Imaging of Surface Plasmon Polaritons Using Femtosecond Laser Excited Two-Photon Fluorescence Microscopy

Abstract

We demonstrate imaging of surface plasmon polaritons (SPPs) on a silver film using a two-photon fluorescence microscopy technique. Surface plasmon waves launched from an edge of a silver film under a light irradiation of 11-fs near-infrared laser pulses promote formation of intensity beats in nearfi elds through SPP-light interference. Dye molecules embedded in a thin PMMA layer on a silver fi lm up-convert the near-infrared surface fi elds to propagating lights in visible range through a two-photon excitation, which enables to image the near-fi elds with using a conventional optical microscope. The wavelength of SPP determined from the beat wavelength of near-fi elds agrees well with an evaluation using dielectric properties of sample materials and the dispersion relation of SPP.