Thulium-doped all-fiber laser mode-locked by CVD-graphene/PMMA saturable absorber.

We report an all-fiber Tm-doped fiber laser mode-locked by graphene saturable absorber. The laser emits 1.2 ps pulses at 1884 nm center wavelength with 4 nm of bandwidth and 20.5 MHz mode spacing. The graphene layers were grown on copper foils by chemical vapor deposition (CVD) and transferred onto the fiber connector end. Up to date this is the shortest reported pulse duration achieved from a Tm-doped laser mode-locked by graphene saturable absorber. Such cost-effective and stable fiber lasers might be considered as sources for mid-infrared spectroscopy and remote sensing.