Influence of laser coupling configuration on chaotic synchronization

Synchronization of chaotic semiconductor lasers has now been demonstrated experimentally using a variety of coupling schemes. Coupling methods include situations where the transmitter laser system is itself chaotic and drives a passive receiver system, both lasers are individually chaotic and, both lasers induced the chaos through mutual self-coupling. The qualitative dynamics for each of these scenarios is adequately captured by an appropriate set of coupled Lang-Kobayashi lumped rate equation models. Such lumped models however cannot distinguish between the possible coupling geometries realizable in real experimental systems and ignore multiple feedback from external reflecting surfaces. For example, real lasers may have AR/HR coated facets and there are several choices of placement of external reflectors and coupling paths relative to these facets. Moreover, nominally single mode FP lasers may exhibit pronounced multi-longitudinal mode dynamics in the presence of weak external reflection and DFB lasers may exhibit dual-wavelength operation or strongly asymmetric spatial hole-burning due to the presence of finite facet reflectivity.