In the recent Letter Opt. Lett. 39, 781 (2014) that proposes a method to design slanted parallelogram gratings based on the simplified modal method, the analysis of the modal field in the grating layer is incorrect; therefore, the validity of the equivalence between slanted parallelogram gratings and upright rectangular gratings that the authors thereby have deduced is questionable or at least in need of substantial modifications.
展开▼