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14 February 2008 Effect of surface scattering on terahertz time domain spectroscopy of chemicals
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The existence of unique absorption spectrum patterns for many chemicals at terahertz frequencies has opened an exciting avenue in non-contact safe detection of such materials by terahertz spectroscopy. However, scattering of THz waves, which have wavelengths on the order of material grain sizes, by surface roughness challenges the sensitivity of this detection scheme in practice. In this work, we present terahertz time domain spectroscopy results for materials with rough surfaces. Both reflection from and transmission through lactose, which has sharp absorption peaks in the terahertz regime, are studied and the effect of increasing scattering through controlled surface roughness is investigated. Such electromagnetic scattering can alter the terahertz absorption spectrum and thus obscure the detection of chemicals. Furthermore we examine electro-optic detection of terahertz signals reflected from randomly rough targets with a theoretical electromagnetic system perspective and provide a method to retrieve coherent reflection responses from rough surface targets.
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M. Hassan Arbab, Antao Chen, Eric I Thorsos, Dale P Winebrenner, and Lisa M Zurk "Effect of surface scattering on terahertz time domain spectroscopy of chemicals", Proc. SPIE 6893, Terahertz Technology and Applications, 68930C (14 February 2008);

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