Investigation of Subband Electron Temperatures of Quantum Cascade Lasers

The electron temperature of each subband is the key to understanding the characteristics of quantum cascade lasers (QCLs). We show herein a method, based on the particle swarm optimization algorithm, to obtain the electron temperature of the conduction band in the active region of QCLs. Accurate subband electron temperatures at room temperature, low temperature, and under various external electric fields are obtained. Furthermore, we discuss the variation and distribution of subband electron temperature that occurs during the operation of QCLs. The laser gain and I–V curves are obtained from the subband electron temperature. A comparison of these results with experimental results confirms that consideration of the subband electron temperature can improve our understanding of QCLs.