Improved spherical wave least squares method for analyzing periodic arrays of spheres

摘要

For analyzing plane wave scattering from a multilayer periodic structure where each layer consists of a two-dimensional periodic array of spheres, a spherical wave least squares method is developed which extends and improves the earlier work by Matsushima et al. [PIER 69, 305 (2007)]. A number of techniques are used to speed up the method and to reduce the memory requirement. Spherical wave expansions are used in one unit cell containing a sphere in each layer, and quasi-periodic conditions are imposed on lateral surfaces of the unit cell in the least squares sense. Unlike the layer-Korringa-Kohn-Rostoker method [Physica A 141, 575 (1987)], the method does not need lattice sums and it is relatively simple to implement.