Direct observation of the build-up and extinction of similaritons in an all-normal dispersion fiber laser.

• The 'memory' ability in the relaxation oscillation state has disappeared in similariton fiber lasers due to the strong spectral filtering effect. • The build-up time is much shorter than the other fiber lasers mode-locked by the nonlinear polarization evolution. • The extinction process of the similariton fiber laser is observed and evaluated for the first time as well. • The spectral broadening and spectral 'breathing' process can be clearly observed in our experiment. Similaritons have attracted considerable attention thanks to their outstanding output performance in recent years. In this paper, we explored the entire dynamic evolution process of similaritons in an all-normal dispersion fiber laser through the time-stretch dispersive Fourier transform technique. Particularly, the narrow-band spectral filtering effect on the pulse evolution dynamics has been discovered. The "memory" ability in the relaxation oscillation state has disappeared in similariton fiber lasers compared with the traditional soliton mode-locked fiber lasers, and the build-up time is much shorter than other fiber lasers mode-locked by the nonlinear polarization evolution. Furthermore, the extinction process of the similariton fiber laser is observed and evaluated for the first time as well. An unstable time period accompanied by a high spectral peak over the spectrum is captured during the extinction process, and then the damped relaxation oscillation state is observed. These results can provide new perspectives into the ultrafast transient process of similaritons in all-normal dispersion fiber lasers and the dynamics of sophisticated nonlinear systems. [ABSTRACT FROM AUTHOR]