Mapping gigahertz vibrations in a plasmonic–phononic crystal

Abstract

We image the gigahertz vibrational modes of a plasmonic-phononic crystal at sub-micron resolution by means of an ultrafast optical technique, using a triangular array of spherical gold nanovoids as a sample. Light is strongly coupled to the plasmonic modes, which interact with the gigahertz phonons by a process akin to surface-enhanced stimulated Brillouin scattering. A marked enhancement in the observed optical reflectivity change at the centre of a void on phononic resonance is likely to be caused by this mechanism. By comparison with numerical simulations of the vibrational field, we identify resonant breathing deformations of the voids and elucidate the corresponding mode shapes. We thus establish scanned optomechanical probing of periodic plasmonic-phononic structures as a new means of investigating their coupled excitations on the nanoscale.

Nanoscale pillar hypersonic surface phononic crystals

“…Very recently, however, there has been a growing interest in hypersonic phononic crystals, exhibiting features at the submicron scale that allow the manipulation of acoustic phonons at GHz to THz frequencies. Such structures will find utility in future broadband wireless communications and also optomechanic and plasmonic coupling in micro-and nanostructures [21][22][23][24][25][26][27] in the GHz regime and potentially even manipulation of thermal phonons (heat) for engineering thermal conductivity and other thermoelectric properties of materials for energy harvesting applications as the THz regime becomes accessible [28][29][30][31]. If it is possible to overcome the current 1-GHz frequency ceiling in acoustically driven microfluidics [32,33], then it should be possible to achieve nanofluidic actuation facilitating biomolecular manipulation and sensing at single cell and even single molecule levels.…”

Ultrafast acousto-plasmonic control and sensing in complex nanostructures

“…Plasmons are effective for localizing light in a subwavelength volume and are ideal candidates for manipulating nanoscale mechanical motion because of their large absorption cross-sections, subwavelength field localization and high sensitivity to geometry and refractive index changes. This efficient absorption makes the plasmon an effective transducer of far-field radiation into phonons 5 : the plasmonic nanostructure absorbs energy from the laser pulse and rapidly expands, generating coherent acoustic phonons through impulsive thermal excitation [11][12][13][14] . When a metallic nanostructure first absorbs an ultrashort laser pulse, a localized surface plasmon, a coherent oscillation of electrons, is excited.…”

Phonon interaction with coupled photonic-plasmonic modes in a phoxonic cavity

“…30,31 Besides, the coupling of localized plasmons with the mechanical oscillations of nanoparticles of various shapes have been extensively investigated (see Ref. 32 for a list of references), in general by pump-probe experiments [33][34][35][36] or by Raman scattering. [37][38][39] In a recent work 32 we extended such an investigation to Au nanoparticles separated from a Au film by a thin dielectric.…”