Spatiotemporal dissipation dynamics: a route to high-beam-quality and high-peak-power spatiotemporal mode-locked fiber lasers

Spatiotemporal mode-locking (STML) opens a new avenue for implementing high-energy, high-peak-power mode-locked fiber oscillators. However, their inferior beam quality is a fundamental issue that restricts their use. Here, spatiotemporal dissipation involving the quenching and reabsorption effects of multimode Erbium-doped fiber is proposed for beam quality enhancement of STML fiber lasers. The spatiotemporal dissipation provides spatiotemporal intensity-dependent losses to modal pulses for obtaining high beam quality, without needing the same rigorous conditions as Kerr beam self-cleaning (BSC) does. Together with Kerr BSC, the spatiotemporal dissipation BSC is utilized to achieve a high energy high-peak-power STML fiber laser operating at 1.5 µm region with high beam quality. Solitons with an energy of 6.7 nJ (the intracavity energy and peak power are 25.6 nJ and >52.8 kW), pulse duration of <489 fs, and beam quality with M²x/M²y=1.23/1.20 are obtained. To the best of our knowledge, it is a record peak power of 1.5 µm band soliton fiber lasers reported so far. Additionally, broad-duration dissipative soliton resonance pulses with M²x/M²y=1.12/1.18, and noiselike pulses with M²x/M²y=1.04/1.13 are shown to prove the universality of the BSC method. This paper provides new insights for designing high-performance STML fiber lasers and for understanding the spatiotemporal dissipation dynamics.