A multi-functional polarization convertor based on chiral metamaterial for terahertz waves

In this paper, a multi-functional polarization convertor for terahertz (THz) light composed of a bilayer wire-split-ring (WSR) structure chiral metamaterial (CMM) was proposed and investigated numerically. Simulation results indicate that when normal incident light is propagating along the – z axis direction through the proposed CMM structure, the y-polarization is converted to the left- and right-circular polarization (LCP and RCP) at 1.14 THz and 1.34 THz, respectively. Meanwhile, the x-polarization is converted to y-polarization in the frequency range of 2.19 – 2.47 THz. The further calculation results show that the proposed CMM structure can transmit a nearly pure circular polarization light with a polarization extinction ratio (PER) of over 30 dB and an orthogonal linear polarization light with a polarization conversion ratio (PCR) of over 90%. The mechanism of the polarization conversion properties is illustrated by the simulated electrical field and surface current distribution. Due to its excellent multi-functional polarization conversion properties, the proposed CMM is useful for the development of the integrated THz polarization manipulation devices.