An innovative method for characterizing the electric field of plasmonic samples, such as gold nanoparticles, has been developed by an international research team from the University of Hamburg, DESY and Stanford University.

The ultrafast physicists led by Prof. Matthias Kling and Prof. Francesca Calegari have developed an instrument that can be used to measure the oscillating electric field on nanoparticles. The electrons in the nanoparticles are set into oscillation by ultrashort laser pulses (a so-called plasmon). Plasmonic materials are of particular interest due to their exceptional efficiency in absorbing light. This is of crucial importance for renewable energies and other technologies. In the experiments, a laser wave was sent through a thin sample of gold nanoparticles. The light wave with the plasmonic signal (signal pulse) was altered in a characteristic way.

The team has now measured these changes with high precision. This involves focusing an intense laser pulse in the air between two electrodes, which generates a measurable current. The signal pulse is superimposed on the intense pulse and modulates the ionization rate and thus also the generated current. An analysis of the delay between the two pulses provides a time-dependent signal that can be used to determine the electric field of the signal pulse. The major advance was the ability to measure the fields up to frequency ranges in the petahertz range. This corresponds to a temporal characterization in the attosecond range. “Field-resolved nanospectroscopy is still in its infancy,” says Prof. Matthias Kling, who heads the group of the same name in the attoworld team. Plasmons can be found in many other applications, from medicine to nanoelectronics.

The researchers report on their study in the journal “Nano Letters”.


Illustration: RMT.Bergues


Original publication:

Kai-Fu Wong, Weiwei Li, Zilong Wang, Vincent Wanie, Erik Månsson, Dominik Hoeing, Johannes Blöchl, Thomas Nubbemeyer, Abdallah Azzeer, Andrea Trabattoni, Holger Lange, Francesca Calegari, and Matthias F. Kling

"Far-Field Petahertz Sampling of Plasmonic Fields"

Nano Lett. 2024, 24, 18, 5506-5512

DOI: 10.1021/acs.nanolett.4c00658