All-fiber mode-locked ultrafast Thulium-doped fiber lasers at 2um

In this work, we demonstrate three original all-fiber ring configurations of passively mode-locked Thulium-doped fiber(TDF) lasers operated around 2mu m wavelength for which the usage of free-space optics components is minimized. Different mode-locking techniques/materials e.g. nonlinear polarization evolution (NPE), graphene-based saturable asbsorbers(GSAs) and single-wall carbon nanotubes (SWCNTs) are developed and used to passively mode lock TDF laser and produce ultrashort pulses at 2mum. Also to achieve higher pulse energy directly from a fiber oscillator, the net intra-cavity dispersion is managed by the introducing of normal dispersion fiber(NDF) at 2mum into the fiber cavity. Both the sign and amount of the net cavity dispersion can be controlled without compromising the merits of all-fiber configuration. Distinctive ultrashort pulses of different pulse shapes and per-pulse energies e.g. solitons, noise-like pulses and dissipative solitons are produced from these fiber lasers for which the generated pulses' features and dynamics are experimentally investigated and characterized. A computational model is built to simulate these mode-locked TDF lasers by numerically solving the Nonlinear Schrodinger Equations(NLSE).