Ternary chalcogenide Ta₂NiS₅nanosheets for broadband pulse generation in ultrafast fiber lasers

In this article, a high-quality saturable absorber (SA) based on a two-dimensional ternary chalcogenide Ta2NiS5 nanosheet has been successfully fabricated and used in 1- and 1.5-μm spectral regions to generate ultrafast laser pulses. The Ta2NiS5-based SA is fabricated by mechanical exfoliation and sandwiched between two fiber ferrules to form a fiber-compatible SA. On the basis of the twin-detector technique, nonlinear optical absorption of the Ta2NiS5-SA is characterized by 64.7% and 11.95% modulation depths with 1.3 and 0.72 MW/cm2 saturation intensities at 1028 and 1570 nm, respectively. When Ta2NiS5-SA is integrated into Yb- and Er-doped fiber laser cavities, stable self-starting Q-switched pulses are observed. Furthermore, by adjusting the cavity structure and optimizing dispersion in the cavity, we obtain hybrid mode-locking and mode-locking fiber laser operation at 1029 and 1569 nm, respectively. These results validate the performance of Ta2NiS5 as a broadband SA for the generation of ultrafast laser pulses, offering new opportunities of ternary transition-metal dichalcogenide alloys in future photonic devices.