Acoustic Coupling between Plasmonic Nanoantennas: Detection and Directionality of Surface Acoustic Waves

Abstract

Hypersound waves can be efficient mediators between optical signals at the nanoscale. Having phase velocities several orders of magnitude lower than the speed of light, they propagate with much shorter wavelengths and can be controlled, directed, and even focused in a very small region of space. This work shows how two optical nanoantennas can be coupled through an acoustic wave that propagates with a certain directionality. An "emitter" antenna is first optically excited to generate acoustic coherent phonons that launch surface acoustic waves through the underlying substrate. These waves travel until they are mechanically detected by a "receiver" nanoantenna whose oscillation produces a detectable optical signal. Generation and detection are studied in detail, and new designs are proposed to improve the directionality of the hypersonic surface acoustic wave.

Optomechanical Hot-Spots in Metallic Nanorod–Polymer Nanocomposites

“…More recent efforts are concentrated on the effect of dynamical morphological changes on plasmons, which can be induced, for instance, with confined acoustic vibrations in the gigahertz (GHz) frequency range . The emerging field of acousto-plasmonics aims to exploit acoustic vibrations and plasmons for sensing and signal-processing applications. − So far, plasmons were mostly utilized for efficient generation of propagating acoustic wavepackets, i.e., as efficient acoustic wave sources. , Given recent developments in all-optical generation and sensing of acoustic waves, an exciting prospect is to realize plasmonically enhanced acoustic detectors.…”

“…In this work, we have used BLS as an optomechanical probe of plasmonic and vibrational interactions between metallic NRs dispersed in a soft polymer matrix. Most acousto-plasmonic systems examined so far consisted of stiff metal-decorated surfaces hosting surface acoustic waves, , particle-on-mirror geometries, molecular-like structures on surfaces, and self-assembled colloids . Metal–soft matter nanocomposites can also be promising materials for acousto-plasmonic devices with a wide range of tunability, especially using anisotropic metal NRs.…”

“… 4 The emerging field of acousto-plasmonics aims to exploit acoustic vibrations and plasmons for sensing and signal-processing applications. 5 − 8 So far, plasmons were mostly utilized for efficient generation of propagating acoustic wavepackets, i.e., as efficient acoustic wave sources. 7 , 8 Given recent developments in all-optical generation and sensing of acoustic waves, 9 an exciting prospect is to realize plasmonically enhanced acoustic detectors.…”

Optical Metasurfaces for Energy Conversion

“…The natural step at this point is to be able to manipulate and to use SAWs generated by a triggering optical process, for example, by creating directional emission, which was achieved in ref . In this work, directionality of SAWs has been achieved first by the use of single V-shaped Au nanoantennas, and then a collection of nanoparticles made from different metals configured in a nanoscopic version of a Yagi-Uda antenna, which we can consider as being a metamolecule, was studied and numerical simulations showed the potential of such an array to generate directional SAWs.…”

Design and Simulation of Broadband Horn Nanoantennas for Nanophotonic Applications

“…The first plasmonic nanostructures were used as optical nanostructures, and since then they have been widely used to redirect light scattering and emission, as they have excellent directional light scattering properties [20]. Among the numerous applications of nanoantennas in the literature, their integration in optical chip applications [23] and [24] stands out; wireless optical nanolink [25] and [26]; biosensors [27] and [28]; nanocircuits [29], [30]; anti-reflective coating [31], solar energy harvesting [32], at the same time spectral and spatial separation of light [33] and [34]; and hydrogen detection [35].…”