We propose and experimentally realize a new class of actively mode-locking technique using pump modulation for rare-earth doped fiber lasers. A Tm-doped fiber laser at 2 μm is mode-locked using the proposed active mode-locking via pump modulation technique. Low-threshold continuous-wave mode-locking is achieved with a transform-limited pulse width of 4.4 ps, a spectral bandwidth of 0.9 nm, and a repetition rate of 12.9 MHz. Second-harmonic mode-locking is also demonstrated by simply driving the pump current at an appropriate frequency. More importantly, we believe that this technique can be applied to mode-lock other rare-earth doped fiber laser systems such as erbium- and ytterbium-doped fiber lasers.
