Energy-managed spatiotemporal mode-locked fiber lasers

This paper proposes an energy-managed spatiotemporal mode-locked (STML) fiber laser, in which the potential enhancement in soliton energy and intriguing spatiotemporal dynamics of solitons are explored. In STML lasers, counteracting modal dispersion is crucial for achieving stable STML solitons. Here, we demonstrate that the energy-managed mechanism is capable of restraining intermodal walk-off in a walk-off-sensitive anomalous-dispersion STML laser. The walk-off suppression not only occurs at an intentionally introduced spectral filter but also in multimode fibers because of enhancing intermodal spatiotemporal interaction for suppressing intermodal dispersion. In the cavity, the effects of filter bandwidth and mode excitation on walk-off suppression are investigated. Experimentally, thanks to the energy management, pulses with 8.9 nJ energy and 5.58 ps duration are achieved from the STML fiber laser. Via adopting a narrower filter and a lower repetition rate, a single-pulse energy of 16.4 nJ is obtained, which represents nearly twofold energy improvement over the previous report in all-fiber STML lasers at the 1.5 μm band, to the best of our knowledge. This approach not only facilitates high-energy pulse generation but also provides insights into suppressing intermodal walk-off in STML fiber lasers.