Ti2CTx (T=O, OH or F) Nanosheets as New Broadband Saturable Absorber for Ultrafast Photonics

Two-dimensional (2D) materials, such as graphene, transition metal dichalcogenides (TMDs), topological insulators and black phosphorus, have been widely used in the generation of ultrafast pulsed lasers due to their strong photo-material interactions and excellent saturable absorption characteristics. In this work, we investigated the optical characteristics of few-layer Ti ₂ CT _x (T=O, OH or F) nanosheets and employed them as saturated absorbers to obtain ultrafast fiber lasers. A stable femtosecond-pulse Er-doped fiber laser with 265 fs at a central wavelength of 1.5 μm and a highly stable picosecond-pulse Yb-doped fiber laser with a high signal-to-noise ratio of up to 75 dB at a central wavelength of 1037.8 nm, we separately obtained by using a few-layer Ti ₂ CT _x nanosheet saturable absorber (Ti ₂ CT _x -SA). The study results show that Ti ₂ CT _x nanosheets have excellent saturable absorption properties, and their absorption properties are comparable to those of other two-dimensional metal carbides and of other nitrides (MXene). It can be used as a broadband nonlinear optical material for broad application prospects in ultrafast photonics.