Self-Organized Structures of Soliton Molecules in 2-μm Fiber Laser Based on MoS2 Saturable Absorber

We report on the experimental investigations of various self-organized structures of soliton molecules in a thulium doped fiber laser mode-locked by a monolayer MoS2 saturable absorber. With the alteration of cavity parameters, soliton pairs, soliton triplets, and soliton quartets were successively generated, and the short-term and long-term stabilities were tested, exhibiting potential coding alphabet extension from the traditional binary coding scheme to higher coding scheme in fiber communication. Soliton pairs with the phase-difference of pi, +/-pi/2, and 0 have been observed systematically in the same thulium-doped fiber cavity, for the first time. Our results might benefit the fundamental physics research of nonlinear dynamics in fiber lasers at the mid-infrared region.