Generalized synchronization of chaos: experiments on a two-mode microchip laser with optoelectronic feedback

Generalized synchronization is characterized by the existence of a functional relationship between the dynamical evolution of a response system driven by an external signal. We observe generalized synchronization of chaos in a neodymium-doped yttrium aluminum garnet (Nd:YAG) microchip laser with optoelectronic feedback. The electronic feedback signal driving the chaotic dynamics of a laser is recorded in a computer. Feedback is removed and the recorded signal is replayed to the laser. Instead of repeating the original dynamics, the laser displays generalized synchronization to the recorded waveform. We observe similar results in numerical simulations using a two-mode laser model. The feedback signal is the total intensity, while the microchip laser dynamics is governed by the mode–mode interaction through spatial hole burning of the population inversion, the description of which requires several additional degrees of freedom. Generalized synchronization can arise from the existence of hidden degrees of freedom in the laser dynamics that are lumped together in the feedback signal.