Resonant and nonresonant diffraction by open image-type slotted structures

The problem of the electromagnetic (EM) wave diffraction by canonical image type slotted structures is studied by the methods of perturbation theory applied to analytical operator valued functions. Fundamental (scattering) frequencies, obtained in the form of expansions in powers of a small parameter (slotwidth), are shown to have negative imaginary parts. Explicit representations for scattered fields are obtained both in the resonant and nonresonant cases, and the amplitude and phase distributions are calculated.