  Using a random array of coupled metallic nanowires as a generic example of
disordered plasmonic systems, we demonstrate that the structural disorder
induces localization of light in these nanostructures at a deep-subwavelength
scale. The ab initio analysis is based on solving the complete set of 3D
Maxwell equations. We find that random variations of the radius of coupled
plasmonic nanowires are sufficient to induce the Anderson localization (AL) of
surface-plasmon polaritons (SPPs), the size of these trapped modes being
significantly smaller than the wavelength. Remarkably, the optical-gain
coefficient, needed to compensate losses in the plasmonic components of the
system, is much smaller than the loss coefficient of the metal, which is
obviously beneficial for the realization of the AL in plasmonic nanostructures.
The dynamics of excitation and propagation of the Anderson-localized SPPs are
addressed too.
