Real-time observation of Q-switched mode-locking in a tin selenide modulated ultrafast fiber laser

Abstract

We build a compact ultrafast Er-doped fiber laser based on the tin selenide (SnSe) saturable absorber (SA). Stable continuous-wave and Q-switched mode-locking operation states are realized. By utilizing the time-stretch dispersive Fourier transform, we explore the distinct evolution process of the Q-switched mode-locking operation in a SnSe SA modulated ultrafast Er-doped fiber laser from a real-time horizon. The real-time spectrum displays an interesting breathing process. Inside a single Q-switching envelope, the real-time spectra exhibit entirely different profiles, intensities and bandwidths. Our results can facilitate the understanding of the intrinsic mechanism of the Q-switched mode-locking pulse dynamics in ultrafast fiber lasers.