Optical Tunneling through Arbitrarily-Shaped Plasmonic Channels and   Sharp Bends
  We propose a mechanism for optical energy squeezing and anomalous light tunneling through arbitrarily-shaped plasmonic ultranarrow channels and bends connecting two larger plasmonic metal-insulator-metal waveguides. It is shown how a proper design of sub-wavelength optical channels at cut-off, patterned by plasmonic implants and connecting larger plasmonic waveguides, may allow enhanced resonant transmission, inspired by the anomalous properties of epsilon-near-zero (ENZ) metamaterials. The resonant tunneling is shown to be only weakly dependent on the channel length and its specific geometry, such as possible presence of abruptions and bends. 
Andrea Alu, Nader Engheta