Interfering Plasmons in Coupled Nanoresonators to Boost Light Localization and SERS

Plasmonic self-assembled nanocavities are ideal platforms for extreme light localization as they deliver mode volumes of <50 nm(3). Here we show that high-order plasmonic modes within additional micrometer-scale resonators surrounding each nanocavity can boost light localization to intensity enhancements >10(5). Plasmon interference in these hybrid microresonator nanocavities produces surface-enhanced Raman scattering (SERS) signals many-fold larger than in the bare plasmonic constructs. These now allow remote access to molecules inside the ultrathin gaps, avoiding direct irradiation and thus preventing molecular damage. Combining subnanometer gaps with micrometer-scale resonators places a high computational demand on simulations, so a generalized boundary element method (BEM) solver is developed which requires 100-fold less computational resources to characterize these systems. Our results on extreme near-field enhancement open new potential for single- molecule photonic circuits, mid-infrared detectors, and remote spectroscopy.

Automated summary

The combination of plasmonic self-assembled nanocavities and micrometer-scale resonators can achieve extreme light localization and intensity enhancement, leading to significantly larger surface-enhanced Raman scattering signals, enabling remote access to molecules without direct irradiation to prevent molecular damage. A generalized boundary element method solver has been developed to reduce computational resources required for characterizing these systems effectively. This opens up new potential for single-molecule photonic circuits, mid-infrared detectors, and remote spectroscopy.