Light confinement by two-dimensional arrays of dielectric spheres

We present a study on the ability of two-dimensional close-packed arrays of submicron dielectric spheres to confine electromagnetic radiation. Substrates having different nature, either dielectric or metallic, are considered, and the evolution of the strong spatial redistribution of the total field intensity is monitored by means of numerical simulations. The physical origin of the different modes of the system is further studied by measuring the optical response of the hybrid structures and reproducing it with an analytic effective medium model. The study evidences that the use of metallic substrates provides the best scenario for enhancing light-matter interaction in this kind of system, pointing out that the hybrid modes arising from the combination of periodic dielectric lattices and metallic substrates cannot be treated as purely photonic or plasmonic.