Plane-Wave Transmission Through an Array of Dielectric-Loaded Slots in a Thick Metallic Screen: Normal Incidence

In this paper, we derive an analytical model for plane-wave transmission through a periodic array of dielectric-loaded slots in an infinite metallic screen of finite thickness (a metagrating). We show the existence of (Fano) resonances associated with the presence of higher order modes in the slots, in addition to the well-known (Fabry-Perot) resonances associated with the dominant mode in the slots. The Fano resonances arise from a physical mechanism distinct from that which is responsible for so-called extraordinary transmission through a grating, which is strongly dependent on the coupling among the slots. Comparison of the analytical model with the results of full-wave simulations shows excellent agreement when the characteristic dimensions of the grating are small compared with a free-space wavelength.