Broadband Nonlinear Response and Ultrafast Photonics Applications in Few-Layer MBene

2D MBenes, the latest derivatives of bulk ternary or quaternary transition metal boride (MAB) phases, have gradually attracted increasing research attention as novae in the flatland. However, the fabrication of MBenes is still a great challenge at present, leading to the lack of reported MBene applications in the photonic field (e.g., ultrafast lasers). Hence, we successfully fabricated few-layer Mo_4/3B_2-xT_z MBenes by selectively etching nanolaminated 3D parent boride (Mo_2/3Y_1/3)₂AlB₂. Density functional theory calculations were used to theoretically analyze its electronic and optical properties. By employing the Z-scan technique, the nonlinear absorption characteristics of Mo_4/3B_2-xT_z MBenes from the visible to mid-infrared regime were revealed for the first time. Compared with mainstream 2D materials and common MXenes, Mo_4/3B_2-xT_z has more potential as a nonlinear optical (NLO) material, such as stronger nonlinear absorption (about 100 times of graphene) and lower saturation intensity (about 1% of black phosphorus). Furthermore, by integrating Mo_4/3B_2-xT_z as a saturable absorber (SA) into three similar gain fiber-based laser resonators, broadband stable ultrafast pulses were obtained with pulse durations of 358.7 ps (1 μm), 582.3 fs (1.5 μm), and 2.31 ps (2 μm). Innovation in MBenes as SA will allow the design of novel photonic systems and devices with broadband functionality, opening a promising paradigm for the conscious design of high-performance NLO materials.