Passively Q-switched 2 µm fiber laser with WO3 saturable absorber

Abstract

We have successfully demonstrated a reliable and simple passively Q-switched Thulium-doped fiber laser (TDFL) utilizing tungsten oxide (WO3) as a saturable absorber (SA). The SA film was fabricated by embedding WO3 material into Polyvinyl alcohol (PVA) host polymer. The saturable absorption and saturation intensity of the fabricated WO3-based SA are about 20 % and 0.04 MW/cm2, respectively. The Q-switched TDFL pulses operate at a central wavelength 1960.2 nm with a 3 dB bandwidth of 1.4 nm, pulse duration of 2.32 μs, maximum repetition rate of 64.27 kHz, maximum output power of 8.2 mW, and maximum pulse energy of 127.58 nJ. To our knowledge, this is the first time that WO3 has been used as a Q-switcher for operation in 2 μm region.