The foci or branch points are found for a sinusoidal boundary. It is shown how they determine the range of validity of Rayleigh’s hypothesis for diffraction gratings.
© 2000 Optical Society of America
(050.0050) Diffraction and gratings : Diffraction and gratings
Joseph B. Keller, "Singularities and Rayleigh's hypothesis for diffraction gratings," J. Opt. Soc. Am. A 17, 456-457 (2000)