Nonlinear absorption property investigation into MAX phase Ti2AlC at 1.9 μm

An experimental and theoretical investigation into the nonlinear absorption properties of MAX phase Ti 2 AlC was conducted at 1900 nm wavelength. First, the nonlinear absorption coefficient measurement of Ti 2 AlC was carried out using an open-aperture (OA) Z-scan technique. This measurement revealed that the nonlinear absorption coefficient of Ti 2 AlC was ∼(-24.13×10 3 ) cm 2 /GW at 1900 nm. Subsequently, the energy band structure of the Ti 2 AlC was calculated through density functional theory (DFT) calculation. This calculation confirmed that Ti 2 AlC had a metallic band structure implying an ultrawide absorption bandwidth. Finally, the feasibility of fabricating an all-fiberized device of a saturable absorber (SA) using Ti 2 AlC was conducted with a side-polished fiber platform. The SA was successfully used for the generation of femtosecond soliton pulses with features of 17.91 MHz repetition rate, 4.3-nm bandwidth, and ∼960 fs pulse width at 1922 nm. To the best of authors’ knowledge, this is the first demonstration of the use of a MAX phase-based SA for femtosecond mode-locking in the 1.9 μm spectral region.