Quantum Cascade Lasers

These lasers offer tunable light sources in the mid- and far-infrared frequency regime and are highly promising gas- and biomolecule sensors. Quantum cascade lasers (QCLs) are unipolar devices, usually n-type. Laser emission is achieved through the use of intersubband transitions in a repeated stack of semiconductor superlattices.

From a theory point of view, quantum cascade lasers are among the most challenging optoelectronic devices since their properties cannot be understood and predicted in terms of the available standard transport methods, such as the semiclassical Boltzmann equation or the Landauer-Buettiker formalism. Rather, they call for a sophisticated quantum transport theory that treats quantum mechanical effects such as interference and resonant tunneling on an equal footing with elastic and inelastic scattering by phonons, impurities, rough interfaces, alloying.