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.
Wang et al. (Fri,) studied this question.