Pulse regulation by additional attenuation in a random erbium-doped fiber laser utilizing EOM and stimulated Brillouin scattering

Abstract In this paper, pulse regulation by the combination of actively Q-switched and passively Q-switched mechanisms in a random erbium-doped fiber laser is demonstrated. Pulse shape is regulated from square wave to quasi passively Q-switched pulse by changing pump power and loss in laser cavity. Pulse shape similar to external modulation signal on electro-optic modulator (EOM) is achieved when the pump power is low. When the pump power is increased and an additional attenuation is inserted, a regular and stable output pulse is generated by the combination of EOM and stimulated Brillouin scattering (SBS) in fiber. The frequency irregular and intensity fluctuation of pulse shown in passively Q-switched random fiber lasers reported previously are greatly eliminated. Not only pulse amplitude and pulse width are controlled by pump power and additional attenuation in the cavity, but also the repetition rate of output pulse is controlled by the external modulation signal on EOM, which has great potential applications in high-resolution imaging, and next-generation laser medical treatment.