Near-to far-field transformation in the aperiodic Fourier modal method

This paper addresses the task of obtaining the far-field spectrum for a finite structure given the near-field calculated by the aperiodic Fourier modal method in contrast-field formulation (AFMM-CFF). The AFMM-CFF efficiently calculates the solution to Maxwell's equations for a finite structure by truncating the computational domain with perfectly matched layers (PMLs). However, this limits the far-field solution to a narrow strip between the PMLs. The Green's function for layered media is used to extend the solution over the whole super-And substrate. The approach is validated by applying it to the problem of scattering from a cylinder for which the analytical solution is available. Moreover, a numerical study is conducted on the accuracy of the approximate far-field computed with the super-cell Fourier modal method by using the AFMM-CFF with near-to far-field transformation as a reference. Keywords: Computational domains; Far field spectra; Finite structures; Fourier modal method; Layered media; Maxwell's equations; Narrow strips; Perfectly matched layer