18 GHz from a σ-cavity Er-fibre laser withdispersion management and rational harmonic active mode-locking

Abstract
The authors demonstrate rational harmonic mode-locking in a sigma-cavity Er-fibre laser. Stable pulse generation at a repetition rate up to 18.4 GHz with mark-to-space ratio better than 10 is achieved with intracavity dispersion management. The influence of the dispersion of intracavity fibre elements on minimum pulse duration is discussed.