Nonlinear optics of MXene in laser technologies

Recently, two-dimension transition metal carbides, carbonitrides, and nitrides called MXenes have attracted huge attention due to their outstanding physical properties in various fields. Here we highlight the enormous potential of MXenes as nonlinear optical materials in the laser technologies, which includes ultrafast laser pulse generation, laser frequency modulation based on four-wave mixing, and photonic diodes with time reversal symmetry breaking. Emphasis is placed on the wide spectral applicability of metallic MXene saturable absorbers in passively mode-locked femtosecond laser technologies, allowing for operation in the visible to mid-infrared range. The Z-scan analysis reveals that Ti3C2Tx MXene has a large nonlinear optical absorption coefficient and a negative nonlinear refractive index, and notably it also possesses the higher threshold for light-induced damage with 50% increase in nonlinear transmittance. The MXene/C60 stacked modules enable the achievement of nonreciprocal transmission of laser pulses for photonic rectification. We strongly believe that MXenes will play a significant role in advanced laser technologies such as optical information processing, molecular spectroscopy, and micromachining, while providing many insightful electro-optical applications.