公海555000kk线路检测・(中国)有限公司

Speaker Bio:

Yi Yang is an assistant professor in the Department of Physics at The University of Hong Kong (HKU). He obtained his bachelor's and master's degrees at Peking University and Ph.D at Massachusetts Institute of Technology (MIT). He continued his postdoctoral research at MIT before joining HKU in 2022. Yi Yang works on optical physics and nanophotonics. His research focuses on the interaction of light with materials, free electrons, and synthetic gauge fields. Yi Yang is a recipient of the Excellent Young Scientists (Hong Kong and Macau), Innovators Under 35 China, and the Asian Young Scientist Fellowship. Yi is also a member of the Early Career Editorial Board in Advanced Photonics.

Abstract:

The interaction between free electrons and photons gives rise to a multitude of fundamental radiative processes in electrodynamics and is foundational for modern electron microscopy and spectroscopy, particle acceleration, and biomedical applications. The dimensionality mismatch between free electrons and photons intrinsically limits their interaction strength. It is thus pertinent to elucidate if there are fundamental bounds to the interaction strength and, if so, how to approach them in nanophotonic environments. We previously derived a single-frequency upper limit to the spontaneous photon emission and energy loss of free electrons, regardless of geometry, which illuminates the effects of material properties and electron velocities [1]. Guided by this upper limit, we identified photonic flatband resonances as a potential candidate for strong free-electron-light interaction [2]. We designed flatband resonances in a silicon-on-insulator photonic crystal slab to control and enhance the associated free-electron radiation by tuning their trajectory and velocity. We observed signatures of flatband enhancement, realized polarization shaping of free-electron radiation, and characterized photonic bands through electron-beam measurements. Very recently, we generalized the upper limit in the quantum regime by deriving the maximal quantum interaction strength between free electrons and photons [3].