Triply resonant cavity electro-optomechanics at X-band

Optomechanical microcavities with high-frequency mechanical resonances facilitate experimental access to mechanical states with low phonon occupation and also hold promise for practical device applications including compact microwave sources. However, the weak radiation pressure force poses practical limits on achievable amplitudes at super high frequencies. Here, we demonstrate a piezoelectric force enhanced microcavity system that simultaneously supports microwave, optical and mechanical resonant modes. The combination of the highly sensitive optical readout and resonantly enhanced strong piezoelectric actuation enables us to build a microwave oscillator with excellent phase noise performance, which pushes the micromechanical signal source into microwave X-band.