Complementary chiral metamaterial with multi-band asymmetric transmission and mutual conversion

Abstract

In this paper, we propose a special chiral metamaterial (CMM) structure with a unit cell lacking mirror symmetry, which exhibits asymmetric transmission (AT) of terahertz radiation (1.4–2.3 THz) propagating through it in opposite directions. It is constructed by double-layered four complementary U-shaped resonators on both sides of a dielectric substrate, and the front and back layers are the same that are rotated by 90º with respect to each other. Numerical simulation results demonstrate that our scheme can realize large multi-band AT in terahertz band with a mutual conversion (x-to-y, and y-to-x) of linearly polarized electromagnetic waves only. The large cross-coupling reveals that the linear polarization of the incident wave is converted to its orthogonal polarization when the wave propagates through the designed structure. The surface current densities and electric field distributions of bi-layered CMM at the resonant frequencies are presented to interpret the multi-band AT with mutual conversion. The AT effect and resonant frequencies can be adjusted by geometric parameters of the unit cell.

Keywords:

• Chiral metamaterial
• mutual polarization conversion
• multi-band
• linear polarization transformer