Double Fano resonance in a side-by-side gratings structure

It is shown theoretically and numerically that a metal-dielectric or an all-dielectric side-by-side gratings structure can support non-degenerate guided modes coupled to the same radation mode. This realizes an easy to fabricate, simple system supporting a nearly degenerate, efficiently coupled, double Fano resonance. The ensuing relatively narrow and high-visibility spectral line-shape can be useful for realizing ultra-thin optical filters.