Controlling phonons and photons at the wavelength-scale: silicon photonics meets silicon phononics

TL;DR

This review explores the integration of phononic and photonic circuits at the wavelength scale using silicon technology, highlighting advances, applications, and future challenges in scalable optomechanical systems.

Contribution

It provides a comprehensive overview of the physics, state-of-the-art nanoscale silicon-based electro- and optomechanical systems, and discusses future potential and challenges in the field.

Findings

Silicon-based nanoscale optomechanical systems enable efficient photon-phonon interactions.

Hybrid electro-optomechanical devices show promise for quantum and classical signal processing.

Scalable fabrication techniques are advancing the development of integrated phononic and photonic circuits.

Abstract

Radio-frequency communication systems have long used bulk- and surface-acoustic-wave devices supporting ultrasonic mechanical waves to manipulate and sense signals. These devices have greatly improved our ability to process microwaves by interfacing them to orders-of-magnitude slower and lower loss mechanical fields. In parallel, long-distance communications have been dominated by low-loss infrared optical photons. As electrical signal processing and transmission approaches physical limits imposed by energy dissipation, optical links are now being actively considered for mobile and cloud technologies. Thus there is a strong driver for wavelength-scale mechanical wave or "phononic" circuitry fabricated by scalable semiconductor processes. With the advent of these circuits, new micro- and nanostructures that combine electrical, optical and mechanical elements have emerged. In these devices, such as optomechanical waveguides and resonators, optical photons and gigahertz phonons are ideally matched to one another as both have wavelengths on the order of micrometers. The development of phononic circuits has thus emerged as a vibrant field of research pursued for optical signal processing and sensing applications as well as emerging quantum technologies. In this review, we discuss the key physics and figures of merit underpinning this field. We also summarize the state of the art in nanoscale electro- and optomechanical systems with a focus on scalable platforms such as silicon. Finally, we give perspectives on what these new systems may bring and what challenges they face in the coming years. In particular, we believe hybrid electro- and optomechanical devices incorporating highly coherent and compact mechanical elements on a chip have significant untapped potential for electro-optic modulation, quantum microwave-to-optical photon conversion, sensing and microwave signal processing.