Broadband saturable absorption properties of 2D Ti₂C MXene and its application in ultrafast fiber laser generation

Two-dimension (2D) materials, such as graphene, black phosphorus (BP) and transition metal dichalcogenides, have attracted much attention in the field of ultrafast fiber lasers due to their unique nonlinear optical (NLO) properties. However, due to the limitation of their intrinsic NLO properties, there is a growing need for novel broadband nonlinear materials in the near-infrared and mid-IR regimes. In this regard, MXene is a promising material due to its outstanding nonlinear properties. Here, we investigated the broadband nonlinear optical properties of 2D Ti₂CT_x MXene, where T_x represents functional groups such as -OH and -F. Using open aperture Z-scan method, we explored the broadband saturable absorption properties in the range 800 - 1560 nm. The large nonlinear absorption coefficient and low saturable intensity of Ti₂CT_x confirmed its potential use in NLO applications. Using Ti₂CT_x as saturable absorbers, we also developed ultrafast mode-locked fiber lasers operating at 1565 nm and 1051 nm with a pulse width of 5.3 ps and 164 ps, respectively. Lastly, we developed Ti₂CT_x-based passively Q-switched lasers that operated in mid-infrared regime at 2.8 um.