Ultrathin 2D Transition Metal Carbides for Ultrafast Pulsed Fiber Lasers

TLDR

Two‑dimensional materials such as graphene, transition‑metal dichalcogenides, and black phosphorus are attractive for ultrafast lasers because of their strong light–matter interactions and large optical nonlinearities, yet most lack suitable bandgaps for near‑infrared operation. This study investigates the nonlinear optical properties of 2D α‑Mo₂C crystals and demonstrates their use as a broadband saturable absorber for pulsed laser generation. The authors measured the nonlinear response of α‑Mo₂C and incorporated it into Er‑doped and Yb‑doped fiber lasers to generate ultrashort pulses. α‑Mo₂C exhibits tunable modulation depth, very low saturation intensity, an ultrafast intraband carrier recovery time of 0.48 ps at 1.55 µm, and enables stable ultrashort pulses at 1602.6 nm and 1061.8 nm, confirming its promise as a broadband nonlinear optical medium.

Abstract

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.