Nankai University makes progress in the field of free electron photon interactions

Recently, a research team led by Professor Cai Wei and Professor Xu Jingjun from the School of Physical Sciences at Nankai University has experimentally confirmed for the first time the generation of polaritons, also known as Smith Purcell radiation, at the two-dimensional scale, and further demonstrated the ability of free electrons to regulate two-dimensional Smith Purcell radiation. The research findings were published online in the internationally renowned journal Physical Review Letters under the title "Smith Purcell Radiation in Two Dimensions".

Electron photon interaction is one of the core topics in physics research. When free electrons bombard an optical structure or pass through its vicinity, it can generate electromagnetic radiation, a phenomenon commonly known as free electron radiation (or cathodoluminescence). The most famous example of free electron coherent radiation is Cherenkov radiation, which has significant applications in high-energy particle detection and was awarded the Nobel Prize in Physics in 1958. As an extension of Cherenkov radiation, Smith Purcell radiation can be generated when charged particles fly over periodic structured surfaces, providing a new solution for utilizing electrons to generate and manipulate light.

Over the past 70 years, the use of Smith Purcell radiation to generate light in three-dimensional space has attracted widespread attention. In recent years, with the rise of nanophotonics and two-dimensional materials, free electrons have injected new vitality into this field as efficient sources of photoexcitation, attracting attention from physicists, materials scientists, engineers, and other fields. As one of the important physical mechanisms for the generation of on-chip light sources, the generation and regulation of two-dimensional Smith Purcell radiation has become a critical issue that urgently needs to be addressed.

The figure shows a schematic diagram of two-dimensional Smith Purcell radiation generated by a free electron excitation periodic nanopore array

The research team observed two-dimensional Smith Purcell radiation through the interaction between free electrons and the designed metal nanopore array, and further demonstrated the active controllability of the two-dimensional Smith Purcell radiation direction by introducing the two-dimensional phased array radar effect. This innovative achievement not only deepens the understanding of the interaction between free electrons and light, but also has significant implications for constructing two-dimensional optical platforms that utilize electrons for generation and manipulation.

This work was first completed by Nankai University, with Sun Zhiguo, a doctoral student from Nankai University, as the first author, and Professors Cai Wei and Xu Jingjun from Nankai University as co corresponding authors. The relevant work has received funding from key research and development projects of the Ministry of Science and Technology of China, major projects of basic and applied basic research in Guangdong Province, and projects funded by the National Natural Science Foundation of China.

Source: opticsky