Electrostatic actuation of microwave phonons in a two-dimensional optomechanical crystal

Microwave-to-optical quantum transducers are essential for future quantum networks, enabling remote connections through optical links. An ideal quantum transducer features high quantum efficiency and low added noise. The electro-optomechanical approach on one-dimensional optomechanical crystals (1D OMCs) has stood out in terms of high coupling rate and monolithic integration. However, optical absorption-induced thermal noise is a dominant limiting factor. Two-dimensional (2D) OMCs have been used to address this issue by increasing the thermal anchoring to the substrate, recently demonstrating low noise photon-phonon conversion. However, these devices have so far realized on higher mechanical frequencies (∼10 GHz), where interfacing with piezoelectric components is challenging, thus precluding the development of a full electro-optomechanical transducer. In this work, we demonstrate microwave-to-optics transduction on a 2D silicon OMC. To achieve this, we develop a novel phononic crystal design to lower the mechanical resonance frequency (∼7.5 GHz) and use capacitive actuation via an electrostatic field as an alternative to piezoelectricity. We present room-temperature characterization of the device and discuss future avenues for the development of efficient and low-noise cryogenic quantum transducers.