Generation of Bright/Dark Pulses in an Erbium-Doped Fiber Laser Mode-Locked With Glycerin

A passively mode-locked Erbium-doped fiber laser using glycerin as a saturable absorber (SA) has been proposed and experimentally demonstrated. The glycerin-SA is made of two fiber ferrules matched into a cannula, and the gap between them is filled with glycerin. Such an SA incorporated into the cavity leads to stable mode-locking operation. The generation of both bright and dark pulses is observed. The bright pulse is centered at 1568.92 nm, with a repetition rate of 23.08 MHz, the maximum output power of 33.5 mW, duration of 3.57 ps, and a signal-to-noise ratio of 55.6 dB, which exhibits good performance on self-starting and stability. Moreover, the dark pulses with the same repetition rate are achieved by adjusting the polarization state properly. The dark pulses are contributed to generating the domain-wall solitons induced by the orthogonal polarization coupling. The effectiveness of glycerin-SA as a mode-locker is validated. Considering its superiority in terms of low cost, easy fabrication, and non-volatile feature, we believe that glycerin-SA can be found many practical applications in ultrafast photonics.