Beaming thermal emission from hot metallic bull's eyes.

We theoretically examine thermal emission from metallic films with surfaces that are patterned with a series of circular concentric grooves (a bull's eye pattern). Due to thermal excitation of surface plasmons, theory predicts that a single beam of light can be emitted from these films in the normal direction that is narrow, both in terms of its spectrum and its angular divergence. Thus, we show that metallic films can generate monochromatic directional beams of light by a simple thermal process.