Laser-induced electron emission from a tungsten nanotip: identifying above threshold photoemission using energy-resolved laser power dependencies

Abstract

We present an experiment studying the interaction of a strongly focused 25 fs laser pulse with a tungsten nanotip, investigating the different regimes of laser-induced electron emission. We study the dependence of the electron yield with respect to the static electric field applied to the tip. Photoelectron spectra are recorded using a retarding field spectrometer and peaks separated by the photon energy are observed with a 45% contrast. They are a clear signature of above threshold photoemission (ATP), and are confirmed by extensive spectrally resolved studies of the laser power dependence. Understanding these mechanisms opens the route to control experiment in the strong-field regime on nanoscale objects.

Keywords:

• laser induced field emission
• nanotip
• above threshold photoemission
• photoelectron energy spectra

Acknowledgements

We thank P. Hommelhoff, H. Batelaan, J. Vigué, P. Labastie and C. Meier for fruitful discussions, E. Baynard, D. Castex and M. Gianesin, for technical support. L. Polizzi is particularly acknowledged for the strong technical support in designing the vacuum apparatus.

Notes

Support by Marie Curie ITN “FASTQUAST”, ANR contract labex NEXT N 11 LABEX 075 and by the region Midi-Pyrénées is gratefully acknowledged.