Active–passive Q-switched fiber laser based on graphene microfiber

We report an active–passive Q-switched laser based on graphene-covered microfiber modulator. The graphene-covered microfiber not only serves as a passive saturable absorber in a single laser cavity, but also can be used as an all-optical modulation device to synchronize two pulses generated from different wavelengths. The laser can not only actively change the output frequency of the Q-switched pulse to achieve the repetition frequency reduction, but also compress the pulse and increase the peak power of the output pulse. We successfully achieve the output of the active–passive Q-switched pulse using this fiber laser with a repetition rate from 41.1 kHz to 50.5 kHz. The fiber laser has potential applications in simultaneous output of multi-wavelength pulse.