High performance of single mode InAs/InGaAs/GaAs quantum dot lasers of 1.3-micron range

Quantum dot (QD) is one of the most perspective candidates to be used as an active region of temperature-insensitive 1.3-micron GaAs based lasers for optical networks. However, the limited optical gain achievable in QD ground state hindered their practical use. In this work we have demonstrated that using of high number of QDs stacks grown under proper conditions by MBE is an effective way to considerably increase the optical gain of QD lasers. Ridge waveguide laser diodes with width of 2.7 μm and 4.5 μm based on various numbers of QD layers (N=2, 5, 10) were fabricated and studied in this work. Ultra-low threshold current of 1.43 mA was achieved for 2-stack QD. Regime of simultaneous lasing at ground- and excited-states was discovered. This effect was accounted for the finite time of carriers capture to the ground-state in QD. Multi-stack QD structures enabled to maintain continuous work ground-state lasing up to the current density of 10kA=100×J_th. Enhanced optical gain allowed us to unite very high differential efficiency (>75%) with low threshold current (<100 A/cm²) and characteristic temperature (T₀>100 K). For example, laser diode of 1-mm cavity length has shown single mode output power of 100 mW at operating current of 195 mA and at high operation power demonstrated insensibility to the changes of temperature. The combination of parameters achieved is quite competitive to all technologies currently used for 1.3-micron lasers including traditional InP-based lasers and makes QD gain medium very promising for VCSEL and telecom laser applications.