Excitation dependences of gain and carrier-induced refractive index change in quantum-dot lasers

The excitation-density dependence of optical gain and refractive index changes in quantum-dot active media is investigated on the basis of a microscopic theory. Carrier-carrier Coulomb interaction and carrier-phonon interaction are treated on the level of a quantum-kinetic description. In the range of small optical gain the authors find small values of the α factor, while in the regime of gain saturation ∫α∫ increases drastically. © 2007 American Institute of Physics.