Ultrathin 2D Transition Metal Carbides for Ultrafast Pulsed Fiber Lasers

Two-dimensional (2D) materials, such as graphene, transition metal dichalcogenides, and black phosphorus, have attracted intense interest for applications in ultrafast pulsed laser generation, owing to their strong light-matter interactions and large optical nonlinearities. However, due to the mismatch of the bandgap, many of these 2D materials are not suitable for applications at near-infrared (NIR) waveband. Here, we report nonlinear optical properties of 2D α-Mo₂C crystals and the usage of 2D α-Mo₂C as a new broadband saturable absorber for pulsed laser generation. It was found that 2D α-Mo₂C crystals have excellent saturable absorption properties in terms of largely tunable modulation depth and very low saturation intensity. In addition, ultrafast carrier dynamic results of 2D α-Mo₂C reveal an ultrashort intraband carrier recovery time of 0.48 ps at 1.55 μm. By incorporating 2D α-Mo₂C saturable absorber into either an Er-doped or Yb-doped fiber laser, we are able to generate ultrashort pulses with very stable operation at central wavelengths of 1602.6 and 1061.8 nm, respectively. Our experimental results demonstrate that 2D α-Mo₂C can be a promising broadband nonlinear optical media for ultrafast optical applications.