We investigated a single mode semiconductor laser system pumped near thresh
old and subject to optical feedback from a short distance. We found both ex
perimentally and numerically that as the feedback strength is increased the
laser undergoes a cascade of bifurcations as one external cavity mode beco
mes unstable and the next one with higher intensity becomes stable only to
be destabilized and replaced by the next stable external cavity mode. In th
e stable regions the laser operates in the so-called maximum gain mode and
the unstable regions exhibit chaos which evolves into low-frequency fluctua
tions characterized by intensity dropouts. [S0031-9007(98)08369-0].