High Power Multi-soliton and Noise-like Pulse Generation Regimes in a Passively Mode-locked Thulium-doped All-fiber Ring Oscillator

We demonstrate regime switching between soliton rain, soliton bunches and noise-like pulses by random adjustment of the polarization controllers in the thulium-doped all-fiber ring oscillator with nonlinear polarization evolution mode-locking in fully negative group velocity dispersion cavity. The regimes are studied at cavity lengths increase from 12.8 to 52.7 m, which corresponds to a change in the total group velocity dispersion from -2.63 to -0.712 pS
²
, and in the pulse repetition frequency from 3.88 to 16 MHz. The maximum average laser output power is equal to 712 m W in all generation regimes. The central wavelength of the laser is approximately 1.9 μm.