All-fiber single-mode actively Q-switched laser at 1120 nm.

An all-fiber single-mode actively Q-switched laser at 1120 nm is demonstrated. The laser cavity consists of a 5 m long Yb-doped polarization maintaining gain fiber, an acousto-optical modulator and a pair of FBGs. At a pump power of 2.5 W, a peak power of 0.8 kW is achieved with a pulse duration of 140 ns at a repetition rate of 1 kHz. A slope efficiency of 16.9% with respect to launched pump power is obtained at 10 kHz. The low achievable gain at 1120 nm, imposed by the parasitic lasing limit at conventional Yb lasing wavelength, has a major role in laser performance.