Femtosecond microscopy of localized and propagating surface plasmons in silver gratings

Abstract

Localized and propagating surface plasmons excited with 10 fs, 400 nm laser pulses in silver gratings are imaged with a sub-wavelength spatial resolution. Microscopic images of two-photon photoemission from the nanostructured silver surface representing nonlinear maps of surface plasmon fields are recorded with a photoemission electron microscope (PEEM). Tuning the laser wavelength into the resonance of a silver grating enhances the emission from the propagating mode and attenuates that from the localized modes. Time-resolved interferometric PEEM movies taken at 330 as/frame intervals reveal the dynamics of the oscillation and dephasing of individual localized surface plasmons.