Optomechanical generation of coherent GHz vibrations in a phononic waveguide

TL;DR

This paper demonstrates the optomechanical generation of coherent GHz vibrations in a CMOS-compatible silicon phononic crystal cavity, enabling efficient phonon control and potential applications in phononic circuitry.

Contribution

It introduces a novel optomechanical platform using a suspended 2D silicon phononic crystal with an air-slot for coherent GHz phonon generation.

Findings

Achieved coherent phonon generation at 6.8 GHz

Demonstrated mechanical lasing in a CMOS-compatible system

Controlled phonons via localized photonic modes

Abstract

Nanophononics has the potential for information transfer, in an analogous manner to its photonic and electronic counterparts. The adoption of phononic systems has been limited, due to difficulties associated with the generation, manipulation, and detection of phonons, especially at GHz frequencies. Existing techniques often require piezoelectric materials with an external radiofrequency excitation that are not readily integrated into existing CMOS infrastructures, while non-piezoelectric demonstrations have been inefficient. In this work, we explore the optomechanical generation of coherent phonons in a suspended 2D silicon phononic crystal cavity with a guided mode around 6.8 GHz. By incorporating an air-slot into this cavity, we turn the phononic waveguide into an optomechanical platform that exploits localized photonic modes resulting from inherent fabrication imperfections for the transduction of mechanics. Such a platform exhibits very fine control of phonons using light, and is capable of coherent self-sustained phonon generation via mechanical lasing around 6.8 GHz. The ability to generate high frequency coherent mechanical vibrations within such a simple 2D CMOS-compatible system could be a first step towards the development of sources in phononic circuitry and the coherent manipulation of other solid-state properties.