Buckling-induced transmission switching in phononic waveguides in the presence of disorder

TL;DR

This paper demonstrates how buckling in MEMS phononic waveguides can induce transmission switching by amplifying disorder effects, leading to mode localization and breaking periodicity, which is crucial for signal control in phononic circuits.

Contribution

The study introduces a reduced-order model showing buckling-induced disorder amplification causes transmission switching in disordered phononic waveguides, a phenomenon not captured by traditional Bloch analysis.

Findings

Buckling amplifies structural disorder effects.

Disorder causes localization of waveguide modes.

Transmission can be switched via buckling-induced disorder.

Abstract

On-chip phononic circuits tailor the transmission of elastic waves, which can couple to electronic and photonic systems, enabling new signal manipulation capabilities. Phononic circuits rely on waveguides that transmit elastic waves within desired frequency passbands, typically designed based on the Bloch modes of the waveguide constitutive cell, assuming linearity and periodicity. MEMS waveguides composed of coupled drumhead (membrane) resonators offer tunable MHz operation frequencies for applications in nonlinear optomechanics, topological insulators, phononic cavities, and acoustic switching. Here, we construct a reduced-order model (ROM) to demonstrate the switching of signal transmission in drumhead-resonator waveguides due to thermoelastic buckling. The ROM shows that buckling amplifies existing structural disorders, breaking the periodicity required for waveguide transmission through the first passband. This periodicity breaking manifests in the localization of the first-passband modes, like classical Anderson localization caused by disorders. The proposed ROM is essential to study the investigated phenomena since Bloch mode analysis fails for weakly-disordered (< 5%) finite waveguides due to the disorder amplification caused by the thermoelastic buckling. The illustrated transmission control should be useful for logical acoustic operations, like switching, and can be extended to 2D circuits in the future.