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.

Tungsten disulphide (WS), which exhibits excellent saturable absorption properties, has attracted much attention in the applications of photonic devices. In this paper, WS is applied for the preparation of a saturable absorber (SA). Using the pulsed laser deposition (PLD) method, WS is deposited on the side surface of the tapered fiber. In order to obtain larger non-linearity of the SAs with evanescent wave interaction, the tapered fiber had a smaller waist diameter and longer fused zone. Gold film was deposited on the fiber-taper WS SAs to improve their reliability and avoid oxidation and corrosion. Employing the balanced twin-detector method, the modulation depth of the fiber-taper WS SAs was measured to be 17.2%. With the fiber-taper WS SA, a generated pulse with 246 fs duration and a 57 nm bandwidth was obtained at 1561 nm. The electrical signal to noise ratio was better than 92 dB. To our knowledge, the pulse duration was the shortest among the reported all-fiber lasers with transition metal dichalcogenide (TMD) SAs. These results indicate that fiber-taper WS SAs with smaller waist diameter and longer fused zone are promising photonic devices for ultrashort pulse generation in all-fiber lasers.

Femtosecond optical pulses have applications in optical communication, astronomical frequency combs, and laser spectroscopy. Here, a hybrid mode-locked erbium-doped fiber (EDF) laser with topological insulator (TI) is proposed, for the first time to our best knowledge. The pulsed laser deposition (PLD) method is employed to fabricate the fiber-taper TI saturable absorber (TISA). By virtue of the fiber-taper TISA, the hybrid EDF laser is passively mode-locked using the nonlinear polarization evolution (NPE), and emits 70 fs pulses at 1542 nm, whose 3 dB spectral width is 63 nm with a repetition rate and transfer efficiency of 95.4 MHz and 14.12%, respectively. Our experiments indicate that the proposed hybrid mode-locked EDF lasers have better performance to achieve shorter pulses with higher power and lower mode-locking threshold in the future.