High Circular Dichroism Terahertz Chiral Metasurfaces Enabled by Quasi-Bound States in the Continuum

The concept of Bound State in the Continuum (BIC) describes a phenomenon where a state remains confined within the radiation continuum of a system. In the context of the terahertz frequency range, BIC offers a promising approach for creating devices with exceptionally high quality factors (Q-factors) and enabling strong interactions between terahertz radiation and matter, contributing significantly to the advancement of terahertz science and technology. In this work, we propose a chiral metasurface design for terahertz frequencies that achieves significant circular dichroism (CD) of 0.944. This is accomplished by disrupting the symmetry within the plane, which leads to the excitation of quasi-bound states in the continuum (quasi-BICs), resulting in a high Q-factor.