Electromagnetic resonances of sub-wavelength rectangular metallic gratings

We present, a theoretical and experimental study of electromagnetic modes of 1D sub-wavelength rectangular metallic gratings exposed to P-polarized light. Reflection properties of gratings composed of deep grooves and transmission resonances of gratings composed of deep slits were both examined. Calculations were made using the modal development proposed by Sheng [1]. The aim of this paper is to give a review and detailed description of the theoretical modal method, considering P-polarized light, for both reflecting and transmitting properties. The validity of the method is confirmed by the measured properties of gold-coated microstructured samples. We show that the complementarity between the experiments and the calculations allows to perfectly characterize the EM resonances of the different gratings and to establish a link between the far-field response of these periodic structures and their EM near-field.