State of the art of InP and GaAs quantum cascade lasers

The key physical phenomena associated with long-wavelength infrared emission and laser action in quantum cascade lasers based on InP/GaInAs/AlInAs and GaAs/AlGaAs heterostructures are reviewed. The effect of different tunnel injection schemes on the hot-electron energy distributions is compared. High-power superlattice lasers with improved high-energy injection schemes are described. The local temperature distribution, the thermal resistance and the hot-phonon effects are monitored in operating devices by micro-probe Raman and luminescence measurements.