The optimization of optical gain in the intersubband quantum well laser

A systematic procedure is described for the maximization of gain in optically pumped intersubband lasers, via optimal tailoring of the quantum well profile. The procedure relies on using the inverse spectral theory, allowing one to shift the bound states as desired, and additionally to make the isospectral reshaping of the well, with the eventual aim of finding the best combination of those optical dipole and electron–phonon scattering matrix elements which are relevant for the laser gain. Example design is presented for a laser based on the AlxGa1−xAs system, and the band nonparabolicity is accounted for in the final design.