Adiabatic conversion between gigahertz quasi-Rayleigh and quasi-Love modes for phononic integrated circuits

TL;DR

This paper introduces a high-efficiency, robust adiabatic phononic mode converter that achieves over 98% conversion efficiency between gigahertz quasi-Rayleigh and quasi-Love modes using a tapered waveguide, enhancing on-chip acoustic processing.

Contribution

It proposes a novel adiabatic mode converter based on anisotropic elastic properties, significantly improving conversion efficiency and fabrication tolerance for phononic integrated circuits.

Findings

Conversion efficiency exceeds 98%.

Bandwidth of 1.7 GHz demonstrated.

Numerical validation shows high fabrication tolerance.

Abstract

Unsuspended phononic integrated circuits have been proposed for on-chip acoustic information processing. Limited by the operation mechanism of a conventional interdigital transducer, the excitation of the quasi-Love mode in GaN-on-Sapphire is inefficient and thus a high-efficiency Rayleigh-to-Love mode converter is of great significance for future integrated phononic devices. Here, we propose a high-efficiency and robust phononic mode converter based on an adiabatic conversion mechanism. Utilizing the anisotropic elastic property of the substrate, the adiabatic mode converter is realized by a simple tapered phononic waveguide. A conversion efficiency exceeds $98\%$ with a $3\,\mathrm{dB}$ bandwidth of $1.7\,\mathrm{GHz}$ can be realized for phononic waveguides working at GHz frequency band, and excellent tolerance to the fabrication errors is also numerically validated. The device that we proposed can be useful in both classical and quantum phononic information processing, and the adiabatic mechanism could be generalized to other phononic device designs.