Chaos synchronization and spontaneous symmetry-breaking in symmetrically delay-coupled semiconductor lasers

We present experimental and numerical investigations of the dynamics of two device-identical. optically coupled semiconductor lasers exhibiting a dela y in the coupling. Our results give evidence for subnanosecond coupling-ind uced synchronized chaotic dynamics in conjunction with a spontaneous symmet ry-breaking: we find a well-defined time lag between the dynamics of the tw o lasers, and an asymmetric physical role of the subsystems. We demonstrate that the leading laser synchronizes its lagging counterpart, whereas the s ynchronized lagging laser drives the coupling-induced instabilities.