Acoustic Far-Field Hypersonic Surface Wave Detection with Single Plasmonic Nanoantennas.

Rodrigo Berte,Yi Li,Martín Poblet,Richard V Craster,Emiliano Cortés,Fabricio Della Picca,Andrea V Bragas,Stefan A Maier

doi:10.1103/physrevlett.121.253902

Abstract

The optical properties of small metallic particles allow us to bridge the gap between the myriad of subdiffraction local phenomena and macroscopic optical elements. The optomechanical coupling between mechanical vibrations of Au nanoparticles and their optical response due to collective electronic oscillations leads to the emission and the detection of surface acoustic waves (SAWs) by single metallic nanoantennas. We take two Au nanoparticles, one acting as a source and the other as a receptor of SAWs and, even though these antennas are separated by distances orders of magnitude larger than the characteristic subnanometric displacements of vibrations, we probe the frequency content, wave speed, and amplitude decay of SAWs originating from the damping of coherent mechanical modes of the source. Two-color pump-probe experiments and numerical methods reveal the characteristic Rayleigh wave behavior of emitted SAWs, and show that the SAW-induced optical modulation of the receptor antenna allows us to accurately probe the frequency of the source, even when the eigenmodes of source and receptor are detuned.

Highlights

The optomechanical coupling between mechanical vibrations of Au nanoparticles and their optical response due to collective electronic oscillations leads to the emission and the detection of surface acoustic waves (SAWs) by single metallic nanoantennas
We take two Au nanoparticles, one acting as a source and the other as a receptor of SAWs and, even though these antennas are separated by distances orders of magnitude larger than the characteristic sub-nanometric displacements of vibrations, we probe the frequency content, wave speed and amplitude decay of SAWs originating from the damping of coherent mechanical modes of the source
The damping through the coupling of nanostructures to the substrate has been shown to lead to the emission of surface acoustic waves (SAWs) which have been successfully obtained in nanowires [17] and in periodic arrays of plasmonic nanoantennas [19,20,21]

Summary

Introduction

We take two Au nanoparticles, one acting as a source and the other as a receptor of SAWs and, even though these antennas are separated by distances orders of magnitude larger than the characteristic sub-nanometric displacements of vibrations, we probe the frequency content, wave speed and amplitude decay of SAWs originating from the damping of coherent mechanical modes of the source. The damping through the coupling of nanostructures to the substrate has been shown to lead to the emission of surface acoustic waves (SAWs) which have been successfully obtained in nanowires [17] and in periodic arrays of plasmonic nanoantennas [19,20,21].

Results

Conclusion