Design Concepts of Terahertz Quantum Cascade lasers: Proposal for Terahertz Laser Efficiency Improvements

Conceptual disadvantages of typical resonant phonon terahertz quantum cascade lasers THz-QCLs are analyzed. Alternative designs and their combination within a concrete device proposal are discussed to improve the QCL performance. The improvements are 1 indirect pumping of the upper laser level, 2 diagonal optical transitions, 3 complete electron thermalization, and 4 materials with low effective electron masses. The nonequilibrium Green’s function method is applied to predict stationary electron transport and optical gain. The proposed THz-QCL shows a higher optical gain, a lower threshold current, and a higher operation temperature. Alloy disorder scattering can worsen the QCL performance