Hot electrons and curves of constant gain in long wavelength quantum well lasers.

In long wavelength quantum well lasers the effective electron temperature (T(e)) is often a strong function of the pump current and hence the T(e) correlates with the carrier concentration n in the active region. On the other hand, the material gain g in the active layer depends on both variables, g=g(n,T(e) ). We discuss a convenient way of analyzing this situation, based on considering the contours of constant gain g on the surface g(n,T(e) ). This is qualitatively illustrated with two model examples involving quantum well lasers, the long-wavelength quantum well laser with current dominated by the Auger recombination and the unipolar quantum cascade laser.