Unconventional electromagnetic surface waves at the Ti-Si interface

It is typically assumed that electromagnetic waves do not penetrate lossy media beyond the skin depth. However, recently it was theoretically predicted that in the presence of a gradual interface, the electromagnetic surface wave would experience low loss propagation along the diffuse boundary of two highly lossy media. Such a surface wave is predicted to propagate along diffuse boundaries over distances which are much larger than the skin depth. In this study, we have experimentally confirmed this prediction for the case of titanium/silicon diffused boundary. Overlap of titanium and silicon 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.