Study On The Nonlinear Optical Properties Of Two-dimensional Transition Metal Carbonitride

Two-dimensional transition metal carbides（MXenes）exhibit metallic properties with a high density of electronic states at the Fermi energy level.MXenes have excellent electrical and optical properties and have potential applications in optoelectronic fields.In this paper,the nonlinear optical properties of three typical MXenes materials（Ti₃C₂,Ti₂C,NB₂C）are investigated.The optical properties of Ti₃C₂ were calculated using Density function theory（DFT）,and the materials have metallic properties by calculating the energy band structure.Multi-wavelength and multi-energy open-aperture Z-scan experiments were performed to of Ti₃C₂.It was found that Ti₃C₂ undergoes reverse saturation absorption（RSA）in the visible wavelength band,and the shorter the wavelength,the lower the excitation energy required for the RSA effect to occur.the nonlinear absorption of Ti₂C was investigated by Z-scan technique.The experimental results show that Ti₂C saturates at different wavelengths（450 to 600 nm）of laser light and the saturated absorption is strongest at 532 nm.It was also found that Ti₂C always shows saturable absorption（SA）at different energies of 500 nm nanosecond laser,and SA increases with increasing laser intensity.the energy band structure and electronic density of states of Nb₂C were calculated using DFT,which showed that it has exhibits metallic nature,and the nonlinear absorption characteristics of Nb₂C at different energies were investigated using multi-wavelength nanosecond Z-scan.It was found that the SA phenomenon was exhibited when the energy was at 180μJ,while at 300μJ,the transition from SA to RSA occurred.The nonlinear absorption results for the three MXenes materials exhibit three different properties,with broadband saturable absorption,antisaturable absorption,and the transition from saturable to antisaturable absorption occurring,respectively,with potential applications in saturable absorbers as well as optical limiters.