Extraction of the electron excess temperature in terahertz quantum cascade lasers from laser characteristics

We propose a method to extract the upper laser level's (ULL's) excess electronic temperature from the analysis of the maximum light output power (P _max) and current dynamic range ΔJ _d = (J _max - J _th) of terahertz quantum cascade lasers (THz QCLs). We validated this method, both through simulation and experiment, by applying it on THz QCLs supporting a clean three-level system. Detailed knowledge of electronic excess temperatures is of utmost importance in order to achieve high temperature performance of THz QCLs. Our method is simple and can be easily implemented, meaning an extraction of the excess electron temperature can be achieved without intensive experimental effort. This knowledge should pave the way toward improvement of the temperature performance of THz QCLs beyond the state-of-the-art.