Ultralow noise optical pulse generation in an actively mode-locked quantum-dot semiconductor laser

We report excellent noise performance of an external-cavity actively mode-locked laser based on quantum-dot gain medium. Optical pulse trains with less than 7.5fs residual timing jitter (1Hzto10MHz) for a 12.8GHz harmonically mode-locked ring laser were obtained. This result represents, to our knowledge, the lowest residual jitter reported from actively mode-locked semiconductor lasers, and shows that quantum-dot mode-locked lasers are promising as sources of ultralow noise optical pulse trains.