Modulation Characteristics Enhancement of Monolithically Integrated Laser Diodes Under Mutual Injection Locking

Modulation characteristics enhancement by mutual injection locking of monolithically integrated distributed feedback (DFB) lasers is studied. Locking bistability in mutually coupled integrated lasers is observed. Resonance frequency as high as 34.3 GHz is recorded, corresponding to more than fivefold enhancement over the relaxation oscillation frequency at free running state. The mutually injection-locked lasers exhibit reduced harmonics and third-order intermodulation distortion, as well as suppressed relative intensity noise near the relaxation oscillation frequency. The spurious-free dynamic range is improved from 75 to 80 dB·Hz^2/3. Furthermore, alleviation of chirp-induced power fading in analog optical links has been demonstrated. To our knowledge, this is the first time that suppressed nonlinear distortion and noise as well as chirp reduction are simultaneously demonstrated for monolithic mutually injection-locked DFB lasers.