Nanosecond pulse generation mode-locked by an artificial saturable absorber based on SMF-MMF-SMF structure

We present a noteworthy demonstration of nanosecond pulse generation utilizing an all-fiber artificial saturable absorber (SA) structure, composed of single-mode multimode single-mode fiber (SMF-MMF-SMF), integrated into a passively mode-locked erbium-doped fiber laser (EDFL). The SMS-based SA effectively phase-locked the longitudinal modes within the elongated EDFL cavity, resulting in the production of mode-locked pulses operating at 1567 nm. Mode-locking is achieved through the Kerr effect of nonlinear multimode interference. The pulse repetition rate is synchronized with the fundamental frequency at 1.28 MHz. At a pump power of 269.1 mW, the laser achieves a remarkable peak average pulse energy of 6.0 nJ. Demonstrating outstanding stability, the laser operation exhibits a peak-to-pedestal extinction ratio of 70 dB for the fundamental frequency. We are confident in the substantial potential of this SMS structure, positioning it as a compelling candidate for integration into ultrafast fiber lasers, with promising prospects in the field.