Output power and its limitation in ridge-waveguide 1.3  m wavelength quantum-dot lasers

Low-threshold (3.7 mA) high-power (150 mW) ridge-waveguide lasers based on 1.3 µm self-organized quantum dots were fabricated and studied at and above room temperature. The output power spectrum of these lasers consists of two components, which correspond to the ground-state (∼1.29 µm) and the excited-state (∼1.22 µm) optical transitions. The ground-state component of the lasing mode saturates with increase in the drive current and then persists. Further growth of the total output power is due to the excited-state component. Design criteria of quantum-dot lasers, which maximize the ground-state output power, are considered by solving the carrier-photon rate equations. Current-induced ground-to-excited-state lasing transition is due to a combination of slow carrier capture/relaxation to and efficient thermoionic emission from the ground-state level.