Nonlinear optical response and ultrafast all-optical modulation of Nb₄C₃

MXenes exhibit a variety of unique electronic, optical, chemical, and mechanical properties. In this work, the nonlinear optical (NLO) properties of Nb₄C₃T_x are systematically investigated. The Nb₄C₃T_x nanosheets exhibit saturable absorption (SA) response from visible region to near-infrared region and better saturability under 6 ns pulse excitation than that under 380 fs excitation. The ultrafast carrier dynamics show a relaxation time of ∼6 ps, which suggests a high optical modulation speed of ∼160 GHz. Consequently, an all-optical modulator is demonstrated by transferring the Nb₄C₃T_x nanosheets to the microfiber. The signal light can be modulated well by pump pulses with a modulation rate of 5 MHz and an energy consumption of 12.564 nJ. Our study indicates that Nb₄C₃T_x is a potential material for nonlinear devices.