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 attainable not only in the autocollimation regime (Littrow mounting), but also for a grazing (Θ = 89°) incidence of a light beam on the grating (Littman — Metcalfe mounting). This high efficiency is observed when leaky modes are excited in the dielectric layer. An experimental check of the calculated results is reported.