Circular Dichroism and Cross Polarization Conversion Using Chiral Metasurface

This paper presents a novel dual-mode chiral metasurface (CM) designed to achieve strong circular dichroism (CD) in both transmission and reflection mode within the Ku-band. The proposed dual-mode CM demonstrates CD i.e., an efficient conversion of linearly polarized (LP) electromagnetic (EM) waves into circularly polarized (CP) waves, both within a broader spectrum as well as at single frequencies in both transmission and reflection mode, exhibiting asymmetric transmission (AT) response. This is achieved through a judiciously designed unit cell structure, which eliminates the requirement for intricate supercell configurations or active circuitry. The metasurface comprises a circular ring structure embedded with intelligently placed angle-induced slot and a metallic strip, fabricated using the cost-effective FR-4 substrate. The structure on the front side of the dual-mode CM is replicated on the back side of the substrate with a 90° rotation to achieve a chiral configuration. Under the forward-propagating y-polarized incident wave, the dual-mode CM demonstrates the capability to convert LP wave into right-handed circularly polarized (RHCP) wave at 14.064 GHz. Additionally, in transmission mode, it converts LP waves to left-handed circularly polarized (LHCP) wave over a wider frequency range of 16.60 -17.03 GHz with AT response. In reflection mode, the dual-mode CM converts LP wave into RHCP wave at 12.048 GHz when subject to x-polarized incident wave propagating in the backward direction.