Two-dimensional gold decorated indium selenide for near-infrared and mid-infrared ultrafast photonics

In this study, we propose an interfacial engineering method to modify indium selenide (InSe) nanosheets via Au particles. The fabricated microfiber-based InSe-Au saturable absorber (SA) exhibited excellent nonlinear absorption properties and enabled to achieve ultrashort pulse output from 1.5-μm and 2-μm mode-locked fiber lasers. To the best of our knowledge, this is the shortest mode-locking pulse (507 fs) achieved from 1.5-μm fiber lasers and the first demonstration of 2-μm mode-locked fiber lasers using the InSe SA. These results indicate that the InSe-Au heterostructure is a promising nonlinear optical material for ultrafast photonics in the near- and mid-infrared regions.