ABSTRACT
Quantum cascade lasers (QCLs) are high-power, coherent light sources emitting in the mid-infrared and terahertz frequency ranges. In QCLs, multiple conduction subbands are formed in the active core by means of quantum confinement. QCLs are unipolar devices, meaning that lasing is achieved through radiative intersubband transitions instead of radiative interband transitions in traditional quantum well semiconductor lasers. Under high-power room temperature continuous wave operation, both electron and phonon systems in QCLs are far away from equilibrium. In such non-equilibrium conditions, both electronic and thermal transport modeling are important for understanding and improving QCL performance. Density matrix and non-equilibrium Green's function formalism are the two most widely used techniques to describe quantum transport in QCLs. The chapter presents a multiphysics and multiscale simulation framework that enables the description of QCL performance under far-from-equilibrium conditions. It also presents the electronic and thermal transport models, and then brings them together for electrothermal simulation of a real device structure.
