Synchronously-pumped pulsed multimode Raman fiber laser

Multimode fiber lasers have emerged as a versatile platform for investigating complex spatiotemporal nonlinearities. However, pulsed multimode Raman fiber lasers remain unexplored. In this work, we demonstrate the first synchronously-pumped multimode Raman fiber laser, elucidate the multimode pulse evolution inside it, and validate the underlying theory through measurements under various experimental configurations. By merely adjusting the pump repetition rate, this laser enables the tuning of both the output wavelength and the spatial mode, while exhibiting a significant beam cleanup capability. This study opens what we believe is a new pathway for further exploration of multimode spatiotemporal nonlinearities and for enhancing the brightness of multimode fiber lasers.