A 150-fs 800-nm 1-μJ laser was used to excited surface plasmons in the Kretschmann geometry in a 500-Å silver film. Multiphoton excitation results in the emission of femtosecond electron bunches (40 fC) as had been seen before. The electron beam is highly directional and perpendicular to the prism surface. A time-of-flight setup has been used to measure the kinetic-energy distribution of the photoelectrons. Surprisingly, we find that this distribution extends to energies as high as 40 eV. Theoretical calculations show that these high energies may be due to acceleration in the evanescent laser field that extends from the silver film out into the vacuum. These results suggest that femtosecond pulses with more energy per pulse or longer wavelength may be used to accelerate electrons to the keV or even MeV level.
|Number of pages||4|
|Journal||Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment|
|Publication status||Published - 1 May 2000|
- surface plasmons
- ultrafast electron acceleration