Passive Q-switching in fiber lasers can be caused by cooperative dynamics of linear Rayleigh backscattering (RS) and Stimulated Brillouin Scattering (SBS) in a fiber configuration. We give a clear physical insight into the RS-SBS mechanism and present new experiments with low- and high-power self-Q-switched fiber lasers. A 15-ns self-stating periodic pulse generation with a peak power up to 40-300 W has been investigated with an Er-doped fiber laser pumped at 20-160 mW from a laser diode. The generation of Q-switched pulses occurs with a perfect pulse shape performance without emitting any parasitic pulse. We have also realized a self Q-switched double-clad Yb-doped fiber laser. For this laser an average/peak power as high as 1.4 W/5 kW has been achieved at a pulse repetition rate in a range of 5-50 kHz and a pulse duration of 5-10 ns.
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