Fast Iterative Physical Optics with Shadowing

A fast iterative physical optics (IPO) algorithm for the analysis of scattering from large complex geometries involving multiple scattering and self-shadowing effects is presented. The algorithm comprises two types of nested iterations: reflection ("bounce") iterations and self-shadowing iterations. Both types of iterations involve time consuming surface integrations carrying an O(N-2) computational cost (N being the number of quadrature points). The nested iterative formulation is accelerated by using the multilevel non-uniform grid algorithm reducing the computational complexity to O(NlogN). The procedure's applicability to complex geometries and numerical efficiency are demonstrated by comparison to a numerically exact method and to the conventional physical optics.