MAX phase V₄AlC₃ for generating Q-switched pulses in 2 µm region

A stable Q-switched Thulium-doped fibre laser (TDFL) operating at 1978.14 nm is demonstrated using a MAX phase thin film as a saturable absorber (SA). The MAX phase film is fabricated by embedding the Vanadium Aluminium Carbide (V₄AlC₃) compound into polyvinyl alcohol (PVA) via a drop-casting technique. The MAX Phase V₄AlC₃ thin film is characterized to has a saturable absorption, non-saturable loss, and saturation intensity of about 30 %, 45 %, and 0.07 MW/cm², respectively. It is sandwiched between two fibre ferrules and integrated into TDFL cavity to induce Q-switching. The pulse train generated records the highest pulse energy of 161.33 nJ, narrowest pulse duration of 2.14 µs, and a maximum repetition rate of 58.45 kHz at the maximum input power of 750 mW. The corresponding signal-to-noise ratio (SNR) of the fundamental frequency is obtained at 55 dB, which indicates a stability of the pulse. The results indicate the MAX phase material has a great potential to serve as SA in future photonics systems.