Electro-optomechanical transduction using GHz-frequency silicon nanomechanics*

Connecting gigahertz electronics with optical fiber networks paves the foundation for high-speed communication infrastructures and future distributed quantum computation systems. Nanomechanics provides the ideal mediator that bridges the frequency gap on integrated platforms. Electro-optomechanical transducers have been realized with piezoelectric materials that not only require sophisticated nanofabrications, but also induce significant loss to phonons in the quantum regime. Here, we demonstrate an alternative approach of electro-optomechanical frequency conversion from 5-GHz microwave photons to telecom-band optical photons on the conventional monolithic silicon-on-insulator platform. The microwave input drives mechanical oscillations via the electrostatic force on a phononic crystal embedded into a charged narrow-gap capacitor, and imparts the resonance of a nanophotonic cavity by optomechanical coupling. We report a room-temperature microwave-to-optical conversion efficiency of 1.8×10^-7 and estimate a microwave cavity-enhanced single-photon conversion efficiency exceeding 50% at mili-kelvin temperatures, benefiting from the long phonon lifetime. Our work opens the path to universal frequency conversion schemes that are independent of intrinsic piezoelectric or Pockels nonlinear materials, thus facilitates efficient interconnects between state-of-the-art silicon electronics and photonics.