It is shown that (1) the exceptional numerical efficiency of the Rayleigh-Fourier method for <i>h/d</i> (<i>h</i> is the height and <i>d</i> is the period of a sinusoidal grating) as large as 0.5 could not have been discovered by Petit and Cadilhac in 1966 and (2) the Rayleigh least-squares method does not converge numerically for all <i>h</i>/<i>d</i>, these facts being in contradication to the assertions made by Hugonin <i>et al.</i> [J. Opt. Soc. Am. <b>71</b>, 593 (1981)].
© 1982 Optical Society of America
A. Wirgin, "Plane-wave expansions used to describe the field diffracted by a grating: comments," J. Opt. Soc. Am. 72, 812-813 (1982)