The influences of refractive index dispersion on the modal gain of a quantum-well laser

A new self-consistent method (SCM) for single-quantum-well (SQW) AlGaAs-GaAs diode lasers is introduced to study systematically the influences of refractive-index dispersion on TE modal gain. The refractive-index dispersion of QW layers is calculated by the density matrix method. It is affected by the effective propagation constant of guided mode. Likewise, the transverse guided mode of QW lasers, as obtained by the transfer matrix method, is also influenced by the refractive-index dispersion. SCM, using the density matrix and transfer matrix methods self-consistently, provides the TE modal gain spectra. SCM's calculated results are compared with those of Dumke's approximation and show a decrease in energy of modal gain peak and a decline of modal gain values at high emission energies. The differences between these two methods are seen to increase with an increase of well width and to be unrelated to barrier height. Although not treated formally in this paper, we suggest that SCM results show a significantly superior match to real phenomena.