjugated gammadion resonators. As the elaborate CCMM operates in the frequency region of off-resonance, it therefore presents loss-less and dispersion-free features. It can achieve flat polarization rotation simultaneously accompanied with high transmission and extremely low ellipticity in a broad bandwidth. In the meanwhile, this intriguing CCMM shows more superiorities in polarization rotation power and operating bandwidth than the pure chiral metamaterial just composed of conjugated gammadions. Due to the fascinating properties, the proposed CCMM is greatly appealing for controlling the polarization state of the electromagnetic waves.