Acousto-optic modulation of a photonic crystal nanocavity with Lamb waves in microwave K band

TL;DR

This paper demonstrates high-frequency acousto-optic modulation in a photonic crystal nanocavity using Lamb waves up to 19 GHz in the microwave K band, enabling efficient and scalable optomechanical devices.

Contribution

It introduces a novel acousto-optic modulation platform using Lamb waves in a suspended aluminum nitride membrane with nanoscale interdigital transducers.

Findings

Achieved acousto-optic modulation at 19 GHz in microwave K band.

Enhanced modulation efficiency compared to surface acoustic wave devices.

Established a scalable platform for strong photon-phonon coupling.

Abstract

Integrating nanoscale electromechanical transducers and nanophotonic devices potentially can enable new acousto-optic devices to reach unprecedented high frequencies and modulation efficiency. Here, we demonstrate acousto-optic modulation of a photonic crystal nanocavity using Lamb waves with frequency up to 19 GHz, reaching the microwave K band. The devices are fabricated in suspended aluminum nitride membrane. Excitation of acoustic waves is achieved with interdigital transducers with periods as small as 300 nm. Confining both acoustic wave and optical wave within the thickness of the membrane leads to improved acousto-optic modulation efficiency in the new devices than that obtained in previous surface acoustic wave devices. Our system demonstrates a novel scalable optomechanical platform where strong acousto-optic coupling between cavity-confined photons and high frequency traveling phonons can be explored.