Free electron lasers have unique advantages of high power, wide frequency tunablility and et al, however, they face challenge in narrowing the spectral linewidth. Prof. Fang Liu’s group proposed and realized the pump-induced stimulated superradiant Smith-Purcell radiation (PIS-SPR) and achieved an ultra-narrow spectral linewidth of 0.3 kHz at ~0.3 THz in a compact device. The mechanism and technique provides a way to further narrow the spectral linewidth of free electron radiation and broaden its applications.

Lin Yuechai (Ph.D candidate 2021), Li Jinyu (Ph.D candidate 2022), and Professor Liu Fang are co first authors of this work; Professor Liu Fang and Professor Huang Yidong are co corresponding authors.

See the article: 

Lin, Y., Li, J., Liu, F. et al. Pump-induced stimulated superradiant Smith-Purcell radiation with ultra-narrow linewidth. eLight 5, 6 (2025).  https://doi.org/10.1186/s43593-025-00083-z