Oxidation‐Resistant MXene Saturable Absorber Enabled Efficient 2.02 µm Pulsed Laser in a Tm:LuAG Single‐Crystal Fiber

Efficient and stable pulsed lasers in the 2 µm spectral region are highly desirable for biomedical, sensing, and industrial applications. However, their development is hindered by two critical challenges: the lack of saturable absorbers (SAs) with long‐term ambient stability, and the absence of gain architectures that can efficiently manage high‐power operation while maintaining beam quality. In this work, we address both challenges by integrating, for the first time, an oxidation‐resistant MXene (OR‐Ti 3 C 2 T x ) SA with a Tm:LuAG single‐crystal fiber (SCF) gain medium. The OR‐Ti 3 C 2 T x exhibits excellent nonlinear optical properties at 2 µm, with a modulation depth of 7.93% and a low saturation intensity of 7.32 × 10 − 5 GW cm − 2 . The resulting passively Q‐switched laser delivers an average output power of 958 mW, a pulse energy of 21.055 µJ, and a peak power of 25.125 W at 2023.7 nm. This work reports the first passively Q‐switched Tm:LuAG SCF laser and the first application of an oxidation‐resistant MXene as an SA in the 2 µm band. The demonstrated material–device synergy establishes a robust platform for advancing mid‐infrared photonic systems.