  We propose a novel class of ultrathin high Q passband filters designed by
properly combining different multipolar resonances sustained by an all
dielectric metasurface. A rigorous analytical model, based on surface impedance
homogenization and accounting for the effects of both dipolar and the
quadrupolar contributions to the overall scattering response, is derived and
verified through numerical simulations. Then, it is described how it is
possible to engineer the interactions between dipoles and quadrupoles in a
metasurface made by core shell spherical elements to design ultrathin and
broadband dielectric mirrors with a narrow transmission band. The proposed
filters exhibit high Q factor resonances and can be implemented using realistic
materials at either microwave or optical frequencies. Finally, we discuss how
the proposed dielectric filters can be used to design self filtering aperture
antennas exhibiting higher out of band selectivity compared with those
implemented through metallic resonators.
