Passively mode-locked cascaded Raman fiber laser in a linear cavity

Abstract Passively mode-locked cascaded Raman fiber laser is proposed and demonstrated in a linear cavity. The mode-locking is based on nonlinear polarization rotation (NPR) with a polarization beam splitter (PBS) in the proposed laser. The passively mode-locked Raman fiber laser with a spectral range of 220 nm operates in a low pump power level, and up to the three orders Raman frequency shift are observed under our pump power conditions. The maximum output average power and single pulse energy of the proposed laser are 119.3 mW and 63.97 nJ with a slope efficiency of 41.7%. Multi-pulse mode-locked operation can also be generated by precisely adjusting polarization controller (PC) under suitable pump power conditions.