Pulse type switchable, spectral bandwidth dynamically adjustable all-fiber laser mode-locked by NALM

We report a mode-locked fiber laser based on the nonlinear amplifying loop mirror (NALM), which allows the output of three different types of pulses: dissipative soliton (DS), bound-state soliton (BSS), and noise-like pulse (NLP). Among them, the spectral widths of the DS and BSS can be adjusted over a wide range, and their pulse widths vary correspondingly. The gain inside the NALM is provided by the polarization-maintaining Er-doped fiber (PM-EDF), which introduces both linear and nonlinear phase shifts so that the laser has a low mode-locking threshold. The gradual change from DS to NLP can be achieved by polarization state adjustment without changing the pump power. Our results provide a fiber laser with tunable spectral bandwidth and switchable pulse type, which offers the possibility of different kinds of application requirements.