High resonant reflection of a confined free space beam by a high contrast segmented waveguide

High resonant reflection of a free space wave from a deeply corrugated slab waveguide is shown to take place in the case of a focused free space beam under normal incidence. It is described as a result of a strong intra-guide coupling coefficient allowing the coupled wave to be closely localized under the incident beam, therefore to interfere with it with high contrast effects. The coupled mode inspired analysis gives the possibility of optimizing the resonant structure; it is related and compared with the photonic crystal vision of the same functional structure to which it confers more intelligibility.