Rostock 2019 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 15: Nano-Optics (Plasmonics)

Q 15.6: Talk

Monday, March 11, 2019, 15:30–15:45, S SR 112 Maschb.

Electron near-field circular dichroism — •Tyler Harvey, Jan-Wilke Henke, Ofer Kfir, and Claus Ropers — IV. Physical Institute: Solids and Nanostructures, University of Göttingen, Germany

Although absorption or emission of a single photon by an electron is forbidden in free space by energy-momentum conservation, this interaction is possible in the presence of a surface. A surface breaks translation symmetry and allows for coupling between electron momentum and the electromagnetic field amplitude [1,2]. The strength of this coupling depends on the shape and optical properties of the surface, as well as the incident optical power. Because electron beams can be focused to sub-nanometer spots in modern electron microscopes, this interaction, called photon-induced near-field electron microscopy (PINEM) can be employed to image plasmonic modes and optical properties with nanometer spatial resolution.

In this presentation, we demonstrate the ability to probe chirality with PINEM. Circular dichroism spectroscopy with visible light and x-rays has long been used to characterize chiral-structured materials, magnetism and chiral electronic states. By illuminating a sample with left- and right-circularly polarized light and measuring the difference in coupling strength with electrons, we probe chiral optical near fields with nanometer spatial resolution. This technique may enable the investigation of chiral optical and electronic states in plasmonic nanostructures, molecules and atoms with sub-nanometer spatial resolution.

[1] B. Barwick et al., Nature 462 (2009) 902.

[2] A. Feist et al., Nature 521 (2015) 200.