Yi YANG

As a traditional branch of physics, the interaction of free electrons and light has been studied for nearly a hundred years, during which countless important milestones have been made for the development of elementary particle physics and optical science. In the past two decades, the development of micro-nano optics has enabled our ability to control the properties of light at the nanoscale, thus injecting new vitality into this traditional field.

Yi Yang has been engaged in the development of improving the interaction strength between free electrons and light. He theoretically derived fundamental upper limits of the spontaneous emission and energy loss of free electrons in arbitrary optical environments as a function of electron velocity, material composition, and electron-structure separation without needing to know geometry details. This upper limit predicted the advantage of using low-velocity electrons to generate radiation at subwavelength distances that is stronger than that from relativistic ones. Another advantage was predicted for optically lossless materials because the upper limit of their emission probability exhibits diverging properties.

In his experiments, he used a silicon-based photonic crystal slab structure that was compatible with the CMOS technology to realize the interaction between free electrons and flatband resonances. The experiment observed a significant radiation enhancement effect and polarization control of free electron radiation.

From a technical point of view, this series of studies reveals the intriguing application prospects based on free electrons on nanophotonic platforms, including high-efficiency slow-electron radiation sources and particle accelerators, biomedical diagnosis and treatment based on Cherenkov radiation and scintillation, and quantum light generation, manipulation and computation based on free electrons.