Fano resonances in plasmonic nanoparticle aggregates

Area of Science:

• Plasmonics
• Nanophotonics
• Spectroscopy

Background:

• Plasmonic nanostructures exhibit unique optical properties.
• Fano resonances arise from interference between distinct optical modes.
• Silver nanostructures are widely studied for their plasmonic behavior.

Purpose of the Study:

• Investigate the plasmonic properties of a symmetric silver sphere septamer.
• Analyze the origin of the observed Fano resonance.
• Explore the tunability of the Fano resonance by structural and environmental changes.

Main Methods:

• Numerical simulations using the plasmon hybridization approach.
• Group theory analysis to identify plasmon modes.
• Extinction spectroscopy to observe optical response.
• Systematic variation of structural parameters and surrounding dielectric permittivity.

Main Results:

• A narrow Fano resonance was observed in the extinction spectrum of the silver sphere septamer.
• The Fano resonance originates from the interference of bonding dipolar subradiant and superradiant plasmon modes of E(1u) symmetry.
• Structural symmetry breaking allowed tuning of the Fano resonance energy and shape.
• High sensitivity of the Fano resonance wavelength to the dielectric permittivity of the surrounding medium was demonstrated.

Conclusions:

• The study elucidates the origin of Fano resonance in silver sphere septamers.
• The findings highlight the potential for tuning plasmonic properties through structural modifications.
• The demonstrated high LSPR sensitivity suggests applications in chemical and biological sensing.