Monitoring the surface quality of silver plasmon waveguides with nonlinear photoemission electron microscopy and in-situ ion sputtering.

We use photoemission electron microscopy (PEEM) with single- and two-photon excitation to study the properties of surface plasmon polaritons (SPPs) in tapered silver stripe waveguides. Arrays of waveguides with different widths, grating coupler geometries, and taper angles are fabricated using electron beam lithography (EBL) on Si and indium-tin-oxide (ITO)-covered glass substrates. The presence of propagating SPP modes is indicated by modulations of the non-linear photoemission intensity which run along the length of the waveguide - the result of interfering SPPs reflected from the edges.