Modulation bandwidth enhancement of an optically controlled single-mode semiconductor laser is achieved by introducing an external cavity into the laser. A calculation based on a rate equation model shows that the 3-dB bandwidth of the optically controlled external cavity laser (OC-ECL) can be substantially enhanced by controlling the feedback light intensity and phase properly. A broad 3-dB bandwidth of 59 GHz is experimentally confirmed by using the fabricated OC-ECL. The results suggest that a combination of cross-gain modulation and photon-photon resonance is suitable to enhance the modulation bandwidth of semiconductor lasers.
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