We report on GaAs-based broad area (100 µm) 1.3 µm quantum dot (QD) lasers with high CW output power (5 W) and wall-plug efficiency (56%). The reliability of the devices has been demonstrated beyond 3000 h of CW operation at 0.9 W and 40 • C heat sink temperature with 2% degradation in performance. P-doped QD lasers with a temperature-insensitive threshold current (T 0 > 650 K) and differential efficiency (T 1 = infinity) up to 80 • C have been realized.
Gain characteristics of injection lasers based on self-organized quantum dots (QDs) were studied experimentally for two systems: InGaAs QDs in an AlGaAs matrix on a GaAs substrate and InAs QDs in an InGaAs matrix on an InP substrate. A ground-to-excited state transition was observed with increasing threshold gain. An empirical equation is proposed to fit the current density dependence of the QD gain. This fitting equation is shown to be valid for both the ground and excited state lasing in the systems under study in the 77-300 K temperature range. The effect of QD surface density on gain characteristics is calculated analytically.
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