  We have observed laser-like emission of surface plasmon polaritons (SPPs)
decoupled to the glass prism in an attenuated total reflection setup. SPPs were
excited by optically pumped molecules in a polymeric film deposited on the top
of the silver film. Stimulated emission was characterized by a distinct
threshold in the input-output dependence and narrowing of the emission
spectrum. The observed stimulated emission and corresponding to it compensation
of the metallic absorption loss by gain enables many applications of
metamaterials and nanoplasmonic devices.
