New publication: Density-Matrix Model for Photon-Driven Transport in Quantum Cascade Lasers (Phys. Rev. Applied)

PhD students Sina Soleimanikahnoj and Michelle King, along with Prof. Irena Knezevic,  coauthored the recently published paper “Density-Matrix Model for Photon-Driven Transport in Quantum Cascade Lasers,” Phys. Rev. Applied 15, 034045 (2021). (2021). [Publisher’s link] [Preprint on arXiv]

Current density versus electric field curve for quantum cascade laser
Calculated dc current density as a function of the applied bias electric field at 300 K, with (open squares) and without (solid circles) the influence of photon-assisted tunneling. Experimental data is the black solid curve.

Abstract: We develop a time-dependent density-matrix model to study photon-assisted (PA) electron transport in quantum cascade lasers. The Markovian equation of motion for the density matrix in the presence of an optical field is solved for an arbitrary field amplitude. Level-broadening terms emerge from microscopic Hamiltonians and supplant the need for empirical parameters that are often employed in related approaches. We show that, in quantum cascade lasers with diagonal design, photon resonances have a pronounced impact on electron dynamics around and above the lasing threshold, an effect that stems from the large spatial separation between the upper and lower lasing states. With the inclusion of PA tunneling, the calculated current density and output power are in good agreement with experiment.