Different preconditioning techniques for the efficient simulation of 2D EC structures

When analyzing wave propagation in electromagnetic crystals using multilevel fast multipole accelerated integral equation methods, the total number of iterations required for the solver to converge is often large. The paper discusses the effectiveness of various techniques for preconditioning the linear systems of equations arising in the analysis of ECs. In addition, it introduces a new physics-based preconditioner that effectively deflates the original system by accounting for all quasi-resonant modes directly (as opposed to iteratively).