Radiation engineering of optical antennas for maximum field enhancement

Tae Joon Seok, Arash Jamshidi, Myungki Kim, Scott Dhuey, Amit Lakhani, Hyuck Choo, Peter James Schuck, Stefano Cabrini, Adam M. Schwartzberg, Jeffrey Bokor, Eli Yablonovitch, Ming C. Wu

Research output: Contribution to journalArticlepeer-review

161 Citations (Scopus)


Optical antennas have generated much interest in recent years due to their ability to focus optical energy beyond the diffraction limit, benefiting a broad range of applications such as sensitive photodetection, magnetic storage, and surface-enhanced Raman spectroscopy. To achieve the maximum field enhancement for an optical antenna, parameters such as the antenna dimensions, loading conditions, and coupling efficiency have been previously studied. Here, we present a framework, based on coupled-mode theory, to achieve maximum field enhancement in optical antennas through optimization of optical antennas' radiation characteristics. We demonstrate that the optimum condition is achieved when the radiation quality factor (Qrad) of optical antennas is matched to their absorption quality factor (Qabs). We achieve this condition experimentally by fabricating the optical antennas on a dielectric (SiO2) coated ground plane (metal substrate) and controlling the antenna radiation through optimizing the dielectric thickness. The dielectric thickness at which the matching condition occurs is approximately half of the quarter-wavelength thickness, typically used to achieve constructive interference, and leads to ∼20% higher field enhancement relative to a quarter-wavelength thick dielectric layer.

Original languageEnglish
Pages (from-to)2606-2610
Number of pages5
JournalNano Letters
Issue number7
Publication statusPublished - 2011 Jul 13
Externally publishedYes


  • Plasmonics
  • ground plane
  • impedance matching
  • nano-optics
  • optical antenna

ASJC Scopus subject areas

  • Bioengineering
  • General Chemistry
  • General Materials Science
  • Condensed Matter Physics
  • Mechanical Engineering


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