Autocollimation diffraction gratings based on leaky-mode waveguides

Multilayer dielectric and metal-dielectric gratings are known to possess waveguiding properties (the ability to guide light along the layers). We have demonstrated the crucial role of leaky modes of a layered corrugated structure in the efficient operation of such a structure as a diffraction grating. We consider grating structures of three types: (1) a corrugated waveguide layer on a planar multilayer dielectric mirror, (2) a multilayer dielectric mirror on a corrugated substrate (i.e., a totally corrugated structure), and (3) an intermediate structure. We compare operation characteristics of these structures in the Littrow regime. A waveguide-grating structure with mode leaking into a substrate is also considered. A 100% reflection of light from one of the waveguide boundaries in this structure is achieved due to total internal reflection. A grating based on a two-layer leaky-mode waveguide is experimentally implemented.