Light travels at 300 nanometers (10^-9 m) per femtosecond (10^-15 s), and nothing is faster than that. Its focusing is limited by diffraction to ~0.5λ, where λ is light wavelength. Then how can we take movies of light with spatial resolution below its diffraction limit as it propagates at a metal-vacuum interface as a light-matter charge density surface plasmon polariton wave? We accomplish this by photoemission electron microscopy where we image the nonlinear two-photon electron emission that polaritons excite in their wake in response to excitation by two identical femtosecond pulses. Scanning the pulse delay with 100 attosecond (10^-18 s) precision records images of plasmon fields as they evolve by 30 nm in every frame. We apply this methodology to image structured light in form of plasmonic vortices. The photonic spin-orbit interaction generates fields with topological spin textures¹ where electric and magnetic fields become parallel to possess joint parity-time symmetry not found in vacuum electromagnetic waves. This property makes them a gateway to coherent magnetoelectric phenomena and axion physics in topological condensed matter. We perform ultrafast microscopy of light towards Poincaré engineering² of high energy physics phenomena at a laboratory scale.  

1. Y. Dai, at al., Nature 588, 616 (2020)

2. Y. Dai, et al., Nature Reviews Physics 4, 562 (2022)  

报告人简介：Prof. Hrvoje Petek obtained BS degree (1980) form MIT, and PhD degree (1985) from the University of California Berkeley both in chemistry. He worked with Keitaro Yoshihara as the National and Yamada Science Foundations postdoctoral fellow and Research Associate at the Institute of Molecular Science, Japan (1985-1992). He was a Senior Research Scientist at the Hitachi Advanced Research Laboratory (1993-2000), where he initiated research on ultrafast electron dynamics in the solid state. He is continuing this research as a Professor of Physics and RK Mellon Chair of Physics and Astronomy since 2000. Petek has been recognized with the Alexander von Humboldt Research Award (2000), Morino Award (2014), Ahmed Zewail Award in Ultrafast Science and Technology (2019), and as distinguished Scientist of the Chinese Academy of Sciences (2022). He is a Fellow of the American Physical Society, and American Academy of Arts and Sciences, the Editor-in-Chief of Progress in Surface Science, and a member of numerous advisory boards.