Chiral Coupling‐Enabled Optical Nonreciprocity in a Cavity Magnomechanical System

Abstract Nonreciprocal optical responses are investigated, induced by the chiral coupling in a cavity magnomechanical system, which contains a ring resonator and an yttrium iron garnet disk. Benefiting from the chiral magnon‐photon coupling, the signal from different directions can exhibit different optical responses for bistability, transmission, group delay, and quantum noise. Notably, optical nonreciprocity with isolation up to 30 dB can be realized based on chiral‐induced the breaking of Lorentzian reciprocity. Moreover, the introduction of magnon modes can achieve directional conversion between fast light and slow light, resulting in that direction‐dependent nonreciprocal fast‐slow light effect can also be achieved utilizing magnetic devices with chirality. At the same time, the nonreciprocal coexistence range of fast light and slow light can also be efficiently broadened by chiral magnon‐photon coupling strength. Furthermore, it can be observed that the quantum noise spectrum of the system is robust to temperature, even at 50 mK. This study not only reveals the important role of chiral coupling in the optical nonreciprocity, but also provides an efficient method for the development of optical nonreciprocal devices.