Transparency Current and Gain Spectrum of InGaAs/GaAs Quantum Well-Dots

The experimental dependence of the transparency current of InGaAs/GaAs quantum well-dots on the photon energy, which corresponds to the difference of quasi-Fermi levels for electrons and holes, has been obtained. It is shown that modal gain spectra can be calculated from spontaneous luminescence spectra using the obtained dependence and the known relationship between spontaneous luminescence and optical absorption. Modal gain spectra of InGaAs/GaAs quantum well-dots at different pump currents have been calculated. The technique can be used to study gain spectra of devices operating in superluminescence regimes, when the position of the gain maximum is unknown.