Tungsten disulfide saturable absorbers for 67 fs mode-locked erbium-doped fiber lasers.

In this paper, we demonstrate 67 fs pulse emitting with tungsten disulfide (WS₂) in mode-locked erbium-doped fiber (EDF) lasers. Using the pulsed laser deposition method, WS₂ is deposited on the surface of the tapered fiber to form the evanescent field. The fiber-taper WS₂ saturable absorber (SA) with the large modulation depth is fabricated to support the ultrashort pulse generation. The influences of the WS₂ SA are analyzed through contrastive experiments on fiber lasers with or without the WS₂ SA. The pulse duration is measured to be 67 fs, which is the shortest pulse duration obtained in the mode-locked fiber lasers with two dimensional (2D) material SAs. Compared to graphene, topological insulator, and other transition metal dichalcogenides (TMDs) SAs, results in this paper indicate that the fiber-taper WS₂ SA with large modulation depth is a more promising photonic device in mode-locked fiber lasers with the wide spectrum and ultrashort pulse duration.