Giant-chirp oscillator for ultra-large net-normaldispersion fiber lasers

We report on the experimental observations for giant-chirped dissipative solitons emitted from a passively mode-locked fiber laser, which has ultra-large normal cavity dispersion. Two types of solitons coexist in the same cavity and evolve with different spectrum shapes, one of which is exhibited as a rectangular-spectrum profile and the other is as a bell-spectrum profile. Both are highly chirped due to the positively nonlinear effect together with strong normal dispersion. The maximal time-bandwidth product of solitons reported here can be as large as 236.3, which is far larger than 0.315 for the classical solitons. The dynamic evolution of solitons versus pump power is demonstrated. The experimental results suggest that the nonlinear polarization rotation and the gain filtering effect dominate the pulse-shaping alternately, which lead to the spectrum profile transforming. With further increasing the pump power, the proposed laser emits multiple pulses one by one, and the number of pulses can be up to five at the pump power of ∼ 505 mW.