VTe₂: Broadband Saturable Absorber for Passively Q-Switched Lasers in the Near- and Mid-Infrared Regions

In this study, we demonstrate the fabrication of a novel 2D transition metal dichalcogenide, VTe₂, into a saturable absorber (SA) by using the liquid phase exfoliation method. Furthermore, the first-principles calculations were conducted to elucidate the electronic band structures and absorption spectrum. The nonlinear optical absorption properties of VTe₂ at 1.0, 2.0, and 3.0 μm were measured using open-aperture Z-scan and P-scan methods, which showed saturation intensities and modulation depths of 95.57 GW/cm² and 9.24%, 3.11 GW/cm² and 7.26%, and 15.8 MW/cm² and 17.1%, respectively. Furthermore, in the realm of practical implementation, the achievement of stable passively Q-switched (PQS) lasers employing SA composed of few-layered VTe₂ nanosheets has manifested itself with broadband operating wavelengths from 1.0 to ∼3.0 μm. Specifically, PQS laser operations from near-infrared to mid-infrared with pulse durations of 195 and 563 ns for 1.0 and 2.0 μm solid-state lasers, respectively, and 749 ns for an Er³⁺-doped fluoride fiber laser at 3.0 μm were obtained. Our experimental results demonstrate that VTe₂ is a potential broadband SA device for achieving PQS lasers. To the best of our knowledge, this is the first demonstration of using VTe₂ as an SA in PQS lasers in the near- and mid-infrared regions, which highlights the potential of VTe₂ for future research and applications in optoelectronic devices.