Resonant scattering by multilayered dielectric gratings

The diffracted orders generated by a plane-wave incident upon a multilayered dielectric grating can undergo strong intensity variations known as Wood’s anomalies or scattering resonances. To clarify these effects, we examine the field and power flux inside the grating region by using a rigorous modal solution of the scattering problem. The results show that, at the peak of a scattering resonance, the power flux is almost identical to that of a leaky wave that can be supported by the grating structure. We thus confirm and generalize previous research that has identified the anomalous intensity variations as a forced-resonance effect associated with the free-resonant character of leaky waves. Quantitative data illustrating the behavior of typical gratings are given, and the special case of normal incidence is discussed.