Observation of dual-band bound states in the continuum emerging from Mie collective lattice resonances

Collective lattice resonances (CLRs) and bound states in the continuum (BICs) are two exciting approaches for achieving high quality factors in metasurfaces. BICs emerging from CLRs have raised great interest for not only the ultrahigh quality factors but also the nonlocal field enhancement. However, experimental demonstrations remain insufficient due to the material absorption or the inappropriate parameter design. Here we experimentally demonstrate dual-band symmetry-protected BICs emerging from Mie CLRs in all-dielectric metasurfaces. We attribute these dual-band BICs to the zero emission at Γ point for the in-plane electric quadrupole and out-of-plane magnetic dipole CLRs, respectively. Such BICs feature nonlocal field enhancement and convenient spectral tunability, which are inherent to CLRs. We expect such nonlocal metasurfaces supporting BICs to find applications especially in nanolasers, nonlinear optics, and biochemical sensing.