▎ 摘　　要

We demonstrate a passively Q-switched Tm3+-doped all-fiber laser (TDFL) at around 2 mu m with a graphene-based saturable absorber (SA). The graphene is prepared by the reduction of graphite oxide (GO), deposited on the fiber core and inserted into a linear cavity as the passive Q-switch. A 793 nm laser diode (LD) is used as the pump source, with a maximum power of 200 mW. A maximum output power of similar to 33.5 mW is obtained at a pump power of 200 mW, with a high optical conversion efficiency of about 17%. The corresponding single pulse energy is 260 nJ and the repetition rate is 128 kHz.