Trapping light in resonant metasurfaces for plasmon lasing

Mitigating radiative losses in resonant structures has been a target of extensive research in photonics, involving various concepts such as optical dark states, multipoles, anapoles, embedded eigenstates, as well as momentum- or symmetry-mismatched lattice resonances in periodic systems. Here, we explore the possibility of improving the quality factors of dispersive lattice resonances within the light cone of a plasmonic metasurface. In particular, we find that antisymmetric modes of a honeycomb lattice of isotropic metal nanoparticles have symmetry-protected degenerate band edges, whereas the same lattice composed of anisotropic nanoparticles has an off-normal bound state along one of the dispersive bands. In addition to theoretical calculations, we also present our preliminary experimental results on distributed feedback lasing in such systems.