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We propose a secure communication scheme based on anticipating synchronization of two chaotic laser diodes, one subject to incoherent optical feedback and the other to incoherent optical injection. This scheme does not require fine tuning of the optical frequencies of both lasers as is the case for other schemes based on chaotic laser diodes subject to coherent optical feedback and injection. Our secure communication scheme is therefore attractive for experimental investigation.

We analyze the bifurcation mechanism responsible for the experimentally observed polarization selfmodulation ͑PSM͒ in a vertical-cavity surface-emitting laser subject to optical feedback. We show that closed branches of time-periodic intensity solutions connecting distinct external-cavity modes ͑ECMs͒ exhibit PSM. Along these bridges, the linearly polarized components of the optical field oscillate in antiphase and with a frequency close to the difference between two ECM frequencies. A beating mechanism between stable ECMs then explains the PSM phenomenon. Our results also substantiate recent theoretical studies of edge-emitting lasers subject to optical feedback.

We demonstrate numerically that low-frequency fluctuations (LFF's) observed in a laser diode subjected to a first optical feedback with a short delay are suppressed by means of an adequate second optical feedback. The general idea of this technique is based on the observation that second feedback can suppress the antimodes that are responsible for the crises in the LFF regime. Furthermore, we observe that the second optical feedback can steer an unstable laser that is biased near threshold into a stable regime.

We investigate correlations of the intensity fluctuations of two-dimensional arrays of nonidentical, locally coupled lasers, numerically and experimentally. We find evidence of a power-law dependence of spatial correlations as a function of laser pair distance (or coupling strength) near the phase-locking threshold.