Passively mode-locked thulium-doped fiber laser based on a SWCNTs@AFI saturable absorber

An all-fiberized, mode-locked thulium-doped laser was demonstrated using single-walled carbon nanotubes (SWCNTs) as the saturable absorber (SA). These SWCNTs were prepared by pyrolyzing tripropylamine confined in the one-dimensional nanochannels of zeolite ZnAPO-5 (AFI) single crystal and then the SWCNTs@AFI SA was transferred onto the end face of fiber connector. By inserting the SA into the fiber laser cavity, stable mode-locked solitons with 810 fs pulse width, 14.12 MHz repetition rate centered at 1913.6 nm was generated, the laser output showed the long-term stability and high signal-to-noise ratio. The experimental results confirmed that the SWCNTs@AFI could be an effective candidate as saturable absorption material for passively generating ultrafast pulses in 2 μm laser systems. This is, to the best of our knowledge, the first demonstration of SWCNTs@AFI SA in fiber lasers at 2 μm.