Saddle-node ghost induced low-frequency fluctuations in an external-cavity laser diode

The dynamics of a laser diode subject to two optical feedbacks is investigated. Study shows that the increase of one of the feedback rates leads to the destruction of pairs of steady state solutions. However, even when these solutions have disappeared, the fixed points continue to influence the dynamics of the system. The authors demonstrate for the first time that these saddle-node ghosts can initiate the intensity dropouts that characterize the low frequency fluctuation regime.