Transitions between mode-locked and noise-like pulsed states in a multimode fiber laser

We experimentally demonstrate transitions between stably mode-locked and noise-like pulse states in a ytterbium-doped fiber laser controlled by adjusting the level of intracavity spectral filtering. In both regimes, Kerr spatial self-cleaning provides high-quality output beams. By using cavities with different lengths of graded-index fiber, we show that, in the mode-locked regime, a proper balance between chromatic and modal dispersion maximizes pulse compressibility. We compress 2.1-kW, 6.7-ps pulses down to 170 fs using an external grating pair, in good agreement with numerical simulations.