Optimizing the coupling of light to plasmons through engineered dipolar scatterers

Abstract

Surface polaritons are key elements in multiple applications within the field of nanopho- tonics because of their ability to concentrate electromagnetic energy down to length scales comparable to the wavelength λ0 of propagating light. However, this confinement property also produces an important reduction in the coupling efficiency (photon-to-polariton) in most practical polariton-supporting structures, and in particular in planar interfaces. In this work, we have addressed this problem by introducing a dipolar scatterer of optimum size, placed at a suitable distance from a metallic surface, giving rise to large photon-plasmon coupling, which our experiments demonstrate to reach a cross section for incident light comparable to the dipolar limit ∼ λ2 0/2. These results represent a practical approach to solve the long-standing in/out problem, rendering polaritons in planar surfaces more easily excitable by means of incident propagating light in practical nanophotonics devices.