Mode-locked and Q-switched Yb-doped Fiber Lasers with Graphene Saturable Absorber

We report high pulse energy generation from an Yb-doped fiber laser mode-locked or passively Q-switched by a graphene saturable absorber. In the case of mode-locked operation, a ring cavity was used. The average output power is 170 mW and the repetition rate is 1.04 MHz, corresponding to single pulse energy of 163 nJ. To the best of our knowledge, this is the highest pulse energy reported for fiber lasers mode-locked with graphene saturable absorber. In the case of passively Q-switched operation, a linear cavity was used. The average output power is 12 mW and the repetition rate is 257 kHz, corresponding to single pulse energy of 46 nJ with pulse width of 70 ns. We beliveve we are among the first to report the stable passively Q-switched operation by graphene saturable absorber in a Yb-doped fiber laser as well. Graphene-based saturable absorber shows promising potential to replace SESAM as mode-locker or Q-switcher for pulsed lasers in the near future because of the good performance, easy fabrication, low cost and wide availability.