Speaker
Johannes Schötz
(Max-Planck-Institute for Quantum Optics, Garching)
Description
The interaction of light with nanostructures shows unique properties such as enhancement and confinement of the electric near field down to a few nanometer. In strong-field photoemission from nanotips, as a consequence of the latter, electrons can experience the decay of the electric field amplitude and therefore the ponderomotive potential already during the time scale of a laser cycle. We experimentally study strong-field electron emission from metal nanotips in mid-infrared few-cycle laser fields. We identify a low-energy peak in the kinetic energy spectrum and investigate its shift to higher energies with increasing laser intensities from 1.7 to 8.9 × 10^11 W/cm2. Comparison to a simple model and numerical simulations shows that the decay of the near field on a nanometer scale leads to a nonadiabatic transfer of the ponderomotive potential to the kinetic energy of emitted electrons which results in the observed shift of the peak. We derive an analytic expression for the nonadiabatic ponderomotive shift of the low-energy peak. After the previously found quenching of the quiver motion, this completes the understanding of the role of inhomogeneous fields in strong-field photoemission from nanostructures.
Author
Johannes Schötz
(Max-Planck-Institute for Quantum Optics, Garching)
