An approximate k·p theory for optical gain of strained InGaAsP quantum-well lasers

We describe an approximate k·p theory for strained quantum wells that includes the bulk valence-band mixing effect and simplifies the envelope function approximation for the subband calculation. We show that such an approach provides analytical results for calculating the quasi-Fermi level and optical gain. We present useful material parameters over the whole parameter space of the InGaAsP system based on the approximate k·p theory. Our approximate k·p subband structure is compared with the results from the exact k·p theory. Using a minimal set of fitting parameters, we show that the calculated gain spectrum agrees reasonably well with experimental data for the gain spectrum and its temperature dependence