Unnested islands of period doublings in an injected semiconductor laser

Using the example of the injected semiconductor laser, an attempt was made to illustrate that period-doubling bifurcation curves do not always accumulate inside each other but often form unnested islands. A saddle-node bifurcation of periodic orbits on a chaotic attractor was identified. Several transitions were found that are embedded in a consistent bifurcation diagram of unnested period doublings.