Bulk and surface plasmon polariton excitation in RuO₂ for low-loss plasmonic applications in NIR.

Transition-metal oxides, such as RuO₂, offer an exciting alternative to conventional metals for metamaterials and plasmonic applications due to their low optical losses in the visible and near-infrared ranges. In this manuscript we report observation of optically excited surface plasmon polaritons (SPPs) and bulk plasmons in RuO₂ thin films grown using DC reactive magnetron sputtering on glass and TiO₂ (001) substrates. We show that both plasmon modes can exist simultaneously for the infrared region of the optical spectrum, while only the bulk plasmons are supported at higher optical frequencies. Finally, we demonstrate that the film properties can be tailored to favor excitation of either SPP or bulk plasmons.