Quantitative optical imaging method for surface acoustic waves using optical path modulation

TL;DR

This paper introduces a simple optical method to quantitatively measure surface acoustic waves by detecting optical path modulation, enabling precise analysis of wave amplitude and surface displacement in SAW research.

Contribution

The authors develop a straightforward optical measurement technique for surface acoustic waves that simplifies and improves the quantification process compared to existing methods.

Findings

Successfully demonstrated optical detection of SAW surface slope and displacement.

Operates effectively in shot-noise-limited regime for high precision.

Provides a practical tool for SAW-related research and applications.

Abstract

A Rayleigh-type surface acoustic wave (SAW) is used in various fields as classical and quantum information carriers because of its surface localization, high electrical controllability, and low propagation loss. Coupling and hybridization between the SAW and other physical systems such as magnetization, electron charge, and electron spin are the recent focuses in phononics and spintronics. A precise measurement of the surface wave amplitude is often necessary to discuss the coupling strengths. However, there are only a few such measurement techniques and they generally require a rather complex analysis. Here we develop and demonstrate a straightforward measurement technique that can quantitatively characterize the SAW. The technique optically detects the surface waving due to the coherently driven SAW by the optical path modulation. Furthermore, when the measurement system operates in the shot-noise-limited regime, the surface slope and displacement at the optical spot can be deduced from the optical path modulation signal. Our demonstrated technique will be an important tool for SAW-related research.