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