Modulation Properties of Self-Injected Quantum-Dot Semiconductor Diode Lasers

This paper investigates the modulation properties of self-injected quantum-dot semiconductor lasers. Using a semianalytical approach, the modulation characteristic of a quantum-dot nanostructure laser operating under the influence of optical feedback is successfully modeled. This novel approach derives a feedback-induced modulation response model based on the incorporation of the specific quantum nanostructure carrier dynamics as well as the effects of nonlinear gain. This study investigates the impacts of the carrier capture and relaxation time as well as other material parameters such as linewidth enhancement factor, differential gain, and gain compression factor for different feedback configurations. It is also shown that, under the short external cavity configuration, the dynamic properties such as the relaxation frequency as well as the laser's bandwidth can be improved through controlled optical feedback. On the other hand, numerical results show that under the long external cavity configuration, any small back-reflection from the laser's facets combined with the large variations of linewidth enhancement factor would significantly alter the laser's modulation response.