A Trigonometric Galerkin Method for Volume Integral Equations Arising in TM Grating Scattering
Provides a provably convergent, easy-to-implement numerical method for electromagnetic scattering from periodic dielectric gratings, a problem in computational electromagnetics.
The paper develops a trigonometric Galerkin method for volume integral equations in TM grating scattering, proving optimal convergence via Fredholm theory and leveraging FFT for efficient implementation, avoiding quasiperiodic Green's functions.
Transverse magnetic (TM) scattering of an electromagnetic wave from a periodic dielectric diffraction grating can mathematically be described by a volume integral equation. This volume integral equation, however, in general fails to feature a weakly singular integral operator. Nevertheless, after a suitable periodization, the involved integral operator can be efficiently evaluated on trigonometric polynomials using the fast Fourier transform (FFT) and iterative methods can be used to solve the integral equation. Using Fredholm theory, we prove that a trigonometric Galerkin discretization applied to the periodized integral equation converges with optimal order to the solution of the scattering problem. The main advantage of this FFT-based discretization scheme is that the resulting numerical method is particularly easy to implement, avoiding for instance the need to evaluate quasiperiodic Green's functions.