Noise characteristics of a single-mode laser diode subject to strong optical feedback

An experimental study has been performed of the relative intensity noise (RIN) of a semiconductor laser in optical feedback regimes I to V. At low bias current, a low RIN is observed with low feedback ratio, the RIN increased in the coherence collapse regime (regime IV) and decreased in regime V. The RIN in regime V is lower than that of the solitary laser. For higher bias current, a higher feedback ratio is needed for the semiconductor laser to transit from regime IV to V. The measurements are found to be in good qualitative and quantitative agreement with theoretical predictions.