Matched coordinates for the analysis of 1D gratings

The Fourier modal method (FMM) is certainly one of the most popular and general methods for modeling diffraction gratings. However, non-lamellar gratings it associated with a staircase approximation profile, leading to poor convergence rate metallic in TM polarization. One way overcome this weakness FMM use fast factorization (FFF) first derived differential method. That approach relies on definition normal tangential vectors profile. Instead, we introduce coordinate system that matches laterally profile solve covariant Maxwell’s equations new system, hence name matched (MCM). Comparison efficiencies computed MCM other data from literature validates