Low-threshold stimulated emission of surface plasmons polaritons

The stimulated emission threshold of surface plasmon polaritons (SPPs) propagating at the interface of silver and dye-doped polymer can be reduced by an order of magnitude if the operation range is changed from visible to near-infrared. The stimulated emission is observed at the polymer thickness, which is much below the cut-off for a regular photonic waveguide, proving SPP origin of the stimulated emission mode. With reduction of the polymer film thickness, the intensity of the stimulated emission decreases, its threshold increases, and the emission line experiences a blue shift-all in agreement with the laser theory. The dependence of the stimulated emission threshold on the polymer film thickness suggests quenching of dye molecule emission in vicinity of the silver surface.