Surface Acoustic Waves (SAWs) are surface-confined elastic oscillations that are of great interest because of their high sensitivity to the mechanical properties of the material in which they propagate. Their penetration depth corresponds to a fraction of the wavelength of excitation, making SAWs an appealing tool for studying the properties of thin films, including interface properties and the mechanical response of nanostructures deposited on, or embedded within, the surface. Studying nanostructured samples of ever decreasing size requires generating and detecting highly surface-confined SAWs with correspondingly short wavelengths, making coherent high harmonic beams an ideal tool. In recent work we probed the shortest wavelength surface acoustic waves to date, demonstrating sensitivity to picometer surface displacements, and films as thin as 2 nm.
Nanoscale high-frequency acoustics for advanced metrologies