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Terahertz field enhancement by a metallic nano slit operating beyond the skin-depth limit

Nature Photonics volume 3, pages 152–156 (2009)Cite this article

Abstract

The unique optical properties of metals are at the core of many areas of research and applications, including plasmonics1,2,3,4, metamaterials5,6, superlensing and subdiffraction focusing7,8,9,10, optical antennas11,12,13,14 and surface enhanced Raman scattering15. One important length scale inherent in metamaterials and plasmonics research activities in the microwave5,16, terahertz17,18,19, infrared20,21, visible22 and ultraviolet ranges7 is the skin depth of metal, which remains at the submicrometre level throughout the broad spectral range. One prominent question is whether terahertz electromagnetic waves can be controlled on the nanoscale to achieve new functionalities in the sub-skin-depth regime. Here, we show that a λ/30,000 slit on metal film acts as a nanogap-capacitor charged by light-induced currents, enhancing the electric field by orders of magnitudes.

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Figure 1: Terahertz nanogap concept and time-domain spectroscopy.
Figure 2: Terahertz time-domain spectroscopy through nearly free-standing nanogaps.
Figure 3: The FDTD analysis of fields around nanogaps.

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Acknowledgements

We acknowledge helpful discussions with J. B. Pendry, D. Grischkowsky and K. J. Ahn. H. Kim is also thanked for discussions concerning diffractive optics correction used in data analysis and for Kirchhoff formalism. This work was supported by the Korea Science and Engineering Foundation (KOSEF) grant funded by the Korea government (MEST), the Korea Research Foundation (KRF), KICOS (GRL, K20815000003) and the Seoul R&BD Program.

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Authors and Affiliations

  1. Center for Subwavelength Optics and Department of Physics and Astronomy, Seoul National University, Seoul, 151-747, Korea

    M. A. Seo, H. R. Park, D. J. Park, G. S. Park & D. S. Kim

  2. Photonic Systems Laboratory, School of EECS, Seoul National University, Seoul, 151-744, Korea

    S. M. Koo & N. K. Park

  3. Department of Physics, Korea University, Seoul, 136-701, Korea

    J. H. Kang & Q. H. Park

  4. Department of Physics and Advanced Materials Science, Sun Moon University, Asan, 336-708, Korea

    O. K. Suwal & S. S. Choi

  5. Faculty of Applied Sciences, Delft University of Technology, Lorentzweg 1, Delft, 2628, CJ, The Netherlands

    P. C. M. Planken

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Correspondence to Q. H. Park or D. S. Kim.

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Seo, M., Park, H., Koo, S. et al. Terahertz field enhancement by a metallic nano slit operating beyond the skin-depth limit. Nature Photon 3, 152–156 (2009). https://doi.org/10.1038/nphoton.2009.22

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