There has been growing interest in the model of semiconductor lasers with non- Markovian relaxation. Introducing senior and graduate students and research scientists to quantum mechanics concepts, which are becoming an essential tool in modern engineering, Engineering Quantum Mechanics develops a non-Markovian model for the optical gain of semiconductor, taking into account the rigorous electronic band-structure and the non-Markovian relaxation using the quantum statistical reduced-density operator formalism. Example programs based on Fortran 77 are provided for band-structures of zinc-blende and wurtzite quantum wells.