Self-induced pulsations, Q-switching and mode-locking in Tm–silica fibre lasers

Abstract

Observations of self-induced pulsations, Q-switching and mode-locking in Tm–silica fibre lasers are described. Continuous-wave (CW) self-mode-locking in single-clad and double-clad Tm–silica fibre lasers operating at 2 µm is demonstrated when pumped at 1.3 µm and 803 nm, respectively. An ideal CW mode-locked pulse train is obtained for output powers greater than 100 mW while, at lower powers, self-pulsations were dominant in both types of fibre. The experimental mode-locked pulse train periods are found to be consistent with theoretical analysis. Self-induced mode-locking for a single-clad fibre laser with an external cavity has also been observed for short fibre lengths when pumped at 1064 nm and Q-switched using an external cavity or pulse pumped. The mechanisms of self-pulsations and mode-locking in heavily doped Tm fibre lasers are discussed.