Flexural Cavity Mechanics in Electrostatically Driven 1D Phononic Crystal

TL;DR

This paper demonstrates high-quality 1D phononic crystal resonators with electrostatic transduction, showing mode degeneracy enhances quality factors and offers potential for low-loss sensing and signal processing devices.

Contribution

It introduces a method to achieve high-Q 1D phononic resonators using electrostatic transduction within a phononic crystal, highlighting mode degeneracy effects.

Findings

Degenerate flexural modes exhibit high and comparable quality factors.

The in-phase mode inside the bandgap shows doubled quality factor.

Enhancement diminishes for out-phase mode outside the bandgap at low temperatures.

Abstract

Phononic Crystals provide a versatile platform for controlling phonons in applications such as waveguiding, filtering, and sensing. To minimize dissipation, cavity resonators are often embedded within the bandgap of phononic crystals and integrated with suitable transduction techniques. Here, we demonstrate one-dimensional (1D) phononic transmission using electrostatic transduction, enabling the realization of high-quality mechanical oscillators. Using a double-ended tuning fork resonator embedded in a 1D phononic crystal, we observe degenerate flexural modes (in-phase and out-phase) exhibiting enhanced and comparable quality factors within the same device due to mode degeneracy. The in-phase mode, whose frequency lies inside the phononic bandgap, shows an approximately two-fold increase in quality factor compared to an anchored resonator, while this enhancement diminishes for the out-phase mode (frequency outside the bandgap) at temperatures where thermoelastic dissipation is negligible. This approach offers a promising route toward low-loss, encapsulated phononic devices for sensing and signal processing applications.