Quasi-1D NbTe for Broadband Pulse Generation from 1.0 to 3.0 μm: Bridging the Near- and Mid-Infrared.

Quasi-one-dimensional (quasi-1D) transition metal chalcogenides (TMCs), a subclass of low-dimensional materials, have attracted significant attention due to their unique optical and electronic properties, making them promising candidates for nonlinear photonics. In this work, NbTe, a quasi-1D transition metal tetrachalcogenide, was synthesized and employed for the first time as a broadband saturable absorber (SA) for pulsed laser applications. The nonlinear optical (NLO) properties of NbTe were systematically characterized at 1.0 μm, 2.0 μm, and 3.0 μm, revealing saturation intensities of 59.53 GW/cm, 14 GW/cm, and 6.8 MW/cm, with corresponding modulation depths of 17.4%, 5.3%, and 21.5%. Utilizing NbTe-SA, passively Q-switched (PQS) pulses were successfully generated in the 1.0 μm and 2.0 μm bands, achieving pulse durations of 86 ns and 2 μs, respectively. Furthermore, stable mode-locked operation was demonstrated in an Er-doped fluoride fiber laser at 3.0 μm, yielding a pulse duration of 19 ps. These results establish NbTe as a highly promising broadband SA material for next-generation ultrafast photonic devices and pave the way for the development of other quasi-1D materials in nonlinear optics.