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 modelocked 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 mu m laser systems. This is, to the best of our knowledge, the first demonstration of SWCNTs@AFI SA in fiber lasers at 2 mu m.