Passively Q-switched thulium-doped fiber laser based on oxygen vacancy MoO3-x saturable absorber

We reported on a passively Q-switched double-clad thulium-doped fiber laser by using oxygen vacancies (OVs) enriched with MoO3-x as a saturable absorber (SA). The MoO3-x was successfully embedded in polyvinyl alcohol and acted as the SA for a stable Q-switching operation in the 2 mu m wavelength region. Stable Q-switched pulses were obtained at a central wavelength of similar to 1992.1 nm with a maximum output power of similar to 62.7 mW, maximum pulse energy of similar to 1.63 mu J and a minimum pulse duration of similar to 2 mu s. The repetition rate of the pulses can be tuned from similar to 15.5 kHz to similar to 38.5 kHz with increasing the pump power. Our experiment was the first demonstrated use of MoO3-x as a SA for pulse laser generation, in which OVs were considered as the original reason for the optical saturable absorption. Moreover, it provides a novel idea for optical SA preparation by controlling the vacancy defects in such materials. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement