Mode-Specific Coupling of Nanoparticle-on-Mirror Cavities with Cylindrical Vector Beams

Area of Science:

• Plasmonics and Nanophotonics
• Quantum Optics
• Materials Science

Background:

• Metallic nanogaps create nanocavities enabling extreme light-matter interaction and small mode volumes.
• Enhanced vacuum fields in nanogaps are known, but efficient far-field to near-field coupling control is less explored.
• Understanding input coupling is crucial for harnessing nanocavity-enhanced phenomena.

Purpose of the Study:

• To experimentally demonstrate selective excitation of nanocavity modes.
• To investigate the control of mode excitation using laser polarization and frequency.
• To bridge the gap between far-field excitation parameters and near-field nanocavity responses.

Main Methods:

• Utilizing cylindrical vector beams for controlled laser polarization.
• Recording confocal maps of Raman scattering to visualize excited modes.
• Comparing experimental near-field patterns with theoretical predictions.

Main Results:

• Selective excitation of nanocavity modes was achieved by tuning laser polarization and frequency.
• Transverse and longitudinal polarization of antenna modes were identified.
• The dependence of the input coupling rate on laser wavelength was quantified.

Conclusions:

• Precise control over nanocavity mode excitation is possible via tailored laser input.
• The developed method offers a versatile tool for studying and engineering light-matter interactions in nanogaps.
• Results provide crucial data for quantitative modeling of nanocavity-enhanced effects.