Heidelberg 2015 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 65: Nano-Optics IV

Q 65.3: Talk

Friday, March 27, 2015, 11:30–11:45, C/HSO

Electron-light interaction in optical near-fields studied by ultrafast electron microscopy — •Armin Feist, Katharina Echternkamp, Jakob Schauss, Sergey Yalunin, Sascha Schäfer, and Claus Ropers — IV. Physical Institute, University of Göttingen, 37077 Göttingen, Germany

Ultrafast transmission electron microscopy (UTEM) is a laser pump/ electron probe technique, utilized to study laser-induced dynamics on a nanometer length scale [1]. Moreover, UTEM can be applied to locally probe optical near-fields [2].

Here, we study the coherent interaction of swift electrons with optical near-fields in UTEM [3]. We recently modified a commercial Schottky field emission TEM (JEOL JEM-2100F) for pulsed operation using localized nonlinear photoemission from a needle-shaped nanoscopic tip. Electron pulses of 700 fs duration and spot diameters below 10 nm are obtained in the sample plane. Positioning the electron beam in close vicinity to an illuminated nanostructure allows an otherwise forbidden dipolar coupling between free electrons and the optical near-field. This leads to the formation of spectral side bands, corresponding to the absorption and emission of multiple photons. Raster-scanning the electron beam enables the mapping of the optical near-fields. The field dependent sideband populations reveal the quantum coherence of the process.

[1] A.H. Zewail, Science, 328, 187 (2010). [2] B. Barwick et al., Nature, 462, 902 (2009). [3] A. Feist et al., submitted (2014).