Conversion of surface plasmon polaritons to light by a surface step

Abstract

A focused electron beam in a transmission electron microscope can excite a surface plasmon polariton (SPP) at any position on a metal surface as a point source. The excited SPP is converted into light at a surface step and the emission intensity depends on the beam position, photon energy, and emission angle. A spectrum image was obtained by scanning the electron beam across a step on a silver surface with a fixed emission angle, demonstrating a characteristic fringe pattern. The dispersion relation of the SPP on a silver surface is derived by analyzing the spectrum image.