Enhancement of Modulation Responses of Directly Modulated Lasers with Passive Feedback and Partially Corrugated Grating

The modulation response of a high-speed directly modulated laser (DML) is enhanced by integrating a passive feedback section to reduce the waveform distortions that is critical for PAM-4 modulation. The partially corrugated grating (PCG) structure helps to maintain >85% single-mode yield under passive feedback.