High-Energy Rectangular Pulse Dissipative Soliton Generation in a Long-Cavity Sigma-Shaped Configuration Mode-Locked Fiber Laser

The high-energy rectangular pulse dissipative soliton (DS) is achieved in a long-cavity sigma-shaped configuration erbium-doped fiber laser. A long fiber is inserted in the linear arm of the sigma-shaped configuration to extend the resonator length twice, which effectively improves the pulse energy. The nonlinear polarization rotation technique is employed to realize the mode-locked state. Stable rectangular pulses with pulse energy of 421.22 nJ are obtained at the pump power of 620 mW. To the best of our knowledge, this high pulse energy is a new record of the rectangular pulse mode-locked DS fiber lasers.