Abstract
We have successfully applied the four-wave mixing (FWM) analysis on a quantum-dot (QD) semiconductor laser subject to optical feedback. The simplified rate equation model of the QD lasers for the FWM analysis is derived and verified. From the theoretical analysis, the characteristic behaviors of the regenerative and amplitude modulation spectra of the FWM signals are predicted by different intrinsic parameters and feedback conditions. By fitting the experimentally obtained regenerative signals and amplitude modulation signals with the respective curves from the rate equations which calculated at different detuning frequencies, the impacts on the QD lasers with different feedback conditions are extracted qualitatively and quantitatively. Moreover, the fitting results show that the linewidth enhancement factor of QD laser has a reduction of up to 40 % from its free-running value, resulting in the reduction of the chirp in optical communication.