Chaos-synchronization of semiconductor laser systems in an open-loop configuration: the short cavity regime and its potential for secure communication systems

This study concentrates on the transmitter operating in the short cavity regime. Broadband chaotic dynamics of the transmitter is demonstrated with corresponding nearly "white" rf-spectra. Under these conditions, the receiver laser is synchronized, revealing a conspicuous potential for secure, broadband and multi-Gigabit-rate communication systems, which are based on chaotic carriers and chaos-synchronization. The influence of the injection current I/sub p/ and the delay time /spl tau//sub del/ on the dynamics of the transmitter laser operating in the short cavity regime is experimentally studied, in which the delay time of the optical feedback /spl tau//sub del/ is shorter than the period of the relaxation oscillation frequency of the laser /spl tau//sub ro/. It is demonstrated that for a well adjusted feedback phase and moderate I/sub p/ the bandwidth of the dynamics can be drastically enhanced compared to the results reported for lasers with longer cavities. Results show an almost "white" rf-spectra extending up to frequencies of several GHz. The bandwidth of the system increases by reducing /spl tau//sub del/ or by increasing I/sub p/, respectively. Furthermore, the autocorrelation function of the dynamics decays rapidly, indicating a strong nonlinearity in the system. These properties are crucial demands on chaotic carriers for the realization of secure communication systems based on synchronization of chaotic carriers.