Population inversion in an optically pumped single quantum well

An optically pumped intersubband laser generator is proposed in which the continuum states above an Al0.2Ga0.8As–GaAs–Al0.2Ga0.8As single quantum well with a width of L=17 nm serve as the highest level in a four-level laser system. The design allows much greater flexibility in the choice of pumping source and simplifies considerably the device fabrication. We have obtained the electronic subband structure of the proposed device and utilized a simple rate equation approach to examine the electron density in different states under optical pumping.