Highly efficient diffraction gratings for use in the Littman-Metcalf mounting

An analysis was made of the operation of a metal-dielectric grating formed by a corrugated film located on a flat surface of a metal. It is shown that the high diffraction efficiency of such a grating for the TE waves is atta inable not only in the autocollimation regime (Littrow mounting), but also for a grazing (theta = 89 degrees) incidence of a light beam on the grating (Littman-Metcalfe mounting). This high efficiency is observed when leaky m odes are excited in the dielectric layer. An experimental check of the calc ulated results is reported.