A theoretical study of near-field detection and excitation of surface plasmons

Recently, optical near-field techniques have been applied to detect or to excite surface plasmons at vacuum–metal interface. In this paper we propose a theoretical study of those experiments. We firstly describe the formalism, the sample being a multilayered structure with flat interfaces. The incident field and the field in each layer are expressed as 3D plane-wave expansions. The spatial Fourier amplitudes in each layer are linearly connected to the incident ones by transmission matrices. We then apply this formalism to describe the excitation of a surface plasmon in a Kretschmann geometry and its detection by a near-field probe. In the second experiment, the tip was used in the emission mode to excite the surface plasmons, which were thus far-field detected. We describe the experiment using the Bethe–Bouwkamp model for tip emission.