High-Q and Strong Chiroptical Responses in Planar Metasurfaces Empowered by Mie Surface Lattice Resonances

Planar chiral metasurfaces have emerged as a versatile platform for manipulating chiral light-matter interactions in diverse applications. However, it remains challenging to achieve high quality factors together with strong chirality. Here, chiral all-dielectric metasurfaces with a high Q factor of 1220 and relatively large planar chirality of circular dichroism -0.37 under normal incidence, or with a high Q factor of 872 and large extrinsic 3D chirality of circular dichroism 0.7, based on Mie surface lattice resonances (SLRs) are proposed and experimentally demonstrated. Both SLR-induced planar chirality under normal incidence and SLR-assisted extrinsic 3D chirality under oblique incidence are achieved by perturbing the square lattice and by slightly tilting the incidence angle, respectively. It shows that the high-Q and strong chirality arises from the different excitation efficiencies of Mie SLRs under the incidences of left- and right-handed circularly polarized light. With these findings, this study provides a new direction for realizing high-performance chiral metasurfaces and holds great promise for chiral nanophotonic applications in biochemical sensing, emission or lasing, and nonlinear optics.