Compact Bends and Low-Loss Junctions for S0 Lamb Modes in Fully Etched Scandium Aluminum Nitride Acoustic Waveguides

This work demonstrates the use of focusing interdigitated transducers (FIDTs) to generate confined S0 Lamb modes, in which they are captured and routed by acoustic waveguides. The waveguides demonstrate acoustic delay lines (ADLs) with 90-degree bends in suspended 30% scandium aluminum nitride (ScAlN) and allow for the characterization of bending losses across various waveguide widths. This work demonstrates that the spatial manipulation of acoustic waves can facilitate the realization of more intricate phononic integrated circuits (PnICs) through the first implementation of a wavelength-scale low-loss Y-junction. These junctions are used for the application of a splitter and combiner in a suspended piezoelectric platform.

INTRODUCTION

The advancement of micro- and nano-fabrication techniques combined with the use of acoustic wave devices using piezoelectric films has sparked the study of phonons with other degrees of freedom in the classical and quantum regimes [1]. Wavelength scale phononic confinement in the gigahertz regime has remained relatively undeveloped until recent investigations of concurrent photon and phonon confinement in 2D- and 3D-systems [2]. This has generated interest in the analogy between photonic devices and phononic devices.