Niobium tellurium as a novel broadband saturable absorber for pulsed fiber lasers

Niobium tellurium (NbTe2) is a kind of typical layered metallic transition metal dichalcogenide (MTMDC) that has drawn considerable attention because of its extraordinary physical properties, such as superconductivity, and charge density waves. Herein, firstly the band structure of NbTe2 is calculated and the results reveal that NbTe2 behaves with a zero bandgap at the Fermi level. Then a NbTe2-PVA (polyvinyl alcohol polymer) saturable absorber (SA) device is prepared and applied to the fiber laser cavities. The NbTe2-PVA SA device exhibits good saturable absorption at both 1 mu m and 1.5 mu m regions. A self-started ultrashort mode-locked Er-doped fiber laser with a pulse duration of 633 fs is constructed. A mode-locked ytterbium-doped fiber laser with 1.96 ns pulse duration is also constructed based on it. According to the experimental results, the VB group metal telluride NbTe2 possesses excellent nonlinear optical properties and exhibits good performance as a broadband SA device for the generation of mode-locked pulses in fiber lasers. To the best of our knowledge, this is the first demonstration that NbTe2 serves as a broadband SA in both 1 mu m and 1.5 mu m regions. This work may pioneer the applications of VB group metal tellurides for the development of ultrafast photonics.