Excitation of Surface Plasmon Polaritons at Planar Interfaces

Abstract

Surface plasmon polaritons propagating at the flat interface between a con- ductor and a dielectric are essentially two-dimensional electromagnetic waves. Confinement is achieved since the propagation constant β is greater than the wave vector k in the dielectric, leading to evanescent decay on both sides of the interface. The SPP dispersion curve therefore lies to the right of the light line beams is not possible unless special techniques for phase-matching are em- of the dielectric (given by ω = ck), and excitation by three-dimensional light ployed. Alternatively, thin film geometries such as insulator-metal-insulator heterostructures sustaining weakly confined SPPs are amenable to end-fire coupling, relying on spatial mode-matching rather than phase-matching. This chapter reviews the most common techniques for SPP excitation. After a discussion of excitation using charged particles, various optical techniques for phase-matching such as prism and grating coupling as well as excitation can also be achieved using illumination in the near-field, making use of evanes- using highly focused beams will be presented. Wave vectors in excess of |k| cent waves in the immediate vicinity of a sub-wavelength aperture. The chapter closes with a brief look at the excitation of SPPs in nanoparticle waveguides and multilayer structures using optical fiber tapers or end-fire excitation. This allows coupling of SPPs to modes in conventional dielectric waveguides. Tech- niques for the excitation and investigation of localized plasmons in metallic nanostructures such as various forms of microscopy and cathodoluminescence will be presented in chapter 10.