Optical synchronisation of chaos in unidirectionally coupled external cavity vertical-cavity surface-emitting semiconductor lasers (VCSELs) has been experimentally achieved. The polarisation of the injected beam is perpendicular to that of the free-running receiver (x-polarisation). Normal (positive-slope) synchronisation is observed between the injected beam and the y-polarized component of the receiver. However, due to the anti-phase dynamics of the receiver, an inverse (negative-slope) synchronisation is found between the injected beam and the x-polarized component of the receiver. A 200 MHz message has been successfully encoded in an external-cavity VCSEL transmitter and decoded in a receiver. Message recovery has been achieved with about 9 dB signal-to-noise ratio.
We have experimentally demonstrated message broadcasting and decoding using a chaotic external-cavity DFB laser transmitter and two stand-alone DFB laser receivers. A GHz message has been successfully broadcast to the two receivers. Message recovery was achieved with greater than 14 dB signal-to-noise ratio.
Strong optical injection and optical frequency matching have been used to effect an experimental demonstration of dual-mode synchronisation using a multi-mode external-cavity chaotic master laser and two single-mode stand-alone slave lasers. It is shown by means of synchronisation diagrams and measured cross-correlation functions that the longitudinal modes of the slave lasers have been successfully synchronised to frequency matched modes of the master laser operating in the low frequency fluctuation regime. The time lag between the lasers identifies that injection-locked synchronisation is achieved.
Nonlinear delayed dynamics was first proposed in Optics by Kensuke Ikeda in 1979. Since then, many different setups based on similar dynamical principles were carried out experimentally, first to explore the numerous and various behaviours, and then to use the high complexity chaotic regimes for optical data encryption. After a brief review of the different setups and principles, we will report on 4 different optoelectronics realizations developed in our group, emphasizing on the characteric properties of each setup, and their implementation in chaos-based secure communication systems.