Visualization of Acoustic Power Flow in Suspended Thin-film Lithium Niobate Phononic Devices

TL;DR

This paper presents a method to directly visualize and analyze gigahertz acoustic waves in lithium niobate phononic circuits, providing detailed insights into their propagation and attenuation for improved device design.

Contribution

It introduces transmission-mode microwave impedance microscopy for visualizing and quantifying acoustic wave propagation in thin-film lithium niobate devices, including power flow and loss analysis.

Findings

Measured propagation parameters such as PFA and PL.

Separated forward and backward waves using FFT.

Quantified attenuation and diffraction effects.

Abstract

We report direct visualization of gigahertz-frequency acoustic waves in lithium niobate phononic circuits. Primary propagation parameters, such as the power flow angle (PFA) and propagation loss (PL), are measured by transmission-mode microwave impedance microscopy (TMIM). Using fast Fourier transform, we can separately analyze forward and backward propagating waves and quantitatively evaluate the propagation loss. Our work provides insightful information on the propagation, diffraction, and attenuation in piezoelectric thin films, which is highly desirable for designing and optimizing phononic devices for microwave signal processing.