Molten fluoride salt-assisted synthesis of titanium carbide (Ti₂C) MXene and its application for 2 µm mode-locking in a thulium-doped fiber laser

Titanium carbide (Ti 2 C), a new two-dimensional material named MXenes, has attracted interest due to its potential applications in numerous fields. Of the many unique characteristics of Ti 2 C MXene, its nonlinear properties are attractive for optoelectronic applications, specifically for ultrafast laser generation. In this work, a Ti 2 C MXene was fabricated by etching a MAX phase precursor titanium aluminum carbide (Ti 2 AlC) using a mixture of lithium fluoride and hydrochloric acid, eliminating the risk of using the harmful hydrofluoric acid. The Ti 2 C MXene was prepared in solution form and then dropped onto a reduced core diameter of tapered fiber before being used as a saturable absorber (SA). The SA device was inserted into a thulium-doped fiber laser to generate stable mode-locked pulses at a center wavelength of 1951 nm with a pulse width of 1.67 ps. The mode-locked laser was highly stable when tested over time, with peak optical power fluctuations of as little as 0.005 dB measured. The results show that the Ti 2 C MXene exhibit outstanding performance for ultrafast laser generation.