Suppression of Chaos Time Delay Signature in a Ring Network Consisting of Three Semiconductor Lasers Coupled With Heterogeneous Delays

The properties of chaos time delay signature (TDS) in a ring network consisting of three mutually coupled semiconductor lasers (MCSLs) are investigated numerically, where heterogeneous coupling delays are proposed to obtain the TDS concealment from the intensity chaos in wide parameter regions. The evolution of the TDS patterns, which are quantified via the autocorrelation function, for a ring network with identical coupling delays as well as that with heterogeneous coupling delays is compared. By analyzing the effects of the coupling strength, frequency detuning, and injection current on the TDS, the parameter regions for successful TDS concealment are identified. It is found that the intensity chaos with a desirable TDS concealment can be generated in the proposed ring network in which the TDS is mainly affected by the injection current and coupling strength, but is not so sensitive to the frequency detuning. In particular, a larger injection current and smaller coupling strength are preferable to obtain chaos with a low TDS. Besides, the ring network with heterogeneous coupling delays allows for better TDS concealment in much wider parameter regions, compared to that with identical coupling delays, and, thus, is highly desirable for the chaos-based random bit generators.