Phonon Enhanced Inverse Population in Asymmetric Double Quantum Wells

Interwell optical-phonon-assisted transitions are studied in an asymmetric double-quantum-well heterostructure comprising one narrow and one wide coupled quantum wells (QW’s). We show that the depopulation rate of the lower subband states in the narrow QW can be significantly enhanced, thus facilitating the intersubband inverse population, if the depopulated subband is aligned with the second subband of the wider QW, while the energy separation from the first subband is tuned to the highest energy optical-phonon mode.