Third-order nonlinear properties and reverse absorption behavior in layered Ti3C2 MXene in the near infrared region

Two-dimensional transition metal carbides/nitrides (MXenes) have attracted a lot of attention as optical materials owing to their unique electronic and optical features. In this paper, we demonstrated the nonlinear optical response of Ti 3 C 2 MXene in the near infrared (NIR) regime at 1 and 1.3 µm. The nonlinear optical absorption behavior was systematically studied by the open/closed aperture (OA/CA) Z-scan techniques. Under a low excitation intensity, the saturable absorption dominated the optical nonlinear process, and the maximum effective nonlinear absorption coefficients β eff were −0.59 cm/MW and −0.68 cm/MW at 1 and 1.3 µm, respectively. The nonlinear refractive index n 2 and the third-order susceptibility of Ti 3 C 2 Mxene at 1 µm were −2.18 ×10 −2 cm 2 /GW and 3.65×10 −3 esu, respectively. While with the excitation laser at 1.3 µm, the nonlinear refractive index n 2 was −1.64×10 −2 cm 2 /GW and the third-order susceptibility was 2.75×10 −3 esu. With the increase of incident optical intensity, the two-photon absorption (TPA) process was observed, leading to the reverse absorption phenomenon. Our results confirmed that Ti 3 C 2 MXene possessed intensity-depended nonlinear optical properties, which could be applied in various nonlinear optical devices.