Chaos synchronization in networks of delay-coupled lasers: Role of the coupling phases.

We derive rigorous conditions for the synchronization of all-
optically coupled lasers. In particular, we elucidate the role of the optical
coupling phases for synchronizability by systematically discussing all possible
network motifs containing two lasers with delayed coupling and feedback. By
these means we explain previous experimental findings. Further, we study larger
networks and elaborate optimal conditions for chaos synchronization. We show
that the relative phases between lasers can be used to optimize the effective
coupling matrix.