Slow propagation of 2 GHz acoustical waves in a suspended GaAs on insulator phononic waveguide

TL;DR

This paper demonstrates slow 2 GHz acoustic wave propagation in a GaAs/Si phononic waveguide, enabling potential on-chip delay lines for improved opto-acoustic device stability and miniaturization.

Contribution

It experimentally shows slow group velocity of 2 GHz acoustic waves in a GaAs membrane, paving the way for integrated delay lines in opto-acoustic systems.

Findings

Group velocity below 1000 m/s achieved

Filtering of 2 GHz acoustic waves demonstrated

Potential for on-chip delay lines established

Abstract

Optoelectronic oscillators have dominated the scene of microwave oscillators in the last few years thanks to their great performances regarding frequency stability and phase noise. However, miniaturization of such a device is an up to date challenge. Recently, devices based on phonon-photon interaction gather a lot of interest thanks to their extreme compactness and working frequency directly in the GHz. In this frame, a still missing element to obtain long-term frequency stability performances is an on-chip delay within the feedback loop. Here, we experimentally show filtering and slow propagation of 2 GHz acoustic waves on a Gallium Arsenide membrane heterogeneously integrated on silicon wafer. By engineering the dispersion of an acoustical waveguide, we evidence a group velocity below 1000 m/s for the mode able to propagate. Thus, an integrated delay implementation is at reach for potential improvement of opto-acoustic devices such as optomechanical oscillators or wireless applications.