Non-reciprocal frequency conversion and mode routing in a microresonator.

The transportation of photons and phonons typically obeys the principle of reciprocity. Breaking reciprocity of these bosonic excitations will enable the corresponding non-reciprocal devices, the fundamental elements in daily applications. Here, we use two optical modes and two mechanical modes in a microresonator to form a four-mode plaquette via radiation pressure force. The phase-controlled non-reciprocal routing between any two modes with completely different frequencies is demonstrated, including the routing of phonon to phonon (MHz to MHz), photon to phonon (THz to MHz) and especially photon to photon with frequency difference of around 80 THz for the first time. The non-reciprocity is derived from interference between multimodes transfer processes involving optomechanical interactions in an optomechanical resonator. It not only demonstrates the non-reciprocal routing of photons and phonons in a single resonator, but also realizes the non-reciprocal frequency conversion for photons, laying a foundation for studying directional routing in an optomechanical hybrid network.