Nonequilibrium effects in quantum well lasers

We present a simple technique of measuring the effect of the finite capture time of carriers in quantum well lasers on the homogeneity of the gain. The effect is measured using an extended cavity laser configuration in which we control the feedback level and compare the two extreme cases of a laser and a nonlasing amplifying gain medium. Broadband measurements of the spontaneous emission at energies near the top of the well and above the barriers show an inhomogeneous gain saturation which depends on the photon density inside the cavity. The results agree with a simple model for carrier injection in quantum well lasers.