Waveguides for surface waves

We numerically model key building blocks of a phononic integrated circuit that enable phonon routing in high-acoustic-index waveguides. Our particular focus is on the gallium nitride-on-sapphire phononic platform which has recently demonstrated high acoustic confinement in its top layer without the use of suspended structures. We start with the systematic simulation of various transverse phonon modes supported in strip waveguides and ring resonators with sub-wavelength cross section. Mode confinement and quality factors of phonon modes are numerically investigated with respect to geometric parameters. A quality factor of up to 10 8 is predicted in optimized ring resonators. Next, we study the design of the phononic directional couplers and present key design parameters for achieving strong evanescent couplings between modes propagating in parallel waveguides. Last, interdigitated transducer electrodes are included in the simulation for direct excitation of a ring resonator and critical coupling between microwave input and phononic dissipation. Our work provides a comprehensive numerical characterization of phonon modes and functional phononic components in high-acoustic-index phononic circuits, which supplements previous theories and contributes to the emerging field of phononic integrated circuits.

High-acoustic-index-contrast phononic circuits: Numerical modeling

/pdf/a-review-controlling-the-propagation-of-surface-acoustic-3ier2d1031.pdf

A review: controlling the propagation of surface acoustic waves via waveguides for potential use in acoustofluidics

We numerically model key building blocks of a phononic integrated circuit that enable phonon routing in high-acoustic-index waveguides Our particular focus is on Gallium Nitride-on-sapphire phononic platform which has recently demonstrated high acoustic confinement in its top layer without the use of suspended structures We start with systematic simulation of various transverse phonon modes supported in strip waveguides and ring resonators with sub-wavelength cross-section Mode confinement and quality factors of phonon modes are numerically investigated with respect to geometric parameters Quality factor up to $10^{8}$ is predicted in optimized ring resonators We next study the design of the phononic directional couplers, and present key design parameters for achieving strong evanescent couplings between modes propagating in parallel waveguides Last, interdigitated transducer electrodes are included in the simulation for direct excitation of a ring resonator and critical coupling between microwave input and phononic dissipation Our work provides comprehensive numerical characterization of phonon modes and functional phononic components in high-acoustic-index phononic circuits, which supplements previous theories and contributes to the emerging field of phononic integrated circuits

High-acoustic-index-contrast phononic circuits: numerical modeling

Topographically guided waves in a thin plate

Ahfruct-The microwave network approach to the solution of guided acoustic wave problems was applied in Paper I to two examples of the class of flat overlay guides: the strip and the slot guides. In this paper, the methods are applied to two different rectangular ridge StNChIeS, the well-known topographic ridge guide and the newer overlay ridge guide. In contrast to the flat overlay guides, for which good analytical results were previously available, no other analytical results have been published for the ridge guides which furnish good accuracy (although excellent numerical methods have been described). In addition, little information is available elsewhere on the pseudo-Rayleigh mode of the ridge guides, which is treated here in detail, and the overlay ridge structure itself is a new one whose properties are not yet appreciated. N THE COMPANION paper [l81 , a microwave network approach was presented for the analysis of waveguides for acoustic surface waves. The philosophy underlying this new approach was discussed, the basic features of the method were presented, and the method was applied to two examples of flat overlay waveguides, the strip and the slot guides. In the present paper, this method is applied to a different class of waveguides: rectangular ridge guides. The rectangular ridge waveguides themselves are of two types: the topographic ridge guide, for which the ridge and the substrate are composed of the same material, and the overlay ridge guide, in which the ridge is comprised of a material different from that of the substrate. The two structures are shown in Figs. l(a) and l(b). Both of these ridge guides are fundamentally different from the strip and slot guides, which appear respectively in Figs. l(a) and l(b) of Paper I. In the latter two guides, thin platings are employed to perturb the Rayleigh mode of the substrate, with the result that almost all of the energy in the waveguide mode resides in the sub

Robert C. M. Li

Papers

Microwave Network Analyses of Surface Acoustic Waveguides - II. Rectangular Ridge Guides