Ternary chalcogenide Ta 2 NiS 5 nanosheets for broadband pulse generation in ultrafast fiber lasers

Abstract In this article, a high‐quality saturable absorber (SA) based on a two‐dimensional ternary chalcogenide Ta 2 NiS 5 nanosheet has been successfully fabricated and used in 1‐ and 1.5‐μm spectral regions to generate ultrafast laser pulses. The Ta 2 NiS 5 ‐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 Ta 2 NiS 5 ‐SA is characterized by 64.7% and 11.95% modulation depths with 1.3 and 0.72 MW/cm 2 saturation intensities at 1028 and 1570 nm, respectively. When Ta 2 NiS 5 ‐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 Ta 2 NiS 5 as a broadband SA for the generation of ultrafast laser pulses, offering new opportunities of ternary transition‐metal dichalcogenide alloys in future photonic devices.