Passively Q-switched ytterbium-doped fiber laser operating at 1120 nm by molybdenum disulfide saturable absorber

Various types of pulsed fiber lasers operating beyond 1100 nm have been developed because of their important applications. In this letter, a passively Q-switched ytterbium (Yb)-doped fiber laser (YDFL) is proposed and demonstrated by a molybdenum disulfide (MoS2)-based saturable absorber (SA). Firstly, the MoS2-based SA is prepared. Then the MoS2-based SA is inserted into a Yb-doped fiber laser with linear cavity configuration and the passively Q-switched operation at wavelength of 1120.34 nm is implemented. The pulse repetition rate varies from 14.42 kHz to 67.56 kHz when the pump power increases from 122.7 mW to 233.5 mW. The shortest pulse width is 1.71 μs with pulse energy of 30.79 nJ. The spectral linewidth is as narrow as 0.072 nm. To the best of our knowledge, this is the first report of Q-switched Yb-doped fiber laser operating at 1120 nm by a MoS2-based SA. The experimental system displays the narrowest linewidth and a good stability.