Synchronization Driven Reciprocity Breaking

Wave transmission reciprocity is broken by exploiting the synchronization of two coupled self-oscillators. The underlying principle is that illumination from one port drives the in phase, while illumination from the other port drives the antiphase synchronization state. Because of its self-adjustment the system is operationally stable. An experimental demonstration with aeroacoustic cavities is presented. They behave as weakly nonlinear limit cycles when driven by a constant airflow, leading to self-oscillations that can couple to the surrounding waveguides via two ports. Incident waves from one port trigger antiphase synchronization, causing destructive interference and low transmission, while waves from the opposite port induce in-phase synchronization, resulting in high transmission. This directional dependence effectively breaks reciprocity, where the operational bandwidth is defined by the synchronization region and can be broader than resonance-based methods. Experimental results show robust nonreciprocal behavior with respect to parameter changes. Moreover, a modified temporal coupled mode theory is proposed, explaining the system's nonlinear dynamics and scattering properties in a quantitative manner. This synchronization-based approach offers a new avenue for directional wave control, complementing traditional reciprocity breaking techniques and offering an intrinsic loss compensation emanating from the self-oscillation of meta-atoms.