Mxenes-based nonlinear optical modulator for ultrafast photonics

As the widely studied two-dimensional materials, MXenes are potential candidates for various nonlinear optical modulators due to their excellent properties, such as the ultrafast carrier dynamics, high optical damage threshold, tunable bandgap, and exceptional photothermal conversion efficiency. This review summarizes the synthesis, material transfer, nonlinear optical properties, and applications of MXenes in nonlinear optical fields. Initially, the preparation methods of MXenes are introduced, including chemical etching method, chemical vapor deposition method, and the latest direct synthesis method. Subsequently, we discuss the integration of MXene-based nonlinear optical modulators, highlighting material transfer methods applicable to both fiber-optic and free- space optical systems. Subsequently, we focus on the nonlinear optical properties of Ti3C2Tx nanosheets, detailing the Z-scan technique used to analyze their nonlinear saturable absorption characteristics and nonlinear refractive index over the wavelength range of 800 to 2000 nm. Based on their outstanding optical nonlinearity, this paper summarizes and discusses the performance of ultrashort pulse lasers based on different MXenes. It also examines free-space optical switches utilizing spatial self- phase modulation (SSPM) and the all-optical modulation output performance of MXenes in fiber optics. In conclusion, the summary and prospect of MXene-based nonlinear optical modulator are presented.