Theory of light reflection and transmission by a plasmonic nanocomposite slab: Emergence of broadband perfect absorption

Abstract

A theory of light reflection and transmission by an optically thin nanocomposite slab which contains randomly distributed metal nanoparticles (NPs) is developed. The underlying model takes into account the reflection of light scattered by NPs from the slab boundaries, enhanced decay of localized surface plasmons in dense NP arrays and light scattering at the slab surface -- the factors which are beyond the scope of the Maxwell Garnett approximation. It is demonstrated that the first two effects lead to broadband perfect absorption observed in such nanocomposites, whereas the last one is responsible for its omnidirectional character and polarization insensitivity. These findings open up new possibilities for engineering broadband perfect absorption in plasmonic nanocomposites.