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A stabilization scheme is proposed for the dynamics of breather waves induced by the coherent-seed modulation instability based on manipulation of phase-space trajectory. Theoretical and numerical analysis show that carefully dispersion- and nonlinearity-managed cascades of fiber configuration allows the system evolution to be stabilized around an elliptic center point, forming stable pulse trains with ultrahigh contrast efficiently. We also demonstrate that the scheme proposed works equally well for near-separatrix dynamics. Our results provide an alternative means to control the unsteady nonlinear waves by abruptly changing the waveguide properties.

We experimentally demonstrated a random distributed feedback fiber laser (RDFB-FL) with an ultra-low threshold, utilizing a highly nonlinear optical fiber (HNLF). A piece of HNLF was used as the random laser gain medium to resolve the contradiction between the lasing threshold and cavity length. Consisting of a half-open cavity structure, the proposed RDFB-FL had a lasing threshold as low as 0.408 W (record low) with a relatively short cavity length of 850 m. In a ring cavity, the lasing threshold could be further reduced to 0.284 W with a cavity length of 950 m by the combined action of distributed feedback and cavity feedback. [ABSTRACT FROM AUTHOR]

A novel h-shaped pulse train with a tunable leading-edge (resembling a h-shaped pulse merging with a weak square pulse) is experimentally generated in a Tm-doped mode-locked fiber laser (MLFL) incorporating a 100 m highly nonlinear fiber. Through carefully adjusting the pump power and cavity polarization states, the leading-edge duration of the obtained h-shaped pulse can be widely tuned from zero (corresponding to the typical conventional h-shaped pulse train) to 567.8 ns (equivalent to the cavity roundtrip time). Our results can further facilitate understanding the intrinsic mechanism and characteristics of novel h-shaped pulse dynamics in MLFLs. [ABSTRACT FROM AUTHOR]