Spectral dependence of the linewidth enhancement factor in quantum dot lasers

The spectral analysis of amplified spontaneous emission is used to determine the linewidth enhancement factor ($\alpha$-factor) in lasers based on InAs/InGaAs quantum dots (QDs) in a wide spectral range near the ground-state optical transition energy. The effect of the pump current and number of QDs on the spectral dependences of the $\alpha$-factor is examined. The temperature dependence of the spectra of the $\alpha$-factor is experimentally determined for the first time for lasers with InAs/InGaAs QDs. An explanation is suggested for the observed anomalous decrease in the $\alpha$-factor with increasing temperature.