Spatiotemporal mode-locked fiber lasers: multidimensional soliton dynamics revealed by real-time measurement.

Spatiotemporal mode-locked multimode fiber lasers have emerged as a promising platform for investigating nonlinear multidimensional physics, with prospective applications ranging from high-energy pulse generation and precise metrology to nonlinear microscopy. The fundamental mechanism governing ultrashort pulse formation in nonlinear multimode resonators, which can be interpreted as multidimensional dissipative solitons (MDS), lies in spatiotemporal mode-locking (STML), which achieves synchronous locking of both temporal and spatial modes. In this review, the general principles of STML are initially elaborated, with a focus on MDS dynamics under real-time measurement. Subsequently, we summarize the operational principles of versatile real-time measurement techniques and recent advancements in characterizing the ultrafast transient MDS dynamics of STML lasers, including spatial mode switching, optical rogue waves, mode-locking buildup process, 3D soliton molecules, soliton explosions, and breathing multimode solitons. Finally, we outline some perspectives on how real-time measurement methods could advance the study of multidimensional soliton dynamics in STML in the near future.