Electro-optic transduction in silicon via GHz-frequency nanomechanics

TL;DR

This paper demonstrates a silicon-based electro-optic transducer operating at room temperature, converting microwave signals to optical photons via GHz-frequency nanomechanics, with potential for quantum information applications.

Contribution

It introduces a silicon-on-insulator platform for GHz phonon actuation and microwave-to-optical transduction without piezoelectric materials, enabling efficient, high-bandwidth quantum interfaces.

Findings

Achieved microwave-to-optical conversion efficiency of 1.8×10⁻⁷

Operated at room temperature and atmospheric pressure

Demonstrated phase modulation with V_π = 750 mV

Abstract

Interfacing electronics with optical fiber networks is key to the long-distance transfer of classical and quantum information. Piezo-optomechanical transducers enable such interfaces by using GHz-frequency acoustic vibrations as mediators for converting microwave photons to optical photons via the combination of optomechanical and piezoelectric interactions. However, despite successful demonstrations, efficient piezo-optomechanical transduction remains out of reach due to the challenges associated with hybrid material integration and increased loss from piezoelectric materials when operating in the quantum regime. Here, we demonstrate an alternative approach in which we actuate 5-GHz phonons in a conventional silicon-on-insulator platform. In our experiment, microwave photons resonantly drive a phononic crystal oscillator via the electrostatic force realized in a charge-biased narrow-gap capacitor. The mechanical vibrations are subsequently transferred via a phonon waveguide to an optomechanical cavity, where they transform into optical photons in the sideband of a pump laser field. Operating at room temperature and atmospheric pressure, we measure a microwave-to-optical photon conversion efficiency of $1.8 \times 10^{-7}$ in a 3.3 MHz bandwidth, and demonstrate efficient phase modulation with a half-wave voltage of $V_\pi = 750 $ mV. Our results mark a stepping stone towards quantum transduction with integrated devices made from crystalline silicon, which promise efficient high-bandwidth operation, and integration with superconducting qubits. Additionally, the lack of need for piezoelectricity or other intrinsic nonlinearities makes our approach adaptable to a wide range of materials for potential applications beyond quantum technologies.