Optical gain in InAs/InGaAs quantum-dot structures: Experiments and theoretical model

The dependence of the mode optical gain on current in InAs/InGaAs quantum-dot structures grown by the method of molecular-beam epitaxy is obtained from the experimental study of ultra-low-threshold laser diodes. The record lowest inversion threshold at room temperature was about 13 A cm². A theoretical model is proposed that relates the optical gain to the ground-state transitions in quantum dots. The effective gain cross section is estimated to be ~7 × 10^–15 cm^–2.