Unconventional electromagnetic surface waves at the interface of two metals

It is well known that electromagnetic waves do not penetrate metal beyond the skin depth. Recently, it was theoretically predicted that in the presence of a gradual interface of two metals, the electromagnetic surface wave would experience low loss propagation along the diffuse boundary. In this configuration, the surface wave is predicted to propagate along such boundaries hundreds of times further than the skin depth. In this study, we have experimentally confirmed this prediction for the case of gold/silver diffused boundary. Overlap of gold and silver thin films was created, and propagation of the visible light was detected along the boundary. This result may enable extension of plasmonics into the UV range and enable novel approaches to silicon photonics.