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Proceedings Paper

Plasmon-enhanced terahertz near-field microscopy for nanometer-scale sensing
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Paper Abstract

The detection of trace quantities of aromatic compounds is important to defense and security applications, including the detection of CB agents, explosives, and other substances. These pose threats to forces and the environment. This paper explores an approach to the detection and identification of quantities as little as single molecules of explosives. It can in principle provide instant warning. Apertureless near-field scanning optical microscopy (ANSOM) is one of several promising methods for obtaining spatial resolution below the diffraction limit at various wavelengths, including in the terahertz regime. By scattering incident light off the junction between a probe with a sub-wavelength tip and the surface of a sample, spatial resolution on the order of the tip size can be obtained. For terahertz time-domain spectroscopy where the wavelength-limited resolution is ~1 millimeter, this is a significant advantage. In the case of a sufficiently small probe tip and a thin metallic substrate, plasmonic interaction between the tip and sample provides an enhancement of the near-field in the junction. This effect is dramatically enhanced for nanometer-scale metal layers, since surface plasmon states from both sides of the film can contribute to the overall field enhancement. We present preliminary results of THz plasmonic field enhancements, using a thin (500 nm) gold film evaporated on glass. We observe an enhancement in the scattered THz wave, which we attribute to the large density of plasmonic states extending throughout the THz range. This result indicates a route to single-molecule spectroscopy at terahertz frequencies.

Paper Details

Date Published: 16 April 2008
PDF: 9 pages
Proc. SPIE 6979, Independent Component Analyses, Wavelets, Unsupervised Nano-Biomimetic Sensors, and Neural Networks VI, 69790F (16 April 2008); doi: 10.1117/12.776779
Show Author Affiliations
Daniel Mittleman, Rice Univ. (United States)
Victoria Astley, Rice Univ. (United States)
Hui Zhan, Rice Univ. (United States)
Feng Hao, Rice Univ. (United States)
Peter Nordlander, Rice Univ. (United States)
Forrest J. Agee, Rice Univ. (United States)

Published in SPIE Proceedings Vol. 6979:
Independent Component Analyses, Wavelets, Unsupervised Nano-Biomimetic Sensors, and Neural Networks VI
Harold H. Szu; F. Jack Agee, Editor(s)

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