Ponderomotive electron acceleration using surface plasmon waves excited with femtosecond laser pulses

We report on the ponderomotive acceleration of electrons using surface plasmon (SP) waves launched on Ag and Au films. High-energy electrons, up to 2 keV, are generated in the high spatial gradient of the SP field. Acceleration gradients of ∼8GeV∕m are produced using 30GW∕cm2, 800 nm amplified 30 fs laser pulses. Investigation of the photoemission characteristics of these metal films reveals a distinct transition between the multiphoton regime and a laser-induced field emission regime. Results of the experiment are in good agreement with those predicted with test particle code, which is based on finite-difference time-domain simulation and incorporates the Drude dielectric function and photoemission properties of the metallic films.