Unpredictability-enhanced broadband chaotic signal generation based on vertical-cavity surface-emitting lasers subject to dual chaotic optical injection

Based on a slave vertical-cavity surface-emitting laser (S-VCSEL) simultaneously driven by dual chaotic optical injection (DCOI) from two master VCSELs (M-VCSELs) with double optical feedback (DOF), an unpredictability-enhanced broadband chaotic signal generation scheme is proposed and numerically investigated. The unpredictability degree (UD) and bandwidth of chaotic signals are evaluated by the peak value (σ) of self-correlation function (SF) at the feedback time and the effective bandwidth (EBW), respectively. The results show that, M-VCSEL with DOF can generate chaos signals with lower time delay signature (TDS) than that with single optical feedback (SOF). Under suitable injection strength and frequency detuning, both two orthogonal polarization components (X-PC and Y-PC) of the S-VCSEL can be driven to generate unpredictability-enhanced broadband chaotic signals with suppressed TDS (σ < 0.1) and wide EBW (EBW < 50GHz). Moreover, a relatively large parameter space to achieve this high-quality chaos signals can be determined.