Terahertz spin-selective perfect absorption enabled by quasi-bound states in the continuum

Spin-selective absorption is broadly applicable to numerous photonic devices. Here, based on a stereoscopic full metallic resonator array, a terahertz chiral metasurface with a single-layer structure is proposed and numerically demonstrated. By employing the coupled-mode theory, we demonstrate that the chiral metasurface can near-perfectly absorb one circularly polarized wave in the quasi-bound states in the continuum-induced critical coupling region but non-resonantly reflect its counterparts. Interestingly, the linewidths and handedness of the proposed chiral metasurface can be flexibly controlled by an in-plane symmetry perturbation. Our designs might offer an alternative strategy to develop chiral metasurfaces apart from conventional methods and might stimulate many potential applications for emerging terahertz technologies. (C) 2022 Optica Publishing Group

Automated summary

A terahertz chiral metasurface with a single-layer structure is proposed and demonstrated numerically based on a stereoscopic full metallic resonator array in this work. By using a coupled-mode theory, it is shown that the chiral metasurface can exhibit near-perfect absorption of one circularly polarized wave and non-resonant reflection of its counterparts in the quasi-bound states in the continuum-induced critical coupling region. The linewidths and handedness of the chiral metasurface can be flexibly controlled by an in-plane symmetry perturbation.