High-Harmonic Generation -- A Universal Response of Matter to Intense Light
Paul Corkum
Joint Attosecond Science Lab
University of Ottawa and National Research Council of Canada
Friday, June 13, 2025
10:00 a.m.
In-person: STC 0020
´¡²ú²õ³Ù°ù²¹³¦³Ù:ÌýWhen we irradiated an atom with intense infrared light, an electron ionizes. Sometimes, an ion wave packet is also launched. The field required for electron tunneling is sufficient to pull the ionizing electron wave packet far from the atom. The wave packet returns to its birthplace after another quarter cycle where it might find its parent in a core excited state. Both components (the electron and ion) can be controlled giving us attosecond science and a new tool for studying core states of atoms.
Transparent dielectrics and semiconductors are like large rare-gas atoms, except for having a higher atomic density and more closely spaced excited states. It seemed quite natural that there was an ion source of harmonic energy in the motion of the holes in solids. Xenon is an atomic analogue. We should expect similar behaviour in molecules.
Metals are still unclear. 99% of the incident electric field does not penetrate silver and we might have expected that no high harmonics are produced. However, we find harmonics in semimetals such as TiN and in more conventional metals such as silver [6]. Simulations suggest that even below multi-shot damage in silver, the highest harmonics that we measure originate from bound d-orbital electrons.
Jean-Philippe Julien received his B.Sc. from McGill University, obtained his Ph.D. from the University of Toronto, and trained as a postdoctoral fellow at The Scripps Research Institute. In 2014, he joined the Molecular Medicine Program at the Hospital for Sick Children Research Institute and the Departments of Biochemistry and Immunology at the University of Toronto where he leads a team of multi-disciplinary researchers. His laboratory focuses on the molecular characterization of antibodies by studies of their interactions with a variety of viral, bacterial, parasitic and cell-surface antigens, providing the atomic blueprints for the development of next-generation therapeutics and vaccines. Notably, he is the Canada Research Chair in Structural Immunology and a Member of the College of the Royal Society of Canada.