Pulse width tunable passively Q-switched fiber laser with graphene saturable absorber

A pulse width tunable passively Q-switched fiber laser is demonstrated by using a graphene saturable absorber (GSA) with graphene-covered-microfiber (GCM) structure. Due to the cross absorption modulation (XAM) effect in graphene, the modulation depth of the GSA could be varied from 3.22% to 2.16%%, which results in that the output pulse width and the repetition rate of the laser could be varied from 3.5 to 7.5 μs, and from 34.5 to 48.8 KHz, respectively, with fixed pump power.