Resonant frequencies for a narrow strip grating

This paper deals with the existence and the distribution of the resonances associated with the Maxwell system in a periodic infinite structure, obtain ed by loading a substrate with a periodic perturbation. We give an integral formulation of the homogeneous diffraction problem. By boundary integral o perators method, the existence and distribution of resonances is reduced to the determination of the characteristic values of two meromorphic operator valued functions. We give existence results on complex resonances close to the resonances of the substrate and also on real resonances. Copyright (C) 1999 John Wiley & Sons, Ltd.