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 & mu;s, 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.