Tunable S-band passively Q-switched thulium-doped fluoride fiber laser using Iron Phosphorus Trichalcogenide-PVA (FePS₃-PVA) film

This work shows the generation of Q-switched pulses in a thulium-doped fluoride fiber (TDFF) using a FePS₃ saturable absorber (SA). The modulation depth of the FePS₃ SA was 34.5%, with a saturation intensity of 0.551 kW cm⁻². The Q-switched laser began at 70 mW pump power, sustained to 166 mW, having an operating wavelength of 1502 nm. Adjusting the pump power between that range allows for altering the repetition rate between 19.7 and 29.8 kHz. At 166 mW value of pump power, the laser showed a high signal-to-noise ratio ∼46 dB and was sustained over an hour with similar results obtained over 8 h. Tunability was achieved from 1450 nm to 1516 nm when a tunable bandpass filter was added. The reported FePS₃ SA-based TDFF Q-switched laser can be utilized in the S-band region for photonics applications.