Fanoshells: nanoparticles with built-in Fano resonances

Area of Science:

• * Nanophotonics and Plasmonics
• * Materials Science
• * Optical Spectroscopy

Background:

• * Dielectric/metallic core-shell nanoparticles exhibit tunable plasmonic properties.
• * Fano resonance arises from the interference of distinct optical modes.
• * Understanding plasmon coupling is crucial for designing advanced optical materials.

Purpose of the Study:

• * To design and synthesize core-shell nanoparticles with overlapping superradiant and subradiant plasmon modes.
• * To investigate the optical response and Fano resonance in these engineered nanoparticles.
• * To model the plasmon interactions using a coupled oscillator approach.

Main Methods:

• * Fabrication of core-shell nanoparticles with SiO(2) and Au layers around a solid Au core.
• * Single-particle dark-field microspectroscopy for optical characterization.
• * Development and application of a mass-and-spring coupled oscillator model.

Main Results:

• * Achieved overlapping superradiant and subradiant plasmon modes, resulting in Fano resonance.
• * Demonstrated additional Fano resonances in nanoparticles with asymmetric cores.
• * The coupled oscillator model accurately described the observed plasmon interactions and optical response.

Conclusions:

• * Engineered core-shell nanoparticles can exhibit complex Fano resonances.
• * Asymmetric core structures offer pathways to further tailor plasmonic behavior.
• * The coupled oscillator model is a powerful tool for understanding plasmonic nanoparticle systems.