Realizing efficient THz circular dichroism using ultra-thin chiral metasurface

Circular dichroism is characterized by distinct optical responses for left-handed and right-handed circularly polarized waves widely used for biological monitoring, analytical chemistry, and plasmonic sensing. This work proposes a chiral metasurface composed of a Mushroom-shaped (MS) pattern to achieve circular dichroism in reflection mode at THz frequencies. The maximum achieved absorption efficiency is 98.49% for the left-handed circularly polarized (LCP) incident wave. In comparison, the right-handed circularly polarized (RCP) incident wave is 7.39% at the resonant frequency of 12.4 THz. This high absorption results in remarkable circular dichroism (CD) of 91. 10%. Moreover, a stable response has been observed with the variation of incident angles from 0° to 30°. Meanwhile, power loss distribution, current distribution, and retrieved effective physical parameters have been used in analyzing the absorption mechanism. The high polarization selective absorption efficiency, angular stability, and compact size qualify the proposed design for a diverse range of THz applications.