Phase-Locked Array Laser Diodes (LDs) by Using $1\times N$ Active Multimode-Interferometer (MMI)

1timesN active multimode-interferometer (MMI) laser diodes (LDs), with integrated phase-match region, are demonstrated as phase-locked array LDs. In general, the phase of output ports of MMI divider is not the same for all N ports. This phase-mismatch leads to enormous excess loss inside the 1timesN active MMI-LD cavity, which results in very low quantum efficiency or even no lasing. Therefore, we integrate the phase-match region, which can lead to regular lasing, without any enormous excess loss. The implemented 1times3 active MMI-LDs showed lasing with no enormous degradation of quantum-efficiency. Additionally, significant output power increase of 200 mW was observed, compared to the regular single stripe LDs fabricated simultaneously, with the phase-locked condition.