The relative intensity noise of a semiconductor laser subject to strong coherent optical feedback

The relative intensity noise (RIN) of a semiconductor laser diode subject to optical feedback has been numerically calculated for both weak and strong optical feedback levels. Good agreement with recent experiment results was only obtained after a modified Lang-Kobayashi model was used. Multiple reflections in the external cavity are required to explain the experimentally observed variation of the upper boundary of the coherence collapse regime with injection current. RIN measurements are shown to offer a convenient method of identifying the various feedback regimes both experimentally and theoretically. The importance of incoherent optical feedback in regime IV is also stressed