Pulsating intensities in external cavity semiconductor lasers

Summary form only given. We have investigated the dynamics of external cavity diode lasers, (L/spl sim/1 cm or shorter), in the context of the single mode single delay Lang-Kobayashi (LK) model. We find that the laser undergoes a sequence of three Hopf bifurcations from the same external cavity mode, as the feedback rate and the roundtrip time are varied. As we increase the feedback rate a supercritical or a subcritical Hopf bifurcation occurs depending on the value of the roundtrip time. For larger feedback rates the laser stabilizes always through a subcritical Hopf bifurcation, and at even larger values of the feedback rate it again destabilizes through a supercritical Hopf bifurcation, which is related to a two mode approximate solution of the LK model. In the region between the two Hopf bifurcations the laser exhibits pulsating intensities. In addition, as the roundtrip time decreases, the two subcritical Hopf points coalesce and the steady state coexists with an isolated pulsating limit cycle. This unusual region is investigated numerically and the Hopf bifurcation boundary is computed analytically.