Harmonic mode-locking in a Tm-doped fiber laser: Characterization of its timing jitter and ultralong starting dynamics

We report an experimental characterization on harmonic mode-locking in a Tm-doped fiber laser, which exhibits pump related timing jitter and ultralong mode-locking starting dynamics. The laser is pumped by a laser diode seeded EDFA. Harmonic mode-locking is initiated by nonlinear polarization rotation and showed a good long term stability. Timing jitter is found to be significantly influenced by the properties of laser diode seed for the EDFA. When switching the seed from a Fabry-Perot cavity laser diode to a distributed feedback (DFB) laser diode, timing jitter decreases from 16 ps to 6 ps. It also takes the laser an ultralong self-starting time (>100s), 3 order of magnitude longer than typical Er-doped or Yb-doped fiber lasers, to reach a steady harmonic mode-locking in some cases. These experimental evidences can contribute to a better understanding of Tm-doped fiber lasers.