Autocollimation diffraction gratings based on waveguides with leakage modes

It is shown that the leakage modes of multilayer corrugated dielectric and metal-dielectric structures are extremely important for the achievement of high efficiency of such structures as diffraction gratings. Three types of grating structures are considered: a corrugated waveguide layer on a flat multilayer dielectric mirror (type 1); a multilayer dielectric mirror on a corrugated substrate (i.e., a totally corrugated structure) (type 2); and a structure of the intermediate type (type 3). The performance characteristics of these structures used in the Littrow mounting are compared.