All-fiber 2 μm thulium-doped mode-locked fiber laser based on MoSe2-saturable absorber

We demonstrate an all-fiber passive mode-locking laser operating in the 2 mu m region that is implemented using a MoSe2-based saturable absorber (SA). A MoSe2-polyvinyl alcohol (PVA) SA is prepared with a modulation depth of 4.98%, a saturation intensity of 168.6 MW/cm(2) and a nonsaturable loss of 29.6%. When the MoSe2-PVA SA was inserted into the fiber laser cavity, highly stable self-starting soliton pulse trains were generated with a center wavelength of 1943.35 nm and a 3 dB bandwidth of 4.38 nm. The pulse waveform has a sech(2) profile with pulse duration of 980 fs. The fundamental repetition rate is 23.53 MHz and the signal-to-background ratio of the fundamental frequency ranges up to 65 dB. The production of stable and robust pulses using this laser indicates that the MoSe2-PVA SA is suitable for generation of 2 mu m femtosecond ultrashort pulses.