Gain optimization in optically pumped AlGaAs unipolar quantum-well lasers

A method is described for the optimized design of quantum-well (QW) structures, in respect to maximizing the stimulated gain in optically pumped intersubband lasers. It relies on applying supersymmetric quantum mechanics (SUSYQM) to an initial Hamiltonian, in order to both map one bound state below the spectral range of the initial Hamiltonian, and to generate a parameter-controlled family of isospectral Hamiltonians with the desired energy spectrum. By varying the control parameter, one changes the potential shape and, thus, the values of dipole matrix elements and electron-phonon scattering matrix elements. The use of this procedure is demonstrated by designing smoothly graded and stepwise-constant Al/(x)Ga/(1-x). As ternary alloy QWs, with the self-consistent potential taken into account. Finally, the possibility of employing layer interdiffusion to get optimal smooth potentials is discussed