Ultrahigh- Metasurface Transparency Band Induced by Collective-Collective Coupling.

The metasurface analogue of electromagnetically induced transparency (EIT) provides a chip-scale platform for achieving light delay and storage, high factors, and greatly enhanced optical fields. However, the literature relies on the coupling between localized and localized or localized and collective resonances, limiting the factor and related performance. Here, we report a novel approach for realizing collective EIT-like bands with a measured factor reaching 2750 in silicon metasurfaces in the near-infrared regime, exceeding the state of the art by more than 5 times. It employs the coupling between two collective resonances, the Mie electric dipole surface lattice resonance (SLR) and the out-of-plane/in-plane electric quadrupole SLR (EQ-SLR). Remarkably, the collective EIT-like resonance can have diverging factor and group delay due to the bound state in the continuum characteristics of the in-plane EQ-SLR. With these findings, our study opens a new route for tailoring light flow in metasurfaces.