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PGI Colloquium:

Prof. Dr. Mathieu Kociak,
Paris-Sud University, Orsay, France
 

PGI Lecture Hall, Building 04.8, 2nd Floor, Room 365

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19 Jan 2018 11:00

Nanooptics in the Electron Microscope

KociakCathodoluminescence in the electron microscope: Left: plasmon mapping in silver nanotriangle and Right: of GaN quantum wells embedded in AlN.
Copyright: Prof. Dr. Kociak


Hunting optical phenomena at the nanometer scale, namely performing nanooptics, is paradoxical. On the one hand, the typical length-scale relevant for optics is of the order of a visible radiation wavelength: few hundred of nanometers. On the other hand, optical properties of nano-objects become to depart from bulk properties when the nano-objects become smaller than a few hundred of nanometers – see the optical properties of a plasmon in a silver nanoparticle in Figure 1, left.

In this case, the optical properties depend on minute variations of the size and shape of the nano-objects, and sometimes the morphology or structure of nano-objects have to been known with atomic resolution – see the variations of emission wavelength in GaN quantum wells in figure 1, right. Therefore, techniques that are not limited by the optical diffraction limit have been developed in the last 15 years to make possible to study novel optical nanomaterials and the novel physics they brought.

In this talk, I will present the use of free electron beams – such as delivered in a transmission electron microscope – to perform optical spectroscopy at the nanometer scale. I will show how they can be used to map plasmons and excitons with unbeatable spatial resolution.

Beyond their impressive success in generating nice images, I will show how it is now possible to quantitatively understand such experiments in pure optical terms, such as extinction and scattering cross-sections or electromagnetic local density of states. Beyond these applications, I will present the use of free electron beams to perform quantum optical measurements, and, if time permits, new trends such as nanometer-scale phase or lifetime measurements of optical excitations at the nanometer-scale.

Contact

Dr. Martina Luysberg
Phone: +49 2461 61-2417
Fax: +49 2461 61-6444
email: m.luysberg@fz-juelich.de

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