Abstract: I will give a brief overview of our group activities, focusing on the use of plasmonic nanostructures to enhance terahertz radiation - matter interaction.
Terahertz (THz) radiation is a powerful tool for the characterization of various elementary excitations in condensed matter systems, such as phonons, excitons, and magnons. Yet, its long wavelength severely hampers its interaction with nano-objects, which has limited traditional far-field THz studies to macroscopic ensembles of nano-compounds. To address such constraint, during the last years we have explored the use of gold nanostructures resonating in the THz range [1,2]. These “nano-antennas” can significantly enhance the THz electric field by confining it on a scale ~ 1000 times smaller than the wavelength. Using properly designed nanocavities made by antennas coupled end-to-end, we have demonstrated nanoantenna-enhanced THz spectroscopy , a technique that allowed retrieving the phonon spectral signature of a single layer of semiconductor quantum dots.
We have also shown that the phonon response of selected nanomaterials can be drastically modified inside such plasmonic nanocavities, without the need of any THz illumination, just exploiting the phonon strong coupling with the cavity “vacuum electric field” . Such phonon response modification could open new avenues for altering the energy dissipation mechanism in nanosystems, towards the improvement of nanodevice performance.
In this talk, I will summarize the above results and also show how advanced nano-architectures can be exploited in combination with intense THz sources for exploring strong-field physics phenomena in this frequency range.
 L. Razzari et al., Extremely large extinction efficiency and field enhancement in terahertz resonant dipole nanoantennas, Opt. Express 19: 26088, 2011.
 L. Razzari et al., Terahertz Dipole Nanoantenna Arrays: Resonance Characteristics, Plasmonics 8: 133, 2013.
 A. Toma et al., Squeezing Terahertz Light into Nanovolumes: Nanoantenna Enhanced Terahertz Spectroscopy (NETS) of Semiconductor Quantum Dots, Nano Lett. 15: 386, 2015.
 X. Jin et al., Reshaping the Phonon Energy Landscape of Nanocrystals Inside a Terahertz Plasmonic Nanocavity, Nat. Commun. 9: 763, 2018.
Biography: Luca Razzari is a full professor at INRS-EMT. He received his Ph.D. degree in Electronic Engineering from the University of Pavia (Italy) in December 2004. He then had postdoctoral experiences at the Institute for Complex Systems (CNR, Italy), at the INRS-EMT, and at the Italian Institute of Technology (IIT, Italy), before being recruited as a junior faculty at INRS in November 2012. He is the author of more than 70 research papers in refereed journals and a member of the editorial boards of Scientific Reports and Opto-Electronic Advances. He is also a former Marie Curie Fellow, Senior Member of the Optical Society (OSA), visiting scientist at the Molecular Foundry (Lawrence Berkeley National Laboratory) and Scientific Program Chair of Photonics North 2021. Dr. Razzari and his group have multidisciplinary research interests, which include nanoscale light-matter interaction, nonlinear optics, ultrafast physics, and terahertz spectroscopy.