Berlin 2005 – wissenschaftliches Programm
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Q: Quantenoptik und Photonik
Q 12: Anwendung ultrakurzer Lichtimpulse I
Q 12.6: Vortrag
Samstag, 5. März 2005, 09:45–10:00, HU 1070
Femtosecond Laser Induced Electron Emission from an Ultrasharp Tungsten Tip — •Peter Hommelhoff1, Anoush Aghajani-Talesh1,2, Yvan Sortais3, and Mark Kasevich1 — 1Stanford University, Varian Physics, Stanford, CA 94305, USA — 2Physikalisches Institut der Universität Freiburg — 3now at Institut d’Optique, Orsay, France
A femtosecond laser emitting 0.6 nJ 40 fs-pulses at 1 GHz at a wavelength of 800 nm is focused onto a tungsten field emission tip. From the polarization dependence, Fowler-Nordheim plots and a clear 1 GHz signal in the electron distribution we infer that the electron emission is due to photo-assisted field emission (tunneling of excited electrons). So far, the probability of seeing one electron per laser pulse is much less than unity. With more energetic 10 fs-pulses we attempt to generate high enough field strengths at the tip so that direct electron tunneling will be dominant (quasi-static regime). For this process we anticipate a much higher emission probability. Both photo-assisted field emission and photo-tunnel emission happen on fs-timescales. Therefore we expect a high brightness electron signal with sub-poissonian noise. With single-atom tips we hope to be able to build a single electron source prompted by the laser beam (see poster). A progress report is given.