Chaos Time Delay Signature Suppression Assisted by a Phased Array With Four Different Waveguide Structures

We propose and demonstrate a chaos generation scheme that conceals the time-delay signature (TDS) by injecting the output of an external-cavity semiconductor laser (ECSL) into a two-element phased array (ECSL-TPA). We consider the case of the ECSL output with obvious TDS, and evaluate the performance of the ECSL- TPA with four waveguide structures in TDS suppression. The numerical results demonstrate that the ECSL-TPA allows for desired TDS suppression in wide parameter space regardless of the waveguide structures considered. However, different TDS behavior exists for these structures, which provides guidance for future design and optimization of the proposed ECSL-TPA. Additionally, the influence of some key parameters including the injection rate, frequency detuning, laser separation ratio, pump rate, linewidth enhancement factor, and frequency offset on TDS is systematically studied. Appropriate settings of these key parameters are beneficial for TDS suppression and thus optimizing optical chaos. The phased array can be extended to include a large number of elements and thus generates multiple independent chaotic signals with indistinguishable TDS in parallel, paying the way for chaos-based applications that require independent, high-quality chaos simultaneously.