Partially polarized wave-breaking-free dissipative soliton with super-broad spectrum in a mode-locked fiber laser

We have reported a novel type of partially polarized dissipative soliton in a mode-locked erbium-doped all-fiber laser with strong net normal dispersion. The output pulses exhibit as quasi-trapezoid spectral profiles with 3-dB width as large as 83 nm. The maximum pulse energy and peak power approach 75 nJ and 6 kW at the available pump power of 1 W, respectively. Experimental observations show that the polarization state of the broadband dissipative soliton changes along the cavity position from totally to partially polarized, which is distinct from the typical dissipative soliton that is completely polarized throughout the cavity. It is found that the polarization state of mode-locked dissipative solitons strongly depends on the peak power of pulses, and the partially polarized state results from nonlinear phase shift accumulated in laser cavity.