  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.
