Single-frequency linearly polarized Q-switched fiber laser based on Nb2GeTe4 saturable absorber

We report a single-frequency linearly polarized Q-switched fiber laser based on an Nb2GeTe4 saturable absorber(SA).The Nb2GeTe4 SA triggers passive Q-switching of the laser,and an un-pumped Yb-doped fiber together with a 0.08-nm-bandwidth polarization-maintaining fiber Bragg grating(FBG)acts as an ultra-narrow bandwidth filter to realize single-longitudinal-mode(SLM)oscillation.The devices used in the laser are all kept polarized,so as to ensure linearly polarized laser output.Stable SLM linearly polarized Q-switching operation at 1064.6 nm is successfully achieved,producing a laser with a shortest pulse width of 1.36 μs,a linewidth of 28.4 MHz,a repetition rate of 28.3 kHz-95.9 kHz,and a polarization extinction ratio of about 30 dB.It is believed that the single-frequency linearly polarized pulsed fiber laser studied in this paper has great application value in gravitational wave detection,beam combining,nonlinear frequency conversion,and other fields.