Conceal Time-Delay Signature of Mutually Coupled Vertical-Cavity Surface-Emitting Lasers by Variable Polarization Optical Injection

In this letter, we quantitatively investigate the time-delay (TD) signature of chaotic outputs generated by mutually coupled vertical-cavity surface-emitting lasers (VCSELs) with variable polarization optical injection (VPOI). The research is performed using a novel estimator, which calculates the peak-to-mean ratio on the basis of the autocorrelation function (ACF). It is shown that the TD signature of mutually coupled VCSELs with VPOI at intermediate polarizer angles can be better concealed than that of mutually coupled VCSELs with conventional polarization-selected optical injection. The effects of bias current and injection delay are also taken into account. The system is further discussed by applying a recent approach that computes the ACF from a phase of chaotic outputs.