4.8 Article

Radiation Engineering of Optical Antennas for Maximum Field Enhancement

期刊

NANO LETTERS
卷 11, 期 7, 页码 2606-2610

出版社

AMER CHEMICAL SOC
DOI: 10.1021/nl2010862

关键词

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

资金

  1. DARPA SERS ST Fundamentals [FA9550-08-1-0257]
  2. Office of Science, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, of the U.S. Department of Energy [DE-AC02-05CH11231]

向作者/读者索取更多资源

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 (Q(rad)) of optical antennas is matched to their absorption quality factor (Q(abs)). 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 similar to 20% higher field enhancement relative to a quarter-wavelength thick dielectric layer.

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