Analysis of electromagnetic scattering from doubly-periodic structures using a hybrid current model

A novel solution is presented for the problem of three-dimensional electromagnetic scattering of a time-harmonic plane wave from a piecewise homogeneous double-periodic structure. Sets of fictitious doubly-periodic properly modulated patches of magnetic current of cross polarization are used to simulate the fields in the homogeneous regions crossed by unit cell boundaries. The fields radiated by these patch-currents are represented in terms of Floquet modes. Sets of fictitious elemental electric dipoles of cross polarization are used to simulate the fields in the homogeneous regions completely enclosed within this cell. The complex amplitudes of the fictitious sources are adjusted to render the tangential components of the electric and magnetic fields continuous at selected sets of points on the boundaries between the regions within the unit cell. The method is applicable to doubly-periodic gratings composed of homogeneous regions of smooth, shape. Perfectly conducting boundaries can also be handled by this procedure