Anomalous Spectral Shift of Near- and Far-Field Plasmonic Resonances in Nanogaps

Anna Lombardi, Angela Demetriadou, Lee Weller, Patrick Andrae, Felix Benz, Rohit Chikkaraddy, Javier Aizpurua, Jeremy J. Baumberg

Research output: Contribution to journalArticlepeer-review

40 Citations (Scopus)


The near-field and far-field spectral response of plasmonic systems are often assumed to be identical, due to the lack of methods that can directly compare and correlate both responses under similar environmental conditions. We develop a widely tunable optical technique to probe the near-field resonances within individual plasmonic nanostructures that can be directly compared to the corresponding far-field response. In tightly coupled nanoparticle-on-mirror constructs with nanometer-sized gaps we find >40 meV blue-shifts of the near-field compared to the dark-field scattering peak, which agrees with full electromagnetic simulations. Using a transformation optics approach, we show such shifts arise from the different spectral interference between different gap modes in the near- and far-field. The control and tuning of near-field and far-field responses demonstrated here is of paramount importance in the design of optical nanostructures for field-enhanced spectroscopy, as well as to control near-field activity monitored through the far-field of nano-optical devices.
Original languageEnglish
Pages (from-to)471-477
JournalACS Photonics
Issue number3
Early online date8 Feb 2016
Publication statusPublished - 16 Mar 2016


  • nanoparticle on mirror
  • plasmonics
  • sensing
  • SERS
  • ultrafast tunable lasers


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