Excitation of surface plasmon waves with a nanoantenna: simple analytical solution and its numerical verification

In this work, we demonstrate a simple analytical approach to the problem of surface plasmon polaritons excitation with a metallic nanoantenna placed above a metal surface. The method uses the reciprocity theorem and is similar to the calculation of amplitudes of dielectric waveguide modes excited by a current distribution. To maximize clarity of the demonstration, we formulate the problem in a simple two-dimensional geometry. The analytical results are shown to agree well with the numerical solution obtained by finite elements in frequency domain and finite difference in time domain methods.