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Proceedings Paper

THz-Raman spectroscopy for explosives, chemical, and biological detection
Author(s): James T. A. Carriere; Frank Havermeyer; Randy A. Heyler
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Paper Abstract

Raman and Terahertz spectroscopy are both widely used for their ability to safely and remotely identify unknown materials. Each approach has its advantages and disadvantages. Traditional Raman spectroscopy typically measures molecular energy transitions in the 200-5000cm-1 region corresponding to sub-molecular stretching or bending transitions, while Terahertz spectroscopy measures molecular energy transitions in the 1-200cm-1 region (30GHz - 6THz) that correspond to low energy rotational modes or vibrational modes of the entire molecule.

Many difficult to detect explosives and other hazardous chemicals are known to have multiple relatively strong transitions in this “Terahertz” (<200cm-1, <6THz) regime, suggesting this method as a powerful complementary approach for identification. However, THz signal generation is often expensive, many THz spectroscopy systems are limited to just a few THz range, and strong water absorption bands in this region can act to mask certain transitions if great care isn't taken during sample preparation. Alternatively, low-frequency or “THz-Raman” spectroscopy, which covers the ~5cm-1 to 200cm-1 (150GHz - 6 THz) regions and beyond, offers a powerful, compact and economical alternative to probe these low energy transitions.

We present results from a new approach for extending the range of Raman spectroscopy into the Terahertz regime using an ultra-narrow-band volume holographic grating (VHG) based notch filter system. An integrated, compact Raman system is demonstrated utilizing a single stage spectrometer to show both Stokes and anti-Stokes measurements down to <10cm-1 on traditionally difficult to detect explosives, as well as other chemical and biological samples.

Paper Details

Date Published: 29 May 2013
PDF: 8 pages
Proc. SPIE 8710, Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XIV, 87100M (29 May 2013); doi: 10.1117/12.2018095
Show Author Affiliations
James T. A. Carriere, Ondax, Inc. (United States)
Frank Havermeyer, Ondax, Inc. (United States)
Randy A. Heyler, Ondax, Inc. (United States)

Published in SPIE Proceedings Vol. 8710:
Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XIV
Augustus Way Fountain, Editor(s)

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