On the Convergence of the Coupled-Wave Approach for Lamellar Diffraction Gratings

Abstract

Among the many existing rigorous methods for analyzing diffraction of electromagnetic waves by diffraction gratings, the coupled-wave approach1 stands out because of its versatility and simplicity. It can be applied to volume gratings and surface relief gratings, and its numerical implementation is much simpler than others. In addition, its predictions have been experimentally validated in several cases2-4. These facts explain the popularity of the coupled-wave approach among many optical engineers in the field of diffractive optics. However, a comprehensive analysis of the convergence of the model predictions has never been presented, although several authors5,6 have recently reported convergence difficulties with the model when it is used for metallic gratings in TM polarization.