Stabilizing optical feedback-induced chaos by sinusoidal modulation beyond the relaxation frequency in semiconductor lasers

We report on stabilizing the chaotic dynamics of semiconductor lasers under optical feedback (OFB) by means of sinusoidal modulation at frequencies far beyond the relaxation frequency of the laser. The laser is assumed to be coupled to a short external cavity, which is characterized by a resonance frequency spacing higher than the relaxation frequency. The study is based on a time delay rate equation model of OFB, which is suitable for treating the regime of strong OFB and considering multiple reflections in the external cavity. We show that the intensity modulation response of the chaotic laser under strong OFB is enhanced over a narrow frequency band near the doubled relaxation frequency due to a photon-photon resonance. Within this high-frequency band, the sinusoidal modulation may convert the chaotic attractor to a limit cycle, and the small-signal modulation suppresses the relative intensity noise (RIN) to a level only 2 dB higher than the RIN level of the solitary laser.