Investigation on the nonlinear optical properties of V₂C MXene at 1.9 μm

Two-dimensional (2-D) transition metal carbides, referred to as MXenes, attracted considerable attention in various application fields such as biosensors, biomedicine, energy conversion, electrocatalysis, environmental sensing, and nonlinear optics and photonics. This study examined the nonlinear optical properties of a vanadium-based MXene, V2C, at 1.9 μm wavelengths both theoretically and experimentally. First, the energy band structure and the corresponding optical parameters (real part and imaginary part of the refractive index and absorption coefficient) were calculated using density functional theory (DFT) calculations to determine the material potential. Second, the nonlinear optical properties of absorption and the refractive index of the V2C MXene were investigated systemically using both open-aperture (OA) and closed-aperture (CA) Z-scan techniques. Through the Z-scan measurements, the nonlinear optical parameters including a nonlinear absorption coefficient (β) and a nonlinear refractive index (n2) could be obtained in the 1.9 μm spectral region. The β and n2 were measured to be ∼-29.67 × 104 cm GW-1 and ∼-0.61 cm2 GW-1, respectively. Finally, the femtosecond mode-locking capability of V2C nanosheets as a base material for an ultrafast mode-locker was tested by fabricating and inserting an all-fiberized saturable absorber into a Tm-Ho-fiber cavity. Stable mode-locked pulses with a temporal width of ∼843 fs were generated at 1900 nm.