Analysis of chaos generated by a modulated self-pulsating laser diode

The Lyapunov exponents and plotted bifurcation diagrams for a self-pulsating laser diode under periodic current modulation have been calculated. Different dynamics are obtained dependent on the modulation depth and frequency of the drive current. It is shown that it is very difficult to distinguish between regimes of high periodicity and true chaos. However by introducing a return map relating the pulse peak height and the inter pulse interval clear differences are observed between these regimes. This has consequences for the use of chaotic self-pulsating laser diodes for data encryption applications.