A general numerical technique for analyzing diffraction gratings of arbitrary groove shape as electromagnetic boundary-value problems is suggested. The method yields the scattered far-field modal amplitude without the necessity of initially computing the induced surface currents, which makes this technique very simple and convenient for analyzing the performance of diffraction gratings under normal and anomalous conditions. Some available computed results for rectangular gratings for the E -polarized case are compared with similar results in the literature and the adequacy and accuracy of the technique are demonstrated.
H. A. Kalhor and M. K. Moaveni, "Analysis of diffraction gratings by finite-difference coupling technique," J. Opt. Soc. Am. 63, 1584-1588 (1973)