Berlin 2014 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 2: Matter wave optics I
Q 2.6: Vortrag
Montag, 17. März 2014, 11:45–12:00, DO26 208
A tungsten tip based electron source triggered by laser pulses in the near-ultraviolet — •Dominik Ehberger, Jakob Hammer, and Peter Hommelhoff — Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudtstr. 1, 91058 Erlangen
Field emission tips as electron sources of nanometric size are known for their extraordinary spatial coherence properties in DC-field emission. By focusing laser pulses on the apex of the tip, electron emission is induced in a temporally well controlled manner.
Here, we will present a fiber based setup for laser-triggered electron emission from ultrasharp tungsten tips. Near-ultraviolet pulses with a mean photon energy of 3.14 eV are generated by frequency doubling of femtosecond Ti:sapphire pulses in bismuth triborate (BiBO). These are coupled to an optical fiber for laser pulse delivery and focused with a gradient-index lens onto a tungsten tip. We will report on our investigations concerning the laser-triggered emission process, which shows a clear signature of a one-photon process. Further emphasis is on the study of the coherence properties of the emitted electrons. From the analysis of electron interference patterns, obtained with an electrostatic biprism made of carbon nanotubes, the figure of merit for spatial coherence, the virtual source radius rv, is deduced. We find rv≤ 7 nm in laser-triggered electron emission for the source presented here.
We will discuss prospects and current limitations of our setup regarding its use as a compact, flexible electron source for various experiments.