Harmonically Mode-Locked Twin-Pulse Dissipative Solitons Yb-Doped Fiber Laser

A harmonically mode-locked (HML) twin-pulse solitons in all-normal-dispersion (ANDi) Yb-doped fiber laser is reported. The mode-locking is based on nonlinear polarization evolution. Using a cascaded long-period fiber grating as the spectral filter, a maximal third HML twin-pulse solitons fiber laser is achieved for the first time in the ANDi system with a pump power of 530 mW. The maximum output energy of a single soliton in each twin-pulse dissipative solitons is 21.73 nJ at the second-harmonic repetition rate of 3.06 MHz and 21.78 nJ at the third-harmonic repetition rate of 4.59 MHz.