Interparticle gap geometry effects on chiroptical properties of plasmonic nanoparticle assemblies

Area of Science:

• Plasmonics
• Nanophotonics
• Chiroptics

Background:

• Chiral plasmonic nanoparticles exhibit optical activity but often suffer from low asymmetry factors.
• A deeper understanding of structure-property relationships is crucial for designing effective chiral optical responses.

Purpose of the Study:

• Investigate the impact of large interparticle gaps in chiral linear nanoparticle assemblies on chiroptical properties.
• Utilize a tetrahelix structure composed of gold (Au) tetrahedra to explore these effects.

Main Methods:

• Employ finite-difference time-domain (FDTD) and finite element methods (FEM) for detailed analysis.
• Evaluate extinction spectra and electric field distributions within the tetrahelix structure.
• Systematically vary geometric parameters to understand their influence.

Main Results:

• The tetrahelix structure supports multiple plasmonic modes.
• A specific plasmonic mode demonstrates strong incident light handedness selectivity.
• This selectivity is linked to the presence of large face-to-face junctions between nanoparticles.

Conclusions:

• Gap engineering in chiral plasmonic assemblies is critical for achieving asymmetry factors (g-factors) greater than 1.
• The findings pave the way for designing chiral nanostructures with tailored handedness-selective optical responses.