Plasmon‐Driven Ultrafast and Highly Efficient Saturable Absorption for Ultrashort Pulse Generation in Ultra‐Thin MXenes

ABSTRACT Plasmon‐driven ultrafast nonlinearities hold promise for advanced photonics but remain challenging to harness in two‐dimensional materials at telecommunication wavelengths. Here, we demonstrate few‐layer V 2 C MXenes as a high‐performance saturable absorber by leveraging its tailored surface plasmon resonance. Combining transient absorption spectroscopy and first‐principles calculations, we unveil a plasmon‐driven relaxation mechanism dominated by interfacial high‐energy hot electron generation (∼100 fs), enabling giant ultrafast nonlinearities. Crucially, at the communication band (1550 nm), V 2 C exhibits a high saturable absorption coefficient of −1.35 cm/GW. Integrating this into an erbium‐doped fiber laser, we generate mode‐locked pulses with a duration of 486 fs at 1569 nm, a 39.51 M Hz repetition rate, and exceptional stability (92 dB SNR). This work establishes plasmonic MXenes as a paradigm for tailored ultrafast photonic devices.