Electrical Driving of Gigahertz Phonons in Nanophotonic Systems

We demonstrate electrical excitation and optical detection of a gigahertz mechanical mode of a silicon photonic wire. The scheme can be implemented in any material. It paves the way for efficient hybrid electro-opto-mechanical systems.

Reducing energy dissipation is a central goal of classical and quantum technologies. Optics achieved great success in bringing down power consumption of long-distance communication links. With the rise of mobile, quantum and cloud technologies, it is essential to extend this success to shorter links. Electro-optic modulators are a crucial contributor of dissipation in such links. Numerous variations on important mechanisms such as free-carrier modulation and the Pockels effect are currently pursued, but there are few investigations of mechanical motion as an electro-optic mechanism in silicon.

In this work, we demonstrate electrical driving and optical read-out of a 7.2 GHz mechanical mode of a silicon photonic waveguide. The electrical driving is capacitive and is not restricted to piezoelectric materials. The measurements show that the mechanically-mediated optical phase modulation is two orders of magnitude more efficient than the background phase modulation in our system. This is indicative of the potential of mechanical devices to reduce the power consumption of existing electro-optic interfaces. The approach forms a potent route to low-energy non-reciprocal acousto-optic modulation and beam-steering systems. It also paves the way for phonon-mediated connectivity in emerging quantum networks consisting of superconducting microwave circuits, color centers and nanophotonic devices.