Selective excitation of localized surface plasmons by structured light

Area of Science:

• Plasmonics
• Nanophotonics
• Computational Electromagnetics

Background:

• Localized surface plasmons (LSPs) are fundamental to plasmonics, enabling light manipulation at the nanoscale.
• Structured light offers advanced control over optical phenomena, but its application to selective LSP excitation is complex.
• Understanding mode excitation and spectral contributions is crucial for designing plasmonic devices.

Purpose of the Study:

• To investigate the selective excitation of LSPs using structured light.
• To derive group-theory-based selection rules for LSP excitation.
• To quantify the contribution of eigenmodes to absorption spectra and control optical responses.

Main Methods:

• Derivation of selection rules using group theory.
• Development of a fitting integral to quantify eigenmode contributions.
• Finite-difference time-domain (FDTD) simulations of nano-oligomers (trimer, quadrumer, hexamer).
• Analysis of optical responses based on incident light polarization and phase patterns.

Main Results:

• Demonstrated control over absorption and scattering spectra by manipulating incident light polarization and phase.
• Showed that fitting between incident light and oligomer modes influences mode oscillation.
• Identified that dark modes significantly impact absorption spectra, while bright modes affect scattering spectra.
• Confirmed the robustness of orbital angular momentum selection rules against experimental precision limitations.

Conclusions:

• Structured light enables precise control over LSP excitation and optical responses in nano-oligomers.
• Group theory and fitting integrals provide a framework for understanding and predicting LSP behavior.
• The findings support the experimental realization of selective LSP excitation with robust selection rules.