Vector Soliton With the Spectrum of Symmetric Sidebands and Noise-Like Pulse in the Yb-Doped Mode-Locked Fiber Laser

In the normal dispersion mode-locked fiber laser (MLFL) without additional filter, a vector soliton with the spectrum of 2nd symmetric sidebands and noise-like pulse (NLP) is obtained in the experiment. The sidebands of the spectrum are symmetrically distributed at a spike wavelength of 1050.14 nm, and the interval of adjacent sidebands is 3.52 nm. The pulse with a Gaussian fitting has a width of 23.05 ps. The output signal light is resolved into two orthogonal components using a polarization beam splitter (PBS). Each component exhibits a central spike and 2 nd symmetric sidebands. With increasing pump power, the order of symmetric sidebands shows an increasing trend and the central spike shifts toward the direction of long wavelength. The numerical simulation verifies that the order of the symmetric sidebands can be increased. In addition, the NLPs are also observed. The variations of the width of coherent spike and wide pedestal, as well as the intensity ratio between them, are systematically studied with the pump power. To the best of our knowledge, the spectrum of symmetric sidebands is obtained for the first time in the normal dispersion MLFL. This provides a new research direction for the field of fiber lasers.