Resonant tunneling of surface plasmon-polaritons.

The tunneling of surface plasmon-polaritons (SPPs) across an interruption in the metallic film supporting them is numerically investigated in details. Both non-symmetrical and symmetrical geometries are considered. A very high tunneling efficiency is calculated for the long-range surface plasmon in the symmetrical geometry, with an amplitude transmission as high as 80% over a 5 microm gap for a 40 nm thick gold film illuminated at lambda= 785 nm. The transmission is somewhat lower in the non-symmetrical geometry. The coupling between the different SPP modes (radiative and non-radiative) in that geometry is also investigated in detail. This coupling depends periodically upon the length of the gap. Overall, the results indicate that SPPs are not very sensitive to technological imperfections and can survive large waveguide interruptions.