Dynamic Modeling of Mode-Locked Quantum Cascade Lasers

Quantum optoelectronic devices based on nanostructured semiconductor materials offer unique control over the device properties by wavefunction engineering. Among other things, these devices serve as mode-locked laser sources for the generation of regular short-pulse trains at custom-tailored wavelengths, complementing the spectral region covered by conventional diode lasers. Examples include quantum cascade lasers (QCLs) which utilize optical transitions between quantized conduction band states in a multi-quantum-well structure, and quantum dot (QD) lasers employing transitions between three-dimensionally confined electron and hole states. For in-depth analysis of the laser dynamics and targeted design optimization, a realistic and computationally efficient simulation model is required. The Maxwell-Bloch type equations offer a suitable semiclassical approach, combining a classical description of optical propagation with a density matrix model for the quantum active region. We extend this model by adding a realistic and efficient description of saturable absorption as required for short-pulse generation by passive mode-locking, and present a suitable numerical approach.