Adjustable dual-wavelength soliton complexes in a mode-locked Tm-doped figure-of-eight fiber laser

Dual-wavelength rectangular and step-like soliton complexes, mixed with single solitons and soliton molecules, as well as a coexistence of soliton bundles and soliton rains, were observed in a mode-locked figure-of-eight Tm-doped fiber laser. Increasing the pump power and tuning the polarization can adjust the pulse energy ratio and switch the laser wavelength between two specified spectral components. The pulse can either resonate with the pump power in the rectangular shape or locally expand in the step-like envelope with polarization tuning, and it may even break up. Spectral fringes of the soliton complexes and the involved pulse dynamics reflected a varying interaction among solitons.