In this paper,the theoretical rate equation model of an in-band pumped gain-switched thulium-doped fiber(TDF) laser is investigated.The analytical formulations of pump energy threshold,peak power extraction efficiency,and pulse extraction efficiency are derived through analyzing the interaction process between the pump pulse and the laser pulse.They are useful for understanding,designing,and optimizing the in-band pumped TDF lasers in a 1.9 μm-2.1 μm wavelength region.The experiment with an all-fiber gain-switched TDF laser pumped by a 1.558-μm pulse amplifier is conducted,and our experimental results show good agreement with theoretical analysis.

We report a continuous-wave Tm-doped fiber (TDF) laser with a single fiber Bragg grating (FBG). The Fresnel effect presenting in the passive fiber end-face and high-reflectivity FBG established the resonator. The peak wavelength of the laser was 1942.25 nm with a spectral linewidth of 194 pm. The maximum output power was 37.5 W, corresponding to a slope efficiency of 63.7% with a beam quality factor of M ² ∼ 1.51. To the best of our knowledge, this is the highest slope efficiency of a TDF laser pumped by 793 nm laser diode.