RESONANT SCATTERING BY MULTILAYERED DIELECTRIC GRATINGS

The diffracted orders generated by a plane-wave incident upon a multil ayered dielectric grating can undergo strong intensity variations know n as Wood's anomalies or scattering resonances. To clarify these effec ts, we examine the field and power flux inside the grating region by u sing a rigorous modal solution of the scattering problem. The results show that, at the peak of a scattering resonance, the power flux is al most identical to that of a leaky wave that can be supported by the gr ating structure. We thus confirm and generalize previous research that has identified the anomalous intensity variations as a forced-resonan ce effect associated with the free-resonant character of leaky waves. Quantitative data illustrating the behavior of typical gratings are gi ven, and the special case of normal incidence is discussed. (C) 1997 O ptical Society of America.