Multipole Coupling in Nanoparticle Lattices with Quasi-Bound States

Metasurfaces and periodic lattices have become promising candidates for numerous photonic applications due to their unique ability to manipulate, control, and confine electromagnetic waves at the nanoscale dimensions. Collective resonances are excited in the periodic lattices of nanoparticles at the wavelength close to the Rayleigh anomaly. Effectively, it occurs at the wavelength equal to the array period or the latter divided by the refractive index of the surrounding medium. In this work, we demonstrate the coupling of multipole modes and quasi-bound states in the continuum with the modes trapped and localized in the nanoparticle array. This behavior is observed due to the suppression of radiative losses and increase in quality factor due to the disappearance of the mode scattering. We show that the combination of different materials in the nanoparticle allows the tuning of electric and magnetic resonances of the nanoparticles and achieving broadband overlap.<br/>This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Los Alamos National Laboratory (Contract 89233218CNA000001) and Sandia National Laboratories (Contract DE-NA-0003525). The work is also supported by Contract DE-2375849.