Ti$_3$C$_2$T$_x$ thin film as a saturable absorber for passively generating Q-switched pulses in thulium-doped fiber laser cavity

We demonstrated a Q-switched thulium-doped fiber laser (TDFL) based on Mxene Ti$_3$C$_2$T$_x$ saturable absorber (SA) as Q-switcher. Ti$_3$C$_2$T$_x$ was obtained using selective etching and embedded into polyvinyl alcohol (PVA) film. As the film was added into a TDFL cavity, a stable Q-switched pulse train operating at 1996 nm was produced within a single mode 1552 nm pump power range from 161.8 to 237.1 mW. When the pump power was varied within this range, the repetition rate increased from 19.6 to 33.3 kHz while the pulse width decreases from 6.71 to 3.55 $\mu$s. To the best of our knowledge, this is the first report of a Ti$_3$C$_2$T$_x$ SA for passively generating Q-switched pulses in the 2 $\mu$m wavelength region.