The optical gain of a quantum-well laser is studied taking into account the valence-band mixing, non-Markovian relaxation and the many-body effects. Conventional gain spectra calculated with the Lorentzian line shape function show two anomalous phenomena: unnatural absorption region below the band-gap energy and mismatch of the transparency point in the gain spectra with the Fermi-level separation, the latter suggesting that the carriers and the photons are not in thermal (or quasi) equilibrium. It is shown that the non-Markovian gain model with many-body effects removes the two anomalies associated with the Lorentzian line shape function with the proper choice of the correlation time.
"Theory of non-Markovian optical gain in excited semiconductors", Proc. SPIE 2693, Physics and Simulation of Optoelectronic Devices IV, (1 May 1996); doi: 10.1117/12.238961; https://doi.org/10.1117/12.238961