Close-to-ideal device characteristics of high-power InGaAs/GaAs quantum-dot lasers are achieved by the application of an annealing and growth interruption step at 600 °C after the deposition of the dots. The transparency current is reduced to below 20 A/cm2 at room temperature. The internal differential quantum efficiency is increased from below 50% to above 90% by improvement of the barrier material and subsequent reduction of leakage current. A peak power of 3.7 W at 1140 nm lasing wavelength in pulsed operation at room temperature is demonstrated.

We analyse the sensitivity of quantum dot semiconductor lasers to optical feedback. While bulk and quantum well semiconductor lasers are usually extremely unstable when submitted to back reflection, quantum dot semiconductor lasers exhibit a reduced sensitivity. Using a rate equation approach, we show that this behaviour is the result of a relatively low but nonzero line-width enhancement factor and strongly damped relaxation oscillations.

High-power semiconductor laser diodes based on multiple InGaAs/GaAs quantum-dot layers grown by metal–organic chemical-vapor deposition are demonstrated. The devices exhibit a peak power of 3 W (4.5 W) at 1100 nm (1068 nm), respectively, during pulsed operation at room temperature and show slope efficiencies of 57% (66%).

4.7 W continuous-wave (CW) and 11.7 W quasi-CW output power have been demonstrated for laser diodes based on six-fold stacks of InGaAs/GaAs quantum dots. Lifetimes beyond 3000 h at 1.0 and 1.5 W output power and 50degreesC heatsink temperature were measured. The output power is limited by catastrophic optical mirror damage occurring at 19.5 MW/cm(2) on the front facet

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