Tailoring chaos characteristics by cascaded optically injected semiconductor lasers

A semiconductor laser under optical injection can induce chaos in a narrow region of its operational parameter space that is inherently devoid of any time-delay signatures (TDSs). Four semiconductor lasers arranged in a cascaded optical injection configuration are employed to expand these chaotic regions and tailor the chaotic behavior for enhanced properties without the limitation of simultaneous suppression of TDS. Tailoring the operating conditions of the three stages in the cascaded optically injected semiconductor lasers enhances chaotic properties such as standard bandwidth, effective bandwidth, and spectral flatness. It is demonstrated that achieving optimal chaotic output requires operating the second optical injection stage near the Hopf bifurcation point while applying strong injection strength and high positive detuning in the third optical injection stage. The cascaded optical injection configuration induces signature-free, complex optical chaotic oscillations characterized by a standard bandwidth of 70 GHz, an effective bandwidth of 55 GHz, and a spectral flatness exceeding 0.9.