A surface plasmon laser

We examine the possibility of stimulated emission of a surface plasma wave (SPW) on a metal-vacuum interface by electron-hole recombination in a forward biased p-n junction located near the interface. We consider a thin layer of n-type semiconductor sandwiched between a metal and a p-type semiconductor, and the p-n junction is forward biased. The mode structure of the SPW, propagating along the metal surface, extends up to the p-n junction, where it induces electron-hole recombination and gets amplified. The optical gain of the SPW laser can be made comparable to that of a diode laser by reducing the thickness of the sandwich layer.