Multi-Band Circular Dichroism and Asymmetric Transmission Using Chiral Metasurface

This paper presents a new bilayer asymmetric transmissive chiral metasurface (ATCM) designed to achieve multi-band circular dichroism (CD) and asymmetric transmission (AT) within the microwave frequency range. The ATCM unit cell consists of a Rogers RO3010 dielectric substrate with metallic strip-based structure designed on both sides. The design structure incorporates two short, unequal strips positioned asymmetrically on opposite sides of a long strip, which induces the necessary anisotropy. The identical structure is replicated on the backside of the substrate with a 180° rotation to effectively establish a robust chiral response. The proposed ATCM exhibits selective polarization transmission under righthand circularly polarized (RHCP) and left-hand circularly polarized (LHCP) waves, with the polarization dependence varying between forward and backward propagation directions. This selective transmission results in a strong CD effect at five distinct frequencies: <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{8. 6 1 G H z}, \mathbf{1 1. 6 5 G H z}, \mathbf{1 4. 1 9 G H z}, \mathbf{1 7. 1 1}$</tex> GHz, and 17.68 GHz, achieving maximum CD values of 0.44, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.64,0.37,0.45$</tex>, and 0.38, respectively. Such an ATCM with multi-band performance could be valuable for applications in polarization-selective devices, imaging systems, sensing, and advanced communication systems.