Scattering of s-polarized electromagnetic waves from an infinitely conducting circular cavity: enhanced fields and dips in the reflectivity

The scattering of s-polarized electromagnetic waves from an open circular cavity ruled on a planar, perfectly conducting surface is analysed by means of an integral method based on Green's theorem. We show novel effects in which s resonances, manifested by the appearance of sharp dips in the curves of scattered intensity versus incident wavelength, give strong enhancement of the local field intensity inside the cavity and near the surface. We show that the position of the dips can be estimated from the knowledge of the resonant wavelengths obtained for a closed resonant cavity.