Interfering plasmons in coupled nanoresonators to boost light localisation and SERS

Angelos Xomalis, Xuezhi Zheng, Angela Demetriadou, Alejandro Martinez, Rohit Chikkaraddy, Jeremy J. Baumberg

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Plasmonic self-assembled nanocavities are ideal platforms for extreme light localisation as they deliver mode volumes <50 nm3 . Here we show that high-order plasmonic modes within additional μm-scale resonators surrounding each nanocavity can boost light localisation to intensity enhancements >105 . 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 sub-nm gaps with μm-scale resonators places high computational demand on simulations, so a generalised Boundary Element Method (BEM) solver is developed which requires 100-fold less computational resource to characterise these systems. Our results on extreme near-field enhancement open new potential for single-molecule photonic circuits, mid-infrared detectors, and remote spectroscopy.
Original languageEnglish
Pages (from-to)2512–2518
Number of pages7
JournalNano Letters
Issue number6
Early online date11 Mar 2021
Publication statusPublished - 24 Mar 2021


  • Nanocavity
  • field enhancement
  • near-field
  • SERS
  • nano-optics
  • plasmon interference
  • remote excitation


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