Stable mode locking via ground- or excited-state transitions in a two-section quantum-dot laser

The authors demonstrate stable mode locking that involves transitions within either the ground state $(1260nm)$ or the excited state $(1190nm)$ in a two-section quantum-dot laser, at repetition frequencies of 21 and $20.5GHz$⁠, respectively. The average power of the mode-locked output was in excess of $35mW$ for operation in the ground state and $25mW$ in the excited state. The selection of pulse generation between these states in the mode-locking regime is controlled by the electrical biasing conditions.