Skip to main content

EELS

Scientific highlights

Three-dimensional vectorial imaging of surface phonon polaritons

figure.jpg

Surface phonon polaritons (SPhPs) are coupled photon-phonon excitations that emerge at the surfaces of nanostructured materials. Although they strongly influence the optical and thermal behavior of nanomaterials, no technique has been able to reveal the complete three-dimensional (3D) vectorial picture of their electromagnetic density of states. Using our monochromated NION-HERMES CHROMATEM, we could visualize varying SPhP signatures from nanoscale MgO cubes as a function of the beam position, energy loss, and tilt angle. The SPhPs’ response was described in terms of eigenmodes and used to tomographically reconstruct the phononic surface electromagnetic fields of the object. Such 3D information promises insights in nanoscale physical phenomena and might be useful to design and optimize nanostructures. This work was published in Science.

Optical polarization analogue in free electron beams

BlochPoincare.jpg

Spectromicroscopy techniques with fast electrons can quantitatively measure the optical response of excitations with unri- valled spatial resolution. However, owing to their inherently scalar nature, electron waves cannot access the polarization-related quantities. Despite promising attempts based on the conversion of concepts originating from singular optics (such as vortex beams), the definition of an optical polarization analogue for fast electrons has remained an open question. Here we establish such an analogue using the dipole transition vector of the electron between two well-chosen singular wave states. We show that electron energy loss spectroscopy allows the direct measurement of the polarized electromagnetic local density of states. In particular, in the case of circular polarization, it directly measures the local optical spin density. This work establishes electron energy loss spectroscopy as a quantitative technique to tackle fundamental issues in nano-optics, such as super-chirality, local polarization of dark excitations or polarization singularities at the nanoscale. Read more »

Publications

Li, X., et al. Three-dimensional vectorial imaging of surface phonon polaritons. Science 37160, 1364 - 1367 (2021).
Mkhitaryan, V., et al. Can Copper Nanostructures Sustain High-Quality Plasmons?. Nano Letters 21, (2021). Download: acsnanolett0c04667(2).pdf (4.15 MB)
Lourenço-Martins, H., Gérard, D. & Kociak, M. Optical polarization analogue in free electron beams. Nature Physics (2021).doi:10.1038/s41567-021-01163-w Download: OpticalPolarizationAnalog.pdf (5.54 MB)
de Seauve, V., et al. Spectroscopies and electron microscopies unravel the origin of the first colour photographs. Angewandte Chemie International Edition (2020).doi:10.1002/anie.202001241
Saito, H., et al. Emergence of point defect states in a plasmonic crystal. Physical Review B 100, (2019).
Yankovich, A.B., et al. Visualizing spatial variations of plasmon-exciton polaritons at the nanoscale using electron microscopy. Nano Letters (2019).doi:10.1021/acs.nanolett.9b03534
Campos, A., et al. Plasmonic quantum size effects in silver nanoparticles are dominated by interfaces and local environments. Nature Physics (2018).doi:10.1038/s41567-018-0345-z Download: CNP.pdf (1.79 MB)
Lourenço-Martins, H., Das, P., Tizei, L.H.G., Weil, R. & Kociak, M. Self-hybridization within non-Hermitian localized plasmonic systems. Nature Physics 89, (2018). Download: LM2018.pdf (3.41 MB)
Syndicate content