Chiral metasurfaces with stabilized high circular dichroism empowered by BICs

Currently chiral metasurfaces are mainly devoted to achieving ultra-high quality factor (Q-factor) while there is a lack of research on achieving circular dichroism for structural stabilization up to date. We propose a chiral metasurface capable of obtaining high and stable circular dichroism empowered by bound states in the continuum (BICs). This ideal circular dichroism is achieved by constructing structures with extreme asymmetry. The circular dichroism for the metasurfaces is higher than 0.8 which the structural parameters fluctuate within 40%. Simulations demonstrate that it has ultra-high Q-factor (with a limiting value of more than 108) and near-perfect circular dichroism at near infrared band. The proposed approach offers an effective means to reduce the fabrication precision requirements of high-performance chiral metasurfaces.