Analytical models for coated plasmonic particles: Effects of shape and size-corrected dielectric function

Area of Science:

• Plasmonics
• Computational electromagnetics
• Nanophotonics

Background:

• Modal expansion methods (MEMs) are established for predicting plasmonic particle optical properties.
• The impact of size-corrected dielectric functions on MEM accuracy for diverse plasmonic nanostructures is not well understood.

Purpose of the Study:

• To evaluate the accuracy of MEMs when using size-corrected dielectric functions for various plasmonic particle shapes.
• To identify limitations of MEMs concerning particle geometry and dielectric properties.

Main Methods:

• Comparison of numerical and analytical extinction and scattering spectra.
• Utilized bulk and size-corrected dielectric functions.
• Investigated various particle geometries: rods, disks, prisms, bicones, and bipyramids.

Main Results:

• Size correction broadens and reduces plasmonic peaks.
• MEM accuracy is preserved for most shapes (rods, disks, prisms, bipyramids) with size-corrected functions.
• MEM fails for sharp bicones due to strong field localization at tips, but performs well for realistic bicones with tip curvature.

Conclusions:

• MEMs remain accurate for most plasmonic nanostructures even with size-corrected dielectric functions.
• Sharp-tipped geometries like bicones present challenges for MEMs, necessitating realistic modeling with tip curvature.
• The study validates MEMs for practical plasmonic nanostructure design, highlighting the importance of geometric considerations.