Gain-assisted excitation and manipulation of surface plasmon-polaritons

The excitation and manipulation of surface plasmon-polaritons (SPPs) are analyzed at a flat interface between a gain medium and a metal in Otto-type configuration. The gain medium is assumed to be a three-level atomic system whose transitions are coupled by two optical and one microwave fields. We show that, by making a transition from lossy dielectric to a gain medium, the losses for plasmonic waves can be greatly reduced, leading to reduced absorption and higher propagation distances for these modes. It is further emphasized that, in comparison to the lossy nature of the medium, maximum excitation can be achieved when the dielectric is a gain medium. Moreover, the SPPs can be manipulated with the frequencies and effective phase of the coupling fields driving the gain medium. The obtained results may find applications in low-loss plasmonic lasers and routers.