Sub-optical wavelength acoustic wave modulation of integrated photonic resonators at microwave frequencies

TL;DR

This paper demonstrates sub-optical wavelength acoustic wave modulation at microwave frequencies in integrated photonic resonators, enabling efficient acousto-optic interactions with potential applications in microwave photonics and quantum optomechanics.

Contribution

It introduces a novel acousto-optic platform with nanoscale transducers on piezoelectric substrates achieving high-frequency modulation with sub-optical wavelength acoustic waves.

Findings

Achieved acousto-optic modulation above 10 GHz.

Demonstrated acoustic wavelength significantly below optical wavelength.

Investigated phase and modal matching for efficient modulation.

Abstract

Light-sound interactions have long been exploited in various acousto-optic devices based on bulk crystalline materials. Conventionally these devices operate in megahertz frequency range where the acoustic wavelength is much longer than the optical wavelength and a long interaction length is required to attain significant coupling. With nanoscale transducers, acoustic waves with sub-optical wavelengths can now be excited to induce strong acousto-optic coupling in nanophotonic devices. Here we demonstrate microwave frequency surface acoustic wave transducers co-integrated with nanophotonic resonators on piezoelectric aluminum nitride substrates. Acousto-optic modulation of the resonance modes at above 10 GHz with the acoustic wavelength significantly below the optical wavelength is achieved. The phase and modal matching conditions in this scheme are investigated for efficient modulation. The new acousto-optic platform can lead to novel optical devices based on nonlinear Brillouin processes and provides a direct, wideband link between optical and microwave photons for microwave photonics and quantum optomechanics.