Correlations in Electrically Coupled Chaotic Lasers
  We show how two electrically coupled semiconductor lasers having optical feedback can present simultaneous anti-phase correlated fast power fluctuations, and strong in-phase synchronized spikes of chaotic power drops. This quite counter intuitive phenomenon is demonstrated experimentally and confirmed by numerical solutions of a deterministic dynamical system of rate equations. The occurrence of negative and positive cross correlation between parts of a complex system according to time scales, as proved in our simple arrangement, is relevant for the understanding and characterization of collective properties in complex networks. 
E. J. Rosero, W. A. S. Barbosa, J. F. Martinez Avila, A. Z. Khoury, J.   R. Rios Leite
physics.optics nlin.CD