Leveraging Non-linearities near Exceptional Points in Coupled Opto-Electronic Oscillators for RF Sensing

We present experimental and theoretical investigations of two time-delay coupled optoelectronic oscillators with emphasis on a variety of distinct operating regimes that are not present in solitary oscillators. Through analytic methods, we characterize oscillation threshold, fold bifurcations, and exceptional points that mark the boundaries of various operating regimes. Furthermore, we identify critical points that denote the intersections of threshold and the exceptional point lines. The critical points indicate an abrupt frequency splitting and a singularity in sensitivity to external perturbations. The fold bifurcations characterize a high-power second attractor state. Hysteresis as a function of the round-trip gains is reported. To probe radio frequency sensing applications, we inject a radio frequency signal and observe a transition from the off state to the second attractor, with a 72-dB power ratio between the output and the injected signal. Results open a field of study in non-Hermitian, nonlinear time delay systems and provide a potential platform for optically integrated computing.