Metasurfaces with Enhanced Optomechanical Coupling through the Colocalization of Plasmonic and Acoustic Fields

Area of Science:

• Acousto-optics
• Plasmonics
• Nanophotonics
• Materials Science

Background:

• Plasmons enhance light scattering with molecular vibrations, enabling sensitive detection and optomechanical studies.
• Plasmon-enhanced optomechanical coupling of gigahertz (GHz) acoustic waves is crucial for signal processing and sensing but remains underexplored.

Purpose of the Study:

• To present an acoustoplasmonic metasurface enabling enhanced optomechanical coupling.
• To demonstrate colocalization of plasmons and GHz acoustic phonons within the metasurface.
• To explore plasmonic enhancement of the moving interface effect for GHz acoustic waves.

Main Methods:

• Fabrication of an acoustoplasmonic metasurface using a gold layer patterned with nanoholes on a silicon wafer.
• Momentum-resolved Brillouin light scattering experiments at two wavelengths (on- and off-resonance with plasmons).
• Finite-element-method (FEM) optomechanical calculations to analyze mode colocalization and coupling.

Main Results:

• Demonstrated colocalization of plasmonic hot spots and GHz acoustic modes within the nanoholes of the metasurface.
• Observed plasmonic enhancement of the moving interface effect due to the colocalized modes.
• Confirmed the metasurface's ability to couple plasmons and GHz acoustic phonons.

Conclusions:

• The acoustoplasmonic metasurface effectively enhances optomechanical coupling by colocalizing plasmons and GHz acoustic phonons.
• This approach offers a pathway for developing novel plasmon-enhanced optomechanical sensors and modulators operating at GHz frequencies.
• The findings open new avenues for manipulating acoustic waves with light at the nanoscale.