Fano-Shape Lattice-Mode Resonances and Near Fields in the E-Polarized Wave Scattering by a PEC Strip Grating on a Dielectric Substrate

We study numerically specific sharp resonance phenomena, observed in the plane E-polarized wave scattering from an infinite flat grating of perfectly electrically conducting strips, backed with a flat dielectric slab. As a tool of accurate numerical analysis, we use the well-known algorithm, based on the analytical regularization with the aid of the Riemann-Hilbert Problem solution. Our numerical experiments demonstrate the Fano-shape resonances on the so-called lattice modes, responsible for the phased array blindness. For thin low-contrast substrates, their frequencies lay near to the Rayleigh anomalies and, if the slots or strips are narrow, may have ultrahigh Q-factors. We compute the near-field portraits in the lattice-mode resonances and discuss them.