Publication in Science Advances
A breakthrough in gate-controlled nanometer-sized light antennas paves the way for electrically driven plasmonic modulators and metasurfaces, utilizing control over nonclassical surface effects.
We are excited to share recently published results from a long-term collaboration between POLIMA researchers and the group of professor Bert Hecht at The Julius Maximilians University of Würzburg (JMU).
Advancements in nanofabrication technologies now enable the routine creation of optical antennas from complex metallic nanostructures, providing fresh insights into nanoscale light-matter interactions and potential quantum corrections to the classical electrodynamics governing these antenna structures. Quantum corrections to spectral resonances are typically investigated by repeatedly fabricating the structure with intentional variations in specific aspects of the antenna's morphology, such as its size, while implicitly assuming that all other geometric properties remain constant, despite unavoidable nanoscale fluctuations between samples.
Electrical gating of a specific antenna structure could potential mitigate the uncertainty caused by inevitable variations between nominally identical antennas. However, this idea is commonly abandoned for metallic antennas, where colloqially speaking the addition of a few extra electrons would drawn in the existing massive sea of electrons already present in the metal. Nevertheless, due to strong screening, the added electrons will occupy the surface of the metal rather than its bulk, thus potentially still causing a significant perturbation in metallic nanostructures with a high surface-to-volume ratio.
State-of-the-art focused ion-beam milling of crystalline gold flakes was used to enable subwavelength metallic antennas with even smaller metallic leads attached to them for electronic gating. Using the well-known concept of lock-in aplifyer – routinely used in electronic setups, but rarely seen in labs for optical spectroscopy of nanostructures –experiments where able to correlate the spectral shifts with even minute additions of electrons, while interestingly showing how the observed shifts require the inclusion of quantum aspects associated with the atomic-scale charge dynamics at the metal surface.
"By perturbing the response functions of the surface, we combine classical and quantum effects, creating a unified framework that advances our understanding of surface effects," explains JMU physicist Luka Zurak, first author of the study.
L. Zurak, C. Wolff, J. Meier, R. Kullock, N. A. Mortensen, B. Hecht, and T. Feichtner, “Modulation of surface response in a single plasmonic nanoresonator”, Sci. Adv. 10, eadn5227 (2024)
https://www.science.org/doi/10.1126/sciadv.adn5227