Tradeoffs between oscillator strength and lifetime in terahertz quantum cascade lasers

We present evidence that the failure of high diagonality alone as a design strategy is due to a fundamental trade-off between large opticaloscillator strength and long upper-level lifetime. We hypothesize that diagonality needs to be paired with increaseddoping in order to succeed, and present evidence that highly diagonal designs can benefit from much higherdoping than normally found in terahertzquantum cascade lasers. In assuming the benefits of high diagonality paired with highdoping, we also highlight important challenges that need to be overcome, specifically the increased importance of carrier induced band-bending and impurityscattering.

Source: Applied Physics Letters - November 14, 2016 Category: Physics Authors: Chun Wang I. Chan, Asaf Albo, Qing Hu and John L. Reno Source Type: research