Asymmetric electromagnetic wave polarization conversion through double spiral chiral metamaterial structure

This paper presents the design, simulation and measurement of a chiral metamaterial with double spiral unit cell structure that can be used to convert the polarization states of linearly polarized electromagnetic (EM) wave. The metamaterial is composed of a dielectric slab sandwiched by a double spiral metallic structure. By full-wave EM simulations and free space measurements, a strong polarization conversion of linearly polarized EM wave has been demonstrated in the microwave band. Moreover, the polarization conversion is asymmetric due to the chirality of the structure, therefore the structure could allow propagation of linearly polarized EM wave along one direction, while almost no propagation along the opposite direction. The proposed chiral metamaterial structure could find applications in designing polarization control devices.