Passively Q-switched linear-cavity erbium-doped fiber laser based on graphene saturable absorber

We demonstrate a passively Q-switched erbium-doped fiber laser (EDFL) based on graphene as a saturable absorber (SA). Two fiber Bragg gratings (FBGs) are used as the end mirrors in an all-fiber linear cavity. The Q-switched EDFL has a pump threshold of 68.2 mW. The minimum pulse duration is 0.85 μs and the highest pulse energy is 40.9 nJ. The pulse repetition rate of the fiber laser can be widely changed from 51.1 to 118.1 kHz by increasing the pump power from 68.2 to 400 mW.