Investigation of linewidth enhancement factor in injection-locked quantum dot lasers with four-wave mixing analysis

The four-wave mixing (FWM) analysis is successfully applied on the injection-locked quantum dot (QD) laser for linewidth enhancement factor extraction. The rate equation model of the QD lasers is simplified and the analytical model for the FWM analysis is derived and verified. By fitting the experimentally obtained regenerative signals and power spectrum signals at different detuning frequencies with the respective curves analytically calculated from the rate equations, the impacts on the injection-locked QD lasers with different injection conditions are investigated. The fitting results show that the linewidth enhancement factor decreases as the injection increases, resulting in the reduction of the chirp that benefits to applications such as optical communications.