Vectorial chaos synchronization and polarization encoding in self-pulsating VCSELs

This study shows that self-pulsating vertical-cavity surface emitting lasers (VCSELs) can exhibit vectorial chaos, i.e. chaos in both intensity and polarization. A novel information encoding scheme is also proposed, where the phase of the vectorial field is modulated while the average total intensity is kept constant, exploiting the polarization degree of freedom. This scheme represents a possible generalization of the previously developed chaos shift keying (CSK) encryption systems. In this approach, the total intensity of the two VCSELs remains synchronized while the intensities in the polarization modes (de)synchronize following the phase modulation. The message can be recovered by detecting the two linearly polarized components of the outcoming field. Previous CSK systems were limited by the relaxation oscillation frequency, while this technique allows, in principles, for transmission of secure data at bit-rates attaining 100 Gbit/sec, since the mean synchronization time is about 1.3 ps.