Rostock 2019 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 30: Matter Wave Optics
Q 30.7: Talk
Wednesday, March 13, 2019, 12:15–12:30, S SR 211 Maschb.
Spatial properties of multiphoton-photoemitted electron pulses from metallic needle tips — •Stefan Meier, Takuya Higuchi, and Peter Hommelhoff — Department Physik, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91058 Erlangen
Tungsten needle tips represent well-suited electron sources for various applications like electron microscopy or holography. These methods strongly benefit from the spatially highly coherent electron beams that such tip sources, usually operated in DC-field emission, can provide. To equip these techniques with high temporal resolution, one can trigger the electron emission with few-cycle laser pulses, leading to electron pulses emitted on ultrashort timescales. Recent experiments show that pulsed electron beams, emitted by either a single photon photoemission process [1] or a multiphoton photoemission process [2], have similar coherence properties as DC-field emitted beams. We show our current progress on the investigation of the spatial properties of multiphoton photoemitted electron beams. By investigating the interference pattern of the electron beam after a beamsplitter, we can determine an effective source size reff of an emitter, which is a quantitative measure for spatial coherence. We report on an upper limit of reff≤(0.65±0.06) nm for multiphoton-photoemitted electrons from tungsten needle tips with a geometrical radius of rgeo=(6.8±1.7) nm. In combination with the spatial distribution of the emitted electrons we can also access other electron optical parameters, like beam emittance or brightness.
[1] D. Ehberger et al., Phys. Rev. Lett. 114, 227601 (2015).
[2] S. Meier et al., Appl. Phys. Lett. 113, 143101 (2018).