The Blackett Laboratory, Department of Physics, Imperial College London, London SW7 2AZ, United Kingdom.
CAPES Foundation, Ministry of Education of Brazil, Brasília, DF 70040-020, Brazil.
Phys Rev Lett. 2018 Dec 21;121(25):253902. doi: 10.1103/PhysRevLett.121.253902.
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.
小金屬粒子的光學特性使我們能夠彌合無數次亞衍射局部現象和宏觀光學元件之間的差距。金納米粒子的機械振動與集體電子振蕩引起的光學響應之間的光機耦合導致單一金屬納米天線發射和檢測表面聲波 (SAW)。我們採用兩個 Au 納米粒子，一個作為 SAW 的源，另一個作為 SAW 的接收器，即使這些天線之間的距離比振動的特徵次納米位移大幾個數量級，我們也可以探測源自源的相干機械模式阻尼的 SAW 的頻率內容、波速和振幅衰減。雙色泵浦探測實驗和數值方法揭示了發射 SAW 的典型瑞利波行為，並表明接收器天線感應 SAW 引起的光學調制使我們能夠精確探測源的頻率，即使源和接收器的本徵模失諧。
