Switchable single-wavelength and dual-wavelength dissipative soliton erbium-doped fiber laser based on SMS and NPR hybrid mode locking

We demonstrate a hybrid mode-locked erbium-doped fiber laser utilizing the synergistic interaction between a single-mode fiber-graded-index multimode fiber-single mode fiber structure (SMS) and nonlinear polarization rotation (NPR). By combining the saturable absorption and comb filter effects of the SMS structure with the tunable polarization-dependent loss induced by NPR, the net gain across different wavebands can be precisely balanced to suppress mode competition. In the net-normal dispersion regime, switchable single-wavelength mode-locking at 1540 and 1570 nm, as well as stable dual-wavelength dissipative soliton generation at 1531.42 and 1559.28 nm, are experimentally achieved. The laser exhibits excellent performance with a maximum signal-to-noise ratio of 92.48 dB and pulse durations ranging from 21.69 to 9.27 ps. This hybrid scheme offers a robust and flexible approach for developing versatile multi-wavelength ultrafast sources.