Third-order Nonlinear Optical Properties And Applications Of Two-Dimensional Transition Metal Carbide

Recently,graphene-like two-dimensional?2D?materials attacted much attention due to their outstanding physical and chemical properties which have shown great potential in the field of optical communication,optical sensing,and biomedicine.Specifically,due to their unique electronics structure,2D materials have exhibited unique ultrabroadband and aultrafast response,which have been widely studied in nonlinear optics and laser technique.Nonlinear optical materials play an important role in the field of laser physics.The requirement for nonlinear optical materials with high thresholdand broadband response promotes the rapid development in nonlinear optical device.To date,2D materials have made great progress in the field of nonlinear optics.Compared with traditional bulk materials,2D materials possess unique electronical energy band structure and electronical transportation.For example,graphene is a widely studied 2D material,and its Fermi-Dirac cone in electronic structure leads to the bulk and metallic state,as well as its broadband absorption from visible to terahertz band.In the field of nonlinear optics,the nonlinear optical effects in graphene,such as second harmonic,higher harmonic,saturabla absorption,reverse-saturatable absorption,Kerr effect,four wave mixing and self-phase modulation,have been widely repoted and investigated,which have been used in the nonlinear optical devices,such as laser,all-optical modulator,and wavelength converter.With the increasing requirement of broadband nonlinear opticl applications,a kind of zero-bandgap 2D layered transition metallic carbide?MXene?has been widely reported and used in electromagnetic shielding,biochemistry,sensors and photocatalysis.MXene possesses a high density of electron states at Fermi level,thus a metallic material.In addition,the bandgap of MXene can be tuned by adjusting the surface termination and elements,which provides great potential for the application in electronics and optoelectronics.Therefore,compared with other 2D materials,the unique tunable electronical structure of MXene make it an advantage material in the field of nonlinear optical applications.As for the application requirement of the broadband and ultrafast nonlinear optical materials,we investigated the broadband third-order nonlinear optical propertie of 2D transition metallic carbide,and systematically studied their application in pulse generation and nonlinear optical devices.The main achievements are as follows:?1?We experimentally investigated the broadband nonlinear optical properties of Ti₃C₂T_x MXene and obtained the broadband nonlinear optical parameter and variation.The high quality Ti₃C₂T_x MXene was prepared by chemical etching method.With the open Z-scan method,we investigated the broadband nonlinear absorption properties of Ti₃C₂T_x MXene from the visivle to mid-infrared regime.The result shows that it exhibited broadband saturable absorption absorption.The spatial self-phase modulation?SSPM?effect of Ti₃C₂T_x MXene was investigated with 532 nm continuous laser?CW?and 1060 nm pulsed laser excitation.Using different laser excitation,we investigated the formation and distortion of SSPM diffraction ring pattern.y investigating the SSPM at different intensities,we calculated the nonlinear refractive index and third-order susceptibility of Ti₃C₂T_x MXene to be 7.78?10^-1010 m²/W and 5.4?10^-7esu wth the 532 nm CW laser excitation;to be 6.13?10^-1414 m²/W and 3.83?10^-1010 esu and 1060 nm pulsed laser excitation.?2?We studied the broadband nonlinear optical properties of Ti₂CT_x MXene for the first time and obtained the broadband nonlinear optical parameter and variation.The high quality Ti₂CT_x MXene was prepared by chemical etching method.With the open Z-scan method,we investigated the broadband nonlinear absorption properties of Ti₂CT_x MXene from the visivle to mid-infrared regime.The result shows that it exhibited broadband saturable absorption absorption.Indition,the SSPM of Ti₂CT_x MXene has been studied using different laser excitation.The nonlinear refractive index and third-order susceptibility of Ti₂CT_x MXene were calculated to be 4.85?10^-1010 m²/W and 7.24?10^-7esu wth 532 nm CW laser excitation;to be 6.78?10^-1313 m²/W and1.14?10^-10esu with 1060 nm pulsed laser excitation,respectively.Also,we analyzed the physical mechanism of diffraction pattern distortion in the SSPM.?3?Based on the nonlinear optical properties of Ti₃C₂T_x MXene and Ti₂CT_x MXene,we performed the MXene-based pulse laser and all-optical phase modulator.Based on the spatial cross phase modulation effect,using Ti₃C₂T_x and Ti₂CT_x MXene as the nonlinear optical medium,we realized the modulation of 532 nm modulation light on633 nm signal light,and observed the evolution of SSPM diffraction pattern in signal light.We obtain the phase change of 12?and 18?in signal light by using the Ti₃C₂T_x and Ti₂CT_x MXene as the information converter,separately.Utilizing the saturable absorption of Ti₃C₂T_x MXene,we obtained the mode-locked pulse with the pulse duration of 968 fs and repetition rate of 8.25 MHz at 1.5?m;obtained the Q-swiched pulse with the pulse duration of 1.19?s and repetition rate of 78.2 MHz at 2.8?m.Based on the saturable absorption of Ti₂CT_x,we obtained the mode-locked pulse with the pulse duration of 164.4 ps and repetition rate of 11.2 MHz at 1?m;obtained the mode-locked pulse with the pulse duration of 5.3 ps and repetition rate of 8.25 MHz at1.5?m;obtained the Q-swiched pulse with the pulse duration of 730.4 ns and repetition rate of 99.47 kHz at 2.8?m.