Surface functionalization of Ta4C3 MXene for broadband ultrafast photonics in the near-infrared region

Recently, MXene has set off a great research boom in the optoelectronic field benefiting from its strong conductivity, eminent broadband absorption, and tailorable electronic/optical properties. In this paper, two-dimensional tantalum carbide (Ta4C3) MXene nanosheets were successfully synthesized based on a two-step liquid exfoliation strategy. Firstly, the role of surface termination with different adsorption structures on the electronic and diverse optical properties of Ta4C3Tx MXene were firstly investigated theoretically via first-principles with density functional theory. Interestingly, the simulation revealed that the oxidized and hydroxylated Ta4C3 MXene featured significantly enhanced optical absorption properties in the near-infrared (NIR) band compared with the pristine bare Ta4C3 nanosheets. Besides, the third-order nonlinear optical (NLO) characteristics of the surfaced terminated Ta4C3 nanosheets were measured by the typical Z-scan techniques at 1 μm. The maximum effective nonlinear absorption coefficient was determined to be -0.78 cm/GW, indicating the great potential as a nonlinear material in NIR band. The nonlinear refractive index, real and imaginary parts of the third-order NLO susceptibility were also obtained. Furthermore, the endowment as an excellent broadband optical modulator was strongly acknowledged utilizing Ta4C3 MXene as saturable absorbers for NIR mode-locking operation at 1044 nm and 1557 nm, respectively. Both highly stable dissipative soliton and traditional soliton pulses were generated. Our results demonstrated the excellent broadband nonlinear absorption in NIR regime of terminal functionalized Ta4C3 MXene and might open a new avenue to the Ta4C3-based advanced ultrafast photonic devices.