Observation of sub-400fs, wavelength-switchable stretched pulse and bound-state pulse in Tm-doped fiber laser

We report on the experimental observation of wavelength-switchable stretched pulse and bound-state pulse in a dispersion-managed Tm-doped laser. At a pump power of 572 mW, a stretched pulse with a pulse duration of 389 fs can be first obtained at 1961 nm. By increasing the pump power and appropriately adjusting the cavity polarization state, the mode-locking wavelength can be switched from 1961 nm to 1980 nm caused by the birefringence filtering effect based on nonlinear polarization rotation, and the corresponding pulse duration is 371 fs. Meanwhile, loosely bound states of two pulses and three pules at 1980 nm can be observed with appropriate cavity parameters.