Electromagnetic diffraction from a metallic bigrating of prolate spheroid cavities

The diffraction of an electromagnetic plane wave from a bigrating of prolat e spheroid cavities hollowed in a perfectly conducting metallic plate is st udied using an exact differential analytic method. The theoretical treatmen t is carried out for any incidence and direction of polarization, but first , numerical results are given for normal incidence in view of comparison wi th previous results obtained in same conditions from a bigrating of hemisph erical cavities. So, original efficiency curves epsilon(ff) (0, 0) (or norm al reflectance) versus the size of cavities are given. (C) Academie des sci ences/Elsevier, Paris.