Nanosecond pulse generation in a graphene mode-locked erbium-doped fiber laser

We demonstrate a mode-locked nanosecond erbium-doped fiber laser (EDFL) using a graphene-based saturable absorber (SA). The laser directly produces nanosecond pulses with pulse duration of 24 ns, repetition rate of 5.78 MHz and central wavelength of 1569.5 nm. The mode-locking is self-starting and the pulse train has no transient effects or signs of Q-switched behavior. The formation mechanism of nanosecond pulses emitted from the laser could be attributed to the pulse duration broadening induced by the large lumped normal dispersion of the graphene SA. Such nanosecond pulse duration as well as megahertz repetition rate makes this mode-locked all-fiber laser a suitable seed oscillator for chirped pulse amplifications and high-power applications.