Efficient generation of surface plasmon by single-nanoslit illumination under highly oblique incidence

Abstract : Using scanning near-field optical microscopy, we investigate the ability of nanoslits in metallic films to launch surface plasmon polaritons (SPPs) under highly oblique incidence at lambda=975 nm. The SPP generation efficiency is inferred by fitting the recorded near-field data with a simple analytical model. We find a remarkably large efficiency of 20% for the front side of the slit, which is in agreement with recent theoretical predictions relying on a fully vectoral electromagnetic formalism. An even larger efficiency is predicted experimentally (44%) and theoretically (33%) for the rear side. The present near-field analysis provides a direct approach to measure SPP generation efficiencies and may find applications for characterizing SPP devices.